Abstract
Low intensity prescribed fire and mechanical thinning are strategies used for managing fuels and forest structure that has been used for the past two decades. The objective of this study was to examine these strategies’ effect on soil exoenzyme activities and soil chemistry. I hypothesized that i) polyphenol oxidase would have greater activity in burned compared to unburned sites, ii) hydrolytic cellulases and chitinases would have less activity in burned compared to unburned sites, and iii) acid and alkaline phosphatase would have contrasting activities in burned versus unburned sites.
To achieve this, I collected soil samples from Blodgett Forest Research Station, in the western Sierra Nevada, which is participating in a national Fire and Fire Surrogate (FFS) study. To assess the efficacy as forestry management strategies, Fire, mechanical thinning, and their combination have been experimentally and repeatedly applied to a mixed coniferous forest. I measured soil pH, soil moisture, and soil organic matter as indicators of changes in soil chemistry. To determine exoenzyme activity, I assayed soil samples using spectrophotometric and fluorometric techniques.
Results from this study indicate that the only effect at this timescale is elevated polyphenol oxidase activity after a combination of mechanical and fire treatments. Variation of exoenzyme activity and soil chemistry characteristics was substantial at multiple scales on the landscape, demonstrating a high degree of spatial heterogeneity. Correlations observed in my samples and results from my principal components analysis confirm predicted relationships between enzyme activity and soil chemistry, despite lack of effect of forestry management treatments.