The effect of microclimate on wood decay is indirectly altered by tree species diversity in a litterbag study

Aims We studied the influence of tree species diversity on the dynamics of coarse wood decomposition in developing forest communities in a natural,topographically heterogeneous landscape.Using the litter bag technique,we investigated how and to which extent canopy tree species richness or the exclusion of mesoinvertebrates and macroinvertebrates affected wood decomposition in the light of natural variations in the microclimate.We compared the relative importance of the two aspects(experimental treatment versus microclimate)on wood decay rates using Schima superba as a standard litter.Methods Coarse woody debris(CWD)was deposited in litter bags with two different mesh sizes in a total of 134 plots along a gradient of canopy tree species richness(0-24 species).Wood decomposition was assessed at two consecutive time points,one and three years after deposition in the field.Local climatic conditions were assessed throughout the duration of the experiment.Microclimatic conditions were assessed both,directly in the field as well as indirectly via correlations with local topography.We used analysis of variance based approaches to assess the relative importance of the treatments(community tree species richness and macro invertebrate exclusion)and microclimatic conditions on wood decay.Important Findings No direct influence of tree species richness on wood decay could be detected.However,the exclusion of macroinvertebrates significantly decreased wood decomposition rates.In addition,microclimatic conditions accounted for a substantial proportion of explained variance in the observed data.Here,wood decomposition was negatively affected by low mean temperatures and high variations in local humidity and temperature.However,tree species richness as well as the respective species composition affected the presence of termites within forest communities.These,in turn,significantly increased the decay of CWD.The strength of both,experimental treatment and microclimate increased with ongoing decomposition.We conclude that,while tree species richness per se has no direct influence on wood decomposition,its influence on the local arthropod decomposer community(especially the presence of termites)does have an effect.