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Disturbance and Succession
Henry C. Cowles (center)
about 1920
Successional Species Types
Early successional,
pioneer,
opportunist
Late successional
long, good
short, poor
growth rate
fast
slow
reach maturity
early
late
number of
offspring
high
low
competitive ability
low
high
seed dispersal
distance
The Kabetogama Peninsula
Kabetogama Peninsula
Beaver – Castor Canadensis
Beaver
Dam
Pond and Bog Succession
Climax Community
Many Communities Experience
Constant Disturbance or Change
Fir Wave on Mt. Coe,
Baxter State Park, Maine
Fir Wave Up Close
Global Patterns of Species Richness
Global Amphibian Diversity
Measures of Biodiversity
• Species richness – the number of species in
an area – the simplest measure of
biodiversity
• Species evenness or equitability – the
relative proportion of number of individuals
of each species in an area
• Often richness and evenness are combined
into a Species Diversity Index
A comparison of species diversity in two communities
A
B
C
D
A: 25%
Community 1
B: 25%
C: 25%
D: 25%
A: 80%
Community 2
B: 5%
C: 5%
D: 10%
Animated Life of A.R. Wallace
• http://www.nytimes.com/video/opinion/100
000002534565/the-animated-life-of-a-rwallace.html
Explanations for Global Patterns of
Species Richness
1) Morphological diversity, spatial heterogeneity
2) High average rarity - no monocultures – in tropics
3) Climatic constancy of tropics
4) Geological age
5) Special adaptations in extreme (harsh) environments
6) Competitive "balance"
7) Alternating competitive advantages
8) "All niches filled theory" - saturation of community
9) Productivity
from A.R. Wallace - 1878
Richness and
Productivity
Richness and
Structural Diversity
Environmental harshness
Richness and Climatic Variability
Richness and Environmental Age
South American Rain Forest – Today and Past Refuges
Richness and High Average Rarity
Global Plant
Richness
Local Centers
Of Diversity
Quality of
Data
Richness and High Average Rarity
Endemic Plant Species Globally
Richness and High Average Rarity
Endemic Plants in Africa