Estimating consumption and remaining carbon in burned slash piles

Abstract

Fuel reduction treatments to reduce fire risk have become commonplace in the fire adapted forests of western North America. These treatments generate significant woody debris, or slash, and burning this material in piles is a common and inexpensive approach to reducing fuel loads. Although slash pile burning is a common practice, there is little information on consumption or even a common methodology for estimating consumption. As considerations of carbon storage and emissions from forests increase, better means of quantifying burn piles are necessary. This study uses two methods, sector sampling and a form of line intersect sampling, for estimating both the percent consumption and conversion to charcoal in slash piles of ponderosa pine ( Pinus ponderosa Douglas ex P. Lawson & C. Lawson) in northern Arizona, USA. On average, burning released between 92% and 94% of the carbon in each slash pile to the atmosphere and converted between 0.05 and 0.34 Mg C·ha–1 to charcoal across the treatment area. These results demonstrate that burning slash piles converts significant quantities of carbon stored in wood to atmospheric carbon and charcoal, both of which should be considered as forest carbon accounting is further refined. Sector sampling and line intersect strategies produced similar estimates of consumption; however, the line intersect protocol was more easily and rapidly implemented.