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Forest Ecology
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2.2 Types of Ecosystem
Ecosystem are categorized into natural and artificial ecosystem.
Natural Ecosystem: Terrestrial and Aquatic
• Terrestrial (28.20 %): Forest, Grass/range, Desert (Tundra)
• Aquatic (71.80 %) : Fresh water and Marine or Ocean
Lentic ( pools, ponds, lakes stagnated or slow moving water , sizes
range up to thousand Km2, season or perinnial, limited biodiversity
because of isolated from other water sources)
Lotic ( streams/rivers or rapidly moving water )
Wetland ( inundated water or soil saturated )
Based on distance from the land surface and depth of light penetration into water Lentic
ecosystem is further divided into 3 zones:
• Littoral Zone
•Limnetic Zone
•Profundal Zone
Littoral Zone: also called euphotic zone
• shallow water zone, close to land surface, light penetrate ( up to 10 m), rich in O2 circulation,
absorb more of the Sun‘s heat and is warmest,
• sustains a fairly diverse community, include several species of algae (like diatoms),
chlorophyll bearing long rooted and floating aquatic plants.
• plants make their own food, photosynthesis and respiration take place,
• transfer of energy and food waves take place from one trophic level to another
• vegetation and animals living in the littoral zone are food for other creatures such as turtles,
snakes, ducks and aquatic birds
• Primary Producers : plants rooted to the bottom and algae attached to the plants and to any
other solid substrate ( Monochoria, cyprus, rumex, water lily, water hysinth, hydrilla, algae
(diatoms)
• Primary Consumers : tiny crustaceans, flat worm, insect larvae, grazing snails, turtles,
• Secondary consumers and top carnivores : clams, insects (the egg and larvae stages of some
insects are also found), fishes, turtles, snakes, ducks, aquatic birds and some other amphibians
• Decomposers : insects and algae, fungus etc
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Limnetic Zone : also called diaphotic zone
• Zone below Littoral zone
• Dipper than Littoral zone
• Far from land surface and up to effective light penetration zone called ( up to 100 m depending
upon turbidity)
• absorb less heat than littoral zone, photosynthesis takes place
• Primary producers ( Autotrophs) : phytoplankton
• Primary consumers (Heterotrophs) : Zooplankton
• Secondary consumers : insects
• Higher consumers : fishes
( Phytoplankton : single celled microscopic plants covered with two shells, photosynthesing
microscopic organisms, needs sunlight, H2O, CO2 and nutrients, use water, CO2 and the
presence of chlorophyll within their cell photosynthesize and prepare foods and acts like primary
producers. This is autotrophic. Ex: seaweed and algae.)
( Zooplankton : are carnivores or herbivores plankton, heterotrophic plankton, feed on
phytoplankton. Ex : jellyfish, Krill, some fishes )
Profundal Zone : also called aphotic zone
• Zone below Limnetic zone
• Dipper than Limnetic zone
• No enough light to support primary producers
• Aphotic zone
• dissolved O2 and CO2
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• decomposers (bacteria and fungi are the community of organisms and they feed on detritus )
and release inorganic nutrient . Detritus are the dead organic matter ( dead bodies of plankton,
OM drifted down from Littoral and Limnetic zones
• Primary consumers : Benthos ( bottom dwelling bacteria or fungi that are attached to or crawl
along the sediments at the bottom of the lake)
• The sediments underlying the profundal zone also support a large population of bacteria and
fungi. These decomposers break down the organic matter reaching them, releasing inorganic
nutrients for recycling.
• The profundal zone is chiefly inhabited by primary consumers that are either attached to or
crawl along the sediments at the bottom of the lake.
• Organisms associated with this zone are only Heterotrophs ( detritus feeder) and carnivores (
snails, crabs, fishes etc)
• Decomposers Primary consumers ( Benthos) Carnivores
Lotic ( streams/rivers or rapidly moving water )
• Differs from lentic ecosystem
• because of water current, the water is usually oxygenated
• photosynthesis play minor role in food chain
• Large portion of energy and food available for the consumers is from land or terrestrial
ecosystem
In conclusion, aquatic ecosystem ( Ponds and lake ecosystem) :
Producers : green plants or algae either flooting or suspended or rooted at the bottom
Consumers : Primary consumers ( Tadpole larvae of frog, fishes, and other aquatic animals that
consume producers). Secondary producers : Big fishes, water snakes, crabs etc. Tertiary
consumers : water birds, dulfin, turtles, crocodile etc
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Terrestrial Ecosystem :
Forest : A forest ecosystem is a natural woodland unit consisting of all plants, animals and
micro-organisms (Biotic components) functioning together with all of the non-living physical
(Abiotic) factors of the environment.
• Complex assemblage of biotic and abiotic components
• Most productive ecosystem than grass land and desert ecosystem
• Forest ecosystem is made up of soil, water, plants, animals, insects, fungi, and bacteria. All of
these things must interact with each other to form the ecosystem.
• Forest ecosystem represent the largest and most ecologically complex systems. They contain a
wide assortment of trees, plants, mammals, reptiles.
• Forest ecosystem represent the largest and most ecologically complex systems.
• Forest ecosystem function as habitats for organisms, hydrological flow modulators, and soil
conservers, constituting one of the most important aspects of the biosphere.
• Physical and chemical processes such as energy flow and nutrient cycling takes place.
• Forested ecosystems have great effect on the cycling of carbon, water, and nutrients, and
these effects are important in understanding long-term productivity. Cycling of carbon,
oxygen, and hydrogen are dominated by photosynthesis, respiration, and decomposition
• Energy flow from producers to carnivores and food web at atrophic levels controls the
productivity of forest ecosystem
• In the energy flow, only 10% of energy passed from one trophic level to next trophic level or
there is diminishing energy or biomass as we move from lowest trophic level to top trophic
level.
• Forest ecosystem provides ecological services and play important role in carbon
sequestration
• Forests are central to all human life because they provide a diverse range of resources, they
store carbon, aid in regulating climate, purify water and mitigate natural hazards such as
floods
• Forests ecosystems sustain human societies and allow them to prosper, due to the nutritional,
environmental, cultural, recreational and aesthetic resources they provide. We all depend
directly or indirectly on the products and services of ecosystems, including crops, livestock,
fish, wood, clean water, oxygen, and wildlife.
World forests biome :
• Borel or taiga forests ( 24%)
• Temperate forests ( 13%)
• Subtropical forests (8%)
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•Tropical forest (49%)
• Plantation (6%)
Life Zone ( Ecological Zone of Nepal)
• By altitude
• Nival Zone > 5000 m : zone of permanent snow, some life such as moss and lichen present on
exposed rock
• Alpine Zone ( 4000-5000m) : alpine grassland/range land with junipers thickets,
rhododendron bushes and cushion plants
• Sub-alpine Zone ( 3000-4000m) : fir, birch and rhododendron species
• Temperate Zone ( 2000-3000m) : evergreen oak and rhododendron, conifers and broadleaf
species
• Sub-tropical Zone (1000-2000m) : blue pine, chirpine, oaks, chilaune,
• Tropical Zone (< 1000m) : Mostly sal and khair
Vegetation Types and Eco-region of Nepal
Vegetation Types Eco-region Altitude
Montane grasslands and
shrublands
Trans-Himalayan alpine
shrub/ meadow 4400-5000
West Himalayan alpine
shrub/ meadow 3700-4400
East Himalayan alpine
shrub/ meadow 4000-4500
North-west Himalayan
alpine shrub/ meadow >4000
Sub-alpine conifer forests Trans-Himalayan subalpine
conifer 3000-4000
West –Himalayan subalpine
conifer 3000-
4000
East –Himalayan subalpine
conifer
3000-4000
Temperate broadleaved
forests
West Himalayan
broadleaved
1500-3000
East Himalayan broadleaved 1500-3000
Tropical forests/sub-
tropical conifer forests
Himalayan sub-tropical pine 1000-2000
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Sub-tropical broadleaved
forests
Himalayan sub-tropical
broad leaved
500-1000
Grassland, savannahs and
shrubl ands
Terai-Duar savannahs and
grassland
< 500
Desert Ecosystem :
Classified on the basis of temperature and rainfall
• Deserts ecosystem are defined as regions wherein the average annual precipitation seldom
exceeds more than 10 inches per year, and the amount of water lost to evapo-transpiration is
much more than the amount of water gained by precipitation.
• A desert ecosystem relies on an area that receives little to no precipitation and the temperature
is very cold to very hot
• In the desert ecosystem, climate is a deciding factor for the existence of life forms. In deserts,
temperatures can reach up to 115° F during the day, and come down to 32° F at night.
• Desert environment is very harsh in terms of climate, soil and plants. Life does exist in this
harsh environment. Numerous plants and animal species have adapted to these unsuitable
conditions
• Such extreme temperature makes it difficult for life forms to survive in the deserts, unless they
adapt to this harsh climate. Many plants and animals have adapted themselves over the years,
and have become an important part of the desert ecosystem
• Deserts are home to a number of species of animal and plant kingdom. Biodiversity of the
deserts ecosystem is as unique as other ecosystem. Each of these species play a crucial role
in the desert ecosystem food chain
• Like in most of the other ecosystems, plants are the primary producers, while rodents, insects
and reptiles which feed on these plants are the primary consumers. Then come the secondary
consumers, who mainly comprise larger reptiles and insects which feed on primary consumers
• Decomposers = Bacteria and fungi
• Two components Abiotic and biotic interacts
• At the top of the desert food chain are the apex predators in the form of birds and mammals.
• Most prominent members of the desert animals include desert tortoise, rattlesnakes, hawks,
owl, ostrich, bobcat, jackals, fox, kangaroo rats, mountain lions, etc.
• Most of these desert animals are nocturnal, i.e. active during the night, and spend the persist
during the day.
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• Water being scarce in deserts, these animals have also modified themselves to make the most
of the available water. Some animals absorb water from plants, while others store it in their
fatty tissues.
• Desert vegetation mostly are cacti sps and sucullent plants.. These plants have modified
themselves to sustain in the desert environment.
• Some plants store water in the specialized tissues, while others have small leaves with hair
like structures which reduce the evaporation of moisture.
• Desert are classified into hot and cold deserts
• Prominent difference between the two is the form of precipitation, which is snowfall in cold
deserts and rainfall in hot deserts. Irrespective of whether it is a hot or a cold desert, the
characteristic traits of both almost remain the same
Hot deserts
• These areas exist under a moisture deficit, which means they can frequently lose more
moisture through evaporation than they receive from annual precipitation.
• The largest hot desert in the world, northern Africa's Sahara, reaches temperatures of up to
122 degrees Fahrenheit (50 degrees Celsius) during the day.
• Desert plants may have to go without fresh water for years at a time. Some plants have
adapted to the arid climate by growing long roots that tap water from deep underground.
• Deserts are part of a wider classification of regions called "drylands."
Cold deserts :
• Cold desert ecosystem : higher elevation, low temperature and rainfall scanty, frost and
snow are common, very poor soil, deficient in organic matter and nutrient but rich in
minerals, cold desert occurs in Himalayan region.
• Cold deserts are also known as polar deserts. Antarctica is the earth's largest cold desert, and
the Arctic is the second largest. Gobi desert in Asia is another example of cold desert
• Low soil productivity, growth of xerophytes, cold desert in Ladhakh and tibet of Himalayas,
• Vegetation sparse, drought resistance, water storing sucullant like cactus,
• They are environments that receive less than 10 inches of rain or snow per year and that have
extremely cold temperatures year-round
• Cold desert never rises above 50 degrees Fahrenheit in the summertime.The type of
environment represented by cold deserts is called tundra.
• This makes for a very harsh environment for plants and animals to survive in
• Plants that grow in the cold desert regions are very hardy and adapted to the extreme winter
cold.
• As with many annual plants, cold desert plants have a summer time and short growing season,
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• Several types of mosses, grasses, herbs and lichens also live cold desert.
Food Web in Desert Ecosystem :
1st Trophic Level: Primary Producers = Trees, shrubs, cactus, wildflowers, grasses
2nd
Trophic Level:
Primary Consumers
Herbivores = camel, mule, deer, rabbits, ants, squirrel, rats and mice, some insects , some
reptiles the largest of which are the tortoise
3rd Trophic Level: Secondary Consumers ( small predators)
Small Carnivores = snakes, lizards,
4th Trophic Level:
Tertiary Consumers ( Large predators)
Carnivores = Eagle, vulture, Fox, wolf, wild cat, panther etc
Grassland Ecosystem :
• About one quarter of the earth is covered by grasslands ecosystem
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• Grasslands are areas where the vegetation is dominated by grasses (Poaceae) and other
herbaceous and non-woody plants.
• Grasslands are defined as lands prevailed by grasses instead than big trees and shrubs
• Grassland ecosystem are influenced over time by : Local climate, plant communities,
variation of local Landscape, disturbances such as fire and floods, organisms that live in them
• Natural grasslands primarily occur in regions that receive between 250 and 900 mm annual
rainfall as compared with deserts , which receive less than 250 mm and forests, which receive
more than 2,000 mm.
•. Grassland ecosystem is in a transition between the desert and the forest.
• Average daily temperatures range between -20 and 30 °C.
•. There are two major classifications of grasslands:
• Tropical grasslands or Savanna are those grasslands that are nearest to the equator or . in the
southern hemisphere They are very hot or warm throughout the year. Tend to get more
precipitation than those in the. Some grasses grow more than 7 feet (2 meters), and have
roots extending several feet into the soil.
• Temperate grasslands are those far away from the equator or in the northern hemisphere with
warm summers and cold winters with rain or some snow
• Grasslands are also classified into : Mixed grasslands grasses that grow up around 50-80 cm
high and about 300-500 mm of rain per year.
• Short grasslands : get very little rainfall per year, less than 200mm rain per year
• Grassland ecosystem consists of grasses, flowers, shrubs, herbs in which shrubs and trees are
hardly can find.
• Each grassland type has its specific herbivores and carnivores
• Grassland herbivores are fleet footed animals that live in herds as protective mechanism
• Characteristics of grassland animals : Run type (blackbuck, wolf, leopard etc) and burrowing
type (rabbit, porcupine, hedgehog etc) as protective and adapting mechanisms
• Grasslands also have an enormous number of insects. These insects attract a large number of
predatory animals like the lizards and birds.
• Various types of grasses that mainly grow up in the grassland ecosystem such as ryegrass,
foxtail, wild oats, buffalo grass and purple needle grass.
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• Tropical and sub-tropical grasslands are home to many large herbivores such as bison,
zebras, rhinoceros , elephant, wild horses etc and carnivores like lions , tiger, wolves ,
leopards etc. Other animals of this region include deer, wild dogs, jackal , mice, jack rabbits ,
snakes fox, owls, etc
• Temperate grasslands herbivores are antelopes, wild boar etc and carnivores are leopards,
wolf, wild cat, fox, jackal etc.
• Several wild sheep and goat such as the Goral are found in Himalayan pastures.
• The largest herbivore of the Terai grassland is the elephant. It requires an enormous amount
of tall grass to feed on. The Terai grasslands form the habitat of the Swamp deer, Wild
buffalo and the Rhinoceros.
• Tropical grasslands are warm year round, but usually have a dry and a rainy season.
• Temperate grasslands have shorter grasses and have two seasons: a growing season and a
dormant season. During the dormant season, no grass can grow because it is too cold.
International Terminology for Grassland Ecosystem :
• The South America‘s grasslands are called ―Pampas‖,
• The North American grassland are called ―Praire‖
• European grassland are called ―Steppes‖
• The African grassland is called the ―Serengeti‖ or ―Savanna‖ . Savanna is also available in
Australia, South America and India
• There is a huge area of grassland that stretches out from Siberia to Ukraine which is known as
the ―Russian steppes‖.
• In Himalayan region, the grassland are normally called pastures which extends up to the
snowline. These grasslands at the lower level are found along with coniferous or broad-leaved
forests.
• The Terai grasslands at the foothills of the Himalayas consist of tall elephant grass along with
Sal forest is usually referred as Terai-Duar savannah and grassland
Grassland Ecosystem of Nepal :
It is an ecosystem in which the plants and animal communities along with the abioitic factors
like soil, air, water, temperature, topography and solar energy interact.
The grassland ecosystem of Nepal can be classified as :
Tropical grassland (upto 1000m) : dominated by the grasses like Saccharum spontaneum and
Imperata cylindrica. Some also contain 2 m tall Cymbopogon jwarancusa and Bothriochloa
intermedia. Eupatorium is gradually replacing many of the palatable species.
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Sub-tropical grassland (1000 -2000m) : mostly associated with Pinus roxburghii forests. They
are heavily grazed and are infested with Eupatorium sps(Banmara), Pteridium aquilinum
(bracken fern), Urtica parviflora and Artemisia vulgaris.
Temperate Grassland (2000-3000m) : are associated with oak or mixed broad-leafed species
such as Quercus or bluepine forests. These grassland very important, but degrading due to heavy
grazing for many years
Sub-alpine Grassland (3000-4000 m) : are associated with a variety of shrubs. The common
genera are Berberis, Caragana, Hippophae, Juniperus, Lonicera, Potentilla, Rosa, and Spiraea
and Rhododendron.
Alpine Grassland (4000-5000m): are associated with Rhododendron shrubs. The main types of
vegetation, based on the specification of areas, are Kobresia, Cortia depressa, and Carex /
Agrostis / Poa associations. Common plant species are Kobresia spp. and Agrostis sps.
Steppe: It is situated in Trans Himalayan area of Dolpa and Mustang. Productivity of these range
is very low due to overgrazing by animals
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Desert food web
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Analysis of Ecosystem :
Structural system, functional system and regulation of an ecosystem
In analysis of ecosystem, we generally undertake study on following elements of an ecosystem :
• Biotic and abiotic components and their properties,
• Quantity of materials needed for organisms
• Rate of organic matter produced and used up in respiratory process
• Quantity of energy passed from one trophic level to another
• Driving forces of light, temperature, rainfall,
• Soil structure and nutrient, litter fall, death of organisms,
• Mineralization, recycling of nutrients,
This is a study or analysis of structural, functional and regulation systems of an ecosystem
with space and time .
• The structural system includes biotic ( autotrophs, heterotrophs, decomposers ) and abiotic
components (Inorganic substance, organic substance, climate, topography and edaphic
factors).
