Sensitivity of soil processes in northern forest soils: are management practices a threat?

There is evidence that forest management practices influence soil-decompose r communities. It is also established that changes in the trophic structure and composition of these communities can induce changes in soil-nutrient d ynamics, thereby affecting plant growth. Whether forest productivity is aff ected by management-induced changes in, e.g. soil faunal structure, is, how ever, yet to be shown. The aim of this study was (1) to determine the resol ution 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 floor to various kinds of forest management practices. A review of laboratory miniecosystem experiments carried out at the Univers ity of Jyvaskyla: is presented to examine the diversity-ecosystem function relationship. The response of tree growth to manipulation of soil-faunal co mposition was measured. A field experiment was conducted in central Finland in spruce stands, including several stand management treatments in additio n to the untreated controls. The fellings took place in winter 1996, and va rious groups of soil animals have been sampled since 1995. Laboratory exper iments revealed that soil processes and plant growth are largely insensitiv e to changes taking place at the species level of soil fauna. Some importan t keystone species may exist, but a change in the functional group architec ture seems to be a prerequisite for altered rates in soil processes. Predat ors high up in the detrital food web had no detectable influence on any of the ecosystem-level processes. In the field, all of the faunal groups studied proved to be highly insensit ive to the stand management practices. As compared to the untreated control s, numbers of enchytraeid worms, collembolans and most of the macroarthropo ds in the managed stands were not significantly different. It is concluded that management practices with minor impacts on the soil organic layer, whi ch buffers soil biota against drastic changes in their environment, have li ttle influence on biotically-controlled soil processes. (C) 2000 Elsevier S cience B.V. All rights reserved.