2.6.5

2.6.5-.7 Succession

5/11/2013 Author -Guru IB/ESS 1

• Succession is usually described as the orderly

succession of communities to a climax

community (biome) over time or as a sequence

of communities (a sere) with each transitory

community as a seral stage.


• There are two main types of succession:

• 1. Primary succession which begins with bare rock exposed by geologic activity

• eg. sere: rock -> lichen -> moss -> grass -> shrub -> trees -> maple-beech -hemlock forest

• 2. Secondary succession which begins on soil from which a previous community has been removed (by fire, agriculture, etc.)


• Secondary succession can proceed much faster

because the soil has already been prepared by

the previous community


Differences between pioneer and

climax communities

Pioneer Community Climax Community

Unfavorable environment favorable environment

biomass increases quickly biomass is generally stable

energy consumption

inefficient

energy consumption

efficient

some nutrient loss Nutrient cycling and

recycling

r - strategists K - strategists

low species diversity, habitat

diversity, genetic diversity

high species diversity,

habitat diversity, genetic

diversity 5/11/2013 Author -Guru IB/ESS 5

• One thing that limits the carrying capacity, during

succession for many organisms, is that the presence

of these organisms (themselves) essentially alters the

environment (eg. shade, pH, moisture, temperature,

chemical composition) sufficiently so that it is no

longer suitable for their own offspring to continue.


• That is, the populations change the environment so

drastically, both biotically and abiotically that it is

now more suitable for other populations and less

suitable for itself.

• This leads to the succession of one sere after another

until a climax is reached and the changes in the

environment are now not so drastic as to produce any

further major changes.


Primary Succession


Succession in South Florida


the succession of a pond ecosystem to a meadow over

250 years.


The following charts summarize the

major trends as the ecosystem

undergoes succession.

Ecosystem

characteristic

Trends in ecological succession

Food chains Simple food chains becoming more complex food

webs

Relative

Species

abundance

Changes rapidly first, changes slower in the later

stages.

Total biomass Increasing

Humus (non-

living organic

matter)

Increasing

Species

diversity

Low diversity in the early stages, then increasing in

the intermediate stages and then stabilizing in the

final stages as an equilibrium is approached 5/11/2013 Author -Guru IB/ESS 11

Productivity

Ecosystem characteristic Trends in ecological

succession

Gross productivity (GP) Increasing during early

stages of primary

succession then little or no

increase during final stages

of secondary succession

Net productivity (NP) Decreasing

Respiration (R) Increasing


Mineral and Nutrient cycles

Ecosystem characteristic Trends in ecological succession

Mineral cycles Becomes more self-contained

in later stages

Nutrient recycling Increases in later stages


2.6.5

Technology