Download 2.6.5-.7 Succession

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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.
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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
Pioneer Community
Climax Community
Unfavorable environment
favorable environment
biomass increases quickly
biomass is generally stable
energy consumption
inefficient
some nutrient loss
energy consumption
efficient
Nutrient cycling and
recycling
K - strategists
r - strategists
low species diversity, habitat high species diversity,
diversity, genetic diversity
habitat diversity, genetic
diversity
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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.
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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.
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- Increasing
living organic
matter)
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
Ecosystem characteristic
Trends
in
succession
ecological
Gross productivity (GP)
Net productivity (NP)
Increasing
during
early
stages
of
primary
succession then little or no
increase during final stages
of secondary succession
Decreasing
Respiration (R)
Increasing
Ecosystem characteristic
Trends in ecological succession
Mineral cycles
Becomes more self-contained
in later stages
Nutrient recycling
Increases in later stages