The intrinsic coordination of tree growth strategy and wood decomposability

Abstract Functional traits control plant detritus decomposition via so called ‘afterlife effects’. While plant traits vary between species due to different growth strategies, it remains poorly understood how tree growth strategies and wood decomposition rates are directly related. We hypothesize that species with a fast growth strategy (i.e. fast‐growing, light‐demanding and high‐mortality) decompose faster than species with a slow growth strategy, due to lower wood density which is preferred by major decomposers like termites. We carried out wood decay experiments of 120 tree species (44 families including Lauraceae, Fagaceae, Symplocaceae and Theaceae) in a 50‐ha forest plot in subtropical China. Species‐specific mean of percentage wood mass loss after 8 or 16 months was based on three replicates deployed at the valley, ridge, and hilltop, to obtain representative estimates of overall wood decomposability across the topographic gradients. Sample‐level termite colonization was documented to indicate the activities of major decomposers. Six functional traits (e.g. wood density) and four population‐level demographic metrics (e.g. 95th quantile of stem growth rate) were measured based on samples and trees across the landscapes. We found that deadwood of fast‐growing species had lower wood density, higher decomposition rates and higher probability of termite colonization than slow‐growing species. Notably, the 95th quantile of stem growth rate accounted for higher variations of 8‐month decomposition rates than wood traits (especially wood density), and had comparable effects as wood traits on 16‐month decomposition rates. This is because demographic metrics, like stem growth rate, are comprehensive indicators for how tree species differ in intrinsic growth and response to environmental fluctuation. In turn, this shapes a complex suite of traits that collectively and inter‐dependently alter the preference of decomposers and weakens the predictive power of single or few traits, especially in species‐diverse forests. Synthesis . Our study highlights the intrinsic coordination between tree growth and wood decay. This coordination seems to be mediated by the growth‐driven change of wood traits and, thus, the trait‐driven activities of major decomposers like termites. In addition, the positive growth‐decay relationship reveals that increased forest productivity may be accompanied by accelerated carbon emissions from deadwood pools, that is, a continuous balance between the inputs and outputs of C from the system. As deadwood stores ~8% of global forest carbon with termites being major decomposers, our study sheds important light on the understanding of forest carbon fluxes, especially in tropical and subtropical regions.