• Functional analysis (Metabolic process of the living plants and animals or organisms.
• Energy flow at various trophic levels, Bio-geochemical cycling i.e pathways of circulation of
organic and inorganic elements within an ecosystem
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• Regulation ie form of adoption or change behavior of an organism of an ecosystem with
change of ecosystem structure.
Ecosystem Analysis : Cause – Effect Relationship
Ecosystem Analysis
Structural System : It includes study of biotic and abiotic components. In biotic
component, we study :
• the composition of biological community ( spp, properties, structure, density,
frequency/number, life history, growth, survival , death of organisms, organisms response to
change in abiotic components and nutrients etc)
• biomass produced by organisms , trophic level (producers, consumers, decomposers),
• quantity of materials needed for the growth and survival of the organisms
• the rate at which the organic matter is built up and disappeared and used up for in the
respiratory process
In abiotic components, we study :
• The driving force of light, temperature, rainfall, range of condition of existence, geology, soil
structure, soil texture, soil nutrient, thickness of soil profile, chemical and physical properties of
soil, mineralization, recycling of nutrients, slope, altitude/topography, aspects , quantity and
distribution of abiotic materials etc
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Functional System : This includes the study of :
• rate of nutrient cycling within an ecosystem,
• range of energy flow or move through an ecosystem via the trophic level/food-web
• photosynthesis and respiration process
• energy loss, energy use by organisms
• decomposition of organic matter, release of inorganic or chemical energy, nutrient pool
• assessment of gross and net primary productivity etc
Ecosystem Regulation : This includes the study of :
• form of adoption or behavior change of organisms of ecosystem with change of ecosystem
structure
• ways in which the ecosystem regulate itself ( Intra and inter specific interactions)
• interactions between biotic and abiotic components
• bottom-up and top-down regulations etc.
Energy in an Ecosystem
• Living organism can use energy in two forms
• Radiant and Fixed energy
• Radiant energy = electromagnetic wave such as sun light
• Fixed energy = chemical energy in organic substances, which is broken down and release for
energy need for plants
• Only a small fraction of incident radiant energy ( about 3 %) can be utilized by plants
• This radiant energy is converted into chemical energy by photosynthetic process of
autotrophs
• 6 CO2 (from atmosphere)+ 6H2O (from soil) + light = 6C6H12O6 ( sugar in plant cell ) +
6O2 ( release in atmosphere)
• Sugar converted into inert energy rich organic substances such as starch, which plants stored
them
• Starch combined with other sugar molecule and form carbohydrates such as cellulose
• Cellulose combined with nitrogen, phosphorus and sulfur produce proteins, nucleic acid and
hormones
• All the above reactions are necessary for plants growth, maintenance of the body tissues and
functions of the plants
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• Sugar produced during photosynthesis will be oxidized and produce CO2 and H2O and usable
chemical energy
• 6C6H12O6 + 6O2 = 6 CO2 + 6H2O + usable energy
• Oxidation of sugar or any organic molecule to get usable energy by organism is called
respiration
• Energy released by respiration is lost permanently to the ecosystem
• In each transformation from one trophic to another some energy is lost as heat energy
Pattern of Flow of Energy Through the Ecosystem
Solar Energy
Producers
( autotrophic plants Primary consumers Primary carnivores
/phytoplankton)
Dead remains Secondary carnivores
Raw materials Decomposers ( bacteria/fungi)
(organic/inorganic salts)
Sun
• Only a small fraction of the light energy reaching the earth is tapped
• Autotrophs or green plants utilize only about 3% of incident energy in photosynthesis
6 CO2 (from atmosphere)+ 6H2O (from soil) + light = 6C6H12O6 ( sugar in plant cell ) + 6O2
( release in
energy
atmosphere)
• Respiration : ( Oxidation of sugar to get usable energy by organism )
6C6H12O6 + 6O2 == 6 CO2 + 6H2O + usable energy ( permanently lost to the ecosystem)
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Inputs and losses of energy at each trophic level : R1 R2 R3 R4 A2 A3 A4 F1 C1 F2 C2 F3 C3 F4 C4 A = assimilation of food by the organisms at each trophic level F = energy loss in the forms of faeces and other excretory /dead products C = energy lost through decay R = energy lost to respiration
Solar radiation
1. Autotrophs
2. Herbivore
3. Primary
carnivore
4. Secondary carnivore
DECOMPOSITION
Ecosystem Productivity :
• All the energy that the plant fixes results formulation of sugar in the plants leaves
• Sugar produced in the leaves of green plants is derived from CO2 and H2O combined with
solar energy
• Thus the energy incorporated into living tissue of plants is either in terms of the light energy
utilized or in terms of the sugar produced
• All the energy used by plants is converted into chemical energy. So the entire energy uptake
of plants can be measured by measuring the total amount of sugar produced.
• This amount of entire energy uptake by plants or sugar produced is known as gross primary
production. This is the total amount of organic matter that plant produces through
photosynthesis. It is a total weight in all the parts of root, steam, leaves, fruits etc
• It is not easy to measure gross primary productivity (organic matter) because some of the
sugar produced by photosynthesis will be lost immediately through plant respiration
• one can measure the total organic matter actually present in the plant (biomass) by deducting
the sugar or energy lost through respiration from the gross primary production, which is called
Net primary production .
• NPP ( energy stored in plant biomass with time or biomass) = GPP – energy loss during
respiration.
GPP = NPP + Energy loss during respiration
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If GPP = respiration, no change in stored energy
GPP < respiration, biomass decreases
GPP > respiration, accumulation of biomass takes place
GPP depends upon climate conditions ( temp, rainfall, solar radiation etc ) availability of
nutrient
( N, P, S ). Productivity is expressed in terms of grams or kilo-calories per sq meter/day or per
year
Ecosystem Productivity : The movement of energy within an ecosystem via producers,
consumers and decomposers is ecosystem productivity (bio-mass or the total living matter in a
given place during a given time).
Primary Productivity (Producers level) : The rate of energy trapping by green plants governs
the rate of production of organic material from simple inorganic substances in a given area over a
given period of time. Therefore, the primary productivity is the rate of energy conversion or
increase in organic biomass produced by green plants
Gross Primary Productivity ( GPP): The rate at which photosynthesis captures energy. In other
word, an ecosystem's GPP is the total amount of organic matter that it produces through
photosynthesis. It is a total increase in weight in all the parts of root, steam, leaves, fruits etc
NPP : The energy that remains (as biomass) after plants and other producers carry out
cellular respiration. Net primary productivity (NPP) describes the amount of energy that
remains available for plant growth after subtracting the fraction that plants use for respiration.
6 CO 2 + 6 H2O + light energy = C6 H12O6 + 6 O2 ( During photosynthesis )
C6 H12O6 + 6 O2 = 6 CO2 + 6 H2O + Heat energy ( During respiration)
Secondary productivity ( Consumers level) : It refers to the production of living maters or
organic matters by consumers and decomposers in a given time and space
Secondary Production :
• Energy required for other trophic levels in an ecosystem will be furnished from the energy
derived from primary production
• Some energy (in the form of food) is consumed by herbivores. Carnivores eat herbivores to
meet the energy required by them
• Much of the eaten (ingested) food will not be absorbed (assimilated) , herbivores assimilate
only 10 % of ingested food.
• Assimilation rate (coefficient) of carnivores will be higher than the herbivores, example fish
assimilate 86 – 96 % of ingested food
• Assimilation of ingested food varies with food substances such as in the form of protein, fat,
carbohydrates etc.
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• Unassimilated food materials leaves the animal‘s body as waste materials which serves as
energy source for other organisms like detritus ( dead organic matters) feeders like saprophage (
many bacteria and fungi)
• Assimilated food or energy use by consumers for metabolic processes, such as respiration,
excretion and secretion.
• The resultant amount of energy stored in the tissues of heterotrops ( herbivores or carnivores)
is called Net secondary production
• Gross secondary production = total food material (energy) ingested by the heterotrophs -
materials lost as waste or faeces or material defaecated
• Gross secondary production can be measured directly by measuring the amount of food
ingested minus material defaecated
Measurement of Productivity :
• O2 Meaurement method ( Light and Dark Bottle Method)
• CO2 Measurement Method (CO2 Assimilation Method)
• Chlorophyll Method
• Harvest Method
• PH Method
• Radioactive Tracers method
1. O2 Meaurement method ( Light and Dark Bottle Method)
• Used for aquatic ecosystem
• Take two bottles one light and another dark of same material and same weight and
volume
• Take samples of concentration of phytoplankton from lake or river or sea suspended at
the bottom of the bottles
• The light bottle ensure light inside the bottle and photosynthesis takes place while dark
bottle excludes light and no photosynthesis takes place and only respiration from the
phytoplankton population takes place
• In light bottle photosynthesis and respiration takes place while in dark bottle only the
respiration takes place but no photosynthesis
• In light bottle some of the CO2 is used by the phytoplankton for photosynthesis and at the
same time some of the O2 is produce due to respiration ( refer the equations for photosynthesis
and respiration)
• In dark bottle O2 is used due to respiration by phytoplankton and release Co2
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•Imagine a base bottle of the same dimension and constituents as of dark bottle and light
bottle.
Expose on
sunlight
Initial bottle Dark bottle
Light bottle
Wt. of Light bottle - wt. of initial bottle = NPP = GPP – respiration ( amount of O2 left )
Wt. of Initial bottle – wt. of Dark bottle = Respiration
Wt. of Light bottle – wt. of Dark bottle = GPP
Example : Assume, weight of O2 in Initial bottle = 8 mg O2 /L ; Wt. of light bottle would be
increased due to added O2 by photosynthesis = 10mg O2/L ; Wt of dark bottle would be
decreased due to use of O2 by respiration = 5 mg O2 / L
Light – Initial bottle = 10-8 = 2 = NPP ; Initial – dark bottle = 8 – 5 = 3 = Respiration
And Light – Dark bottle = 10 – 5 = 5 = GPP
• CO2 Measurement Method (CO2 Assimilation Method)
• Used for terrestrial ecosystem
• Take two plastic tents or plastic cover one light and another dark of same material and
same size
• Take two sample sites at ground assuming that plant materials, soil , moisture
conditions etc. of these sites are identical.
• Cover one site by light plastic cover or tent and another by dark plastic cover or tent
• In the site having light plastic cover or tent, plant photosynthesis inside the cover takes
place while in the site having dark plastic cover or tent only the plant respiration takes
place but no photosynthesis
• In the white plastic cover site, inject air from one side and draw air from other side
Draw air Incoming air
site with white plastic tent or cover site with dark plastic tent or cover
• Measure the CO2 concentration in incoming and out going air by infrared gas analyzer
• In the white cover site, the CO2 concentration in the drawn air will be less than the CO2
concentration in the incoming air ( because some CO2 of the incoming air is used by the
plants in the photosynthesis
•CO2 concentration in incoming air - CO2 concentration in drawn air = CO2 use by plants for
photosynthesis = NPP (OM)
• In the site of dark plastic cover there is no photosynthesis and only respiration of plants
take place I, e CO2 release by plants
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• The CO2 use by plants for photosynthesis in the white cover site + CO2 release by plants in
dark cover site = GPP
( Refer the formula that GPP = NPP + respiration )
3. Chlorophyll method :
• Used for aquatic ecosystem
• Estimation of production can be done by using chlorophyll and light data
• Calculate the chlorophyll content of plants by using Colorimeter
• Involves the determination of chlorophyll content of a plant per gram or per square meter
•The quantity of chlorophyll content tends to increase or decrease with the amount of
photosynthesis , which varies at different light intensities
•The chlorophyll per square meter indicates the food manufacturing potential of plants which is
proportional to the NPP.
4. Harvest method
• Widely used in terrestrial ecosystem
• Most useful for estimating production on ecosystem of cultivated land and range where
production starts from zero at seeding or planting time and becomes maximum at harvest
• It involves clipping or removal of vegetation at periodic intervals and drying , which gives the
biomass in grams per square meter
• The caloric value of the material can also be determined by bomb calorimeter and the biomass
is converted into kilocalories per square meter
• To be more accurate, plant material must be sampled and clipped through out the growing
season and the production can be measured for each individual species determined
Modified Dimension Analysis Method :
• Measurement of height and diameter (DBH) of sample trees in sample plots
• A set of sample trees of sample plots are cut , measured and weighed at the end of growing
season ( green and dry weight of wood, leaves, barks, twigs, roots, flower are taken )
• By calculations, annual production of barks, leaves, twigs, roots, flowers, roots etc can be
estimated ). This gives NPP of trees of sample plot and estimate for whole area of forest
5. PH Method
• This method is used for aquatic ecosystem
• This method is based on the principle that the water PH is a function of dissolve CO2 content
in water ( which is decreased by photosynthesis and increased by respiration by aquatic
animals)
• This method is useful for laboratory analysis of micro-organisms ecosystem
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• At laboratory, sample water is bring and by the use of pH electrode and recorder the day time
photosynthesis and night time respiration of micro-organisms is determined and the primary
and gross production is calculated for the samle water and then to the whole ecosystem
Plant variability and diversity
Phenotypic and genotypic variation :
Phenotype :
• Observable characters or traits (height ,leaf number, leaf size etc ) of an organism such as
morphology, development, physiological properties , behavior etc. is called phenotype. Or it is
observable properties of an individual organisms. Phenotype is an organism's actual observed
properties, such as development of morphologic parts or behavior of plants
• The phenotype is the descriptor of the physical properties of the organism, its physiology,
morphology and behavior.
• Phenotype physical properties are controlled and are the results from an organism‘s genes and
the influences of the environment and the interactions between them.
• In other words, phenotype (the physical expression of a traits or observable properties) is a
product of the interaction between a set of genes and an environment.
Genotype :
• The genetic constituent of an individual is termed as genotype. Genotype characteristics or
traits are never observable or visible.
• Genotype is the genetic makeup of a cell, an organism, or an individual usually with reference
to a specific character under consideration. ― Genotype " gives full hereditary information of an
organism. The genotype represents its exact genetic makeup — the particular set of genes it
possesses.
• Genotype is influenced by : internal environment of cells, tissue, and biochemical reaction and
external environment like temperature, moisture and light.
• Genotype of an organism is the inherited characteristics it carries within its genetic code. Not
all organisms with the same genotype look or act the same way because appearance and behavior
are modified by environmental and developmental conditions.
Variability or variation : To what extent an individual can be changed
Sources of plant variability : Genetic sources (major sources) and Environmental sources
Genetic sources : mutation, recombination, gene flow and hybridization
Environmental sources : internal environment of an organism ( cells , tissues etc) and external
physical environment ( biotic and abiotic )
Phenotypic and Genotypic variation :
• Phenotypic variation represents to what extent an individual can be changed or enable to adapt
to change over time,
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• Phenotypic variation is due to interaction of underlying heritable genetic variation and the
environment
• Genotypic variation represents adaptation by the population enabling it to change over time
• Genotypic variation originates in mutation and recombination, which is affected by natural
selection, migration and genetic drift (random change in gene frequency)
• Genotype variation are Continuous or Regular (quantitative or polygenic traits such as body
size and skin pigmentation ) and Discontinuous or Sharp ( qualitative traits such as form,
structure etc) .
•
• Phenotype is a result of the effect of environment on genotype
• The relationship or interaction between phenotypic, genotypic variation and the environment is
as follows :
Phenotype variation = Genotype variation + External environment
Vp = Vg + Ve, where
Vp = Phenotypic variation; Vg = genetic variation ; Ve = external environmental variation
Vp = Vg + Ve + V ge (genetic environment)
• The degree of genetic control over phenotypic organisms is a heritability, which is expressed
by the ratio of Vg/Vp
• If this ratio is more than 75 %, which means the high heritability ( indicates strong genetic
control over trait characteristics like branchiness , bole form, bark structure, stem wood density,
diameter, height, susceptibility to insects and diseases are genetically controlled)
• If the ratio is less than 75 %, which indicates low heritability or weak genetic control and
indicates a strong environment control (like soil, moisture, temperature etc) over the trait
characteristics
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Sources of Phenotype differences ( variations) or what causes phenotype variation or differences : Interrelationship of genotype, environment and phenotype variation
Genotype : Gene
Plant Process Plant processes Phenotype variation
+ External Factors
DNA and RNA
Time, space, light, heat, water, soil, nutrients,
chemicals, other organisms
Photosynthesis, respiration, water and chemical uptake, transpiration, cell division , chemical reactions etc,
Age, growth rate, habit, complexity,
resistance to : Pests, moisture
stress, light extremes, heat
stress, symbiosis
Summary : Genotype is genetic make up or genetic constituents of individuals which
represent the sum total of heredity and is not visible, where as Phenotype of an individual
is visible traits, characteristics, properties, functions which are produced by the interaction
between genotype and environment such as tallness and dwarfness etc
DNA : Deoxyribonucleic acid, a self-replicating material present in nearly all living organisms
as the main constituent of chromosomes.
A nucleic acid that carries the genetic information in the cell and is capable of self-replication
and synthesis of RNA
RNA : Ribonucleic acid, a nucleic acid present in all living cells. Its principal role is to act as a
messenger carrying instructions from DNA
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Genetics and the Evolutionary Sequence
Genetics : Came from Greek word ― gene‖ which means ― become or to grow. Genetics is
―Biological science‖, which deals with the mechanism of hereditary, causes of variations in
genes ( hereditary unit) , evolution (change in gene pool) and development in living organisms.
Genetics cause evolutions and development in living organisms.
(Gene : a particular segment of DNA molecules, which determines the heredity of a particular
trait or characteristic of an organism)
Evolutionary Sequence : The word evolution has a variety of meanings. The fact that all
organisms are linked via descent to a common ancestor is often called evolution.
• The cumulative change in genotype or genetic make up of population of species overtime or
during the course of successive generations is evolution or simply this is a change in gene
frequencies.
• In biology, evolution is the process by which populations of organisms acquire and pass on
traits ( phenotypic) from one generation to generation through the change in genotype or gene
frequency.
• Biological evolution is genetic change in a population from one generation to another
• Therefore, evolution is a change in the gene pool of a population over time. A gene is a
hereditary unit that can be passed on unaltered for many generations. The gene pool is the set of
all genes in a species or population.
• For example, all living organisms alive today have descended from a common ancestor (or
ancestral gene pool).
