Temporal shifts in soil nitrogen cycling responses to plant diversity across global terrestrial ecosystems

Abstract Nitrogen (N) is essential to all life on Earth. Despite ongoing biodiversity loss, the influence of plant diversity on soil N cycling over time remains uncertain, which limits our ability to predict terrestrial N pools and transformations globally. To determine the long‐term effects of plant diversity on soil N pools and N transformations, we conducted a global synthesis using 2129 paired observations of plant mixtures and corresponding monocultures from 135 studies across 32 countries. On average, plant mixtures have 3.1% higher soil total N content than monocultures, but 7.7% to 31.6% lower soil ammonium content, nitrate content and rates of soil N mineralization, nitrification, denitrification and N 2 O emissions. Notably, the effects of plant mixtures on soil total N content and rates of N mineralization, nitrification and denitrification shift rapidly over time from negative to positive. However, their effects on soil nitrate content and N 2 O emissions are consistently negative. Furthermore, these plant mixture effects remain consistent across ecosystems. Synthesis and applications . These findings suggest that conserving and restoring plant diversity can enhance long‐term N transformation rates and total soil N content, while reducing N 2 O emissions, collectively promoting soil N cycling sustainability and mitigating climate change‐related risks. Read the free Plain Language Summary for this article on the Journal blog .