Plant morphological traits are expected to determine demographic performance and thus to underlie the trade-off between growth and survival. Rates of growth and mortality vary with tree size but it is not yet known how size-dependent change of demographic performance is related to functional traits. We examined the relationships between size-dependent changes in relative growth rate in stem diameter (RGR) and mortality rate, and morphological traits which include maximum stem diameter (D_max), wood density (WD) and tree architecture (top height, lowest foliage height and crown width) across 145 co-occurring tree species in a Malaysian rainforest. High RGR at small tree size was associated with large D_max as well as low WD and wide crown. High mortality was associated with low WD and wide crown. Positive correlations between RGR and mortality were found for most sizes but it was significant only for small trees.

Species performance is tightly linked with species-specific architectural traits, such as adult stature, wood density and capacity of horizontal crown expansion for small trees that live in dark understory. Those traits were expected to underlie the trade-off between growth and survival, and to contribute to tree species coexistence in a species-rich rainforest.