Community Ecology Part 2 AP Biology Community Ecology Part 2

Disturbance and harmful effects With Pisaster (control) 20 15 Number of species present Without Pisaster (experimental) 10 5 1963 ’64 ’65 ’66 ’67 ’68 ’69 ’70 ’71 ’72 ’73

Disturbance (Beaver Dams)

Fire and Disturbance Before a controlled burn. A prairie that has not burned for several years has a high propor-tion of detritus (dead grass). During the burn. The detritus serves as fuel for fires. After the burn. Approximately one month after the controlled burn, virtually all of the biomass in this prairie is living.

Stages of Succession Pioneer stage, with fireweed dominant Dryas stage 60 50 40 Soil nitrogen (g/m2) 30 20 10 Pioneer Dryas Alder Spruce Successional stage Spruce stage Nitrogen fixation by Dryas and alder increases the soil nitrogen content.

Succession (Mount St. Helens, WA)

Primary Succession (Remember Hawaii?)

Primary Succession (Pioneer species)

Primary Succession

Primary succession

Primary Succession Climax Community (Hawaii today)

Secondary succession (Forest fire destroys the forest)

Secondary Succession (Then over time…life returns)

Richness vs. Abundance

Richness and land area size

Richness and Land area

Equitorial Gradients and Species

E.O Wilson A Native Alabamian

Richness and Islands

Pygmy Elephant of Indonesian Islands