Effects of Forest Gaps on Litter Lignin and Cellulose Dynamics Vary Seasonally in an Alpine Forest

Han Li,Bo Tan,Liya Xu,Wanqin Yang,Jie He,Fuzhong Wu,Xiangyin Ni,Yi Hu

doi:10.3390/f7020027

Abstract

To understand how forest gaps and the associated canopy control litter lignin and cellulose dynamics by redistributing the winter snow coverage and hydrothermal conditions in the growing season, a field litterbag trial was conducted in the alpine Minjiang fir (Abies faxoniana Rehder and E.H. Wilson) forest in a transitional area located in the upper reaches of the Yangtze River and the eastern Tibetan Plateau. Over the first year of litter decomposition, the litter exhibited absolute cellulose loss and absolute lignin accumulation except for the red birch litter. The changes in litter cellulose and lignin were significantly affected by the interactions among gap position, period and species. Litter cellulose exhibited a greater loss in the winter with the highest daily loss rate observed during the snow cover period. Both cellulose and lignin exhibited greater changes under the deep snow cover at the gap center in the winter, but the opposite pattern occurred under the closed canopy in the growing season. The results suggest that decreased snowpack seasonality due to winter warming may limit litter cellulose and lignin degradation in alpine forest ecosystems, which could further inhibit litter decomposition. As a result, the ongoing winter warming and gap vanishing would slow soil carbon sequestration from foliar litter in cold biomes.

Highlights

Foliar litter decomposition plays crucial roles in bioelement cycles, energy transformation, and the maintenance of soil fertility in forest ecosystems [1,2,3,4]
Among the four gap positions, FTC was lowest at the gap center during the snow cover and formation periods, and it reached its maximum value during the snow melt period (Table 1)
The changes in litter cellulose and lignin were significantly affected by the interactions between and among gap position, period and species

Summary

Introduction

Foliar litter decomposition plays crucial roles in bioelement cycles, energy transformation, and the maintenance of soil fertility in forest ecosystems [1,2,3,4]. As two of the most abundant and resistant components in foliar litter, cellulose and lignin play important roles in litter decomposition [5]. Little information is available on how forest gaps and the associated hydrothermal dynamics on the forest floor influence lignin and cellulose changes in foliar litter. The formation of forest gaps manipulates the regeneration of trees and plant diversity [9,10] and determines the hydrothermal dynamics on the forest floor and the community and activity of soil organisms by redistributing light and precipitation [11,12]. Forest gaps and the surrounding canopy can distribute the snowpack in the winter and regulate the temperature, precipitation and solar radiation during the Forests 2016, 7, 27; doi:10.3390/f7020027 www.mdpi.com/journal/forests

Methods

Results

Discussion

Conclusion