Ecological Communities

1. Communities (like populations) series of attributes

Biodiversity – species richness (controls?)

Growth form & structure – trees, shrub, grasses etc. 3-D aspect

Relative abundance – Relative proportions of different species

Trophic structure – Who eats whom?

2. Communities different “states”

Successional – changing over time

“Climax” – quasi steady state

3. Successional – changing over time

Primary Succession

Example: Mount St. Helens sw WA May 18, 1980

Primary succession slow

Erosion

Low-nutrient soils

Chronic drought stress

Limited dispersal

>100 yrs vegetation climax

4. Succession Models: 4 Major Hypothesis of Succession

5. Biodiversity – Dominates in tropics in contrast to temperate/polar

Example: Terrestrial Geographic pattern biodiversity land birds

Example: Aquatic (marine) copepods Pacific to Arctic Ocean

-Some location N-S gradient nonexistent – Central Australia

Australian carnivorous marsupials highest arid zone

-Latitude dominant factor influencing biodiversity patterns globally

Mammals of the Americas Similar gradients N & S America

6. Factors Hypothesized influence Biodiversity

7. Intermediate Disturbance Hypothesis

8. Trophic Structure-Community Organization

9. Antarctic Food web – Trophic levels (food chains length interactions)

10. More terms

Guild=functional role group species

Keystone spp.=imp. func. role 1 spp.

            Dominant spp = most abundant