Meta-analysis shows that plant mixtures increase soil phosphorus availability and plant productivity in diverse ecosystems

Soil phosphorus (P) availability is critical to plant productivity in many terrestrial ecosystems. How soil P availability responds to changes in plant diversity remains uncertain, despite the global crisis of rapid biodiversity loss. Our meta-analysis based on 180 studies across various ecosystems (croplands, grasslands, forests and pot experiments) shows that, on average, soil total P, phosphatase activity and available P are 6.8%, 8.5% and 4.6%, respectively, higher in species mixtures than in monocultures. The mixture effect on phosphatase activity becomes more positive with increasing species and functional group richness, with more pronounced increases in the rhizosphere than in the bulk soil. The mixture effects on soil-available P in the bulk soil do not change, but with increasing species or functional group richness these effects in the rhizosphere soil shift from positive to negative. Nonetheless, enhanced soil phosphatase activity stimulated available P in diverse species mixtures, offsetting increased plant uptake effects that decrease soil-available P. Moreover, the enhancement effects of species richness on soil phosphatase activity are positively associated with increased plant productivity. Our findings highlight that preserving plant diversity could increase soil phosphatase activity and P availability, which sustain the current and future productivity of terrestrial ecosystems. In a meta-analysis of studies comparing monocultures to plant species mixtures, the authors show that mixtures increase three different variables related to the phosphorus cycle: soil total phosphorus, phosphatase activity and available phosphorus.