Linking leaf venation traits with demography and distribution across 54 co-occurring tree species in Taiwan

Background/Question/Methods

An important goal in plant community ecology is to understand how species traits determine demographic performance and consequently shape distribution patterns. Several functional traits have been shown to correlate with growth and mortality rates in trees, but leaf traits related to the "leaf economics spectrum" are found to be only weakly related with demographic rates in community-wide species comparisons. One possible reason for these weak results is that ontogenetic variation in leaf traits and demographic rates are rarely measured and analyses of species means provide weaker relationships. Another reason is that unobserved leaf traits relating to the water economy such as leaf venation may be important for plant demographic performance. However, less is known about how leaf traits in the water economy are related to demographic rates across co-occurring diverse species at the community scale. To address the question if leaf traits related to the water economy are good indicators of demographic performance and distribution patterns, we examined leaf venation traits and related them with environmental variables and species potential demographic rates for 54 co-occurring species in a Taiwanese forest. Relative growth rate (RGR) and mortality were estimated using a hierarchical Bayesian approach to separate size-dependent changes in demography.

Results/Conclusions

Leaf venation traits were significantly correlated with environmental variables and potential demographic rates as were other species traits such as wood density, maximum height and leaf morphological and chemical traits. Species with relatively wider and denser leaf veins, denser wood, taller adult height and leaves with low specific leaf area and mass-based phosphorus tend to have higher potential RGR. Species with leaves having relatively wider veins, small leaf area, low specific leaf area, low mass-based phosphorus and nitrogen of leaves and dense wood tend to have low potential mortality. Significant correlations between these traits and environmental variables such as available nitrogen, elevation and convexity were also found, suggesting that species functional traits influence their distribution patterns within a community. This study showed that several functional traits including leaf venation traits affect potential demographic rates and shape species distribution patterns along environmental gradients in a Taiwanese subtropical forest. The work also shows that alternative aspects of leaf form and function are more related to tree species performance than other commonly measured leaf traits and that consideration of ontogenetic changes in demography is likely critical for linking traits to performance.