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Succession
Changes in Communities
What is Succession? The orderly process of change over
time in a community. Occurs both on land and water
Primary Succession Succession in a newly formed area Occurs in new lakes, ponds, cooled
lava, sand dunes and bare rock Takes place in areas that have never
previously supported life Ex - rock -> lichen -> moss -> grass ->
shrub -> trees -> oak hickory forest
Secondary Succession Sometimes an storms or fire destroy
the species growing in a community. Succession resumes again until there
is a climax community. Succession that occurs where an area
has been disturbed. Ex - grass -> shrub -> trees -> oak
hickory forest
Secondary Succession Human activities usually cause secondary
succession.– Cutting for timber– Clearing for farming– Construction
Some Natural Causes– Forest fires– Volcanoes– Hurricanes– Tornados
Stages of Succession
1. Pioneer Community– First inhabitants of the area– r-strategists– Ex. Lichen and mosses
Sere A set of communities that succeed one
another over the course of succession at a given location
Succession from start to finish
Stage of Successsion2. Seral Stages – stages at which species
are replaced through competition Ex – grasses, small herbs, shrubs, coniferous
trees
3. Climax Community – final stage of succession.
Ecosystem has stopped changing Reached a state of permanence
Climax Community High stability High species diversity Complex food chains K-strategists Ex. oak - hickory trees
To sum up During succession species modify the
environment making it more suitable for new species
Pioneer species are often poor competitors and are replaced by stronger competitors with greater environmental demand
Later communities are more complex than the communities they replace.
Animated link
Zonation The sub-classification of biomes into
smaller zones that share unique physical characteristics.
A unique habitat that will favor various species will in turn exist in these zones.
Comparison of Structure of Early and Late Succession
Immature Ecosystem
1. Small plant size2. Low species diversity3. Mostly producers, few
decomposers4. Few ecological niches
(generalized)5. Low community
organization
Mature Ecosystem
1. Large plant size2. High species diversity3. Mixture of producers,
consumers and decomposers
4. Many ecological niches (specialized)
5. High community organization
Comparison of Function of Early and Late Succession
Immature Ecosystem
1. Low biomass2. High primary productivity3. Simple food chains and
webs (mostly plants herbivore with few decomposers
4. Low efficiency of nutrient recycling
5. Low efficiency of energy use
Mature Ecosystem1. High biomass2. Low primary
productivity3. Complex food chains
and webs (dominated by decomposers)
4. High efficiency of nutrient recycling
5. High efficiency of energy use