• For evolution to take place there should be : population ( collection of individuals, each
harboring a different set of traits.) , mutation of genes of different individual species ,
individuals are selected,
• Individual organism do not evolve, they retain the same genes throughout their life. But
population evolve.
• When a population is evolving, the ratio of different genetic types is changing
• Evolution can be divided into microevolution and macroevolution. The kind of evolution at
phenotype or genotype level is microevolution. Larger changes, such as when a new species is
formed, are called macroevolution.
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• Different individuals have different capabilities to survive and reproduce in a given set of
environmental conditions
• This different survival and reproduction capabilities are the results of having genotype
variation in individuals
• The genotype having best survival and reproduction capabilities are the best adapted to their
environment and will make the largest contribution to the next generation by producing much
more off-spring than those of others.
• Evolution takes place for that genotype that are fittest and the best adapted in the existing
environmental condition and provide much more off-springs than those of others
The speed and direction of evolution are variable with different species lines and at different
times.
• Continuous evolution over many generations can result in the development of new varieties
and species ( we can now see the diversity of millions of species).
• Likewise, failure to evolve in response to environmental changes can, and often does, lead to
extinction.
• Evolution results from natural selection and adaptation
Natural selection
• The process of evolution by which forms of life having traits that better enable them to adapt
to specific environmental pressures, such as predators, changes in climate, or competition for
food or mates, will tend to survive and reproduce in greater numbers than others of their kind
• Some types of organisms within a population leave more offspring than others. Over time, the
frequency of the more productive type will increase. The difference in reproductive capability is
called natural selection.
• Natural selection is the only mechanism of adaptive evolution; it is defined as degree of
difference of reproductive success of pre- existing classes of genetic variants in the gene pool.
• The most common action of natural selection is to remove unfit variants as they arise via
mutation. In other words, natural selection usually prevents new alleles from increasing in
frequency.
Adaptation : Genotype changes in an individual or population so that any living organism
survives or grows better to the existing environment.
Organisms can respond to environmental stress in such a way that their tolerance zones may
change. The genetic changes that occur during the evolution of the species because of mutation
and natural selection are called adaptation.
Gynecology : Concept of ecotype, ecophene and types of ecotype
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• first used by Swedish scientist : Turession (1923)
• Study of variability of plant species population, hereditary, habitat types , variations of
gene frequency, adaptive property of population of species, mutation, local inter breeding
in relation to change in the environment etc
Ecotype : A species that is specially adapted to a particular set of environment. It is also
defined as the product arising as a result of the genotypic response of a population to a
particular habitat.
( species show different levels of tolerance to a given limiting factor over its geographical
distribution, these locally adapted populations are called ecotypes and is the result of
genetic change resulting in different physiological responses to different environment)
• Species with wide geographical distribution almost always develop locally adopted
populations, which is called ecotype. These populations have optimum and limits of
tolerances adjusted to local conditions.
Ecotype: A locally adapted population of a widespread species. Such populations show minor
changes of morphology and/or physiology, which are related to habitat and are genetically
induced. Nevertheless they can still reproduce with other ecotypes of the same species.
Typically, ecotypes exhibit phenotypic differences (such as in morphology or physiology)
stemming from environmental heterogeneity and are capable of inter-breeding with other
geographically adjacent ecotypes without loss of fertility or vigor.
Examples :
• Reindeer species (population ) : found in tundra and forest ecosystem. So ,there are two
ecotypes of reindeer. They migrates between two ecosystems ( habitats , environments)
•Arabis fecunda, a herb, is divided into two ecotypes : One low elevation group live near the
arid, warm environment and are tolerance to drought and another group is found in high
elevation .
• Dolphin has two ecotypes : Riverine and oceanic ecotypes
• Scot pines ( Pinus sylvestris) : has 20 ecotypes ( Scotland to Siberia) all capable of inter
breeding
Important characteristics of Ecotype :
• variations are phenotypic : morphological, physiological or phenology
• phenotypic difference is due to population response on phenotypic variance and
environmental heterogeneity
• ecotypes are isolated and disconnected entities
• genetically and environment based
• adapted to specific environment condition
• capable of inter-breeding with other geographically adjacent ecotype without loss of fertility
or vigor
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• variations are associated with habitat types
Types of Ecotypes : Climatic ecotype , Edaphic ecotype, Biotic ecotype
Climatic ecotypes: are species that are found adaptive in different climatic zones
Edaphic ecotypes : occurs especially in saline soils and in soil having moisture stress or in
harsh edaphic conditions
Biotic ecotypes : occurs in areas subject to heavy grazing pressure. Example : around a drinking
hole in a game reserve. Plants are usually upright height, prostrate and less liable to have their
vegetation and reproductive portions removed.
Four different ecotypes of Physcomitrella patens,
Ecophene or Ecades : Individual plants of same species within a population differ in visible
appearance such as height, erectness, thickness of leaves etc in differing environmental
conditions are known as Ecophene or Ecades
Story of moths : distinct
1. Moth ( Biston betularia) : two types : light and dark colored
Prior to 1848 , the population of dark colored = < 2 % and light colored more
In 1898, frequency of dark colored moth increased to 95 % and light color less
This change in increase in population of dark colored from light color moth = change in gene
pool ( set of all genes in a population) = This change in gene pool is Evolution
Moth color is single gene = hereditary unit
2. At the time of industrial revolution in England, dirt from industries darken the trees around .
Two types of moths, light and dark colored used to landed on the trees.
Birds could see only the light colored moths at the dirt environment, and mostly eat light colored
moth.
As a result dark colored moth survived, produce more offspring against predator( birds). This
increase in frequency of dark colored moth is Natural Selection.
Ecological considerations at the species level :
• As population of a species change over time, and if the segment of the population migrate
into new areas or new environment , then the migrated population of that species become
diverse in terms of their genetic characteristics
• Due to geographic separation and diverse environment factors of the new site, the migrated
population become less able to exchange genes with other population and becomes
reproductively isolated
• These geographic isolation and reproductive isolation are the main cause among others for
speciation
This phenomena can be shown as follows :
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1st. Stage : a single population of species in a homogenous environment
2nd. Stage : Migration to the new environment produces separation of race and species
environment separation
3rd. Stage : Further separation and migration produces geographic isolation of some species
geographic isolation
4th. Stage : Some of these isolated species separate with respect to genic and chromosomal changes which controls reproductive isolating mechanism
reproductive isolation
5th. Stage : If these geographically isolated population re-exit together in the same region , then they remain diverse because of the reproductive isolation barriers which separate them. No inter breeding with the original species takes place
This says that geographic isolation leads to reproductive isolation which in turn leads to speciation
Geographic isolation can lead to reproductive isolation, divergence and speciation.
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Four steps leading to speciation.
different habitats, the divided populations become differentiated through
the accumulation of differences.
and they overlap again. Interbreeding does not occur.
New species typically evolve by two steps:
•geographic isolation–separation into distinct populations with different evolutionary pressures;
•reproductive isolation–evolutionary changes in each population that prevent interbreeding when
populations come into contact.
The Process of Species Formation Four Steps:
•Single population or reproductive community.
•Development of a reproductive barrier (formation of allopatric populations).
•Differentiation of the separated populations.
•New species can no longer interbreed if barrier disappears and become sympatric.
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Unit 4 : Autecology
• Autecology deals with the ecological study of one species of organism. It includes the study of
life history, population dynamics, behavior, habitat of a single species and so on. Such as Bengal
tiger, sal tree, sal borer,
• Synecology : deals with the ecological studies of communities or entire ecosystem. For
example the study of whole deserts, caves or temperate or tropical forests or grassland as a whole
• Autecology and synecology are interelate.
• Synecoliogist makes a outline of the whole pictures where as autecology describes the minute
and finer details of organism s of an ecosystem
Introduction to concept of site productivity and Law of Minimum :
• Tree crown is surrounded by heat, light, O2,CO2, precipitation, wind, lightning etc and affects
the tree life. These are climatic factors related to atmosphere in which the areal portion of the
tree grows
• Tree roots are surrounded by soil nutrients and water , soil is also a medium for anchorage of
soil or soil is the storehouse of minerals and water.
• Soil factors also comprise of all physiographic components ( altitude, aspect and slope),
physical, chemical and biological components of soil
• These factors (soil and climatic factors) which a particular site must supply to the plants.
Productivity of the site directly depend upon these factors.
• The individual of climatic and soil factors is not acting in an isolated way but are acting
interdependently and interrelated
• Among these factors only few factors exert more influence and needs more in quantity for
plant growth such as air temperature, sunlight, water and macro nutrients ( C,H,O, S,N, P, K, Ca,
Mg) while other factors needs in small quantity ie micro nutrients ( B, Cu, Cl, Fe, Mn, Mo,
and Zn) and are also essential.
Forest site productivity : is the production that can be taken at a certain site with a given
genotype and a specified management regime.
•The term site productivity is often use to refer to that part of the site potential pick up by the
trees for wood production
• Forest site productivity may be defined as the potential of a particular forest stand to produce
aboveground wood volume, which is calculated on stem wood volume for conifers, but may
include branch volume for broadleaved tree species.
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• Forest Site productivity is a quantitative estimate of the potential of a site to produce plant
biomass, which is based on two concepts : site potential and how that site potential is taken up
by a given forests stand
• site potential is the capability of the site to produce plant biomass (net primary production),
irrespective of how much of this potential is utilized by the vegetation
• Site productivity depends both on natural factors inherent to the site and on management-
related factors
•The natural or environmental factors which influence the life and development of organisms
and in turn the site productivity are grouped into four main factors. They are climate, soil,
topography and biotic influences
• The greatest impact on tree growth or site productivity decrease or increase is made by climate,
soil, topography and biotic . The distribution of species and community, physiological and
reproductive process are greatly influenced by these factors
• For many purposes, the maximum mean annual volume increment is considered a suitable
measure of site productivity.
• Within this narrower context, site productivity is often quantified as an index, typically site
class or site index . Such indices are defined in different ways and are widely used for
management purposes.
• Site Index - A relative measure of forest site quality based on the height (in feet) of the
dominant trees at a specific age (usually 25 or 50 years, depending on rotation length). Or, this
is a height of a tree at a specified index or base age and are used as an indicator of site quality .
Site index information helps estimate future returns and land productivity for timber and wildlife.
• Site quality : A classification of sample tree according to how well the tree reflects the
productive potential of the site.
Liebig's law of the minimum
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• The concept first stated by J. von Liebig in 1840, Liebig's Law of the Minimum, often simply
called Liebig's Law or the Law of the Minimum, is a principle developed in agricultural science
• It states that growth, size etc. of a plant and composition of a population of species is
controlled not by the total of resources available, but by the scarcest resource.
•This concept was originally applied to plant or crop growth, where it was found that increasing
the amount of plentiful nutrients did not increase plant growth but the growth of plant was
improved with increasing amount of the limiting nutrient (the one most scarce in relation to
"need")
• Justus von Liebig's Law of the Minimum states that yield is proportional to the amount of the
most limiting nutrient, whichever nutrient it may be. From this, it may be inferred that if the
deficient nutrient is supplied, yields may be improved to the point that some other nutrient is
needed in greater quantity than the soil can provide, and the Law of the Minimum would apply in
turn to that nutrient.
•The examine the relative role of these factors for plant growth is known as ― Law of
minimum‖ proposed by Liebig . Which is also called Liebig ― Law of Minimum‖
Example :
• Liebig used the image of a barrel-now called Liebig's barrel-to
explain his law. Just as the capacity of a barrel with staves of
unequal length is limited by the shortest stave
• This is same in case of plant . So a plant's growth is limited by the nutrient in shortest supply.
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Example :
• Imagine you are building a dog house using nails and boards. As long as you have both, you
can continue building. When you run out of nails, you have to stop building. Nails (or rather lack
of nails) are ―limiting‖ your building process. So you buy a 5 kg of nails and return to work.
Inevitably, you will run out of boards next. Even though you still have plenty of nails, you need
more boards to continue building. Now boards are ―limiting‖. You could have truckload of nails
brought to your house, but it won‘t help the doghouse get built, because you need boards.
•This is an example of Liebig‘s Law of the Minimum, which states that plant growth will
continue as long as all required factors are present (e.g. light, water, nitrogen, phosphorus,
potassium etc.). When one of those factors is depleted, growth stops. Increasing the amount of
the ―limiting‖ component will allow growth to continue until that component (or another) is
depleted.
• Liebig's Law has been extended to biological populations. For example,
the growth of a biological population may not be limited by the total
amount of resources available throughout the year, but by the minimum
amount of resources of the greatest scarcity available to that population at the time of year.
•The nutrient most typically ―limiting‖ algae growth in lakes is phosphorus. If phosphorus
concentrations can be controlled, then algae can be controlled…usually. Sometimes, other
nutrients or conditions can limit algae. In some lake , for example, light is the factor that most
often limits algae growth.
•That is, the growth of a population of animals might depend not on how much food is available
in summer, but on how much
food is available in winter.
• Law of Minimum apply not only to nutrients but also to climatic and edaphic factors
The size and composition of a population may control by either available minimum quantity of
mineral nutrients or climatic and edaphic factors
• The law that those essential elements for which the ratio of supply to demand (S/D) reaches a
minimum will be the first to be removed from the environment by life processes
• J. von Liebig, recognized phosphorus, nitrogen, and potassium as minimum in the soil
• In the ocean the limiting elements are phosphorus, nitrogen, and silicon.
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Minimum limit Optimum Maximum limit
limit
Growth
Low Environmental factor High
( i.e temperature)
Factors affecting ecosystem :
• Light :
• Only sunlight has greatest ecological significance, most vital and essential abiotic
element of ecosystem, photosynthesis or syntheses of food by green plants depends , in
turn support all animals and most microbial life of earth
• Daily and season activities of plant and animal and microbial life
• From ecological point of view, light controls plant‘s structure, form, shape, tissue
differentiation, chlorophyll production, leaf structure, stomata , transpiration, growth and
development flowers, seeds, fruits, locomotion, local distribution etc.
• Light is extremely variable, variance in quality ( wave length or color), intensity ( gram
calories) and duration ( length and duration of day) influence on different ecosystem
• Regulating of amount and quality of light in particular ecosystem depends on
transparency of air and water and strata of vegetation, angle of incidence, latitude,
altitude, aspects, season, time of day, amount absorbed and dispersed by atmosphere,
fog, clouds, suspended dust and water particles etc,
• In forests, major portion of light absorbed by trees vegetation and light receiving in the
exposed area will be reduced by approx 90-98 %.
• About 10% of the total light reaching on the water surface reflects back to the atmosphere
and only 90% pass in the downward of water surface., which will be selectively
absorbed at different depth of water.
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• Non-lethal limiting factors both at maximum and minimum level, however the efficiency
of photosynthesis process declines steadily with increasing light intensity
Effects of light on plants :
• Formation of Chlorophyll : formation of chlorophyll pigments, ( full sun light in the upper
most surface has larger number, while leaves under shade has few in number )
• Quality of photo synthesis : increases with intensity and saturates at certain level and the
process declines afterwards , this point called compensation intensity. Low intensity low rate of
photosynthesis. At full sunlight it best utilizes only 5% of light energy for photosynthesis.
• Plants are grouped based on the level of photosynthesis : Shade loving ( maintain high rate of
photosynthesis at low intensity of light) ; Photophobic or Sciophytes ( grow better in sun but can
also grow fairly well in shade) and photophilous or heliophytes ( needs high intensity of light
and adversely affects by shade)
• Sunlight prefering plants are P. roxburghii, D. sisso, A. catechu, T. grandis, A. cardifolia,
Terminalia spp and Sal ( heliophytes)
• Shade prefering plants are . A. pindrow, C. deodara, D. latifolia etc (Sciophytes)
• At high intensity, reduces the rate of synthesis of carbohydrates and protins. ( (because the
photo-oxidation of chlorophylls takes place)
• Light effects the movement of plants which is called heliotropism or phototropism ( stem
elongation towards light ( positive phototropism) and roots are negative phototropism. Leaves
grow transversely to light.
• Light inhibits the production of auxins or growth harmones so influences on the shape and
size of plants
• Development of flowers, fruits and seeds is affected by light intensity. Diffused light or
reduced light promotes the development of vegetative structures and causes delicacy. Intense
light favors the development of flowers, fruits and seeds
• Light intensity affects the growth of bacteria and fungi, their spore and germination are
regulated by light factors
• Light effects opening and closing of stomata and has heating effects which in turn affect
transpiration and affects absorption of water
• In most of the plants, respiration rate increases with increase in light intensity. Some plants
respiration rate decreases with increases in intensity of light
• Seeds of many plants are light sensitive ie either their germination requires light or is inhibited
by light
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• Photoperiodism in plants : Actual duration or length of the day is a significant factor in the
growth and flowering of wide variety of plants. Based on this, plants are classified into Short-
day plants, long day plants and day neutral plants
•The stomata remain opened in the light and closed in the dark, the opening of stomata during
daytime increases CO2 and O2 exchange between plants and atmosphere.
• Transpiration and respiration of plants increases during daytime
• Light is an important factor in the distribution of plants.
The Temperature :
• Temperature is a measure of heat energy content in an object
• Solar radiation is the main source of heat that controls the temperature regime on the earth
• Soil surface temperature depends upon the rate of absorption of solar energy and the rate at
which it is dissipated
• Dissipation of heat or temperature depends upon the amount of vegetation and litter cover and
also on the color, moisture content and other physical properties of soil
• Solar radiation warms up atmosphere and soil and thereby raising their temperature
• The temperature of the atmosphere affects the activities of shoots while the soil temperature
affects that of their roots
• Temperature helps warming of plants/animal bodies and initiate continuation of various
physiological activities such as transpiration, respiration and photosynthesis.
• High temperature increases transpiration and respiration while low temperature decreases them
.
• In general the rate of respiration increases as temperature rises from O to 4o degree C while
it decreases at temperature < o and > 40 degree C, however it varies with the type of vegetation
• Air temperature regulates the activities of enzymes and controls all chemical reactions in the
plant body.
• Increases cambial activity in the shoot portion and essential for germination of seeds
• Affects physiological and cambial activities and thereby growth of the plants
• Soil temperature influence on absorption of soil moisture which increases with increase in
temperature up to a certain limit.
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• The intensity of Soil moisture absorption by plants depends on soil temperature gradient .
Higher the soil temperature decreases the absorption and lower the temperature also decreases
the absorption capacity, depending upon plant types and their response to soil temperature.
