Plant species natural abundances are determined by their growth and modification of soil resources in monoculture

Abstract

The abundance of a plant species in a diverse community may depend on two aspects of a plant’s resource niche: its ability to garner limiting resources for its own growth, and its ability to reduce resources available for other species. Given that these two aspects of niche can be quantified in monoculture, we tested whether plant growth or plant modification of soil resources in monoculture relate to plant abundance in naturally-assembled California grassland communities. We grew 18 native and exotic grassland plant species in replicated monocultures, measured plant biomass and soil resources in these monocultures, and then assessed how well the measured variables for each species in monoculture correlated with natural abundances of the species across the local landscape. Both aboveground and belowground plant biomass in monoculture were positively correlated with species abundances in naturally-assembled communities; aboveground monoculture biomass alone accounted for 63% of the natural variability in species abundances, whereas shallow and subsurface root biomass accounted for 28 and 38%, respectively. Nitrogen concentrations in shallow monoculture soils were also positively correlated with a species’ natural abundance in the field, accounting for 43% of the natural variability in species abundances. Our results suggest that the performance of species when grown alone—e.g., biomass production and impacts on soil resources—can inform their performance in diverse communities and across heterogeneous landscapes.