Succession and Stability

Introduction Succession: Gradual change in plant and animal communities in an area following disturbance. Primary succession on newly exposed geological substrates. Secondary succession following disturbance that does not destroy soil. Climax Community: Late successional community that remains stable until disrupted by disturbance.

Primary Succession at Glacier Bay Reiners et.al. studied changes in plant diversity during succession. Total number of plant species increased with plot age. Species richness increased rapidly in early years of succession and more slowly during later stages.

Primary Succession at Glacier Bay

Model of Ecosystem Recovery Biomass Accumulation Model Reorganization (10-20 yrs) Forest loses biomass and nutrients. Aggradation (100+ yrs) Ecosystem reaches peak biomass. Transition Biomass declines from peak. Steady-State Biomass fluctuates around mean.

Community and Ecosystem Stability Stability: Absence of change. Resistance: Ability to maintain structure and function in face of potential disturbance. Resilience: Ability to recover from disturbance.

Humboldt hiked up Mt. Chimborazo to an elevation of 5878m. Are populations organized into discrete communities? Humboldt hiked up Mt. Chimborazo to an elevation of 5878m. He recorded vegetation along the elevational gradient. What order? * Ferns and palms * Grass and lichens * Oak forest * Broad-leaved herbaceous plants * Evergreen shrubs http://soulchaser.blogspirit.com/images/medium_pdr_0249.jpg

Are populations organized into discrete communities? Clements and others (ex. Kuchler map) felt communities were essentially superorganisms

Clements idea of distribution Are populations organized into discrete communities? Clements idea of distribution

Are populations organized into discrete communities? Gleason argued for subtle transitions as opposed to sharp boundaries. He suggested a continuum.