Decomposition of aspen (Populustremuloides) leaf litter modified by leaching

Abstract

In a Rocky Mountain aspen forest, the detailed pattern of mass loss from decomposing leaf litter of trembling aspen (Populustremuloides Michx.) during the first 6 months of decay was compared with that from aspen leaves modified to produce a more recalcitrant litter type by removal of leachable material (31.7% of original mass). Leaching litter removed substantial quantities of N (24%) and P (54%), but did not change the litter's C/N ratio (77:1); and leached leaves still contained 33% labile (benzene alcohol soluble) material. Decomposition of intact aspen litter was best described by a double exponential model (k1 = −7.91/year, k2 = −0.21/year), except during the first 2 weeks, when an extremely rapid mass loss (14.2%) apparently resulted from leaching. Microbial metabolism was probably responsible for most of the subsequent decay (35% total in 6 months). In contrast, decomposition of leached aspen showed no exponential trend and was best described by a simple linear regression with a slope of −19.7%/year. Additional data from a 2nd year (12–15 months decay) reduced the regression estimates of decay rates but did not alter the best fit models. Fits were improved slightly if temperature sum replaced time in the regressions, especially if 2nd-year data were included.