Litter Decomposition, Nitrogen Dynamics and Litter Microarthropods in a Southern Appalachian Hardwood Forest 8 Years Following Clearcutting

Abstract

.' SUMMARY (1) Litter decomposition rates, nitrogen dynamics and litter microarthropods on the xeric slopes of a watershed 8 years after clearcutting (WS 7) and on an adjacent reference watershed (WS 2) at the Coweeta Hydrologic Laboratory were measured using litterbags. Litter of Comusflorida L., Acer rubrum L. and Quercusprinus L. was used as experimental substrates in three plots on adjacent areas of both watersheds. Results from this study were compared with those obtained before and after cutting to assess the longer-term changes induced by canopy removal. (2) Reduced litter decomposition rates were associated with clearcutting. Litter nitrogen dynamics were also affected. Net immobilization of nitrogen in litter substrates was lower on WS 7. Lower net nitrogen immobilization was related to slower increases in nitrogen concentration per unit mass lost in litter on WS 7. (3) Mean annual densities of total litter microarthropods remained 28% lower on WS 7 than on WS 2, 8 years after cutting. Previous studies indicated clearcutting initially reduced mean annual densities of litter microarthropods by>50%. Mesostigmata and Oribatei densities averaged 50 and 54% lower, respectively, than on WS 2. Prostigmata and Collembola densities averaged 20 and 24% lower, respectively, than on WS 2. This differential response changed the relative abundances of major groups. Changes in litter decomposition rates and nitrogen dynamics were consistent with effects associated with lower microarthropod densities and suggest that reduced microarthropod densities may be important. (4) Results of this study differ from those at northern hardwood forest sites where clearcutting caused increased decomposition rates. This suggests that generalizations from northern hardwood forests may not apply to other regions. Instead the effects of canopy