This study was designed to determine how edges generated by clear-cutting old-growth forests influence patterns of soil carbon and nitrogen cycling and the distribution of ectomycorrhizal mats and to determine how these patterns change with time after harvest. A secondary objective was to measure how clear-cutting within different climatic regimes influenced soil nitrogen and carbon cycling.
Alan K. Swanson, Donald L. Henshaw, Robert P. Griffiths
Forest fragmentation has been recognized as an important problem for forest managers interested in maintaining ecosystem health. As further fragmentation takes place, the size of plots decrease and edge to volume ratios continue to climb (Franklin and Forman, 1987; Hunter, 1997). As the total length of edges increases with continued forest harvests, the possibility of significant sifts in soil processes over the landscape also increases. There is a long-standing interest in how forest edges influence plant and animal distributions (Harris, 1988). Typically, shade-intolerant and weedy species proliferate along edges, there are increased wind-shear forces resulting in mature tree mortality, changes in bird, mammal and insect distributions and distinctive microclimatic gradients along edges (Laurence and Yensen, 1991).
Recent studies by Chen et al. (1993, 1995) have shown that microclimate effects can be detected as far as 240 m into a Douglas-fir OG forest from edges of an adjacent 15 year stand (15YS) stand. Near the edge, greater extremes in relative humidity, wind velocity, solar radiation, and soil temperature were observed when compared to values observed deep within the OG forest or in the middle of the clear-cuts (Chen et al., 1995). Shifts in vegetation have also been observed up to 120 m from an edge (Chen et al., 1992). Much less is known about how forest edges influence biological and chemical characteristics of forest soils. This lack of basic information should be a major concern as forest managers attempt to assess the effects of forest harvesting patterns on biogeochemical processes over large watersheds.