• In general, temperature plays vital role in the growth, distribution, germination etc of the plant
communities. Increase in temperature creates conditions to grow vegetation well . while
decrease in temperature limits the vegetation growth
Temperature and Plant growth :
• Temperature ia an important factor in the life process of plants
• Water, which is a major constituent of of protein of plants is highly sensitive to temperature
range
• Difference in temperature also affects the availability of moisture in the soil and atmosphere
• Plants activities normally takes at temperature range from 0 to 50 degree centigrade, but it
depends on types of plants
• Plants normally die if the temperature exceeds 50 degree C
• Rise in temperature beyond the optimum range results decrease in plants activities and plants
die with excess of the optimal level
Plant
activity
0 10 20 30 40 50
------ Optimum ------ Temperature ( C)
range
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Plant types according to heat requirement :
• Megathoms : high degree of heat required throughout the year ( desert plants)
• Mesothoms : neither very hot nor very cold conditions required ( tropical/subtropical)
• Microthoms : required cold (temperate plants)
• Hekistothoms : very cold condition, severe winter ( alpine plants)
Plants types according to dormant condition :
• Phanerophytes : seeds bearing plants, dormant buds in the plant body
• Chamaephytes : buds are situated close to the ground
• Hemicryptophytes : buds pass the unfavorable season in the soil surface, protected by soil
itself or by litters
• Cryptophytes : buds survive completely in the ground
• Therophytes : complete their life cycle within a single favorable season and remain dormant
in the form of seed throughout the unfavorable season
Water :
• Water is Important factor influencing vegetation.
• The growth, reproduction and distribution of animals are also affected by water factors. The
germination of seeds and establishment of seedlings are directly affected by water.
•water is essential for respiration , transpiration, germination and viability of seeds
• Water is a raw material for photosynthesis, translocation of manufactured food inside the plant
body. For all chemical activities inside the plant body require water
• Water is essential for physiological activities and soil formation process.
• Water acts as universal solvent and dissolves all mineral nutrients as solutes enters to the plant
and move through the tissues
• Water is required for physical and chemical weathering of soil and translocation of the
weathered materials from one place to another
• Water forms 90 to 95 % constituent part of cell wall and 80% part of protoplasm which is the
physical basis of life form of plants.
• The areas having high water tables invites shallow rooted plants and are sensitive to draught
and frost. The areas having low water table invites long rooted plants to tap much water from
down surface. Too much and too little water are both detrimental to plants and animals
•Water determines the nature of vegetation that survive in a particular area and used as a basis
of classifying vegetation in broad temperature zones. Water is also responsible for the
distribution of important plant species and forests. The mosture and temperature acting together
determine the distribution of plants and animal lfe
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Total amount of rainfall Name of zone Nature of vegetation
2500 mm or more Wet zone Wet evergreen
< 2500 to > 900mm Intermediate or moist 1. Wet semi-evergreen
2. Moist deciduous
< 900 mm Dry zone 1. Dry deciduous
2. Desert and semi desert
thorn forests and scrub
•The main sources of water available to the plants are precipitation ( rain, snow, ice, clouds , hail
etc - contributing major part ) where as dew and frost, atmospheric moisture or humidity
contributes negligible portion
• Plants use water in two ways, firstly in the process of photosynthesis and secondly in
transpiration.
• Water loss in photosynthesis is negligible almost 1 % of the water absorbed by the roots, where
as loss through transpiration accounts for more than 90% of the water taken from soil.
• The mechanism of water absorption and rate of water flow from soil to plants are primarily
controlled by water evaporating from the leaves, which in turn depend on air temperature and the
velocity of wind.
• For survival and growth, plants must maintain water balance i.e they must gain as much water
as they lose.
• In plants, the rate and magnitude of photosynthesis, respiration, absorption of nutrients, growth
and metabolic process are influenced by amount of water availability.
Movement of water inside the plant body :
Root epidermis root cortex root xylem stem xylem leaf veins
leaf mesophyll stomata atmosphere
7 epidermis
6 cortex
5 Bast fibre
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4 phloem
• Xylem
2 protoxylem
• Availability of water in the soil : It has three categories :
• Gravitational water = water retain in soil for short period, plants use. This may not be
available for long period since the gravitational force drained them beyond the root zone
• Hygroscopic water = water retain in the soil particles near the root level after the
gravitational water has been drained away and may not be available to the plant because the
gravitational force drained them out
• Capillary water = available to the plant from the gravitational water through the capillary
action
Exchange of water vapor between plant and atmosphere :
Transpiration
• Transfer of water vapor from plants to atmosphere
• Water vapor will move out from the leaves into the surrounding air unless the vapor pressure
between the air and plant body is in equilibrium or unless the outside air is saturated ( moisture
equilibrium )
Evaporation
• Transfer of water vapor from land, water surface and from the canopy of tree (intercepted
water) to the atmosphere
Evapo-transpiration
• Transfer of water vapor by both evaporation and transpiration
•The actual rate of water movement is proportional to the vapor pressure gradient between the
plant/soil or surface and the atmosphere
• Lower the RH, the greater the evaporation from the soil and higher the transpiration from the
plants
• Absolute Humidity : amount of water vapors present in atmosphere
• Relative humidity : ratio of the actual amount of water vapors in the atmosphere to the
amount of water vapor that can be held in the air at a particular air temperature and pressure.
• As the air warms, The RH drops as long as the moisture content of the air is constant.
• RH is lower by day and higher by night. The daily range of RH is greater in the valley and less
at high elevation
• Low relative humidity increases water loss through transpiration and affects plant growth
where as high relative humidity reduce transpiration loss of water.
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• In lower plants, water is essential for fertilization where as in higher plants the pollination and
seed dispersal are affected through the agency of water in many ways
• Prolonged flooding and drought are both detrimental to plants and in both the cases plants die
in the absence of oxygen in the root zone.
• Soil drought reduce plant growth causing dieback of plants. Drought injured plants are very
susceptible to out break of insects and fire.
Ecological groups of plants in relation to soil and water : Plants and animals exhibits
considerable variations in the requirements of water and has been classified on the basis of soil
and water requirements .
1. Hydrophilous : hydrophytes ( in water) and Helophytes ( in marsh)
2. Xerophilous plants : on the basis of soil - Oxylophytes ( on acid soil) and Psychrophytes ( on
saline soil) and Psammophytes ( on sand and gravel), Chersophytes ( on waste lands),
Eremophytes ( deserts and steppe), Psilophytes ( on savannah) Sclerophyllous foramation ( bush
and forests) Coniferous frmations ( forests)
3. Mesophilous Plants : On the basis of water requirement : Hydrophytes ( plants living in
water and require large quantities of water) , Xerophytes ( tolerate extremely dry condition and
survive long period without water ), Mesophytes ( requires moderate amounts of water)
Climate :
• Sum total of all climatic factors such as temperature, air pressure, humidity,
precipitation, sunshine, cloudiness, winds throug out the year or averaged over a series of
month, season, years, decade or even longer.
• climate differs from weather, which is short lasting meteorological events and the time
scale is for few days
• Weather refers to the unpredictable changes in air that take place over a short period of
time. Climate is the usual, predictable pattern of weather in an area over a long period of
time.
• Climate is affected by the sun, the wind, the oceans and other bodies of water, landforms,
and even people.
• Climate, statistics of weather averaged over a time period that contains many weather
events, usually at least a month or Long term weather over a period of 30 to 40 years
or more constitutes climate
• Climate is a major dominant of the distribution of vegetation on a broad or regional scale
• Microclimate : the more variable climate between the ground surface and few meters above
the ground surface ( short distance) over a long period.
• Microclimate directly imposes on most organism being the zone of greatest disturbances and
showing the greatest differences within short distance
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• Microclimate may significantly determine the local distribution of species and communities
viewed over thousands of year .
Major components of climate system :
• Atmosphere : circulation, absorption and transmission of solar radiation
• Oceans : Regulator of atmospheric temperature, gas concentrations, storage and transport of
heat and gases
• Cryosphere : ( ice caps and floating sea ice) - influences the surface
energy balance by albedo and contributes to energy exchange between the surface and
atmosphere.
• Land/biosphere : size and position of land, characteristics of lakes, rivers, soil moisture, and
vegetation ( a vital climate control concerning the carbon up take) etc
The climate system involves interaction in many ways :
• Living organisms, particularly forests and plants, play a key role
in atmospheric heat, moisture and energy budgets close to the surface.
• the interaction of the air, sea, ice, land/biota with solar
radiation
• Variations of gaseous and particulate constituents of the Atmosphere and changes in the Earth
position relative to the sun vary the amount and distribution of sunlight received.
• The temperature of the oceans has a marked influence on the heating and moisture content of
the atmosphere.
• The sun radiant energy drives the atmospheric circulation by wind and heat transfer and it
drives the circulation of the oceans.
• The atmosphere and oceans are both influenced by the extent and thickness of ice, as well as
by the shape and composition of the land surface.
World classification of climate :
Classification Criteria
1. Precipitation
2. Temperature
3. Soil Water Balance
4. Air Masses
5. Geographic Distribution
The Koeppen’s System of Climate Classification The Köppen Climate Classification System is the most widely used for classifying the world's
climates. The Köppen system recognizes five major climate types based on the annual and
monthly averages of temperature and precipitation.
A - Moist Tropical Climates : high temperatures year round and large amount of year round rain.
Moist with adequate precipitation in all months and no dry season. Rainforest climate in spite of
short, dry season in monsoon type cycle
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B - Dry Climates: little rain and high daily temperature range. Two subgroups : semiarid or
steppe, and arid or desert Dry-hot with a mean annual temperature over 18°C (64°F). Dry-cold
with a mean annual temperature under 18°C (64°F)
C – Humid Climates : land/water differences play a large part. warm,dry summers and cool, wet
winters. Moist with adequate precipitation in all months and no dry season. Hot summers where
the warmest month is over 22°C (72°F). Warm summer with the warmest month below 22°C
(72°F). Cool, short summers with less than four months over 10°C (50°F)
D - Continental Climates : can be found in the interior regions of large land masses. Total
precipitation is not very high and seasonal temperatures vary widely. Moist with adequate
precipitation in all months and no dry season. Hot summers where the warmest month is over
22°C (72°F). Warm summer with the warmest month below 22°C (72°F). Cool, short summers
with less than four months over 10°C (50°F) . Very cold winters with the coldest month below -
38°C (-36°F)
E - Cold Climates : These climates are part of areas where permanent ice and tundra are always
present. Only about four months of the year have above freezing temperatures.
Water Balance ET=evaporation from surface + transpiration from plants
Ocean water balance => P + R = E
Land water balance => P = ET + R
Global => P = E
Soil Water Budget Potential ET-how much water a plant could use if it had unlimited supply-depends on temp
Actual ET-how much water plants actually used
P=PET medium climate ex:Ontario
P<PET dry climate ex:Sudan
P>PET wet climate ex:tropical rainforest
general water balance equation is:
P = Q + E + ΔS where
P is precipitation Q is runoff E is evapotranspiration ΔS is the change in storage (in soil or the
bedrock)
Elements affecting climate :
I. The Sun and Climate
• The original source of climate is the sun. Wind and water carry the sun‘s heat around the
globe.
• climate is also affected by latitude. The sun‘s rays hit the earth more directly at low latitudes.
Places at higher latitudes receive only angled rays of the sun.
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• The areas near the Equator are known as the Tropics. They lie between the Tropic of Cancer
(23 ½˚ N latitude) and the Tropic of Capricorn (23 ½˚ S). The Tropics experience a hot climate
year-round.
II. The Wind’s Effect on Climate
•. Movements of air are called winds. Winds follow typical patterns, affecting climate.
• Monsoons are powerful seasonal winds that blow over continents for months at a time. They
are found mainly in Asia and some areas in Africa.
• Thunderstorms sometimes produce tornadoes, or funnel-shaped windstorms.
• Violent tropical storms called hurricanes form over the warm waters of the Atlantic Ocean in
the late summer and early fall. When the same type of storm hits Asia, it is called a typhoon.
• A long period of extended dryness is called a drought.
III. Ocean Currents and climate
• Moving streams of water called currents carry warm or cool water through the oceans.
These currents affect the climate of land areas. Winds that blow over warm currents, for
example, carry warm air to land areas.
IV. Landforms and Climate
• The shape of land and the location of landforms in relation to one another and to water also
affect climate.
• Local winds are patterns of wind caused by landforms in a particular area. Some local winds
occur because land warms and cools more quickly than water. AS a result, cool sea breezes keep
coastal areas cool during the day. After the sun sets, the land cools down, and cool breezes blow
out to sea.
• The higher the elevation a place has, the cooler it will be.
• As air moves up the windward side of mountain peaks, it becomes cool and loses its moisture.
The air that crosses over the peaks is dry, creating a rain shadow. A rain shadow is a dry area on
the leeward side of the mountains. The dry air of a rain shadow warms up again as it moves
down mountainsides, giving the region a dry or desert climate.
Climate role on vegetation development :
• Areas with tropical rain climate have year-round rains that produce lush vegetation and thick
rain forests. Tall hardwood trees such as mahogany, teak and ebony form a canopy, or top layer
of the forest.
• Tropical savanna areas have a definite wet season, while the remainder of the year is hot and
dry. Savannas, or broad grasslands with few trees, are found in these areas.
• Humid subtropical climate where rain falls throughout the year. Oak, magnolia and palm trees
grow here
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• The marine climate occurs along coastal areas that receive winds from the ocean. Winters are
rainy and summers are cool in these areas. Deciduous and coniferous trees grow in this climate.
• The coastal Mediterranean climate also has rainy, mild winters. It differs from the marine
climate in that the Mediterranean climate experiences hot, dry summers. Shrubs and short trees
grow in this climate.
• The humid continental climate has long cold and snowy. Summers are short and may be very
hot. Deciduous trees and vast grasslands grow here.
• In the subarctic climate, winters are severely cold and bitter. Huge evergreen forests called
taiga grow here.
• Tundra climate : Closer to the Poles than the subarctic zone lie areas of vast rolling plains
without trees. This region is known as the tundra and is harsh and dry. In these parts, much of the
lower layers of soil stay permanently frozen and are known as permafrost. Only sturdy grasses
and low berry bushes grown here.
• The ice cap climate is found at the Poles and on the ice sheets of Antarctica and Greenland. No
vegetation grows here. Only lichens can live on the rocks.
• Highland Climate : A highland, or mountain, climate has cool or cold temperatures throughout
the year. No trees grow above the timberline.
• Desert climates—the driest climates—have less than 10 inches of rainfall a year. Only
scattered plants like cacti can live here. Many deserts are surrounded by partly dry grasslands
known as steppes. The Great Plains of the United States has a steppe climate, which averages 10
to 20 inches of rain a year.
Nepalese context :
Climate types Vegetation development
1. Tropical Mostly broadleaf and hardwood type of vegetation and grassland
2. Sub-tropical Chir pine and broad leaf type of vegetation
3. Temperate Blue pine, Spruce, Oak Juniper, Rhododendron, Maple, Cedar and
Cypress etc.
4. Alpine Alpine medows, Alpine scrubs, Fir-blue pine, Larch, Oak etc.
5. Arctic or Tundra Lichens and mosses, exposed rock and mostly covered by snow
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type
The Impact of People on Climate :
• People‘s actions affect climate. For example, cities are warmer than rural areas because
streets and buildings absorb more heat than plants and trees do. In addition, people burn
fuels, which raises temperatures.
• People are burning coal, oil and natural gas as sources of energy. The buildup of the gases
from the burning of these substances has prevented warm air from rising and escaping into
the atmosphere. This is known as the greenhouse effect, in which the earth‘s temperature
will increase.
• Dense forests that receive high amounts of rain each year are known as rain forests. People
burn trees to clear rain forests, which leads to the greenhouse effect. Also, less water
evaporates if there are fewer trees, decreasing rainfall.
Soil and its importance on vegetation
• outermost layer of earth crust where plats grow
• composed of organic and mineral nutrients
• factors responsible for soil formation are climate, biological agencies, parent rock, topography
and time
• weathering (physical and chemical) and climate ( temperature and precipitation) acts together
to disintegrate the parent rocks or earth crust in a process of soil formation
Physical properties of soil includes : soil texture, structure and porosity
• Soil texture : size groups of soil particles
clay = particles < 0. 002 mm ; silt = 0.002 – 0. 02; fine sand = 0.02 – 0.2 mm ; coarse sand = 0.2
– 2.0 mm; gravel = > 2.0 mm
Soil class or textural group such as : clayey soil = < 50% sand particles, < 50 % silt particles
and 30% or more clay particles
Loamy soil = 30-50% sand particles, 30-50% silt particles and < 20% clay particles
• Soil Structure : combination of the individual soil particles of different sizes into aggregates.
Such as : Single grained ( sand dunes); Crumby ( aggregates 3mm or less in diameter); Granular
(aggregates up to 6 mm in diameter); Cloddy ( irregular shaped aggregates > 25 mm in diameter)
• Porosity : the extent to which the gross volume of the soil is unoccupied by solid particles or
the space unoccupied by solid particles
Forest soil profile :
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O1 : surface litter
O2 : humus layer
A : the upper most horizon or surface layer of mineral soil (eluviation)
B : zone of accumulation (illuviation) enriched with materials washed
from A horizon
C : upper most layer of parent material, which is in the process of
forming true soil under the influence of weathering
D : The unaffected parent rock or other material
Soil formation, transportation and deposition by agents
Rocks/minerals deposited in lake Lacustrine
streams Alluvial
Ocean marine
water transported ice till/moraine
wind transported
Gravity transported
Formed in place wind Dunes(sand
Loess(silt)
gravity colluvial
residual
parent
materials
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Soil Texture and Tree growth relationship :
Poor medium good medium poor
Sandy loam clay loam heavy clay
Soil and vegetation :
• Soil is an important for the growth of vegetation. The soil is important to tree growth in
numerous ways
• Soil provides water and nutrient for the vegetation to grow. vegetation acts as a media to
anchorage the soil.
•Vegetation can improve the physical and chemical properties of soil.
• Besides rainfall intensity, the physical and chemical properties of soil are also responsible
to degree of soil erosion in which the plant grow
•It provides trees with essential nutrients and is a store house for water and oxygen, all of
which are necessary for the physiological processes associated with tree growth.
