Meta-analysis shows that planting nitrogen-fixing species increases soil organic carbon stock
Sun et al., 2025
Nitrogen (N)-fixing species are widely used in forestation and agriculture. The effects of planting N-fixing species on soil organic carbon (SOC) stock, however, remain uncertain, limiting policy development and their application towards a possible climate change mitigation strategy. Here we conduct a global meta-analysis of 385 datapoints from 136 studies comparing SOC stock with planting N-fixing versus non-N-fixing species. Planting N-fixing species increases SOC stock by 16% compared with non-N-fixing species. This SOC increase is closely accompanied by soil N increases, with an average accumulation of 7.8 g of SOC per gram of soil N increase. Climate mediates SOC responses, with greater SOC sequestration observed in drier and warmer regions, particularly in the tropics. We estimate that an additional increase of 0.29–0.75 PgC yr−1 in global SOC stock could be achieved by adopting N-fixing species for forestation, agriculture and regeneration of marginal lands, highlighting their potential for climate change mitigation.
Global distribution of the selected studies testing the effects of planting N-fixing species on SOC stock in this meta-analysis. Green and orange dots represent the geographic locations of studies on tree and crop planting, respectively. The green and orange shaded areas show the distribution ranges of planted forests and croplands, respectively. Inset: the distribution of the sites in the global biomes based on climatic conditions: MAT and MAP. Black dots indicate study sites in this meta-analysis.