Traits mediate a trade‐off in seedling growth response to light and conspecific density in a diverse subtropical forest.

Understanding tree species responses to biotic and abiotic factors is fundamental for stronger predictions of community assembly and dynamics. However, several challenges remain. These include a failure to investigate whether there is evidence for key hypothesized life‐history trade‐offs and to link these trade‐offs to functional traits.In this study, we seek to explicitly address the above outstanding challenges by constructing models for individual seedling growth in response to abiotic and biotic factors using 3 years of seedling census data from a 20‐ha subtropical forest dynamics plot in a diverse subtropical forest and correlated these responses with functional traits.We found that light and conspecific neighbours increase and decrease the RGR of tree seedlings respectively. We also found that the ability of a species to positively respond to canopy openness trades‐off against susceptibility to conspecific negative density dependence (CNDD). This trade‐off was evident across seasons and could be predicted on functional trait—stem and leaf dry matter content.Synthesis. Our findings indicate species that can grow quickly in high‐light environments also tend to suffer more CNDD. The results highlight that strong evidence of a trade‐off relating to growth and defence widely hypothesized to be of importance in diverse tree communities and that this trade‐off occurs across seasons and can be linked to a commonly measured functional trait. [ABSTRACT FROM AUTHOR]