Woody debris (WD) represents a substantial reservoir of carbon in forests. Disentangling the effects of factors affecting wood decomposition rates is therefore important. We examined the abiotic and biotic factors affecting wood decomposition across a tropical disturbance gradient from mature forest to open land in a tropical montane site in Xishuangbanna, SW China. Wood logs of two native species (n = 280) with contrasting wood specific gravity (WSG) were left exposed on the ground for three years. For each log, WSG was monitored at intervals by taking cores from top-half (up) and bottom-half (down) of the log. Mass loss was measured at the end of the experiment.
Results/Conclusions
Rates of WSG loss were similar across the disturbance gradient and the species effect varied with core position. For the species with higher initial WSG, which also had higher initial wood N concentration and much thicker bark, up cores had consistently higher WSG loss over the study period, whereas this pattern was reversed for the species with low initial WSG. The first species also had substantially higher WSG loss for up cores, but interspecific difference among down cores was small.
For mass loss, there was a complex interaction between species, habitat and the presence of termites. The species with low initial WSG experienced approximately two-fold higher mass loss in the absence of termites, but the difference between species was smaller in the presence of termites. Both species experience higher mass loss in open habitats than in forests, but the termite effect was smaller in open habitats especially for the species with low initial WSG. There was no interspecific difference in susceptibility to termite infestation, but infestation rates were higher in regenerating forests and open land than in mature forest. WSG loss explained 0 % and 35 19 % of mass loss variation in the species with low and high initial WSG, respectively and only in absence of termites.
Wood functional traits appear to have important afterlife effects, but these interact with abiotic conditions and decomposition processes (microbial decomposition, macro-organisms (termites), photo-degradation) with varying consequences. WSG loss is not a reliable predictor of mass loss. Our results have important implications for understanding the carbon cycle in tropical landscapes.