Global evidence for joint effects of multiple natural and anthropogenic drivers on soil nitrogen cycling

• Published in: Global change biology 2024-05, Vol.30 (5), p.e17309-n/a
• Main Authors: Zhang, Yong, Cheng, Xiaoli, Terrer, Cesar, Choi, Woo‐Jung, Chen, Ji, Luo, Yiqi, Ciais, Philippe
• Format: Article
• Language: English
• Subjects: Anthropogenic factors; Climate; Climate models; Climatic conditions; Continental interfaces, environment; Cycles; Empirical analysis; Latitude; Machine Learning; Models, Theoretical; natural and anthropogenic forcings; Nitrogen; Nitrogen - analysis; Nitrogen - metabolism; Nitrogen Cycle; nitrogen isotope; Nitrogen Isotopes - analysis; Ocean, Atmosphere; plant traits; Rayleigh theory; Sciences of the Universe; Soil - chemistry; Soil properties
• ISSN: 1354-1013; 1365-2486
• DOI: 10.1111/gcb.17309

Global soil nitrogen (N) cycling remains poorly understood due to its complex driving mechanisms. Here, we present a comprehensive analysis of global soil δ15N, a stable isotopic signature indicative of the N input–output balance, using a machine‐learning approach on 10,676 observations from 2670 sites. Our findings reveal prevalent joint effects of climatic conditions, plant N‐use strategies, soil properties, and other natural and anthropogenic forcings on global soil δ15N. The joint effects of multiple drivers govern the latitudinal distribution of soil δ15N, with more rapid N cycling at lower latitudes than at higher latitudes. In contrast to previous climate‐focused models, our data‐driven model more accurately simulates spatial changes in global soil δ15N, highlighting the need to consider the joint effects of multiple drivers to estimate the Earth's N budget. These insights contribute to the reconciliation of discordances among empirical, theoretical, and modeling studies on soil N cycling, as well as sustainable N management. The stable N isotope (δ15N) has emerged as a useful tool for integrating N cycling processes into a single metric. Early studies hold that climatic conditions predominantly control soil δ15N and N cycling, whereas our comprehensive analysis reveals prevalent joint effects of climatic conditions, plant N‐use strategies, soil properties, and other natural and anthropogenic forcings on global soil δ15N. Considering the joint effects of multiple drivers is critical for better understanding and assessing the Earth's N balance.