Controls on soil biodiversity: insights from extreme environments

Research in low biodiversity extreme environments allows separation of the climatic, soil and biological interactions that determine soil biodiversity and community structure. Studies focused on the response of low diversity communities in soils of the Antarctic Dry Valleys and the Chihuahuan Desert of the southwestern USA, to manipulations of soil resources and climate, o ffer the best opportunity to learn about the environmental controls on soil biodiversity and the role of biodiversity in soil functioning. We propose that insights based on research in these extreme environments should be app licable to understanding soil biodiversity in more complex, temperate and t ropical ecosystems. The study of extreme soil ecosystems may also provide i nformation on the response of soil biodiversity to increasing occurrences o f environmental extremes that are predicted to occur from global change mod els. Studies from hot and cold deserts show that decomposition-based food w ebs can be very simple, that aridity produces similar mechanisms for surviv al and dispersal of organisms in temperate and polar systems, that suitable soil habitats are patchily distributed in arid environments, and the low b iodiversity of extreme soil ecosystems creates little or no functional redu ndancy making these systems susceptible to disturbance. We suggest that spe cies within the same functional group can have small differences in ecology that are sufficient to affect ecosystem processes. When this occurs, diffe rential responses of species to disturbance within a functional group will not stabilise the soil ecosystem, but rather lead to dramatic changes in co mmunity composition and ecosystem process rates. 1999 Elsevier Science B.V. All rights reserved.