Prescribed Fire and Timber Harvesting Effects on Soil Carbon and Nitrogen in a Pine Forest

Thinning and prescribed fire are common management tools used to eliminate thick fuel loads that could otherwise facilitate and encourage a more severe catastrophic wildfire. The objective of this study was to quantify the lasting effects of prescribed fire on forest floor and soil nutrients approximately 9 yr after a burn occurred near Truckee, CA. The study site includes a prescribed fire following various harvest and understory removal treatments: whole-tree thinning, cut-to-length thinning, and no thinning. Data were collected before, immediately after, and 9 yr later following a prescribed burn. All forest floor and soil samples were analyzed for nutrients (O horizon: total N; mineral soil: total N, total C, mineral N). Fuel reductions were evident 9 yr after the fire in the burned plots. No significant changes in total C or total N in surface (0-20-cm) mineral soils occurred during the 9-yr period. Mineral N concentrations in surface soils were greater in unburned than in burned cut-to-length thinning treatments after 9 yr. These differences were attributed to N inputs from decomposing slash and to the reduction in the biomass of N-2 fixers by burning.