geography of communities. communities community as a superorganism (clement) – highly integrated...
TRANSCRIPT
Geography of Communities
Communities
• Community as a superorganism (Clement) – highly integrated system
• Gleason – groups of species that happen to be at same place and time
• Either way, there is organization, even predictability
Community Organization: Energetics
• Body mass (size) and trophic status• Basal metabolic rate (m) – energy uptake
and metabolism of animals at restm = cM0.75
Where c = taxonomic-specific constant M = body mass
Larger animal requires more total energy BUT less energy per unit of mass (0.75) than small animal
Can also be applied to plants
Implications of Body Size
• Larger body size = storage potential• Size influences size of environment needed• Patchiness greater at smaller spatial scales
= finer divisions of environment by smaller organisms (explaining why so many tiny species despit advantages of large body)
• Large animals contrained to large geographic range
• Low carrying capacity
Relationship between range and body mass
Community Organization: Energetics
• Energy flow ---- Food chains/webs
• Laws of thermodynamics place limit on complexity of community
• Productive-ecosystem-hypothesis
Communities in Space and Time: Transitions
• Ecotones – transitional areas between habitats
• Coenocline – a gradient of communities through transition in abiotic conditions or habitat
Discrete Communities
Not comm. somespecies replace
GradualReplacement
Indep. sp.No abruptreplacement
Nested,segregated
Hypothetical Coenoclines
Communities in Space and Time: Transitions
• Are community changes causal or independent?
• Whittaker – examined mountain communities• Found evidence of independence (no abrupt
changes)
Communities in Space and Time: Transitions
Yeaton and pine distribution
Communities in Space and Time: Succession
• Sequential changes in community composition over time
• Implications – changes in community composition from– Differences in life history strategies (r vs. K)– Unintentional engineering– Competition
• Clementsian view• Gleasonian view
Terrestrial Biomes
Biogeographic Units
Climatic Regions
Net PrimaryProductivity
Ecosystem Geography
• Examines how processes of production, energy flow, and nutrient cycling influence distribution of ecosystems
• Basis for development of ecoregions