ENVS10001 Lecture Notes - Lecture 14: Intermediate Disturbance Hypothesis, Population Ecology, Biogeography
17 May 2018
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ECOSYSTEM PROCESSES
• Physics: drives most forces which influence landscapes + can be
used to determine age of landforms + rate of such processes
o Climate: physics of climatic patterns give rise to ordered
landscapes (air movement, wind strength, size of
particles)
• Evidence of humans in landscape = sharp transitions in vegetation
Biogeography
• Explain the spatial + temporal patterns of change in a landscape
• 3 fundamental processes:
o Evolution
o Dispersal – movement of organisms away from a point of
origin
o Extinction – process of species becoming permanently
eliminated from a specific area
" Classed as local, regional + complete extinctions
" Affects function of an environment ! all species in a
food chain have adaptations to the presence of a certain
species sharing a habitat ! processes disrupted when one
species removed
• In between these 3 phases are states of competition
o Co-existence leads to different patterns + levels of diversity
Environmental Gradients
• Gradients: changes in environmental parametres (temp, precipitation etc)
across landscapes
• Incline of the gradient is termed steep or shallow
• Populations respond to environmental gradients in constrained way
(respond well)
• Communities respond in a less consistent fashion ! due to competition
between populations + environmental constraints
• Distribution + abundance change along gradients
o Most of population exists in zone of optimal conditions
Diversity
• Alpha Diversity: FINISH
• Beta Diversity: FINISH
• Gamma Diversity: diversity of large regions
• On a global scale ! highest around tropics, impact of humans
+ continental influence due to geologic change
• Assumption that high productivity (measured in biomass) leads
to high diversity
o Anomalies: S. Africa + SW W.A
• Small-scale diversity
o Intermediate disturbances hypothesis
Ecosystems:
Communities: group of a
single species
Populations: usually
mixes of different species
Habitats:
Ecotones: boundaries
between ecosystems
Autecology: study of
individual species
Synecology: study of a
group of organisms
