Sensitivity of soil processes in northern forest soils: are management practices a threat? H. Seta Èla È a,* , J. Haimi a , A. Siira-Pietika Èinen b a Department of Biological and Environmental Science, University of Jyva Èskyla È, P.O. Box 35, FIN-40351, Jyva Èskyla È, Finland b Finnish Forest Research Institute, P.O. Box 18, FIN-01301, Vantaa, Finland Accepted 6 October 1999 Abstract There is evidence that forest management practices in¯uence soil-decomposer communities. It is also established that changes in the trophic structure and composition of these communities can induce changes in soil-nutrient dynamics, thereby affecting plant growth. Whether forest productivity is affected by management-induced changes in, e.g. soil faunal structure, is, however, yet to be shown. The aim of this study was (1) to determine the resolution of the ecological hierarchy (e.g. species, functional groups, trophic levels) at which a change in soil fauna would alter biotically-controlled processes in soils, and (2) to examine the sensitivity of soil fauna of the boreal forest ¯oor to various kinds of forest management practices. A review of laboratory miniecosystem experiments carried out at the University of Jyva Èskyla È is presented to examine the diversity-ecosystem function relationship. The response of tree growth to manipulation of soil-faunal composition was measured. A ®eld experiment was conducted in central Finland in spruce stands, including several stand management treatments in addition to the untreated controls. The fellings took place in winter 1996, and various groups of soil animals have been sampled since 1995. Laboratory experiments revealed that soil processes and plant growth are largely insensitive to changes taking place at the species level of soil fauna. Some important keystone species may exist, but a change in the functional group architecture seems to be a prerequisite for altered rates in soil processes. Predators high up in the detrital food web had no detectable in¯uence on any of the ecosystem-level processes. In the ®eld, all of the faunal groups studied proved to be highly insensitive to the stand management practices. As compared to the untreated controls, numbers of enchytraeid worms, collembolans and most of the macroarthropods in the managed stands were not signi®cantly different. It is concluded that management practices with minor impacts on the soil organic layer, which buffers soil biota against drastic changes in their environment, have little in¯uence on biotically-controlled soil processes. # 2000 Elsevier Science B.V. All rights reserved. Keywords: Biodiversity; Disturbance; Ecosystem functioning; Forest management; Forest soil 1. Introduction Soil processes, such as decomposition of organic material and mineralization of nutrients bound to this matter, are fundamentally important not only for tree growth but also for the functioning of the entire forest ecosystem (Tamm, 1991). These life-supporting pro- cesses are largely regulated by soil organisms, includ- ing soil microorganisms and soil fauna (Coleman et al., 1983; Verhoef and Brussaard, 1990; Lee and Pan- khurst, 1992). Consequently, factors affecting the activity and survival of soil biota should, at least in Forest Ecology and Management 133 (2000) 5±11 * Corresponding author. Tel.: 358-14-602300; fax: 358-14-602321. E-mail address: hsetala@dodo.jyu.fi (H. Seta Èla È) 0378-1127/00/$ ± see front matter # 2000 Elsevier Science B.V. All rights reserved. PII:S0378-1127(99)00293-5