An understanding of the patterns of plant trait dispersion in a community can provide insights into the relative importance of different processes structuring that community. Two general types of processes have been proposed, namely habitat filters and niche differentiation. Habitat filters may restrict the range of trait values and niche differentiation may affect species’ spacing leading to broad trait distributions. We characterized nine functional traits from 80 dipterocarp species in the 52-hectare plot in Lambir Hills National Park (LHNP), Sarawak, Malaysia. Four soil types, characterized by increasing fertility and moisture, have been identified in LHNP. We calculated the mean, variance, range, kurtosis and standard deviation of neighbor distances divided by the range (SDNDr) of the trait values per quadrat and compared these values to those of a null community. Specifically, we addressed two questions. (1) Are trait distribution patterns consistent with a prediction based on habitat filters and niche differentiation? (2) Does the strength of habitat filtering and niche differentiation change across soil types?
Results/Conclusions
We found nonrandom patterns in trait distribution and evidence for habitat filters, however there was little evidence for niche differentiation except for seed mass and wood specific gravity (WSG). There were significant differences in the means of specific leaf area, leaf toughness, leaf succulence, and WSG across soil types. These quadrat mean traits were associated with soil fertility and moisture. Although the variance, range, kurtosis and SDNDr of some traits had significant differences among soil types, we found no consistent pattern in these differences across soil types. The observed patterns of trait distribution suggest that diversity of soil types and other abiotic factors shape the dipterocarp community of LHNP. Additionally, the diversity of dipterocarp species may be maintained by within habitat strategy differences.
