Community Ecology
I. Introduction
II. Multispecies Interactions with a Trophic Level
III. Multispecies Interactions across Trophic Levels
IV. Succession
A. Definitions
- succession: a change in community composition through time
Community Ecology
I. Introduction
II. Multispecies Interactions with a Trophic Level
III. Multispecies Interactions across Trophic Levels
IV. Succession
A. Definitions
- succession: a change in community composition through time
- sere: a particular stage or sequence
Community Ecology
I. Introduction
II. Multispecies Interactions with a Trophic Level
III. Multispecies Interactions across Trophic Levels
IV. Succession
A. Definitions
- succession: a change in community composition through time
- sere: a particular stage or sequence
- pioneer: first community
Community Ecology
I. Introduction
II. Multispecies Interactions with a Trophic Level
III. Multispecies Interactions across Trophic Levels
IV. Succession
A. Definitions
- succession: a change in community composition through time
- sere: a particular stage or sequence
- pioneer: first community
- climax: self-replacing community
B. Classifying Vegetative Communities
1. Focus on the Climax
Clements’ view of the climax as a
‘closed, mature, developmental
state,’ dependent solely on climate.
In North America, he recognized
only 9 climax community types:
2 grasslands (prairie, tundra)
3 scrub (sagebrush, desert,
chaparral)
9 forests
B. Classifying Vegetative Communities
1. Focus on the Climax
Curtis and McIntosh:
‘Continuum’ index
B. Classifying Vegetative Communities
1. Focus on the Climax
Whittaker’s view:
‘Dominance’ classification
Red oak
Sugar maple
B. Classifying Vegetative Communities
1. Focus on the Climax
2. Classification by Indicator Species
Braun-Blanquet method of
vegetative classification:
Based on whole floristic
surveys and the identification
of ‘indicator’ taxa – typically
neither dominants nor
extremely rare species.
440 vegetation types in South
Africa.
B. Classifying Vegetative Communities
1. Focus on the Climax
2. Classification by Indicator Species
Jennings, et al. 2009. Standards for associations and alliances of the U.S. National Vegetation Classification. Ecological
Monographs 79:173-199.
Community Ecology
I. Introduction
II. Multispecies Interactions with a Trophic Level
III. Multispecies Interactions across Trophic Levels
IV. Succession
A. Definitions
B. Classifying Vegetative Communities
C. Types of Succession
1. Primary succession: on previously unvegetated substrate or ‘devoid of life’
1. Primary succession: on previously unvegetated substrate or ‘devoid of life’
1. Primary succession: on previously unvegetated substrate or ‘devoid of life’
1. Primary succession: on previously unvegetated substrate or ‘devoid of life’
1. Primary succession: on previously unvegetated substrate or ‘devoid of life’
2. Secondary Succession: follows a disturbance (removes biomass)
3. Disturbance-mediated Succession
Fire, grazers, predators, etc.
3. Disturbance-mediated Succession
The effect of the disturbance depends on its intensity and size.
Small, low intensity disturbance:
One tree and a few plants
underneath die.
Small canopy gap is quickly filled
by neighboring trees in the
understory; recovery by
individual growth.
3. Disturbance-mediated Succession
The effect of the disturbance depends on its intensity and size.
Large, high intensity disturbance:
Entire canopy gone; many species
driven to local extinction.
Recovery by colonization.
These effects are really true of most successional seres, not just
disturbance-mediated succession.
4. Heterotrophic succession
4. Heterotrophic succession
Eberhardt, TL and DA Elliot. 2007.A preliminary investigation of
insect colonisation and succession on remains in New Zealand.
Forensic Science International 176:217-223.
4. Heterotrophic succession
no
yes
Community Ecology
I. Introduction
II. Multispecies Interactions with a Trophic Level
III. Multispecies Interactions across Trophic Levels
IV. Succession
A. Definitions
B. Classifying Vegetative Communities
C. Types of Succession
D. Mechanisms
- facilitation, tolerance, and inhibition
Facilitated:
early species change
environment and increase the
probability of successful
colonization by later species.
examples: colonization of bare
rock: lichens, moss, herbs;
colonization of carcasses:
beetles, flies, etc.
Effects of wildebeest
Aspen fix nitrogen that helps nitrogenlimited trees colonize
Tolerance:
Tolerance: early species have no
effect on later species. This
occurs if there is 'ecological
equivalence' among the species.
Many stages in later forest
succession seem dominated by
this mechanism.
Also, later species
tolerate early species... so shade
tolerant species come to
dominate because they tolerate
the shade of early species, but
inhibit those early species with
their own shade.
Inhibition:
Early species retard the
colonization success of later
species. If these effects vary
among early species, there can
be "priority effects". The
species that gets there first has
a differential and deterministic
effect on the subsequent
structure of the community.
Important where allelopathic
interactions occur. Bryozoans
block colonization of tunicates
and sponges.
Community Ecology
I. Introduction
II. Multispecies Interactions with a Trophic Level
III. Multispecies Interactions across Trophic Levels
IV. Succession
A. Definitions
B. Classifying Vegetative Communities
C. Types of Succession
D. Mechanisms
- facilitation, tolerance, and inhibition
E. Invasive Species
“Invasive species” are facilitated or tolerated by natives, and subsequently inhibit them.
Often they have escaped their predators or pathogens, and are ‘tolerated’ by native
predators/pathogens…thus escaping limitation and increasing to densities where they
compete with natives.
Here, field plants are affected by transplantation into a different mycorrhizal environment.
F. Modelling Succession: Tilman (1985)
A
A, B
B
Our old 2-species model with stable
coexistence possible.
F. Modelling Succession: Tilman (1985)
A
A, B
B
If resource supply rates are negatively
correlated, then the community may succeed
from A to A-B coexistence to B as
concentrations change
F. Modelling Succession: Tilman (1985)
A
A, B
B
B, C
C
...and then to B,C and C.... and etc....
F. Modelling Succession: Tilman (1985)
A
A, B
B
B, C
C
...and then to B,C and C.... and etc....
C, D
D
Community Ecology
I. Introduction
II. Multispecies Interactions with a Trophic Level
III. Multispecies Interactions across Trophic Levels
IV. Succession
A. Definitions
B. Classifying Vegetative Communities
C. Types of Succession
D. Mechanisms
- facilitation, tolerance, and inhibition
E. Invasive Species
F. Modelling Succession
G. Characteristics of Plants through Succession
Community Ecology
I. Introduction
II. Multispecies Interactions with a Trophic Level
III. Multispecies Interactions across Trophic Levels
IV. Succession
A. Definitions
B. Types
C. Mechanisms
D. Model – Tilman 1985
E. Community Patterns
E. Community Patterns
(From Morin, 1998)
Variable
Early
Late
Organism Size
small
large
life history
r
K
Biomass
low
high
Richness, Diversity
low
high
Structural complexity
low
high
Niches
broad
narrow
Nutrient cycles
open
closed
Stability
low
high
trophic relationships
linear
web-like
connectance
low
high