Environmental factors appear to control decomposition at continental scales, whereas biotic effects (wood traits and organismal interactions) likely regulate decomposition regionally and locally. The majority of dead wood begins decomposing in situ above the forest floor, but the local processes affecting decomposition of elevated wood are unknown. This is particularly important because regulators of decomposition (microclimate and decomposer community assembly) change dramatically from the forest floor to the canopy. Here we used standardized, sterile wood sticks to quantify vertical patterns of microbial (fungal and prokaryotic) primary succession, wood decomposition, and microclimate in a tropical forest.
Results/Conclusions
We determined that fungal and bacterial communities differ compositionally across a vertical forest gradient. Phylogenetic dispersion indicated that environmental filtering regulates microbial community assembly at higher levels of the forest, whereas competitive interactions are more important on the forest floor. Using a mechanistic model, we determined that fungal composition and microclimate variability predict rates of wood decomposition. However, due to microclimate effects on fungal community assembly, it is apparent that microclimate is the primary factor controlling rates of decomposition locally in this tropical forest. This result is contrary to our expectations and the contemporary understanding of decomposition processes, and it indicates that environmental factors potentially regulate decomposition globally, regionally, and locally.