The Effects Of Phylogenetic And Functional Diversity On Plant Community Productivity In Alpine Meadows Of Qinghai-Tibetan Plateau

How biodiversity affects ecosystems functioning is one of the most studied and controversial issue in ecology. In fact ’biodiversity’ itself can be quantified in many different ways.The simplest measure, species richness, has repeatedly been shown to correlate with biomass production. We know that different diversity measures can explain a substantial amount of the variation in productivity in experimental settings, where a large range in phylogenetic relationships or trait variation has been explicitly designed. But these different measures of biodiversity and their interactions explain variation in productivity in natural assemblages has rarely been tested. We developed a diversity-productivity experiment in alpine meadows of the Tibetan Plateau where we manipulated the naturally occurring species, functional and phylogenetic diversity in replicated removal treatments. And we combined different biodiversity measures (functional, phylogenetic, richness, evenness) in generalized linear models to determine which combinations provided the most parsimonious explanations of variation in biomass production. The results show that:i) species functional traits show no or weak phylogenetic signal, again demonstrating that they were weak or unimportant. ii) When compared to individual traits, the multivariate functional diversity predictors were always outranked by phylogenetic diversity and some combination of single functional traits to explanations of variation in biomass production. iii) The combination of evolutionary distinctiveness (Hed) and maximum plant height provided the most parsimonious explanations of variation in biomass production. Evidence for a phylogenetic signal in the trait of maximum plant height appears to arise from the larger mean maximum height of species within the Poaceae & Cyperaceae. iv) The strong relationships among most of the raw indices, especially between species richness (S), evenness (H’), the multivariate functional diversity indices and phylogenetic diversity indices.