Global distribution and drivers of relative contributions among soil nitrogen sources to terrestrial plants
Chao‐Chen Hu, Xueyan Liu, Avery W. Driscoll, Yuanwen Kuang, E. N. Jack Brookshire, Xiao‐Tao Lü, Chong-Juan Chen, Wei Song, Rong Mao, Cong‐Qiang Liu, Benjamin Z. Houlton
Abstract
Abstract Soil extractable nitrate, ammonium, and organic nitrogen (N) are essential N sources supporting primary productivity and regulating species composition of terrestrial plants. However, it remains unclear how plants utilize these N sources and how surface-earth environments regulate plant N utilization. Here, we establish a framework to analyze observational data of natural N isotopes in plants and soils globally, we quantify fractional contributions of soil nitrate ( f NO3- ), ammonium ( f NH4+ ), and organic N ( f EON ) to plant-used N in soils. We find that mean annual temperature (MAT), not mean annual precipitation or atmospheric N deposition, regulates global variations of f NO3- , f NH4+ , and f EON . The f NO3- increases with MAT, reaching 46% at 28.5 °C. The f NH4+ also increases with MAT, achieving a maximum of 46% at 14.4 °C, showing a decline as temperatures further increase. Meanwhile, the f EON gradually decreases with MAT, stabilizing at about 20% when the MAT exceeds 15 °C. These results clarify global plant N-use patterns and reveal temperature rather than human N loading as a key regulator, which should be considered in evaluating influences of global changes on terrestrial ecosystems.