Contribution of Soil Fauna to Foliar Litter-Mass Loss in Winter in an Ecotone between Dry Valley and Montane Forest in the Upper Reaches of the Minjiang River.

Yan Peng,Wanqin Yang,Bin Wang,Chuan Zhang,Jun Li,Fuzhong Wu,Kai Yue,Martin Schädler

doi:10.1371/journal.pone.0124605

Abstract

Litter decomposition during winter can provide essential nutrients for plant growth in the subsequent growing season, which plays important role in preventing the expansion of dry areas and maintaining the stability of ecotone ecosystems. However, limited information is currently available on the contributions of soil fauna to litter decomposition during winter in such ecosystems. Therefore, a field experiment that included litterbags with two different mesh sizes (0.04 mm and 3 mm) was conducted to investigate the contribution of soil fauna to the loss of foliar litter mass in winter from November 2013 to April 2014 along the upper reaches of the Minjiang River. Two litter types of the dominant species were selected in each ecosystem: cypress (Cupressus chengiana) and oak (Quercus baronii) in ecotone; cypress (Cupressus chengiana) and clovershrub (Campylotropis macrocarpa) in dry valley; and fir (Abies faxoniana) and birch (Betula albosinensis) in montane forest. Over one winter incubation, foliar litter lost 6.0%-16.1%, 11.4%-26.0%, and 6.4%-8.5% of initial mass in the ecotone, dry valley and montane forest, respectively. Soil fauna showed obvious contributions to the loss of foliar litter mass in all of the ecosystems. The highest contribution (48.5%-56.8%) was observed in the ecotone, and the lowest contribution (0.4%-25.8%) was observed in the montane forest. Compared with other winter periods, thawing period exhibited higher soil fauna contributions to litter mass loss in ecotone and dry valley, but both thawing period and freezing period displayed higher soil fauna contributions in montane forest. Statistical analysis demonstrated that the contribution of soil fauna was significantly correlated with temperature and soil moisture during the winter-long incubation. These results suggest that temperature might be the primary control factor in foliar litter decomposition, but more active soil fauna in the ecotone could contribute more in litter decomposition and its related ecological processes in this region.

Highlights

Global warming and human disturbance have increased drought conditions worldwide, and the area of arid and semi-arid land is expanding at an overwhelming rate [1]
The soil fauna had an obvious effect on the litter decomposition in the ecotone during the winter, with the greatest effects observed in the ecotone ecosystem compared with those of the dry valley and montane forest; the results supported our first hypothesis
The contributions of soil fauna to the loss of litter mass were highest during the thawing period except for birch litter, which indicated a higher contribution during the pre-freezing period

Summary

Introduction

Global warming and human disturbance have increased drought conditions worldwide, and the area of arid and semi-arid land is expanding at an overwhelming rate [1]. As a functional transition region and buffer zone of environmental change, the ecotone between a dry valley and montane forest provides important ecological functions, such as conservation of water and nutrients and modulation of micro-climate, and hinders the upward advance of arid regions [2]. Previous studies have suggested that soil fauna exhibit certain activities in winter and provide obvious or significant contributions to litter decomposition [8]. Soil fauna in ecotone may contribute more to litter decomposition and other related ecological processes. Several studies have investigated litter decomposition in ecotones [11,12], few attentions have been paid on the contribution of soil fauna to litter decomposition in ecotone, especially such ecosystems between montane forest and dry valley

Objectives

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Results

Conclusion