Transcript Geography 1001: Climate & Vegetation

Geography 1001:
Climate & Vegetation
Instructor: Andrés Holz
Teaching Assistant:
Eungul Lee
Lecture 12: Wednesday June 28
• Review lecture 11
– Chapter 20
• Tundra: Properties
– Arctic vs. Alpine Tundra
– Chapter 19
• Basic terms
– Ecology & Biogeography
– Ecologies of
» Individual
» Population
» Community definition &
characteristics
» Habitat & niche
– Role of scale
Lecture 12: Wednesday June 28
• Review lecture 11
• Ecosystem Components
–
–
–
–
–
Plants essential component
NPP
Abiotic & Biotic components
Life zones
Limiting factors
• Biotic Ecosystem Operations
– Producers, Consumers, and
Decomposers
– Food Chains and (Complex) Food
Webs
» Biomass consumption & Efficiency
» Toxins accumulations
Lecture 12: Wednesday June 28
• Lecture 12
– Chapter 19
• Ecosystems and Succession
– Ecosystem Stability, Dynamics, and
Diversity
– Community Ecology & Ecological
Succession
» Historical views of a community
» Conceptual issues
» Clements versus Gleason
• Changes of a community
– Initial Floristic Composition versus
Relay Floristics
• Primary and Secondary succession
Lecture 12: Wednesday June 28
• Lecture 12
– Chapter 19
• Ecosystems and Succession
– Vegetation dynamics & Scale
– Patch dynamics– role of
disturbances (Historical
shift…“catastrophic” versus normal
process; e.g. fires, floods, etc…)
– “Climax” concept
– Vegetation dynamics
» Terrestrial Succession
Ecosystem Stability, Dynamics, and
Diversity
Stability
– Inertia stability and resilience
• resistance of an ecosystem to
change
• ability of an ecosystem to return
to normal after a disturbance
– What increases the stability of
an ecosystem?
• Diversity
• Dynamics
• Growth interaction reduction
factors
Ecosystem Stability, Dynamics, and
Diversity
• Diversity
– (Bio) Diversity =
richness*abundance*genes*habitat diversity
• Dynamics (dynamic balance)
– Biotic & abiotic factors enhancing growth
– Disturbances & its regime
• Size, frequency, intensity, severity, etc…
Population Controlling Factors
Growth interaction Reduction factors
Figure 19.21
Ecosystem Stability, Dynamics, and
Diversity
– (Dynamic) equilibrium, and non-equilibrium
• Various aspects of the ecosystem change from day
to day, season to season, and year to year
• Changes are within limits and are usually small
• Only mature ecosystems are stable and in
dynamic equilibrium
• Mature ecosystems have resilience and inertia
Ecosystem Stability and Diversity
• The more diverse a community, the more
or less stable the community?
• The more stable a community, the
higher/lower its inertia & resilience?
• The higher the species diversity the
greater the inertia and resilience of the
ecosystem is.
Agricultural Ecosystems
Increase or decrease the resilience and general stability?
At the short-term? At the mid- & long-term?
Figure 19.23
Community Ecology &
Ecological Succession
• Historical views of a community
– Conceptual issues
• Clements versus Gleason
• Changes of a community
– Initial Floristic Composition versus Relay Floristics
• Primary and Secondary succession
• Vegetation dynamics & Scale
• Patch dynamics– role of disturbances (Historical
shift…“catastrophic” versus normal process; e.g. fires, floods, etc…)
• “Climax” concept
• Conceptual Issues
– What is a community (Clements v Gleason)
• Individualistic responses versus super-organism
Community as super-organism (Clements)
Comm. A
B
C
UP
DOWN
any environmental gradient
• Conceptual Issues
– Community integrity (Clements v Gleason)
• Individualistic responses versus super-organism
INDIVIDUALISTIC RESPONSES (Gleason)
UP
DOWN
any environmental gradient
Community change: concepts
Initial Floristic Composition
Relay Floristics
Comm. A
B
C
Late
Early
Time
Community change: concepts
Initial Floristic Composition
Relay Floristics
Early
The idea is that all species enter early on, but
dominate at different points along the way
Ecological Succession
Figure 19.26
Ecological Succession
• Def.: Succession refers to a directional change
in species composition across space and
time,
• which usually include a change in spatial
structure
– (e.g. spruce fir regeneration within a lodgepole pine
forest)
– Primary
– Secondary
Mount St. Helens
Mount St. Helens
Mount St. Helens: primary
or secondary succession?
Forest fires: primary or secondary?
Figure 19.27
Other examples of primary &
secondary succession?
Other examples of primary &
secondary succession?
Vegetation dynamics & Scale: a brief
review of the basic concepts of forest
dynamics
• Vegetation dynamics
– Is less deterministic than succession Patch
dynamics  “Shifting Mosaic”
– includes succession and
regeneration/maintenance dynamics
Vegetation dynamics concepts
• Regeneration/maintenance dynamics refers
to:
– a spatio-temporal change in structure
– keeping the species composition constant (e.g.
spruce fir regeneration within a spruce fir forest)
Vegetation dynamics concepts
• The dynamic part of the concept is
emphasized by frequent occurrence of
disturbances, which interrupt the
successional pathway to a dynamic
endpoint, and promote spatial
heterogeneity
The role of disturbances
across scales
• Spatial heterogeneity: At a stand scale
The role of disturbances
across scales
• Spatial heterogeneity: At a landscape scale  patch
dynamics & the “shifting mosaic”
Patch Dynamics
“Shifting Mosaic”
Climax concept
– Largely viewed as a
dead concept (but
still in many books!)
– Communities rarely
reach a predetermined
“equilibrium”
– Disturbances promote
a constant change,
and heterogeneous
environment