Chapter 10 - Community Dynamics

Abstract

Community structure changes over a range of timescales, from annual to decadal to millennial time periods. Community structure changes over short time periods as population sizes respond to seasonal and annual variation in environmental conditions. Changes in resource quality, competition, and predation lead to population irruptions of some species and local extinction of others. Ecological succession is the sequential stages of community development on newly exposed or disturbed sites. Although most studies of succession have focused on plants, insects show successional patterns associated with changes in vegetation, and the relatively rapid heterotrophic succession in decomposing wood and animal carcasses has contributed much to successional theory. A number of factors influence successional pathways, including the composition of the initial community that can affect the success of subsequent colonists. Several models of succession have augmented the early model of succession as a process of facilitated community development, in which earlier stages create conditions more conducive to successive stages. In some cases succession may advance only as a result of plant injury or death from subsequent disturbances or animal activity. Paleoecological research provides evidence of community changes over geologic time periods. Recent research has provided important evidence for the evolution of species interactions, including insect vectoring of vertebrate diseases. The relationship between species or functional diversity and community or ecosystem stability has been highly controversial. Much of the discussion reflects different definitions of diversity and stability. Although a particular site may not recover to its predisturbance community structure, the distribution of metacommunities on the landscape may represent a stable regional distribution of species and communities.