Long-term effects of logging residue addition and removal on macroarthropods and enchytraeids.
The long-term effects of logging residue addition and removal on soil macroarthropods and enchytraeids were examined in a Scots pine (Pinus sylvestris) stand in central Sweden. The study was performed 15-18 yr after the treatments had been applied following clear felling in 1976. In comparison with plots receiving roughly twice the normal amount of residues, removal of logging residues (above-ground whole-tree harvesting) resulted in decreases in the total numbers of Collembola (springtails), gamasid mites (Mesostigmata), spiders, predatory insects and dipterous larvae, whereas no significant effects on enchytraeids and diplopods could be detected. Few effects on single species of Collembola and Gamasida were found. The composition of the soil fauna community, as well as food web structure, were significantly affected by whole tree harvesting, but the effects were quantitative rather than qualitative - most organism groups decreased, but the relative importance of different groups did not change markedly. Over the 4 yr studied, community predictability (specifically, constancy) at the levels of higher taxa, functional groups and species did not differ substantially between the treatments. Predictabilities of higher taxa and functional groups were higher than predictability of species of Collembola and gamasid mites. Values of community predictability were similar to those found in other studies of forest soil fauna. It is concluded that whole tree harvesting may result in long-term decreases in the abundances of many soil animal groups. The possible impact of decreased abundances of fungivores and predatory arthropods on nutrient cycling and site productivity is discussed. It is argued that the direct effects of these changes on nitrogen mineralization are likely to be small. However, the possibility that the soil fauna may be involved in a positive feedback loop towards lower site productivity means that the observed long-term decreases in several organism groups should be of concern, at least on sites dominated by internal nutrient dynamics.