Evolution of Diversity, Efficiency, and Community Stability

The response in species diversity associated with successional change in vegetation, or in a more general sense, species diversity as a function of time in any system of primary producers, has been the subject of much speculation but little direct study. All evidence available shows that pioneer communities are low in diversity, that in mesic environments the peak in diversity in forest communities can be expected 100-200 years after the initiation of a secondary successional sequence (when elements of both the pioneer and the stable communities are present), and that a downturn in both diversity and primary production takes place when the entire community is made up of the shade-tolerant climax species.