Relative scarcity of juveniles is often attributed to the decline of population in the community of forest trees. However, such properties as high longevity, high growth rate and low fecundity promote populations with low juvenile frequency in an equilibrium state. The theory of vertical foliage partitioning suggests the the difference in tree size structure among species contributes to stable coexistence.

To examine whether or not inter-specific variation in tree size distribution reflects demographic differentiation, we analysed census data of abundant 365 species (with 100 or more trees >= 2 cm in trunk diameter) in the 50-ha plot of Pasoh Forest Reserve in Malaysia. We examined how the observed size distribution in terms of maximum diameter and skewness is related to demographic rates over around 5 years of census interval, by comparing the observed distribution and the projected equilibrium distribution from demographic rates.

We found that the observed inter-specific variation in size distribution was associated, to a fair extent, with demographic properties, thus the foliage partitioning mechanism may contribute to the stable coexistence in a species-rich tree community of tropial rainforest.