Effects of forest gap on hemicellulose dynamics during foliar litter decomposition in an subalpine forest

Abstract

Aims As part of fiber structures, the hemicellulose degrades and transforms during foliar litter decomposition along with other components of leaf tissue. Forest gaps and crown canopies may regulate hemicellulose dynamics during foliar litter decomposition by redistributing winter snow cover and altering the temperature, precipitation and solar radiation during the growing season, but little information is available concerning those effects and the consequences. Therefore, our objective was to study the effects of forest gap on hemicellulose dynamics during foliar litter decomposition in an subalpine forest. Methods A field litterbag experiment was conducted in an subalpine fir(Abies faxoniana) forest in a transitional area located in the upper reaches of the Yangtze River and the eastern Qinghai-Xizang Plateau. Litterbags containing cypress(Sabina saltuaria), red birch(Betula albosinensis), larch(Larix mastersiana), azalea(Rhododendron lapponicum) and fir(Abies faxoniana) were placed on forest floor from the gap center to under the closed canopy. Samples of litterbags were retrieved at the stages of snow formation, snow cover, and snowmelt as well as during the growing season. Hemicellulose contents of the remaining litter were measured. Important findings After one-year decomposition, all five types of foliar litter exhibited a tendency of hemicellulose accumulation. The needle-leaved litter and broad-leaved litter showed greater hemicellulose losses at the snow cover and snowmelt stages, respectively. Greater hemicellulose losses in the gap center and under the canopy were observed at both snow cover and snowmelt stages. In contrast, there was less litter hemicellulose accumulation in the gap center during the growing season. Statistical analysis of the resulting data indicated that both environmental factors and litter quality were significantly correlated with the litter hemicellulose losses. Our results suggested that forest gap enhanced the hemicellulose losses in winter and constrained the hemicellulose accumulation during growing season, implying that the formation of forest gap in subalpine forest promoted hemicellulose degradation during litter decomposition.