Disturbance and resilience in soil animal communities

I discuss basic ecological concepts on disturbance and resilience, and give examples from forest soils. There are basically three types of disturbances: (i) pulse disturbances that are parts of ecosystem dynamics and to which most organisms are adapted, (ii) large infrequent disturbances, and (iii) press disturbances, which are usually anthropogenic and to which organisms are seldom pre-adapted. Resilience has two meanings, engineering resilience and ecological resilience. Ecological resilience recognizes that ecosystems have several stability domains and no fixed global equilibria, It is often the most relevant in ecology, and is defined as the magnitude of disturbance that can be absorbed by an ecosystem before its structure and the processes controlling its behaviour change, and it moves into another stability domain. Diversity and heterogeneity are necessary for long-term ecological resilience. I propose that reorganization of soil communities usually takes a long time and involves dynamic interactions between many species. Single snapshots are insufficient to examine resilience. Small-scale studies and experiments are not necessarily relevant for large-scale landscape changes. Key questions deal with the ability of species to recolonize disturbed areas by dispersal, the survival of species and structures in disturbed areas, and how these processes contribute to ecological resilience. (C) 2002 Editions scientifiques et medicales Elsevier SAS. All rights reserved.