What drives plant species diversity? A global distributed test of the unimodal relationship between herbaceous species richness and plant biomass

Question For over a century, ecologists have grappled with the question “what drives species diversity?” Urgent global issues such as loss of biodiversity and the relative importance of species richness for ecosystem function and services has heightened the relative importance of understanding processes that control species diversity. Here we present the plans for a global coordinated distributed experiment for herbaceous communities, the H erb D iv N et, to test the hump‐backed model, a unimodal relationship between species richness and aboveground plant biomass plus dead plant litter HBM , to determine whether scale may influence the HBM , and to explore drivers of plant diversity. Location Globally distributed experiment. Methods We propose a nested, standardized sampling design 8 × 8 m, with 1 m 2 plots, taken from multiple site locations along a range of sites varying in primary productivity. Results and Conclusions We welcome others with an interest in using global, standardized, coordinated distributed experiments to explore patterns and processes in herbaceous plant communities to join H erb D iv N et in the search of new insights to drivers of plant species diversity.