•The soil also provides space for root growth and the entire plant with mechanical support.
•The type of soil dictates how best it can be managed to obtain the highest yield as well as
the type of tree to grow and silvicultural management to adopt.
• From stand point of tree growth is recognized as productive only, if the soil has adequate
water intake and water holding capacity, good aeration, adequate depth, and adequate
supply of essential nutrients in available accounts.
• distribution and rate of growth of forest stands are influenced mainly by those
physical, chemical and biological characteristics of the soil which favour the availability of
water, nutrients and air to the trees.
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• The physical properties such as texture, structure , porosity of a soil largely determine
the ways in which the plants grow. Once the physical properties of soil deteriorate it will be
difficult to recover its properties.
• physical properties are harder to alter than chemical ones
• must chemical shortcomings can be made good simply by adding the necessary fertilizer
while.
• The effects of soil texture are frequently reflected in the composition and rate of growth
of forest vegetation.
• Generally loam and day soils appear suitable for trees with high moisture and high
nutrient requirements.
• Soil aggregate can greatly modify the effect of texture as a factor affecting some
important
phenomenon related to the growth depending on the size, shape and management.
• Soil structures largely determine the porosity and pore size distribution of soil; and the
movement air and water within the soil.
• Aggregate soils, readily infiltrated by rain water, are well aerated and facilitated
penetration of root systems.
• Soils of single aggregate or puddle structure hinder the growth of trees through being
impermeable to rain water or being easily waterlogged and poorly aerated.
• Air in the soil is also very important to tree life.
• The supply of oxygen available in the soil influences seed germination, while all the parts of
the tree below ground, require oxygen for respiration.
• Soil reaction influences both the distribution and growth of forest vegetation.
• Soils with low oxygen content cannot be tolerated for a long period by tree which respire
aerobically except they posses special adaptive devices such as stilt roots, breathing roots
• shallowness of soil limits its utility restricting the supply of moisture, air,
and utility by restricting the supply of moisture, air, and nutrients available to the forest stand
and through reduction of stand stability.
• Generally, deep permeable soils through which tree
roots can develop extensively If moisture is limited for instance.
•Deeper rooted plants may be able to find enough water to keep alive. This is usually the case
with deep-rooted savannah trees which survive the dry season even through the associated
grasses dieback.
• The importance of soil chemical properties in tree growth are the
mineral content, soil reaction or degree of acidity or alkalinity (pH) and the cation exchange
capacity of the soil.
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Silvicultural techniques can be employed to improve soil conditions. E.g. drastic opening of
canopy is done with the aim of stimulating decay of organic matters by increased rate of
decomposition.
• In some cases drainage schemes may improve the growth of non-mature spp which can do well
in water logged condition.
Nutrient cycle :
• Ecologists may refer to ecological recycling, organic recycling, biocycling, cycling,
biogeochemical recycling, natural recycling, or just recycling in reference to the work of nature
• A nutrient cycle (or ecological recycling) is the movement and exchange of organic and
inorganic matter back into the production of living matter.
• The process is regulated by food web pathways that decompose matter into mineral nutrients.
Nutrient cycles occur within ecosystems. Ecosystems are interconnected systems where matter
and energy flows and is exchanged as organisms feed, digest, and migrate about.
• Minerals and nutrients accumulate in varied densities and uneven configurations across the
ecosystem.
• Ecosystems recycle locally, converting mineral nutrients into the production of biomass, and on
a larger scale they participate in a global system of inputs and outputs where matter is exchanged
and transported through a larger system of biogeochemical cycles.
• global biogeochemical cycles describe the natural movement and exchange of every kind of
particulate matter through the living and non-living components of the Earth, nutrient cycling
refers to the biodiversity within community food web systems that loop organic nutrients or
water supplies back into production.
• Solar energy flows through ecosystems along unidirectional and non-cyclic pathways, whereas
the movement of mineral nutrients is cyclic.
• Nutrient cycle include carbon cycle, sulfur cycle, nitrogen cycle, water cycle, phosphorus
cycle, oxygen cycle, among others that continually recycle along with other mineral nutrients
into productive ecological nutrition.
• Global biogeochemical cycles are the sum product of localized ecological recycling regulated
by the action of food webs moving particulate matter from one living generation onto the next.
Earths ecosystems have recycled mineral nutrients sustainably for billions of years.
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Nutrient inputs, accumulation and return :
• Minerals that are taken up into forest trees are eventually returned to the forest soil except for
the amount carried out of the forest in logs and other forest products
• Minerals are returned to the surface of the soil by litter fall and through the washing and
leaching effects of rain on tree foliage and stems
• Mammals, insects, earthworms, fungi and bacteria on the forest floor and in the soil attack the
accumulating organic matter, decompose it and makes it re-available for plants nutrition
• Sources : ----- litter
---- -rainfall and stem fall, through fall
----- Acid precipitation
----- Soil biota (soil organism)
• Litter fall : leaves, small twigs, bark, flower, fruits etc add 1500-5000kg of oven dry organic
materials to the surface by a fully stocked forest/ha/year. Leaf litter roughly accounts 70% of the
total. Total litter production of evergreen forests exceeds than deciduous forests by 13 % ( global
scale)
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• Understory vegetation plays important role in the circulation of nutrient. It often contribute up
to 28% of total litter ( this part is often neglected)
• Large woody debris such as decaying tree trunk and stumps constitute a major component of
the organic matter of the forest floor
• Below ground litter such as root materials that dies each year and decay in the soil and release
nutrient in the soil
Mineral Cycling : Carbon cycle
Carbon is an essential part of life on Earth. It plays an important role in the structure,
biochemistry, and nutrition of all living cells
• Carbon cycle is the biogeochemical cycle by which carbon is exchanged among the
Lithosphere ( Earth crust) , Hydrosphere( ocean and water bodies) , Biosphere (vegetation) of the
earth and and Atmosphere.
• Soils/geology, oceans / water bodies, forests/vegetation and the atmosphere store carbon.
These stores can act as sources or sinks at different times. Sources release more carbon than they
absorb, while sinks soak up more than they emit. A carbon sink can store carbon for a long period
of time. Carbon on Earth is stored in the following major sinks:
• Lithosphere (Earth‘s crust). The lithosphere consists of fossil fuels and sedimentary rock
deposits such as limestone, dolomite and chalk. It is by far the largest carbon sink on earth. It
contains around 4000 gigatonnes of carbon.
• Biosphere. Biosphere carbon is also known as green carbon. Around 42,000 gigatonnes of
carbon are present in the biosphere. Biosphere carbon is divided into three carbon pools: living
biomass, dead biomass and soil.
• Hydrosphere ( ocean/water bodies) . The oceans contain around 36,000 gigatonnes of carbon,
mostly in the form of bicarbonate ion (over 90%, with most of the remainder being carbonate).
Ocean waters contain dissolved carbon dioxide and calcium carbonate in the form of shells and
marine organisms.
• Atmosphere. Carbon exists in the atmosphere in the form of carbon dioxide. Around 750
gigatonnes of carbon are present in atmosphere. Although it is a small percentage of the
atmosphere (approximately 0.04% ), it plays a vital role in supporting life. Other gases
containing carbon in the atmosphere are methane and chlorofluorocarbons.
The movement of carbon, in its many forms, between the four major sinks mentioned above is
described as the carbon cycle.
•
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Mineral Cycling :Carbon cycle :
• The movement of carbon, in its many forms, between the four major sinks mentioned above is described as the carbon cycle.
The basic carbon cycle is:
1. Plants convert atmospheric carbon dioxide to carbohydrates by photosynthesis;
2. Animals and microorganisms consume and oxidize these carbohydrates to produce carbon dioxide and other products; and
3. Carbon dioxide returns to the atmosphere. On a global level, the total carbon cycle is more complex and involves carbon stored in fossil fuels, soils, oceans and rocks.
Animal assimilation
(dead, decay, decomposition
and respiration)
Animal Fats
CHO and protein in
plant
Photosynthesis CO2 Atmosphere
Fossilization
Industries vehicle
fire / fuel
•Carbon (C) is the building block of life. It is the fourth most abundant element in the universe,
after hydrogen (H), helium (He) and oxygen (O).
• All life is made up of carbon.
• Fifty percent of the dry weight in the human body is made up of it.
• It also exists in the environment as an element in carbonate rocks, petroleum, natural gas, steel,
organic matter, and the air we breathe.
• In the form of carbon dioxide, carbon is a greenhouse gas.
• Massing of greenhouse gases in the atmosphere threatens to raise the temperature of the earth,
acid rain, raising sea levels and disrupting the climates that agricultural systems depend on. T
• The concentration of CO2 in the atmosphere has increased by 30 percent since the beginning
of the industrial revolution.
Minral Cycling : Nitrogen cycle :
Cyclic movement of nitrogen in different chemical forms from the environment to organism and
then back to environment is a nitrogen cycle..
•Nitrogen is a macro nutrient used by plants.
•Nitrogen cycles have an atmospheric component linked to the soil by nitrogen fixation, and de-
nitrification; so falls more or less under edaphic nutrient cycles type.
•Plants obtain most of their nitrogen from soil as nitrate or ammonium ions, former being more
important.
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•Worldwide, atmospheric fixation accounts for around 10 KG/Ha/Yr of the biosphere nitrogen
flow.
•On land, more than 60% fixation is due to agro-ecosystems, and most of the remainder is fixed
in forests.
•Other ecosystem accounts for about 7% of total nitrogen fixation
•Overall, atmospheric fixation represents abut 2% of global nitrogen assimilation, rest being
cycled in nongaseous forms.
Some Symbols used in N2 Cycle : Nitrogen N2
Nitrite NO2-
Nitrate NO3-
Ammonia NH3
Ammonium NH4+
Stages of Nitrogen Cycle :
• Fixing atmospheric N2 : Through the precipitation /lightning some atmospheric N2
mixed with water falls on the ground.
• Nitrogen Uptake ( Ammonification) : A few kinds of bacteria on soil convert gaseous
nitrogen to ammonia (NH3). The decomposers also decompose the dead plant parts and
animal body and the dropping of animals add NH3 . This NH3 (ammonia ) quickly
dissolves into cytoplasm to form ammonium (NH4), which can be taken by plants
(organism bacteria from genus rhizobium; occurs generally in legume), which is called
ammonification. N2 NH3 ( ammonia) NH4 ( ammonium)
• Nitrogen Mineralization : The animals eat these plants and add organic N2 to soil by
dropping and decomposition of dead body. This organic nitrogen again converts into
inorganic nitrogen compound (NH4) . This process is called nitrogen mineralization. It is
the process of converting the organic nitrogen into inorganic nitrogen . Organic N
NH4
4. Nitrification Nitrification is a two steps process by which ammonium (NH4
+) in the soil is converted first to
nitrite ions (NO2-), then to nitrate ions (NO3
-) by nitrifying bacteria in the soil. Nitrate ions are
easily taken up by plants as a nutrient and also are readily leached from most soils.
NH4+
NO3- (Nitrate)
Step 1
NH4+ + O2 NO2
- + 2H
+ + H2O + 275 KJ energy
Step 2
NO2- + 1/2O2 NO3
- + 76 KJ energy
5.Denitrification
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Certain bacteria convert nitrite (NO2-) or nitrate (NO3
-) to gaseous nitrogen. This returns
nitrogen to atmosphere. It is an anaerobic process that is carried out by denitrifying bacteria,
which convert nitrate to dinitrogen in the following sequence:
NO3- NO2
- NO N2O N2.
Nitrogen Cycle :
Nitrogen Cycle :
Atmospheric Nitrogen
herbivores, carnivores
(1. Fixing N2)
N2 Dead bodies and OM PPT / Lightning
innert N2
ground
decomposers N fixing plants
(Dinitrification) add N2 Action of ( 3.Mineralization bacteria
denitrifying bacteria Ammonia (NH3 (2. Ammonification) Nitrate Nitrite Ammonium (NH4)
4.Nitrification ( by Nitrifying bacteria)
(Nitrification)
Mineral cycling : Phosphorus cycle :
• Phosphorus is the key to energy in living organisms,
• phosphorus gives energy to animals, driving an enzymatic reaction, or cellular transport.
• Phosphorus is also the glue that holds DNA together, binding deoxyribose sugars together,
forming the backbone of the DNA molecule. Phosphorus does the same job in RNA.
• Keystone of getting phosphorus into trophic systems are plants. Plants absorb phosphorous
from water and soil into their tissues, tying them to organic molecules. Once taken up by plants,
phosphorus is available for animals when they consume the plants.
• When plants and animals die, bacteria decomposes their bodies, releasing some of the
phosphorus back into the soil.
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• Once in the soil, phosphorous can be moved 100s to 1,000s of miles from were they were
released by riding through streams and rivers. So the water cycle plays a key role of moving
phosphorus from ecosystem to ecosystem.
• In some cases, phosphorous will travel to a lake, and settle on the bottom. There, it may turn
into sedimentary rocks, limestone, to be released millions of years later.
• Unlike other cycles of matter compounds, phosphorus cannot usually be found in air as a gas.
This is because at normal temperature and circumstances, it is a solid/liquid in the form of red
and white phosphorus. . .
• It usually cycles through water, soil and sediments.
• Phosphorus is typically the limiting nutrient found in streams, lakes and fresh water
environments
•As rocks and sediments gradually wear down, phosphate is released.
• In the atmosphere phosphorus is mainly small dust particles.
• Initially, phosphate weathers from rocks. The small losses in a terrestrial system caused by
leaching through the action of rain are balanced in the gains from weathering rocks.
• In soil, phosphate is absorbed on clay surfaces and organic matter particles and becomes
incorporated (immobilized).
• Herbivores obtain phosphorus by eating plants, and carnivores by eating herbivores.
• Herbivores and carnivores excrete phosphorus as a waste product in urine and feces.
•Phosphorus is released back to the soil when plants or animal matter decomposes and the cycle
repeats.
• Phosphates move quickly through plants and animals; however, the processes that move them
through the soil or ocean are very slow, making the phosphorus cycle overall one of the slowest
biogeochemical cycles.
Phosphorus cycle .
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Rock cliff
Weathering of rock
Phosphorus in soil
Plants assimilate
phosphorus from soil
Herbivores and
carnivores
Decomposition by fungi and
bacteria
Phosphorus in river and
Ocean
Feces and
urines
Phosphate from
fertilizer
Mineral Cycling : Potassium Cycle :
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Potassium exists in the soil as dissolved K+ ions (solution K), exchangeable K, nonexchangable
K, and mineral K .
Plants take up potassium as K+ ions.. Plants can only directly absorb solution K, and
exchangeable K.
K is not bound in organic forms, but is quickly released back into the soil from crop residues and
roots.
Mineral K is contained largely in un-weathered primary minerals such as feldspars and micas.
K exists in finite quantity in the soil and can limit plant use of other nutrients
K in the soil is primarily controlled by inorganic processes
. Plants require K for photosynthesis, translocation of sugars, starch
production in grains, nitrogen fixation in legumes, and protein synthesis.
•In corn and other crops, K strengthens stalks and stems, thus helping with disease and
lodging.
Fire and adaptation to fire :
Kinds of Fire :
• Ground fire : Takes place where there is a heavy accumulation of litter. In a dry litter, fire is
rapid and extinguishes quickly, but in moist litter the fire is slow and the heat of the fire makes
the inner surface of soil get dry. Fire persists for a longer period. All herbaceous plant die and
some woody shrubs and trees survive because of thick protective bark and deep roots
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• Surface fire : Fire burns the surface litter and herbaceous species and are less destructive and
sweeps faster. Fire burns the tree, shrubs and soils. After the fire, lots of new seedlings and new
shoots emerge in the ground
• Crown fire : Affects the crown of the trees. Spreads in the top layer from the canopy of one
tree to another tree. It kills the trees, shrubs and herbs most devastatingly. The nest of birds, the
baby birds and the insects hibernating on the tree crown are killed. The underground plant parts
and buried seeds escape the death.
Influences of Fire :
Chemical and Physical properties of soil:
• Increases the soil pH ( because of acid combustion and chemical reaction at high
temperatures)
• Decreases cation exchange capacity of soil
• Alters OM, reduces soil organisms and nutrient loss through oxidation and volatization (result
is nitrogen loss), loss of N, S,K, Na, Z, Fe, Cu.
• Affects on the dry matter accumulation, which in turn, decreases the carbon and nutrient pools
of soil.
• Destroy texture, structure and porosity of soils by affecting the clay content
• Removing overhead vegetation, fire can lead to increased solar radiation on the soil surface by
day, resulting in greater warming at day, and to greater cooling at night.
• Disappearance of leaves reduce plant transpiration and leaf interception of rain,
• Creates an impermeable crust at the soil surface, which may lead to increased soil erosion
through surface run-off and reduce water holding capacity,
• Exposure to sunlight, wind and high evaporation will make soil more dry.
• Reduce fungi but increases bacteria.
• While in prescribed burning, fire is a management tool that releases soil nutrient
available to the plants. Reduces the devastating fire havocs. Releases complex organic
compound
Genetic adaptation of plant species
• Fire is a dominant factor for genetically adopted plant community. Grassland and pine forest
are genetically adapted community which foster frequent fire.
• There is a symbiosis relationship between pine forest community and grassland with fire.
• Grassland and Savanna communities might not have existed without fire.
• Fire is one of the basic natural forces that has influenced plant community over evolutionary
periods of time.
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• Certain community require fire to maintain their position in the ecosystem and fire is a driving
force for their management such as chirpine, teak, eucalyptus
• Fire encourages species establishment, development, composition and diversity in certain
plant communities. The composition of the plant community and diversity are some
consequences of fire impact on ecosystem.
• After fire, succession takes place and over a period of time some species reached to its climax.
• Repeated fire invites regeneration and establishment of fire resistant and fire adapted species
in the community
• Area devastated by fire will be colonized by the hardy and most promising species able to
adopted in deteriorated soil and other environment condition created by fire.
• Fire create wildlife habitat. For instance, the repeated fire on the shrub land of Africa and north
America have developed grass communities where the condition were suitable to develop
wildlife habitats and attracting wildlife population
• After fire the site will have abundance of insects , parasites and fungi
Fire : Adaptation to it :
• Plant species adaptation to fire .
