10 - Community Dynamics

Abstract

This chapter focuses on the temporal patterns in a community structure. As with population dynamics, the study of changes in a community structure requires long periods of observation. Few studies have continued over sufficiently long time periods to evaluate many of the factors presumed to affect a community structure. Temporal patterns of community organization and their sensitivity to environmental changes can indicate their stability to anthropogenic changes. A community structure changes on annual time scales as population sizes respond to environmental conditions. Changes in resource quality, competition, and predation lead to population irruptions of some species and local extinction of others, thereby affecting their interactions with other species and leading to changes in the community structure. Although most studies of succession have focused on plants, insects show succession patterns associated with changes in vegetation, and the relatively rapid heterotrophic succession in decomposing wood and animal carcasses has contributed a lot to successional theory. A number of factors influence successional pathways. Local substrate conditions can restrict initial colonists to those from the surrounding species pool that can become established on distinct substrates, such as serpentine, volcanic, or water-saturated soils. 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 the successive stages. Much of this discussion reflects different definitions of diversity and stability. Stability can be seen to have two major components: resistance to change and resilience following perturbation. Succession is the expression of resilience.