Short-Term Effects of Experimental Burning and Thinning on Soil Respiration in an Old-Growth, Mixed-Conifer Forest

To understand the roles of forest management practices in meeting the goals of forest sustainability and CO2 sequestration, we evaluated the effects of burning and thinning treatments on soil respiration and soil environments in an old-growth, mixed-conifer forest in California’s southern Sierra Nevada. Six experimental treatments with two levels of burning and three levels of thinning were implemented across three dominant patch types: closed canopy (CC), Ceanothus shrub (CECO), and open canopy (OC). We measured soil respiration rate (SRR), soil temperature (T10), moisture (Ms), and litter depth (LD), in the summers of 2000 and 2002. Soil total C and total N were measured in 2002. SRR was significantly different among the three patch types. In 2000, SRR was 0.75, 0.86, and 0.26 g CO2 m-2 hr-1 in CC, CECO, and OC, respectively. In 2002, SRR was 0.79, 0.97, and 0.44 g CO2 m-2 hr-1 in CC, CECO, and OC, respectively. The analysis of variance indicated that burning and thinning significantly affected soil respiration and soil environments. In particular, SRR significantly decreased in burned CECO patches but increased in unburned and thinned CECO. SRR in CC and OC did not significantly change. T10 and Ms increased, whereas LD and soil C decreased in treated patches. We also developed pre- and posttreatment exponential models to predict SRR using soil environmental variables. The effects of burning and thinning on soil CO2 efflux and soil environments imply that forest carbon pools would be reorganized with widespread application of these forest management practices.