Soil nitrogen (N) availability is of critical importance to the productivity of terrestrial ecosystems worldwide. Plant diversity continues to decline globally due to habitat conversion and degradation, but its influence on soil N remains uncertain. By conducting a global meta-analysis of 1,650 paired observations of soil N in plant species mixtures and monocultures from 149 studies, we show that, on average across observations, soil total N is 6.1% higher in species mixtures. This mixture effect on total N becomes more positive with the number of species in mixtures and with stand age. The mixture effects on net N mineralization rate and inorganic N concentrations shift from negative in young stands to positive in older stands with greater positive effects in more-diverse mixtures. These effects of mixtures were consistent among cropland, forest and grassland ecosystems and held across climate zones. Our results suggest that plant diversity conservation not only enhances the productivity of current vegetation but also increases soil N retention that will sustain the productivity of future vegetation.
Bibliographical noteFunding Information:
We thank the authors whose work is included in this meta-analysis. We thank X. Chen for his suggestions on data analysis. This study was funded by the Natural Sciences and Engineering Research Council of Canada (RGPIN-2019–05109, RGPIN-2014– 04181, RTI-2017–00358, STPGP428641, and STPGP506284), Long-Term Ecological Research (LTER) grant DEB-1831944 and Biological Integration Institutes grant NSF-DBI-2021898.
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