Introduction to GeographyPeople, Places, and Environment, 4eEdward F. BergmanWilliam H. Renwick

Chapter 4: Biogeochemical Cycles and the Biosphere

Victoria Alapo, Instructor

Geog 1010

Biogeochemical Cycles

Pathways by which energy & matter are transformed & recycled in Earth systems. See Fig. 4-1, pg 133 (next slide).

In the Atmosphere, hydrosphere, lithosphere e.g. water cycle.

Law of conservation of energy and matter – “matter cannot be destroyed or created under ordinary conditions, but it may be changed from one form to another”.

Two important biogeochemical cycles Hydrologic cycle Carbon cycle

Hydrologic Cycle

Flows (cycles) of water among land (lithosphere), sea (hydrosphere) and air (atmosphere). See next slide, but use the simpler version for exam.

Water changes between 3 states, but the amount remains constant. Gas Solid Liquid

All living things are primarily water

Water Storage and Sources on Earth

Water Budget An accounting of inflows and outflows of water

within a given system over some time period.

Evapotranspiration Sum of evaporation and transpiration Seasonal variation

Low in winter High in summer

Local water budgets Compares precipitation and evapotranspiration

Vegetation and Hydrologic Cycle

Trees and forests require large amounts of water. E.g. one tree in the Amazon can transpire an average of 1000 liters per day into the atmosphere!

Therefore, trees play key role in returning rainwater to the atmosphere So deforestation affects water balance of

regions. Ex. Amazon, and other parts of the world.

The Carbon Cycle

Processes that cycle carbon and oxygen between the environment and living things (next slide). Photosynthesis

Determined by climate/ more in summer Respiration

Opposite reaction of photosynthesis (Oxygen is used) Combustion

Coal, oil, natural gas Industrial Revolution

The lithosphere stores carbon (from 1000s of years e.g. coal).

Soil

Is a dynamic, porous layer of mineral and organic matter

Six principal components of soil Rocks and rock particles Humus Dissolved substances Organisms Water from rainfall Air

Soil Formation

Weathering The first step in soil formation Mechanical and chemical

Soil horizons (next slide) Layers of substances found in soils Formed through vertical movement of water,

minerals and organic matter

Soil Horizons

Types of Soils

Soil orders 11 orders (next slide)

47 suborders 230 great groups 1,200 subgroups 6,000 families Thousands of soil series There’s nothing simple about “ordinary dirt”!

USDA Natural Resource Conservation Service maps (soils maps used in Planning Commissions & by farmers).

Ecosystem

Includes all living organisms and the physical area in which they exist

Fundamental elements Producers Consumers Decomposers Material/energy needed for production

Food Chains

Food that plants produce are distributed via a food chain (distribution)

Trophic level – each step in the food chain.

Biomagnification – e.g. when persistent chemicals remain in animal tissues and magnifies as it goes up the food chain. As in the case of humans, lions, etc.

Food Chains

These 3 are all “consumers” (i.e. they’re just types of consumers):

Herbivores Carnivores Omnivores

What category does a “Venus fly trap” fall in???

Community Succession Sequence – how comm. succession happens Succession – each plant community is succeeded

by a new one until… Climax community – when the community or

environment becomes stable

Biomes Named for dominant vegetation/climate

Major Biomes

Forest Tropical & temperate rainforest (based on location). Boreal – needle leaf/coniferous evergreen found closer

to poles e.g. Alaska & Canada. Called Taiga in Russia. Savannah – Woodland & Scrubland

Location of the Serengeti National Park (“Safari”) found in Tanzania & Kenya – also a world heritage site.

Grassland – Prairies Desert Tundra

Human & Natural Effects on the Environment

Humans influence ecosystems 37% of land area = cropland or pasture

(see next slide) Desertification – when a previously non-

desert area becomes one over time. E.g. fringes of the Sahara, etc. See further slide. This could be due to misuse by humans or because of global warming.

Desertification Hazard

The most severe desertification hazards are in northern Africa, central Australia, and the southwestern parts of Africa, Asia, North America,

and South America (the fringes of the major deserts of the world).