11/3/2010
Geography 1001:
Climate & Vegetation
Limiting Factors &
Microenvironment
Dr. Barnard
Physiognomy
Life Zones &
Plant Life Forms
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Raunkiaer life forms
(based on perennating bud)
Biotic Ecosystem Operations
(Function)
• Producers, Consumers, and Decomposers
– autotrophs and heterotrophs
• Examples of Food Chains and (Complex) Food
Webs
• Efficiency in a Food Web
Equilibrium, Stability & Diversity
• Stable conditions
– hard to change its
conditions
– When changed, may return
back to original stable
conditions
• Unstable conditions
– Easy to change its
conditions
– When changed, may never
return back to original
stable conditions
Equilibrium, Stability & Diversity
• Stability
– Inertia stability and resilience
– Disturbances
• A discrete & stochastic event that disrupt (any)
part(s) or (any) component(s) of a biotic community.
• Chronic disturbances
– A large changes in ecosystem processes in response to a
continuous & directional variation in the environment.
• Neutral intermediate
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Stochastic & Chronic Disturbances
Number of species
Low---------------------------High
Species-Area Curves
Small------------------------------------------------Large
Size of area
Number of species
Low---------------------------High
Number of species
Low---------------------------High
Latitudinal gradients
0-------------------------------------------------------90
Latitude
Intermediate disturbance
hypothesis
Low---------------------------------------------------High
Disturbance
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Ecological Succession
What is ecological succession?
• Ecological Succession
– Primary and Secondary succession
– Ecological Succession
• Terrestrial succession
• Aquatic Succession
Photo: D. Kulakowski
Photo: A. Holz
Primary Succession
Why does ecological succession
occur?
Photo: A. Holz
Figure 19.25
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Mount St. Helens
Mount St. Helens
Mount St. Helens
Mount St. Helens
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Secondary succession
Mount St. Helens
Photo: A. Holz
Figure 19.27
Ecological Succession
Aquatic Succession
– Forest development (4 stages)
What about Beavers?
•
•
•
•
Stand initiation
Stem exclusion
Understory re-initiation
Old growth
– Gap phase dynamics
– Continuous regeneration mode
– Early vs. Late stages of
succession characteristics
Figure 19.30
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Forest development of whole stands
Stand initiation
Photo: A. Holz
Stem exclusion
Photo: D. Kulakowski
Understory reinitiation
Photo: D. Kulakowski
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Old growth
Forest development &
regeneration modes at fine-scale
• Gap phase dynamics
– Tree regeneration is dependent on canopy
openings created by the death of the former
canopy occupants (e.g. canopy opening
diameters of c. 4 m to 40 m). E.g. New England
forest, Tropical Rain Forests, etc.
Photo: A. Holz
Forest development &
regeneration modes at fine-scale
• Continuous regeneration mode (more rare)
– Shade tolerant species can complete their life
cycle beneath a relatively closed forest canopy.
E.g. Tropical Rain Forests, some Aspen stands.
Early vs. Late stages of succession
• Attributes
• Characteristics
Photo: A. Holz
Photo: A. Holz
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Early Stages of
Succession
Late Stages of
Succession
Plant Biomass
Small
Large
Plant Longevity
Short
Long
Well dispersed
Poorly dispersed
Low
High
Litter and Soil
Living Biomass
and Litter
Role of Decomposers in Cycling
Nutrients to Plants
Minor
Great
Rate of Net Primary Productivity
High
Low
Plant Species Diversity
Low
High
Attribute
Seed Dispersal Characteristics of
Dominant Plants
Photosynthetic Efficiency of Dominant
Plants at Low Light
Site of Nutrient Storage
Take home messages
• Ecosystems are dynamic and change is to
be expected
Does ecological succession ever stop?
Terrestrial Biomes
• Biogeographic Realms
• Earth’s Major Terrestrial Biomes
• Long intervals between disturbances
results in a broad range of natural
conditions
• There is no single snapshot that can
describe how a healthy ecosystem should
look
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Biogeographic Realms
Biogeographic Realms
• Transition Zones
• Terrestrial Ecosystems
Figure 20.1
Earth’s Major Terrestrial Biomes
•
•
•
•
•
•
•
•
•
•
•
Equatorial and Tropical Rain Forest
Deforestation of the Tropics
Tropical Seasonal Forest and Scrub
Tropical Savanna
Midlatitude Broadleaf and Mixed
Forest
Needleleaf Forest and Montane Forest
Temperate Rain Forest
Mediterranean Shrubland
Midlatitude Grasslands
Deserts
Arctic and Alpine Tundra
Major Terrestrial Biomes
Figure 20.4
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Rainforest Canopy
Rainforest
Canopy
Figure 20.5
Amazonian Rain Forest
Figure 20.5
Buttressed Trees and Lianas
Figure 20.6
Figure 20.6
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Deforestation of the Tropics
Figure 20.7
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