Functional traits are more strongly correlated with biomass than diameter growth

Abstract

Abstract The functional basis of tree growth is often evaluated based on trunk diameter even though diameter is only one dimension of growth that may not be an integrative measure of resource allocation. We tested the hypothesis that growth—functional trait relationships are stronger when key sources of variation in tree growth are also accounted for, namely tree height and DBH, as well as size‐related variation in wood density and seed production using data from 3881 trees of 24 species in a subtropical forest using ordinary least square regression and standard major axis regression. Wood density varied with tree size for 14 of 24 species, generally increasing with size. For 18 of 24 species, the correlations of leaf mass per area and an index of photosynthetic investment (PI) with biomass growth was stronger than with diameter growth rate. Juveniles did not show stronger relationships than adults but biomass growth adding up with seed production showed stronger relationships with PI than biomass growth alone for three of eight species. Synthesis. Thus, our study helps resolve a paradox of trait‐based ecology, that is, weak growth—trait relationships, as stronger relationships emerged when accounting for more sources of intraspecific, among‐tree variation in resource allocation.