Disturbance may lead to fundamental changes in the structure and function of microbial communities (Balser Forest harvesting and site preparation alter many features of the et al., 2001; Schimel and Gulledge, 1998). Forest harvestsoil environment affecting biological activity and litter decomposition. ing and site preparation practices often disrupt organic One aspect of biological activity, "lignocellulase" enzyme activity, and mineral surface horizons, remove wood and slash, has been found to be a good predictor of litter mass loss. We deterincrease soil water content, temperature, and light intenmined the effects of postharvest treatments (SLASH, BROADCAST BURN, and CHIP AND PILE treatments with the intact FOREST sity at the soil surface, cause a loss of nutrients through treatment as a control) on lignocellulose degrading and nutrient releasvolatilization, leaching, and surface erosion, and alter ing enzyme activities (␤-glucosidase, cellobiohydrolase, ␤-xylosidase, microbial community composition and decomposition N-acetyl-glucosaminidase, phenol oxidase, and phosphatase) in de

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Secondary compounds are known to be associated with the resistance of conifer xylem against insects and fungi. The effects of long-term forest fertilization with nitrogen (N) or with N, calcium (Ca), and phosphorus (P) on secondary compounds in the xylem of 50-yr-old Scots pine (Pinus sylvestris L.) trees were examined. Xylem samples were collected from trees growing in three locations in southern Finland: Vilppula, Padasjoki, and Punkaharju. Forests were fertilized every fifth (Vilppula and Padasjoki) or tenth (Punkaharju) year since the 1950s. We compared concentrations of individual and total monoterpenes and resin acids in the heartwood and sapwood of Scots pine. Terpene emissions were analyzed from the sapwood and total phenolics from the heartwood. Fertilization did not have any significant effect on the concentrations and emissions of xylem monoterpenes. Concentrations of several individual terpenes in sapwood were positively correlated with the corresponding terpene emission. The concentrations of individual resin acids (i.e., abietic and dehydroabietic) decreased significantly in Punkaharju, but increased in the sapwood of N-fertilized trees compared with control ones at Padasjoki and Vilppula. The concentrations of resin acids in the heartwood were not significantly affected by fertilization. Both fertilization treatments decreased the total phenolic concentrations in the heartwood of trees growing in Padasjoki. There was a significant positive correlation between the total phenolics and total resin acid concentration. Overall, resin acids and phenolics seemed be more responsive than monoterpenes to N treatment. These results suggest that forest fertilization might cause slight changes in secondary compound concentrations of xylem, and thus might have significance in the decay resistance of wood.

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