There are four mechanisms (pillars or strategies ) for species adaptation on fire:
a) Preventing from fire damage (before the fire occurs)
b) Recovering from fire damage (after the fire occurred)
c) Colonizing sites after fire (after the fire occurred)
d) Promoting fire occurrence
a) Thick insulated bark ( many pines and oak species) , deep rooting tap root in young plants
(oaks), rapid juvenile growth ( many pine species), branching habit and self pruning
ability ( upper branching and high self pruning)
• Quick sprouting from various portions of the plants, recovering from root collar or
stump, Dormant buds near the soil surface initiate new shoots after the crown is killed,
dying back ability
• Early seed production, light wind-borne seeds, heat induced germination
• Leaves coated in flammable oils that encourage an intense fire and cones of some pines
shed seeds only in high temperature induce by fire or smoke
Some more points on plant adaptation to fire :
• Various species of plants, have adaptations to ensure their species‘ survival after a fire.
• To survive a fire, a plant must be able to insulate itself from the heat of the flames. Bark
thickness is one of the most important factors determining fire resistance of trees. Ponderosa
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pine, Douglas Fir, longleaf pine, slash pine, oaks are examples of trees with thick bark that acts
as insulation.
• Small woody plants and shrubs, which normally have thin bark, tend to use the soil as an
insulating layer to protect them. Individual plants resist being killed in fires by producing new
growth (shoots) from underground roots or tubers.
• Some plants protect their buds as an adaptive strategy to survive a fire. Buds can be protected
by layers of succulent foliage. The buds of the longleaf pine are protected by a thick cluster of
needles. Some plants even protect their buds by locating them within the main stem and roots. A
few species of poplar trees in several parts of the world possess this characteristics.
• Retention of seeds by plants until a fire does occur and seed dispersal takes place by fire are
other examples of fire adaptation. A number of pine species around the world, have cones open
only as the result of heat from a fire. Their cones are held closed by a resin that is sensitive to
and opens in high temperatures generated by wild land fires
• There are some plant species called ―Obligate seeders‖ . These plants have large, fire-activated
seed banks that germinate, grow, and mature rapidly following a fire, in order to reproduce and
renew the seed bank before the next fire.
• Some plant species are called ― Resprouters.‖ that is fire-tolerant species, which are able to
withstand a degree of burning and continue growing despite damage from fire. These species
store extra energy in their roots to recover and re-growth following a fire. For example, the
Mountain Grey Gum tree (Eucalyptus cypellocarpa) starts producing a mass of shoots of leaves
from the base of the tree
• Some plants are Fire-resistant plants, which suffer little damage from fire . These include
large trees whose flammable parts are high above surface fires. Ponderosa Pine (Pinus
ponderosa) is an example of a tree species that suffers virtually no crown damage under a
naturally mild fire, because it sheds its lower, vulnerable branches as it matures
• Some plants have leaves coated in flammable oils that encourage an intense fire. Heat causes
their fire-activated seeds to germinate and the young plants can then establish in a burnt site .
• Some trees like Pinus, Larix, Quercus etc. have deep rooting taproot and fire resistant thick
bark which insulating effect against heat. They have tall trunk and pruning ability so avoid from
ground and surface fire.
• Some tree species have fire resistant foliage with lots of water on leaves and very little resin or
oil content can also escape from fire damage
• Litter of some hardwood species like maple tree species decompose very quickly so reduces
the opportunity for fire ignition and spread
• Many Eucalyptus species of Australia have dormant buds located in the lower part of the
trunk and under the soil surface stem and root parts, escape from fire killing and get activated to
produce new branches after fire is over.
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• Some tree species like oaks and hickories develop deep root system and store food reserves
for rapid regeneration of new shoots after the fire is over
• Some tree species produce hard coated seeds and protect embryo of seeds from the heat of sub-
surface soil by fire. Germination takes place in a favorable season when the seed coat is cracked
by fire.
• Certain tree species like Pinus, Rhus species have no true seed dormancy period, so germinate
at any favorable season following post fire rain
• Re-sprouting ability and bark thickness , stimulation of seed dispersal are adaption against
fire.
• Desert shrubs of different parts of world have deep roots, small leaves, and high tolerance to
hot, dry conditions.
2. Animals adaptation to fire :
• Fire has less effect on mammals and birds than that of plants
• Like plants, animals display a range of abilities to cope with fire, but they differ from plants in
that they must avoid the actual fire to survive.
• Although birds are vulnerable when nesting, they are generally able to escape a fire; indeed
they often profit from being able to take prey fleeing from a fire and to re-colonize burned areas
quickly afterwards.
• Birds have ability to fly and run quickly over along distance
• Mammals are often capable of fleeing a fire, or seeking cover if they can burrow.
• Amphibians and Reptiles may avoid flames by burrowing into the ground or using the
burrows of other animals. • Amphibians in particular are able to take refuge in water or very wet mud.
• Some arthropods also take shelter during a fire, although the heat and smoke may actually
attract some of them.
• Microbial organisms in the soil vary in their heat tolerance but are more likely to be able to
survive a fire the deeper they are in the soil.
• Soil fauna like earthworm, snails, spiders, ants and nematodes are reduced quickly and
increases there after
• Death of mammals and birds are largely due to smoke suffocation than by burning
• Wildlife species have developed different methods or strategies to escape fires.
• Animals such as deer, bear and kangaroo, which are accomplished runners and jumpers, use
their skills to escape the flames.
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• Other animals such as mice, shrews, snakes, lizards, and tortoises use burrows to escape fire.
• Mature birds can fly to a safer area until the flames have passed.
• However, since nestlings and chicks may be unable to fly, they cannot escape the fire‘s path.
Their remains attract scavengers and predators, such as wild dogs, foxes, and vultures, to
recently burned areas.
• Sawflies, red pine cone beetles, and maple leaf cutters are examples of nuisance pests whose
numbers are reduced by wildland fires.
• Although some insect populations decline as a result of fire, ants seem to increase. Ant
populations have been recorded as more numerous in burned areas than in unburned areas.
• Many microbial organisms (decomposers) also increase in numbers following fire.
• Plants and animals that have structural and behavioral adaptations to survive in habitats
frequented by fire are said to live in a fire dependent community. Plants that are highly adapted
to fire are called Pyrophytes.
The Atmosphere :
• Protective blanket over the Earth, able to nurture life on earth
• Atmosphere constitutes sources of many gas out of which CO2, O2, N2 and transport water
from the land and ocean and back to the land.
• Absorbs most of the cosmic rays from the outer space and electromagnetic radiation from sun
and protects living things from their effects.
• Atmosphere maintain the heat balance of the earth
Composition of atmosphere near the ground surface (% by volume) :
Major components : Minor components Trace components Nitrogen (78.09) Argon ( 9.34 × 10 -1) Neon(1.82 × 10 -3
Oxygen (20.94) Carbon dioxide ( 3.25 × 10 -2) Helium ( 5.24 × 10 -4)
Water vapor ( 0.1-5) Methane ( 2 × 10 -4)
Krypton ( 1.14 ×
10 -4 )
Nitrous oxide (
2.5 × 10 -5)
Hydrogen ( 5 ×
10 -5)
Ozone (trace) and
others
Different Layer of Atmosphere
Thermosphere:
• Altitude range : 85 to 500 km
• Temperature range : - 92 to1200 C
• Important chemicals : O2 +, O+, NO+
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Mesosphere :
• Altitude range : 50 to 85 km
• Temperature range : - 2 to -92 C
• Important chemicals : O2 +, NO+
Stratosphere :
• Altitude range : 11 to 50 km
• Temperature range : - 56 to -2 C
• Important chemicals : O3
Ozone in this region absorbs ultraviolet radiation
Troposphere :
• Altitude range : 0 to 11 km
• Temperature range : - 15 to -56 C
• Important chemicals : N2, O2 , CO2, H20
Role of Animals in Ecosystem :
• Contribute in food chains, energy flow and nutrient cycling
• Breakdown OM and release nutrient
• Allows natural regeneration and succession ( by dispersing seeds and pollen) and
germination of seeds
• Regulate forest composition and development
• Influence forest pattern and process
• Provide ecosystem services such as recreation, hunting, meat, milk and medicine
• Rich biodiversity creates ecological integrity in changing climate
• Carnivores predation can keep herbivores population balance , which minimize over
utilization of plants and over grazing
• Herbivores grazing enhance uniform utilization of the plant community and maintain
population balance in the ecosystem
• Decrease the epidemic of pest and injurious insects population
Plant Defense Adaptation
(Plants and its parts are subject to attack at all stages in their life cycle by organisms. Plants
develop defense mechanism to survive or adapt against the attack )
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Plant Adaptation : a heritable or genetically characteristics or trait that enables plants to
better survive and reproduce within a given set of environmental conditions.
An alteration in structure or function of a plant or animal that helps it change over the course of
successive generations in order to be better suited to live in its environment.
These alterations in structure and function in a plant can be visualized through :
• Texture and composition of plant surface
• Presence of specialized organs of tissues ( thorns)
• Absence of nutrients required for the pests or animals ( unpalatable)
• Presence of hormones like structure that repel the insects
• Accumulation of secondary compounds ( alkaloids, tarpenes )
The kinds of defenses use by plants are : Thorns, resin ducts, accumulation of alkaloids,
terpenes, phenolics, cacogenic glycosides
• Trees like orange, junipers, pine, roses etc have prickles, spines, thorns or sharp needle
leaves that deter browsing.
• Oil or resin come out of resin ducts in needle and shoots and bark in conifers deter foliage
feeders and bark beetles.
• A high concentration of tannins in oak leaves deter insect feeding.
• Presence of toxic vines and parasites also deter animals from feeding on associated tree species
( symbiosis relation ) .
• Produce distasteful chemicals that deter further feeding.
• Produce chemicals that affect herbivores‘ physiology
Damage in Forest Stands :
• Animals do damage in forest stand.
• From seeds and seedlings to mature tree, no forest tree is free from animal damage.
• Seedlings of all woody species bark removed by hares, stem and root girdling by mice as well
as trampling and browsing by deer.
•Mature trees are subject to attack by insect feeders.
• Bark eaters rodents ( hares, mice, monkey, bear etc. ) may kill a large number of trees.
• Juice sucking insects ( wood pickers), bud eating birds ( sparrow), squirrel and other animals
cause great harm to the forest stand.
• Elephant detach the branches of the tree and sometime uproot the trees.
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• The insects, birds, squirrels, mice and rodents eat seeds.
• Some animals eat and destroy seeds at sowing time.
• Squirrels cut conifer cones.
• Deer browsing is probably the most common injury in the forest.
• High deer population limits the seed germination, forests regeneration and stand development.
Unit 5 : Synecology
Synecology is a study of groups of organisms ( or species) which are associated together in an
ecosystem .
• A group of individuals of the same species is population. Population of different species in a
given set of environment is community, which is the biotic component of an ecosystem.
• Biotic community as ― assemblage of plants, animals, bacteria and fungi that live in an
environment and interact with one another forming a distinctive living system with its own
composition, structure, environmental relations, development and function
• Therefore the study of the community properties and the interaction among organism s of the
community is termed as Synecology.‖
Site or habitat : The whole environmental set up which is occupied by organisms is site or
habitat
Forest site Quality : Sum total of all the factors ( climatic, edaphic, and biological) affecting
the capacity of the site to produce forest biomass.
• Site quality refers to the combination of physical and biological factors of a particular
geographic location or site. Site quality are generally inherent to the site, but may be influenced
by management.
Production vs site productivity : Production is the quantitative measurement of forest
biomass in terms of cu. m / year/unit area ( yield table or volume table) , where as
Site productivity : quantitative estimate of the potential of a site (capability of the site to produce
plant biomass ) to produce plant biomass.
• Forest site productivity may be defined as the potential of a particular forest stand to produce
aboveground wood volume.
• Site productivity is often quantified as an index, site class or site index, which are widely used
for management purposes.
• Most commonly, site indices are based on estimates of stand height at a given age.
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• Site productivity reflects potential of site on the production of forest biomass,
• Site productivity depends on site quality, which in turn , depends on natural factors inherent
to the site ( soil and climate) and the management regime such as silvicultural practices like
site preparation , choice of species, thinning, spacing, regeneration etc.
Measurement of Forest Productivity ( or site quality or site productivity ) :
1. Direct Measurement
• Generally measured in terms of the gross volume of bole wood per unit area per year over the
normal rotation.
• Gross volume : the total amount of wood in all trees within a given unit of time without
deduction for natural mortality, removal by human or decrease in wood volume by diseases or
pests
• It is measured in the form of mean annual increment ( MAI)
• MAI : Average annual rate of growth ( total increment/age)
2. Indirect Measurement of Forest Productivity ( or site quality or site productivity of a
given species)
-- Site index Method
-- Plant Indicator of site
-- Environment factors as a measure of site
-- Multiple factor methods of site classification
• Mean annual increment (MAI) or mean annual growth
• It refers to the average growth per year a tree or stand of trees has exhibited/experienced to a
specified age.
• For example, a 20-year old tree that has a dbh of 10.0 inches has an MAI of 0.5 inches/year.
• MAI is calculated as MAI = Y(t) / t where Y(t) = yield at time t. Mean Annual Increment
m3/ha/yr (MAI) = Volume of stand (m3/ha)/Age of stand (yrs)
• The Mean Annual Increment is simply the average volume production per year for a forest of
known age:
•MAI starts out small, increases to a maximum value as the tree matures, then declines slowly
over the remainder of the tree's life. Throughout this, the MAI always remains positive.
• Periodic or Current Annual Increment (CAI) is the increase in volume at a particular age and is
determined by annual measurements of standing volume.
Example:
Periodic or Current Annual Increment (CAI) at age 2 (m3/ha/yr) = (Volume at age 3) - (Volume
at age 2)
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• MAI differs from Periodic or current Annual increment (PAI or CAI) because the PAI or CAI
is simply the growth for one specific year
• The point where the MAI and PAI or CAI meet is typically referred to as the Biological
rotation age . This is the age at which the tree or stand would be harvested if the management
objective is to maximize long-term yield.
• the PAI or CAI will increase rapidly in the early years, up until competition for light, moisture
or nutrients causes CAI to reach its peak. The decline in CAI can be more rapid than the early
rise.
•Direct methods are not based on site factors, which are not pragmatic because the
productivity is based on site factor but also are based on genetic factors
Indirect Method of Measuring Forest Productivity
a. Site Index Method :
• The relationship between tree height and age
• The height of the dominant portion of forest stand at a specified standard age ( rotation) is
commonly termed as site index
• The height of trees of a given species in a given forest stand and of a given standard age
is more closely related to the capacity of a given site to produce wood of that species
• Site index curves : Site index curves are drawn for different sites for a particular given
species with height-over-age
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• Tree height measure at specified age is best related to the site productivity of a given species
• Marked differences in the height growth of dominant trees occur on site of different quality
• The height of the dominant trees on the richest site may be 3 to 4 times more than on the
poorest site
In Nepal, the Sal tree has attain a height of more than 35 meter at the age of 120 years at the
richest site while less than 15 meters on the poorest site . The richest site is termed as quality I
and the poorest site quality IV
The normal correlation of height with different quality class is as follows :
Quality Class Height of dominant trees in a stand
I 35 m and above
II 25 m to < 35 m
III 15 m to < 25 m
IV < 15 m
• Plant Indicator of site :
• Plants of the site themselves are measures of the site ( called photometers)
• Both the trees and understory plant species ( herbs, shrubs) can be used as indicator
species.
---- ‖ Steno ― species are indicator of good site quality such as Black
walnut, white ash, yellow poplar
---- ― Eury ― species are indicator of bad site quality such as black
oak, white oak
---- Ground vegetation or understory species are useful indicators
because they are long lived, relatively unaffected by stand density and
easily identified in all season
----- Species groupings along the environment gradient can also be
used as site indicators
---- Occurrence of Vitex negundo or indigofera pulchella in Sal forest
indicates a very poor site
• Environment factors as a Measure of Site
• Environment factors are used to measure the forest site productivity
• This is primarily used for the growth of forest in abandoned agricultural land; area subjected
to fire; logged in areas; heavy grazed areas ; and areas having other disturbances, area to be
converted from one forest type to another type
• In such areas a small supply of in the environment or physical factors will result in measurable
changes in the growth of forests ( based on law of minimum)
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• Site productivity can be measured from the analysis of the physical environment rather than
from the vegetation
Climatic factors : Site with high rainfall deficits produce less forest growth than sites with
small rainfall deficits, high and low temperature both reduce forest growth
• With increasing elevation, normally precipitation will be high and temperature will be low. Site
quality may be increased or decreased with the combined effects of precipitation and
temperature
• Therefore, precipitation and temperature are related to forest tree growth as a measure of site
quality
Topographic and Soil factors :
• Topography and soil should also be considered in determining the site quality of forest and are
the indicators of forest productivity.
• Soil physical and chemical properties as well as elevation, slope, aspects, longitude and
latitude of the site are variables to determine the site index to measure the productivity of forest
D. Multiple Factor Method of Site Classification :
• Multiple factor method is also used to determine the site quality
• This is based on the fact that the site quality is the sum of the total factors affecting the
capacity of land to produce forest
• The more factors are taken better is the estimate of site productivity
• Multiple factor system, also called ―The Baden-Wurttemberg System ― has integrated
geography, geology, climate, soil, and sociology in determining the site quality
• In this method, Regional classification of growth were determined and the areas were sub
divided into growth districts
• Districts were sub divided into local and local classification of site quality were done
• Site quality mapping at local level were done
• Evaluation of growth and productivity were done at local level site quality
• Silvicultural and management recommendations were made for each species and species
mixture foe each site
• Comprehensive summary for each growth areas and comparison between different growth
areas were done
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Regional classification of growth were determined and the areas were sub divided into growth districts
Districts were sub divided into local and local classification of site quality were done
Site quality mapping at local level were done
Evaluation of growth and productivity were done at local level site quality
Silvicultural and management recommendations were made for each species and species mixture foe each site
Comprehensive summary for each growth areas and comparison between different growth areas were done
Concepts of competition and survival :
• As the number of individuals of a sps. increase at the limited space, plants compete each
other for space, nutrient , moisture and light.
• Since the competition is within the individual of the same sps . of a population, the
competition is called intra-specific competition.
• They may also compete with individuals of other sps that enter into that area, which is called
inter-specific competition.
