Geographical patterns of functional trait means and variances of tree and herbaceous plant assemblages across the New World

Background/Question/Methods

Although the latitudinal gradient in species richness has been thoroughly described, the latitudinal variation in other important biodiversity aspect, functional traits, has gained much less attention. This can be due to the data limitation, large trait databases has been compiled only very recently. Here we used the largest database to date compiling the observations and functional traits of plant species in the whole New World (BIEN, Botanical Information and Ecology Network) to access the pattern of functional trait variation across the New World. We focused on the assemblage means and variances of 5 major plant functional traits: height, specific leaf area, seed mass, leaf nitrogen and leaf phosphorus content per mass. We tested for the strength of trait environmental filtering using three main climatic descriptors (temperature, precipitation and evapotranspiration). We compared these trait patterns for woody and herbaceous species.

Results/Conclusions

We found strong spatial patterns of means and variances for most of traits for both woody and herbaceous species. Whereas the pattern of means and variances in height was similar for both woody and herbaceous species, the patterns in all other traits often varied between these life-form groups. Mean annual temperature and evapotranspiration were the most important predictors for variation in means and variances in traits for both woody and herbaceous species. Overall we highlight that the  composition of herbaceous and woody species across the New World is strongly driven by climate, particular patterns for each trait and each life-form group, however, vary.