Effects of forest postharvest management practices on enzyme activities in decomposing litter

Forest harvesting and site preparation alter many features of the soil environment affecting biological activity and litter decomposition. One aspect of biological activity, lignocellulase enzyme activity, has been found to be a good predictor of litter mass loss. We determined the effects of postharvest treatments (SLASH, BROADCAST BURN, and CHIP AND PILE treatments with the intact FOREST treatment as a control) on lignocellulose degrading and nutrient releasing enzyme activities (beta-glucosidase, cellobiohydrolase, beta-xylosidase, N-acetyl-glucosaminidase, phenol oxidase, and phosphatase) in decomposing pine litter in litterbags and in the forest floor and compared them with patterns of decomposition. In the forest floor, the SLASH treatment decreased phenol oxidase and phosphatase activities by half; the CHIP AND PILE treatment decreased beta-glucosidase, cellobiohydrolase, phenol oxidase, and phosphatase activities by 50 to 75%; and the BROADCAST BURN treatment decreased N-acetyl-glucosaminidase, phenol oxidase, and phosphatase activities by 30 to 60%. In the litterbag litter, phenol oxidase activity, N-acetyl-glucosaminedase activity, and mass loss were lower in the BROADCAST BURN treatment than in the FOREST treatment. SLASH and CHIP AND PILE treatments did not affect enzyme activities or decomposition of the litterbag litter. The relationship between enzyme activities and incremental mass loss was significant in the FOREST and CHIP AND PILE treatments for beta-glucosidase, cellobiohydrolase, and N-acetyl-glucosaminidase enzymes (r > 0.50, p < 0.05), but not significant in the BROADCAST BURN and SLASH treatments. Although reduced enzyme activities were accompanied by lower decomposition rates, enzyme activities were not always a dominant control of decomposition in certain highly disturbed treatments.