Methods and modeling equations to quantify the litter layer of coniferous forests in California national forests

Forest litter is a dead fuel layer comprised of recently fallen vegetative particles from trees and other plants such as leaves, needles, cones, and bark flakes. A variety of methods exist for quantifying litter and estimating loading. Quantification of forest litter is important in estimating fire behavior, substrate cover, erosion potential, and in tracking changes in both natural and management activities. This study analyzed monitoring data from fuel treatment projects in fourteen California National Forests to create litter loading estimates and equations. Litter samples were dried, weighed, and correlated with litter depths that had been measured along planar fuel transects. Nineteen mixed conifer study sites were grouped according to location and tree species relative basal area. This simplified analysis used eight conifer forest types in seven ecological regions. Estimated litter depths, loadings, bulk densities, and modeling equations were developed and compared to those published for many western regions. These comparisons highlighted the extensive variation of litter quantities available for fuel estimations and emphasized the need to evaluate methodologies to increase accuracy. Accurate litter quantities are an essential part of modeling natural processes, such as fire behavior and fuel buildup.