• Due to intra and inter specific competitions and interaction s with biotic and abiotic
components of that area , the environment of the site will be modified and slowly it becomes
unsuitable for the existing community, and the site will slowly be replaced by new invaders
or community
• Finding the modified environment more suitable for other sps, more sps will enter into the
area and compete with the previous occupants.
• This results the former species subdominant or eliminated completely
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• Addition of OM, nutrient and moisture by the plant communities makes increase availability
of food and home for animals to join the community
• The interactions between the plants , animals and the environment further takes place and
modify the environment , consequently fresh invasion of other species and animals takes place
which leads to the process of succession.
• Finally a stage is reached when the final community becomes stabilized and can maintain
itself in the equilibrium or study state with the climate of that area.
• This last stage is mature, self maintaining and reproducing community and relatively
permanent
• The vegetation is tolerant of the environmental condition, contains wide diversity of species,
well developed structure, complex food chain, equilibrium in nutrient uptake and return and its
living biomass is in steady state
Forest and grass communities, structure and diversity
• Forest community, structure and diversity
Community ( individual plant, population, community). The vertical profile of a plant
communities is known as its structure. Diversity is (sps. richness and abundance)
• Well developed forest ecosystem has several layers of vegetation from top to bottom : Top
story or canopy and under story . Within under story : shrub layer, seedling or herb layer;
mosses and lichens layer and finally forest floor or ground layer ( where decomposition of
litter takes place and nutrient are released to the nutrient cycle) and lower than this is root
layer or soil strata
• The canopy is a major site for energy fixation and has major influence on the forests
• With fairly open canopy, the sunlight reach to the understory strata and the understory
vegetation richly developed, while in the closed canopy the vegetation of the understory will
poorly developed
• At the canopy level, the tree must spend some of its energy of the photosynthesis for the
development of woody tissue of stem and branches.
• At closed canopy, the under story strata will receive less light for photosynthesis and to
survive but the advantage is that the understory need not share much of its energy for the
development of woody tissue of stem and branches. The herbs does not need to spend more
of its modest energy for the development of woody tissues and branches.
• Therefore, the Forest Structure involves a gradient of growth forms . That is upper and
lower trees ; upper and lower shrubs; upper and lower herbs and soil surface mosses for the
adaptation in the gradient of light intensity
• Along the gradient of the growth forms, two extremes that is ranging from upper canopy level
to herbs or mosses/ lichens level exists.
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• The upper extreme i.e upper canopy level : photosynthesis at full level of light intensity ,
massive investment of energy to stem and branch structure and formation, accumulation of
food reserve in a root system or root mass is smaller than the above ground structure.
• The lower extreme i.e lower herbs level : photosynthesis at low level of light intensity, small
investment of energy to above ground supporting structure, accumulation of food reserve in a
root system more massive than the above ground structure.
• Therefore, variety of life in the forest is directly related to the number and development of
layers of the forest. For example : the rain forest has greater species diversity and so the layer or
stratification of forest is more.
• If certain layer is destroyed or absent , the animals they shelter and support are also missing.
• Thus a well developed forest supports a rich diversity of life
Grassland communities :
• In grassland communities, only three strata such as : herbaceous layer ; ground or mulch layer
; and the root layer are recognized.
• The root layer is more pronounced in grassland ecosystem than any other ecosystem.
• The root layer provides permanent residence to soil bacteria, fungi, protozoans, nematodes,
earthworms, spiders, insects and other invertebrates
Species diversity in communities :
• Species diversity is a measure of the diversity of plant sps. within an ecological community
• It includes both species richness (the number of species in a community) and the ―evenness of
species‗ or ―abundances‖.
• Species diversity is influenced by species richness. All else being equal, communities with
more species are considered to be more diverse. For example, a community containing 10
species would be more diverse than a community with 5 species.
• Species diversity is also influenced by the ―evenness of species‖, which is a relative
abundance of individuals in the species found in a community. Evenness measures the variation
in the abundance of individuals per species within a community. Communities with less variation
in the relative abundance of species are considered to be more ―even‖ than a community with
more variation in relative abundance. Consider the following two communities.
Species richness in a community = No. of species in a community (, communities with more
species are considered to be more diverse. For example, a community containing 10 species
would be more diverse than a community with 5 species. )
Evenness or abundance = relative abundance of individuals in the species
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• In A and B species richness is same ( 5 in both the cases)
• In A, all five species have the same abundance, no variance and more even
• In B, there is great variation in abundance , and not even
• Communities with greater evenness are considered to have greater species diversity, even
though species richness of the two communities is equal
• Community A is more species diversity than Community B
Relationship of species richness and abundance :
Species richness = ( S – 1 )/ log N, where S = Number of species and N = Number of
individual in each species ( abundance)
Diversity Index
H = - ∑ Pi log Pi, where, H is diversity index ( Shannon-weaver Function), Pi is proportion of
the total number of plants( individuals) consisting in i th species and i = 1 to S
• Species diversity tends to be low in physically controlled ecosystem and high in biologically
controlled ecosystem
Forest communities and changes in the ecosystem :
Forest communities is the complex of biotic and abiotic factors
Biotic factors includes : trees, shrubs, herbs, bacteria, fungi, protozoa, arthopods, vertebrates and
many others
Abiotic factors include : gases, minerals, soil, geology, waters and other site factors.
Changes in forest ecosystem : occurs due to changes in weather and climate
• Diurnal change :
During night – temperature low, moisture and humidity relatively high, plant active on
respiration ( consume O2 and release CO2 ). Some animals are in dormant stage and some are
active. During daytime- the conditions will be reverse .
• Seasonal change : Forest ecosystem changes seasonally around the year, Biotic community
and their activities will be changed as season changed ( such as growth, leaf fall, sprouting ,
pollination, reproduction, pollination etc )
• Long term climatic change : Forest ecosystem changes over the change in climatic condition
• Ecosystem biota change : Biota changes over time, colonization, immigration, migration,
dispersal , mutation, natural selection etc
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Competition :
• In an ecosystem, there exists various kinds of relationship among species inhibiting the
ecosystem
• One of the relationship is competition among species, plants compete with each other for
space, nutrient, light, moisture, air, warmth etc. They compete for these elements for the growth,
reproduction and survival
• Limited supply of at least one resource (such as space, nutrient, food, light, warmth,
moisture) used by both usually facilitates competition
• When two or more organisms in the same community seek the same resource (e.g., nutrient,
food, water, light, warmth, air, space etc ), which is in limiting supply to the individuals seeking
it, they compete with one another.
• Birds, rodents and ants may compete for seeds in desert environment
• Competition in animals is often for food, water and mates, space, nesting sites, wintering sites,
safer sites from predators
• Competition in plants is for light, water, nutrients and space, pollinators
• Competition is an important process affecting the distribution and abundance of plants and
animals
• Species competition may have a negative effect upon one another. But they also have
neutral and beneficial effect.
• If the competition is among members of the same species, it is called intraspecific.
• Competition among individuals of different species it is referred to as interspecific
competition.
• Individuals in populations experience both types of competition to a greater or lesser degree.
• Interspecific competition is normally not as fierce as intraspecific competition, unless in case
of a sudden drastic change. Intraspecific competition is the most conspicuous competition in
grasslands, where, for example, cheetahs and hyenas are often killed by lion .
• Intraspecific competition does not effect the composition of the forest type and therefore has
no effect on forest succession
• Interspecific competition results in a natural succession from one forest composition to another
• In the case of forests, competition takes place in even and uneven aged stands and in the
main canopy or over storey of the forest and in the under storey
• Competition between species at the same trophic level of an ecosystem, who have common
predators, increases drastically if the frequency of the common prey in the community is
decreased.
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There are two different process of competition :
1. Exploitation or Resource competition ( Scramble competition)
• competition occurs when a number of organisms of same or different species utilize common
resources that are in short supply
• competition occurs between individuals when the species or individuals reduce the supply of
the limiting resource or resources needed for survival.
• By such competition , the exclusion of one organism by another can occur when the dominant
organism requires minimum amount of the limiting resource to survive ( Law of minimum).
• The dominant species reduce the quantity of the resource to some critical level with respect to
the other organism.
2. Interference or Interface competition : ( contest competition) :
• Competition occurs when the organisms seeking a resource harm one another in the process
even if the resources is not In short supply
• Competition occurs when an individual directly prevents the physical establishment of another
individual in a portion of a habitat.
Example : established plants can preempt ( prevent) the invasion and colonization of other
individuals by way of dense root mats, peat and litter accumulation etc.
Interaction :
• Limited supply of at least one resource (such as space, nutrient, food, light, warmth, moisture)
used by both usually facilitates this type of interaction,
• competition may also exist over other services and 'amenities', such as females for
reproduction (in case of male organisms of the same species).
Types of interaction
The neutral effect is called neutralism and the beneficial effect is called mutualism or proto-
cooperation , if one species is benefited and other is harmed is called predation and one benefit
but does not harm the other is called commensalism and one species is harmed by any other
species and derives no benefits is called amensalism
Types of
Interaction
Species
A
Species
B
Nature of competition Example
Competition (
interference and
resource use type)
- - Both A and B are affected competition of Sal
and Khair trees
Neutralism O O Both A and B are not affected Rabbits/deer and frogs
live together in a
grassland no
interaction between
them.
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Mutualism + + Favorable to both A and B and is
obligatory
Insect pollination of
flowers
Predation or
parasitism
+
(predator)
- (prey) A benefited B affected (
predation/prey relationship)
Wolf and rabbit
Commensalism + O A benefited but B not affected Insects decomposing
Caracas
Amensalism O - B affected but A not affected The walnut tree
secretes a chemical
from its roots that
harms neighboring
plants
Mutualism interaction
Symbiotic Non-symbiotic
Symbiotic : In this interaction , individuals live together and interact physically and their
relationship is biologically essential for survival. At least one member of the pair cannot live
without close contact with the other. For example, the fungal-algal symbiosis that occurs in
lichens. Lichen is a mass of fungal hyphae that forms around a algae cells. In this mutualism, the
algae produces carbohydrates and other food by products through photosynthesis and
metabolism, while the fungus absorbs the required minerals and water to allow for these
processes to occur.
Non- symbiotic : In this interaction, the two organisms live independently, but cannot survive
without each other. The most obvious example of an interaction of this type is the relationship
between flowering plants and their insect pollinators.
Tolerance :
• Tolerance is the capacity of a plant to maintain its fitness through growth and reproduction
after sustaining damage.
• In a broad sense, tolerance deals with the general capacity of a plant to be genetically adopted
and physiologically compatible with unfavorable conditions
• Tolerance often may Influence the evolution of plant defense and the composition of plant
communities.
• Forest tree that can survive and prosper under a forest canopy is said to be tolerant. It also
refers to the relative capacity of a forest plant to survive and prosper in the under storey
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Recognition of tolerance
• Occurrence in the under storey
• Response to release rapid growth following removal of over storey
• Crown and bole development ( lower branches will be foliated longer and the boles tend to be
more tapered)
• Stand structure ( tolerant trees persists over long periods of time in natural mixed stands )
• Growth and reproductive characteristics ( height grow of tolerant Sps. is faster than the non-
tolerant species, tolerant tree mature later, flower later and more irregularly and live longer than
intolerant trees
Law of Tolerance ( Shelford’s Law ) :
“ Each ecological factor to which an organism responds has maximum and minimum limiting
effects between which lies a range or gradient that is known as the limits of tolerance‖
Example : CO2 is necessary for the plant growth, small increase in CO2 in atmosphere will
increase rate of plant growth. If the increase in CO2 is too much then results toxic effect to
plant. So there is gradient of minimum and maximum requirement of CO2 for the plant growth.
Similarly, a small amount of additions of arsenic to human diet will have a tonic effect, but the
increase in the arsenic dose more than the requirement may cause fatal death.
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( Lower limit of tolerance)
Zone of intolerance Zone of physiological Zone of physical (upper limit of toleran
stress stress Zone of intolerance
Minimum limit Optimum Maximum limit
limit
Growth
Organism organism organism organism
Absent infrequent infrequent absent
Low Environmental factor High
( i.e temperature)
Forest stand structure :
• Dominant :
--- trees with crowns extending above the general level of the canopy
--- receiving full light from above and partly from side
--- crown well developed
• Co-dominant :
--- trees with crowns forming the general level of the canopy or somewhat below
--- receiving full light from above but only moderate amounts from the side
--- usually with medium sized crowns and more or less crowded in the sides
• Intermediate :
--- trees shorter than the co-dominant class but with crowns extending into the canopy formed
by the dominants and co-dominants
--- receiving some direct light from above but little from sides
--- usually with small crowns considerably crowded on the sides
• Suppressed :
--- trees with their crowns entirely below the general canopy level
--- receiving no direct light from above or from the sides
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Succession : Progressive replacement of one community by another until a relatively stable
community occupies the area is called ecological succession. It is the ―birth‖ of an ecosystem
and subsequently ―aging‖ process of its abiotic and biotic features
• The development of the community by the action of vegetation and the geological factors on
the environment leading to the establishment of new species is termed as succession .
• The occurrence of relatively definite sequence of communities over a long period of time in the
same area resulting in establishment of stable or climax community, is known as ecological or
biotic succession.
• Succession is a continuing and directional process marked by large number of changes in the
vegetation, the fauna, the soil, and the microclimate of the area with the passage of time
• These changes occur together mutually affecting one another with simple cause and effect
relationships
• Ecological succession is a complex dynamic interaction between the species composition of
the community inhibiting the ecosystem
• Due to the close interactions between site factors and the plant communities, a continuous
changes take place in the biota of a particular area
• In succession, involvement of both flora and fauna takes place. Changes in fauna is led by
changes in flora
• It is the universal process of directional change in vegetation during the course of time
.
•The first community which is inhabiting the area will be referred as 'pioneer community' and
the last and stable community formed in the area will be referred as 'climax community'.
• The intermediate communities are called 'transitional or seral communities'. The whole series
of changes in community characteristics from pioneer stage to climax stage constitute a 'sere' and
the intermediate stages are the 'seral stages'.
• Usually the initial stages of succession are comprised of lower forms.
Causes of succession :
1. Biotic factors : Interactions among the organisms in a community, as called biotic factors, influence the
structure, composition and function of a community. In succession, during period of time a
community makes the area less favourable for itself and more favourable for the next serial
community.
2. Physiographic factors : Includes physical and chemical factors of the environment such as landslides, erosion,
catastrophic factors, etc.
3. Ecesis or continuing factors : These are the processes such as migration, aggregation,
competition and reaction etc, which causes succession of population as a result of changes,
chiefly in the soil features of the area
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Process of Succession (F.E. Clement , 1916)
1. Nudation: Succession begins with the development of a bare site or area , called Nudation by
several reason s such as vocanic eruption, landslide, flooding, erosion, deposition, fire, disease
or other catastrophic agency.
2. Migration: It refers to arrival of propagules of various organisms and their settlement in the
nude or bare areas. The seeds , pores or other propagules of the species reach the bare area
through the action of air, water or animals
3. Ecesis: It involves successful establishment of immigrant plant species or initial growth of
vegetation in the new area. It includes germination of seeds or propagules, growth of seedlings
and starting of reproduction by plants.
Aggregation : the successful invasive or immigrants individual s of species increase their
number by reproduction and aggregate in a large population
4. Competition: As the numbers of individuals of species increase due to reproduction and
multiplication, species began to compete for space, light and nutrients. ( inter-specific and intra-
specific competition takes place, biotic and aboitic interactions takes place, ),
5. Reaction: During this phase autogenic changes affect the habitat resulting in replacement of
one plant community by another.
--- Environment is modified and progressively becomes unsuitable for the existing community,
which sooner or later is replaced by new invaders or another community ( serial community).
---- Finding the modified area more suitable, more species enter the area and compete with the
previous occupants. This results in a balance among the species in which the former species is
brought down to a sub-dominant status or is completely eliminated.
---- The addition of OM, nutrients, and more moisture in the substratum by small plants makes it
suitable for larger ones.
---- Increase availability of foods allows various kinds of animals to join the community and the
resulting interactions further modified the environment and paves the way for fresh invasion by
other species and animals .
---- This process coninues until a stabilized community exists. . Reaction phase leads to
development of a stabilization or climax community.
6. Stabilization or climax : Eventually a stage is reached when the final terminal community
becomes more or less stabilized for a longer period of time and it can maintain itself in the
equilibrium or steady state with the climate of that area
--- This last serial stage is mature, self-maintaining, self reproductive and are relatively
permanent and is tolerant of the environmental condition it has imposed itself
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Stages of succession :
• Pioneer stage
--- Initial stage of succession
-- Species grow in this stage are termed as ― Pioneer ‖
--- Species that invades a bare area such as newly exposed soil or environment
• Serial stage
--- Intermediate stage
--- Species grow in this stage are termed as ―Sere‖
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• Climax stage
--- Final stage
--- no further primary succession exists
Stage of succession ( continued) : The primary and secondary successions may be of the
following types depending on the moisture contents :
• Hydrach or hydrosere : The succession when starts in the aquatic environment such as
ponds, lakes, streams, swamps, bogs etc
• Mesarch : the succession when begins in an area where adequate moisture is present
• Xerach or xerosere : the succession when starts in xeric or dry habitat having minimum
amounts of moisture such as dry deserts, rocks etc. It has 3 types
a) Lithosere – succession initiating on rocks. b) Psammosere – succession initiating on sand
and c ) Halosere - succession starting on saline soil
• Sometimes, succession is classified as Autotrophic and Heterotrophic succession
• Autotrophic succession : characterized by early and continued dominance of
autotrophic organisms like green plants. It begins in a predominant inorganic
environment and the energy flow is maintained indefinitely
• Heterotrophic succession : characterized by early dominance of heterotrophs such as
bacteria, fungi and animals
Stages Xerach Mesarch Hydrach
1 Dry rock /soil Moist but aerated Water
2 Lichens - Submerged water
3 Lichens and mosses - Semi Floating plants
4 Mosses and forbs Mostly annuals Floating plants/ emergents
5 Perennial forbs and grasses Perennial forbs/grasses Sedges and mat plants
6 Mixed herbaceous Mixed herbaceous Mixed herbaceous
7 Shrubs Shrubs Shrubs
8 Intolerant sps Intolerant sps Intolerant sps
9 Semi-tolerant trees Semi-tolerant trees Semi-tolerant trees
10 Tolerant trees Tolerant trees Tolerant trees
Primary Succession :
• The development of the biota in unoccupied sites without any catastrophic disturbances
• It is also termed as autogenic succession
• The displacement of one group of species by another results from the development within the
ecosystem itself by the development of the vegetation, soil and micro-climate of the site etc
• This process terminates after a long period or series of intermediate stage
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• It is the process of species colonization and replacement in which the environment is initially
or virtually free of life. That is the process starts with base rock or sand dunes or river delta or
glacier debris and it ends when the climax is reached. The sere involved in primary succession is
called pre-sere.
