1. Community Disturbance

2. Nonequilibrium Model Early ecologists thought of nature as being in equilibrium. Actually, environments are constantly changing.

3. Examples: Floods, Fires, drought, storms, overgrazing and human activity

4. Frequent small scale disturbances sometimes prevent large scale disturbances Yellowstone 1988

5. Intermediate disturbance hypothesis __________________________________ ______________________

6. 2005-2006 Ecological Succession From bare soil, then… –____________ ______________ –____________ make soil { ______________________________

7. Ecological Succession Primary Succession: ___________________ ______________________________________

8. Secondary Succession: __________________ _______________________________________ Mount St. Helens 1980

9. 2005-2006 Climax forest  ___________________ The species mix of climax forest is dependent on the abiotic factors of the region birch, beech, maple, hemlock

10. A glacial retreat in southeastern Alaska

12. The Pattern of Succession on Moraines in Glacier Bay

13. Alders and cottonwoods covering the hillsides

14. Spruce coming into the alder and cottonwood forest Climax Community: old Growth Forest

15. Change in soil nitrogen concentration during succession after glacial retreat in Glacier Bay, Alaska

16. Cedar Creek Higher diversity communities are more __________________________________ ________from environmental stresses, such as droughts. Diverse communities are more __________________ From year to year. Diverse communities ________________ ________________