Microarthropod Response Following Cable Logging and Clear‐Cutting in the Southern Appalachians

Abstract

Litter and soil microarthropod populations were monitored following cable logging and clear—cutting of a forested watershed (WS 7) at the Coweeta Hydrologic Laboratory in the southern Appalachians of North Carolina. Annual mean densities of microarthropods in litter bags were reduced over 50% on the clear—cut watershed when compared with an adjacent forested watershed (WS 2), and averaged 8.4 individuals/g of litter on WS 7 vs. 20.4/g on WS 2 (P < .01). Density estimates obtained from 5 cm deep sections of litter and soil indicated a 25% reduction in densities on WS 7, with a 17—mo average of 98 900 microarthropods/m2 on WS 7 vs. 133 500 microarthropods/m2 on WS 2 (P > .001). In contrast, densities of microarthropods increased over 100% in deeper soil horizons (5—55 cm), averaging 89 800 microarthropods/m2 on WS 7 vs. 43 700 microarthropods/m2 on WS 2 (P < .001). Clear—cutting by methods that do not destroy the integrity of the litter—soil environment engenders two kinds of perturbations: (1) removal of the canopy, and (2) addition of organic matter inputs, primarily woody litter debris, to the forest floor. Without a protective canopy, temperatures at the litter—soil interface on WS 7 were increased; daily maximum summer temperatures averaged over 40°C. Thus, lethal or nearly lethal temperatures reduced microarthropod densities in the top 5 cm of litter and soil on WS 7; declines were attributed primarily to oribatid mite mortality. Increased densities below 5 cm were attributed primarily to increased prostigmatid mite abundance. The relationships between microarthropod densities, standing crops of organic matter and litter and microbial production were examined. The amount and vertical distribution and organic matter appears to be the best predictor of microarthropod densities and vertical distributions in most forest ecosystems.