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