• Primary succession takes a very long time (more than thousands of years in case of climax
forest on bare rock).
Secondary succession :
• It is the process of change in primary succession that occurs after an ecosystem is disturbed but
not totally demolished.
• Succession following severe disturbance or removal of a pre-existing community are called
secondary succession
• In this situation, organic matter and some organisms from the original community will remain,
thus the successional process does not start from scratch.
• Consequently, secondary succession is more rapid than primary. It is seen in areas burned by
fire or cut by farmers for cultivation. The sere involved in secondary succession is called sub-
sere
Sere = The transitional series of community which develop during the process of
succession
The concept of climax :
• If the succession allowed to progress without any disturbances a stage is reached when no
more changes in vegetation structure and soil are seen. This is climax
• Climax is a stage when the final terminal community becomes more or less stabilized for a
longer period of time and it can maintain itself in the equilibrium or steady state with the climate
of that area
• At this stage the vegetation is in equilibrium with the environment and stays unchanged.
• Climax stage is mature, self maintaining, self re-producung and relatively permanent
•. The vegetation in the climax stage is tolerant to environment conditions imposed upon it.
The climax community is characterized by an equilibrium. It has wide diversity of species, a well
developed spatial structure, complex food chain and its living organisms is in steady state.
Climax : a final, mature, stable, self maintaining and self reproducing state of vegetational
development that culminates ( ends) plant succession on any given site.
In climax, the equilibrium exists between :
• Gross primary production and total respiration
• Energy captured from sunlight and energy released by decomposition
• Uptake of nutrients and the return of nutrients by litter fall
Characteristics of Climax
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•The vegetation is tolerant of environmental conditions.
•It has a wide diversity of species, a well-drained spatial structure, and complex food chains.
• The climax ecosystem is balanced. There is equilibrium between gross primary production and
total respiration, between energy used from sunlight and energy released by decomposition,
between uptake of nutrients from the soil and the return of nutrient by litterfall to the soil.
• Individuals in the climax stage are replaced by others of the same kind. Thus the species
composition maintains equilibrium.
• It is an index of the climate of the area. The life or growth forms indicate the climatic type.
Climax Theories : In the concept of climax, there are three different kinds of theoretical
approaches :
• Mono-climax theory : Developed by Frederick Clements. This theory says there is only
one climax solely determined by the climate, no matter how great the variety of
environmental conditions is at the start. In other word , vegetational climax is
determined by climate only , irrespective of other factors
• All seral communities in a given region if allowed sufficient time, would ultimately
converge to a single climax
• The whole landscape would be clothed with a uniform plant and animal community
• All other communities than the climax one are recognized as sub-climax, dis-climax, pre-
climax and post climax
Mono –climax theory : There is only one climax i.e climatic climax which is controlled or
determined by regional climate. This theory is not popular/possible as there are other
environment factors such as soil and topography, fire, animals etc that control the climax .
Ecologists have lots of criticisms in this theory
2. Poly-climax theory : Developed by Tansley. This theory says the climax vegetation of a
region consists of not just one type i.e climatic type but a mosaic of vegetational climaxes
controlled by soil moisture, soil nutrients, topography, slope exposures, fire and animal activities
• Each stable community at the climax stage is prefex as edaphic climax, topographic climax,
biotic climax and fire climax etc
For instances : grassland communities are often influenced by fire , grazing and other biotic
factors so are considered as biotic climax
3. Climax Pattern Theory : Developed by : Whittaker, Mac Intosh and Sellack.
This theory says , the composition, species structure and balance of climax community are
determined by the total environment of the ecosystem not only by climatic factor alone. The
pattern of climax vegetation will change as the physical environment factor change
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Types of Climax :
• Climatic climax: It is the climax which is developed or controlled by climatic factors or
climatic influences. Climate as the dominant community – forming factor. It is also recognized
the importance of soil, topography, relief and biotic factors as being additional dimensions to the
climatic factor which delayed the progress of vegetation to a climatic climax.
• Edaphic climax: A climax community ( differing from the climatic climax) of the area which
is formed due to the influence of soil factors such as chemical, physical and water content of soil.
Succession ends in an edaphic climax.
• Pre-climax : The plant community with more xerophytic vegetation than the general climax (
climatic climax) on drier condition or low moisture containing sites. Pre-climax vegetation is
found under conditions drier than the usual climate of the region.
• Post climax: A plant community with more mesophytic vegetation ( plants that grow in
neither too dry or too wet condition) on wetted condition or high moisture containing sites than
the general climax (climatic climax). It actually occurs on sites very much moister than the
normal sites in that climatic region.
• Biotic climax or sub-climax: A climax owing to the action of biotic factors which differs from
the general climax (climatic climax) of the area.
• Catastrophic Climax: Emergence of climax vegetation due to the effect of repeated
catastrophic event such as a wildfire.
• Dis-climax: When a stable community, which is not the climatic climax or edaphic climax for
the given site, is maintained by man or his domestic animals is designated as Dis-climax
(disturbance climax) or anthropogenic sub-climax (man-generated). For example, overgrazing by
stock may produce a desert community of bushes and cacti where the local climate actually
would allow grassland to maintain itself.
Retrogression : It means a return to simpler and less dense or even impoverished form of
community from an advanced or climax community.
• In most cases, the causes of retrogression are allogenic ( forces from outside the ecosystem
become severe and demanding. For example : most of our natural forest stands are degrading
into shrubs, savanna or desert like stands by the severity of grazing animals, excessive removal
of woods, leaf , biomass etc lead to retrogression
• Retrogressive succession occurs where a disturbance causes the climatic climax vegetation to
revert to a previous phase
• It results therefore in the replacement of a community of plants of higher ecological order with
a community of lower ecological order.
•This means that the community becomes increasingly simplistic with a lower biomass and a
fewer species
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•This may occur e.g. due to a change in climate. For example; increased frequency of drought
will cause a decrease in plant productivity and diversity – this would be likely to result in the
replacement of perennial species by annuals
• Overgrazing and a change in soil stability may also cause retrogression following vegetation
deterioration
• A retrogression may be temporary or permanent, depending on the extent of the disturbance.
Adaptations to a change in the environment may be short-term or long term.
–Short-term
•Physiological–ex. increased respiration at high altitudes.
•Morphological–ex. increased insulation (fur) in winter.
•Behavioral–ex. Hibernation
Adaptations cont‘d
–Long term adaptation involves evolution and natural selection. Ex. animals in cold
environments have decreased surface area compared with relatives in warm environments.
Herbivores have developed adaptations to deal with fluctuations in available food supplies:
–Put on extensive layers of fat during seasons of abundance.
–Some will migrate to where food is available.
–Others hibernate during seasons of hardship.
–Respond to seasons of scarcity by making do with foods of relatively low nutritional value.
Regulating (climate, floods, nutrient balance, water filtration)
Provisioning (food, medicine, fur, minerals)
Cultural (science, spiritual, ceremonial, recreation, aesthetic)
Supporting (nutrient cycling, photosynthesis, soil forma
tion)
Generally, aboveground volume production is calculated on stem wood volume for conifers, but
may include branch volume for broadleaved tree species. For many purposes, mean annual
increment (volume) is considered a suitable measure of site productivity.
Natural selection : the process by which forms of life having traits or characters that better
enable them to adapt to specific environmental pressures, as predators, changes in climate, or
competition for food or mates, will tend to survive and reproduce in greater numbers than others
of their kind, thus ensuring the perpetuation of those favorable traits or characters in succeeding
generations.
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Contents
1.Definition, Concept, Scope and Importance of Carbon
Sequestration
2. Methods of measurement of Carbon Sequestration
3.Basic concept of Kyoto Protocol (Carbon trade)
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Background
• How do we keep CO2 out of the atmosphere? - sequester it
What is Carbon Sequestration ?
The removal and storage of carbon from the atmosphere (that would otherwise be released
into the atmosphere) in carbon sinks (such as oceans, forests or soils) through physical or
biological processes, such as photosynthesis. (Source: Green Facts)
CS is a way of managing the amount of carbon dioxide (Co2) that is released into the
atmosphere by burning carbon-based fuels—predominantly carbon-rich petroleum fuels.
A relatively new idea brought about by the concern that high concentrations of atmospheric
C02 contribute to global warming.
CS is the general term used for the capture and long-term storage of carbon dioxide. Capture
can occur at the point of emission (e.g. from power plants) or through natural processes (such
as photosynthesis).
Understanding differently, CS is the process of increasing the carbon content of a reservoir
other than the atmosphere.
Climate Change
Adaptation Mitigation
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The process through which agricultural and forestry practices remove carbon dioxide (CO2) from
the atmosphere.
The term “sinks” is also used to describe agricultural and forestry lands that absorb CO2.
Ecosystems are important source and sinks of carbon
It is critical to define whether a system releases or absorb CO2 from atmosphere.
Through the photosynthesis green vegetation absorb CO2 from the atmosphere and store some
of this carbon in plant above and below ground biomass.
Decomposition of organic matter, respiration, disturbance such as fire release CO2 to
atmosphere as a source.
Why CS ?
• Reduce the level of atmospheric Co2 to the optimum level.
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• Prevent global climate change by enhancing carbon storage in trees and soils, preserving
existing tree and soil carbon, and by reducing emissions of green house gases.
• Environmental and social benefits for sustained livelihoods.
Type and methods of CS
There are three main methods in various states of discovery and development:
Near term storage in the terrestrial biosphere where vegetation would soak up the C02 and
store it in biomass and soil.
Long term storage in the earth’s soil by pumping CO2 into existing or drilled/excavated sub-
surface reservoirs.
Long term storage in the earth’s oceans where CO2 would be injected thousands of feet deep
and trapped by the water.
Sequestration methods include:
Enhancing the storage of carbon in soil (soil sequestration);
Enhancing the storage of carbon in forests and other vegetation (plant or Bio-sequestration);
Storing carbon in underground geological formations (geo-sequestration);
Storing carbon in the ocean (oceansequestration); and
Subjecting carbon to chemical reactions to form inorganic carbonates (mineral carbonation).
Nature of sequestration in terrestrial ecosystems
Various TEs such as forests, grasslands, agricultural systems and degraded land, have different
potential of carbon storage. For instance, forest ecosystems contain more carbon per unit area
than any other land types (accounting for 60% of total C in TEs) and their soils are of major
importance for CS (FAO 2001).
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However, CS rates vary depending on plant species, soil type, region, climate, topography and
management practices that can affect plant productivity (Lal 1999).
At a local scale, CS in TE is largely influenced by light conditions, water availability, soil water
holding capacity and its nutrient content.
Local conditions could modify the frequency and severity of natural risks such as forest fires,
strong winds etc., increasing the probability of CO2 emissions and hence carbon loss from these
systems (Heimann and Reichstein 2008).
TEs sequestered about 2.6 x109 g C per year of all atmospheric emissions during the period
2000-2007 representing net reductions of about 30% (according to 2006 levels) (GCP 2008).
They have the potential of eventually sequestrating about 2 Gt C/year under intensive
management and/or manipulation scenarios of a significant fraction of these systems (DOE
1999). Table 1 shows the different present stocks and net primary production (NPP) of various
terrestrial biomes.
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Rh (respiration by
microorganisms
Components of the terrestrial carbon cycle
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Terrestrial sequestration
Bio sequestration
– Global forest resource assessment report indicate that the total carbon content in the world forest
ecosystem
• biomass account 44%
• Soil carbon upto 30 cm depth include 46%
• Dead wood 6%
• Litter 4%
– Average estimated carbon stock in the nepalese forest is 203 ton/ha (including shrub land)
– Worlds’ average 161.1 ton/ha (FAO 2006)
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Scope of CS in various forms
Bio Sequestration
Terrestrial sequestration consists of storing CO2 in soils and vegetation near the earth’s surface.
Tree-plantings, no-till farming, wetlands restoration, land management on grasslands and
grazing lands, fire management efforts, and forest preservation.
More advanced research includes the development of fast-growing trees and grasses and
working out in the genomes of carbon-storing soil microbes.
The uptake of CO2 by vegetation will decrease with time as plants grow to their full capacity and
become limited by other resources such as nutrients, and regrowth potential in previously
cleared or sparsely vegetated areas is fulfilled.
Biological storage could be enhanced through agricultural and forestry practices and
revegetation, but the capacity is limited and longevity of storage depends on the final fate of the
timber or plant material. However, carbon sequestration from revegetation and plantation
programs could provide a significant shorter-term contribution to climate change mitigation.
Soil sequestration
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It is estimated that soils contain between 700 giga tonnes (Gt,109 tonnes) and 3000 Gt of
carbon, or more than three times the amount of carbon stored in the atmosphere as carbon
dioxide.
However, most agricultural soils have lost 50–70 per cent of the original soil organic carbon pool
that was present in the natural ecosystem prior to clearing and cultivation. When forests are
converted to agricultural land, the soil carbon content decreases.
Given the enormous carbon storage capacity of soils, it has been suggested that with
appropriate changes in management practices, they could represent a significant sink for
atmospheric CO2. Managing agricultural soils to increase their organic carbon content can also
improve soil health and productivity by adding essential nutrients and increasing their water-
holding capacity.
Oceanic Sequestration
Pumping CO2 into the deep ocean basins (350-3000 meters), where it is anticipated it may form
lakes of liquid, supercritical, or solid hydrates.
The thinking on this disposal scenario is that it would stabilize in the ocean depths, or slowly
dissolve into the ocean waters.
This option has been under study for several years, but there are many potential environmental
downsides to its implementation, and it is not a high priority research focus till this time.
Geo-sequestration
Geo-sequestration is the injection and storage of greenhouse gases underground, out of
contact with the atmosphere. The most suitable sites are deep geological formations, such as
depleted oil and natural gas fields, or deep natural reservoirs filled with saline water (saline
aquifers).
Geo-sequestration is part of the three-component scheme of carbon capture and storage (CCS),
which involves:
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capture of CO2 either before or after combustion of the fuel
transport of the captured CO2 to the site of storage, and
injection and storage of the CO2.
Research is continued. Not commonly practiced
Mineral sequestration
Mineral sequestration (otherwise known as mineral carbonation) involves reaction of CO2 with
metal oxides that are present in common, naturally occurring silicate rocks.
The process mimics natural weathering phenomena, and results in natural carbonate products
that are stable on a geological time scale.
There are sufficient reserves of magnesium and calcium silicate deposits to fix the CO2 that
could be produced from all fossil fuel resources.
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Though the weathering of CO2 into carbonates does not require energy, the natural reaction is
slow; hence as a storage option the process must be greatly accelerated through energy-
intensive preparation of the reactants.
The technology is still in the development stage and is not yet ready for implementation
Methods for carbon measurement and assessment
Measurement of carbon biomass
Different methods are used for measuring carbon in soil, water or atmosphere.
Conventional methods such as dry combustion
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Sophisticated methods such as laser-induced breakdown spectroscopy (LIBS) for rapid carbon
analysis
Methods used for measuring carbon in biomass include:
Non-destructive sampling for biomass (application of algometric or cylinder equations or
estimation tree root biomass from proximal root and algometric relations)
Destructive sampling of soil and vegetation (harvesting vegetation, taking samples of litter and
soil); and
Remote Sensing methods that assess carbon in vegetation but less useful to measure soil C
directly (unless bare)
Measurement of the Forest Carbon in Nepal (ANSAB, ICIMOD, FECOFUN)
1 Delineation of project boundaries
2 Stratification and boundary mapping of stratum
3 Pilot inventory for variance estimation
4 Capacity building and orientation of the locals
5 Field measurements in the permanent plots (AGB, BGB, soil, dead wood, herbs & litter)
6 Data analysis (calculation of carbon stock density)
7 Leakage analysis belt and monitoring
8 Report preparation
Source: Guidelines for measuring carbon stocks in community-managed forests
Carbon sequestration
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Kyoto Protocol
– It is an intergovernmental agreement to stabilize greenhouse gases in the atmosphere,
at a level that would prevent adverse changes to the climate.
– A protocol was outlined in Kyoto in 1997 which is popularly known as the Kyoto
Protocol.
– The developed countries with emission reduction targets are called the Annex 1
countries,
– whereas those without targets are known as non-Annex 1 countries.
– The Annex 1 countries can invest in JI (Joint Implementation)/CDM projects as well as
host JI projects, and non-Annex 1 countries can host CDM projects.
– The Kyoto Protocol negotiations were completed in late 1997.
– The protocol establishes legally binding, mandatory emissions reductions
for the six major greenhouse gases.
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– Carbon dioxide (C02)
– Methane (CH4)
– Nitrous oxide (N20)
– Hydrofluorocarbons (HFCs)
– Perfluorocarbons (PFCs)
– Sulphur hexafluoride (SF6)
– It requires that Annex I countries (listed again in Annex B of theProtocol)
reduce their aggregate greenhouse gas emissions by 5% below 1990 levels
Key Existing Kyoto Protocol Provisions
– Obligations of All Parties
– Emissions Reductions
• emissions of such gases by at least 5% below 1990 levels in the commitment period 2008 to
2012.”
• two of the most difficult issues unresolved in 1997 at Kyoto and still under discussion are
related to counting emissions of a nation,
• (1) emissions trading — specifically, how much of a country’s obligation to reduce emissions
can be met through purchasing credits from outside, vs. taking domestic action; and
• (2) the extent to which carbon sequestration by forests, soils and agricultural practices can
be counted toward a country’s emission reductions.
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Carbon or Emissions Trading
Carbon / Emissions Trade
A market proposed by the Kyoto Protocol in which each country participating receives a limit on
the carbon emissions.
Countries (and/or companies) may buy and sell the emissions limits assigned to them.
Carbon trade is intended to be an attempt to reduce overall carbon emissions while still allowing
companies that may have difficulty doing so to have an outlet for transition. It is also called
emissions trading.
Carbon sequestration