Effects of fire and fire surrogate treatments on forest C and N storage

Understanding how fire and fire surrogate treatments impact C and N storage is critical to the evaluation of these management alternatives in the context of increasing atmospheric CO₂ and deposition of anthropogenic N. In this study we evaluated the impacts of the FFS treatments on network-wide C and N stocks in soil, forest floor, coarse woody debris (CWD), vegetation and the entire forest ecosystem. C and N were mainly stored in soil and live trees. At the FFS Network scale, meta-analyses indicated that burning alone significantly decreased C and N storage in forest floor and live trees, but had no significant impacts on storage in soil, CWD, or the whole ecosystem. Mechanical thinning alone increased C and N storage in CWD but decreased C and N in live trees and the whole ecosystem. Burning+thinning decreased C and N storage in forest floor, live trees, and for the whole ecosystem.  Among the twelve individual FFS sites, burning alone significantly reduced C and N storage in 10 site-by-C and 9 site-by-N compartment combinations.  Mechanical treatment alone resulted in decreases in 10 and 9 site-by-C and site-by-N compartment combinations, respectively. The combination of mechanical treatment and fire resulted in significant decreases in C and N storage in 18 and 15 site-by-compartment combinations.  Mechanical treatment and mechanical+fire resulted in increases in CWD C and N in 1-2 sites. We will present the results of Bayesian analysis designed to separate the relative effects of treatments and inter-site variations on changes in C and N storage.