Factors controlling bark decomposition and its role in wood decomposition in five tropical tree species.

Gbadamassi G O Dossa,Kunfang Cao,Ekananda Paudel,Rhett D Harrison,Douglas Schaefer

doi:10.1038/srep34153

Abstract

Organic matter decomposition represents a vital ecosystem process by which nutrients are made available for plant uptake and is a major flux in the global carbon cycle. Previous studies have investigated decomposition of different plant parts, but few considered bark decomposition or its role in decomposition of wood. However, bark can comprise a large fraction of tree biomass. We used a common litter-bed approach to investigate factors affecting bark decomposition and its role in wood decomposition for five tree species in a secondary seasonal tropical rain forest in SW China. For bark, we implemented a litter bag experiment over 12 mo, using different mesh sizes to investigate effects of litter meso- and macro-fauna. For wood, we compared the decomposition of branches with and without bark over 24 mo. Bark in coarse mesh bags decomposed 1.11–1.76 times faster than bark in fine mesh bags. For wood decomposition, responses to bark removal were species dependent. Three species with slow wood decomposition rates showed significant negative effects of bark-removal, but there was no significant effect in the other two species. Future research should also separately examine bark and wood decomposition, and consider bark-removal experiments to better understand roles of bark in wood decomposition.

Highlights

Authors have suggested that the presence or absence of bark may inhibit or enhance the decomposition of dead wood, but few studies have tested these ideas
We examined the following hypotheses: (i) Bark contains higher C and N than wood among the study species, (ii) bark decomposition rates decline across species as the proportions of lignin, cellulose and tannins in bark tissue increase; (iii) meso- and macro-fauna promote bark decomposition, both through enhancing microbial decomposition and fragmentation of bark; and (iv) logs retaining bark decompose faster than logs without bark, and this effect decreases with bark decomposability
The tannin content of bark tissue increased in the following order: Kleinhovia hospita

Summary

Introduction

Authors have suggested that the presence or absence of bark may inhibit or enhance the decomposition of dead wood, but few studies have tested these ideas. Coupling bark decomposition studies with additional experiments investigating the decomposition of logs with and without bark is likely to enhance our understanding of the mechanisms affecting wood decomposition. We investigated factors affecting bark decomposition and the effects of bark on wood decomposition for five important tree species in a secondary seasonal tropical rain forest in Xishuangbanna, SW China. We examined the following hypotheses: (i) Bark contains higher C and N than wood among the study species, (ii) bark decomposition rates decline across species as the proportions of lignin, cellulose and tannins in bark tissue increase; (iii) meso- and macro-fauna promote bark decomposition, both through enhancing microbial decomposition and fragmentation of bark; and (iv) logs retaining bark decompose faster than logs without bark, and this effect decreases with bark decomposability

Methods

Results

Conclusion