Rapid release of labile components limits the accumulation of humic substances in decomposing litter in an alpine forest

Abstract

Recent evidence suggests that recalcitrant compounds are not selectively preserved in soils and that labile components are the precursors of humic substances, but the relationship between the slow accumulation of humic substances and the rapid release of labile components during litter decomposition is not well understood. In an in situ litterbag experiment, we quantified the litter mass loss, release of acid‐soluble labile components, and accumulation of alkali‐soluble humic substances during four years of decomposition of fir (Abies faxoniana) needle and twig litters in an alpine coniferous forest. We found that fresh litter had high contents of humic substances (121 and 151 mg/g for needle and twig litters, respectively), with needle litter showing increases in humic substances contents at the early decomposition stage and decrease later, whereas twig litter showed the reverse pattern. However, the net accumulation of humic substances in both needle and twig litters decreased during decomposition, and the decrease was related to the rapid release of labile components. We conclude that the rapid release of labile components limits the accumulation of humic substances in plant litter during decomposition in this alpine coniferous forest.

Changes in Soil Organic C Fractions and C Pool Stability Are Mediated by C-Degrading Enzymes in Litter Decomposition of Robinia pseudoacacia Plantations

“…Our results also highlighted that the differences in cellulose and lignin in the early and late stages of litter decomposition were closely related to hydrolase and oxidase activities. Labile compounds and soluble substances are rapidly degraded by fast-growing microorganisms in the early stage of decomposition [29,30]. Soil microorganisms accelerate the secretion of hydrolase activities involved in the utilization of labile C sources to enhance the utilization e ciency of substrates [15,31].…”

Effects of Forest Gaps on Abies faxoniana Rehd. Leaf Litter Mass Loss and Carbon Release along an Elevation Gradient in a Subalpine Forest

“…The forest soil is classified as Cambisols [40]. The concentrations of total C, N, and P in soil (0~20 cm) were 363, 6.6 and 1.6 g•kg −1 , respectively [33].…”

“…Both functions would promote litter decomposition in winter [31,32]. Moreover, enhanced photodegradation and eluviation from sunlight exposure and heavy rain wash would also stimulate the litter decomposition within gaps when compared to that under closed canopy [33,34]. In subalpine regions, relevant information is scarce, especially when discussed in conjunction with different elevation effects.…”