Nitrogen use efficiency of terrestrial plants in China: geographic patterns, evolution, and determinants.

Background: Plant nitrogen use efficiency (NUE) is an important ecological indicator that reflects the capacity of a plant to transform nitrogen into production, which is essential for further elucidating plant growth and terrestrial ecosystem productivity. Although there are a growing number of studies that address NUE changes at local scales, the variations of NUE over large spatial scales remain unclear. In this study, we analyzed the geographic patterns of NUE and explored its phylogenic and environmental drivers across 1452 species at 1102 sites in China. Results: NUE tended to decrease with latitude (r = − 0.56), whereas it increased with longitude (r = 0.54), and varied widely in different ecosystems and plant life forms. Furthermore, NUE was negatively correlated with plant foliar phosphorus concentration (r = − 0.53), soil pH (r = − 0.10), soil total phosphorus (r = − 0.13) and available phosphorus (r = − 0.05), but positively with the mean annual temperature (r = 0.32), annual precipitation (r = 0.27), and aridity index (r = 0.26). NUE was significantly altered with phylogeny and evolved toward a lower value (r = − 0.28), which may have been due to increasing nitrogen deposition and fixation in biogeochemical evolution. Overall, the combination of foliar phosphorus concentration, phylogeny, climate, and soil properties accounted for 52.7% of the total variations of NUE. In particular, foliar phosphorus concentration was the most important factor, whereas plant evolutionary history was second in contributing to NUE variations. Conclusions: Our study emphasizes the pivotal role of plant stoichiometry and phylogeny in nitrogen cycling and suggests incorporating them into earth system models to better understanding plant growth and nitrogen cycling in the context of environmental changes. [ABSTRACT FROM AUTHOR]