Local‐Scale Controls Over Leaf N and P Stoichiometry of 121 Plant Species in the Inner Mongolia Grassland.

Nitrogen (N) and phosphorus (P) stoichiometry in plant leaves plays an important role in linking plant physiological processes with community assemblage and species distribution. Studies have revealed that temperature is a major driver of leaf stoichiometry, however, whether current global warming will alter leaf N and P stoichiometry on a local scale remain poorly understood. Taking advantage of an unique data set on leaf element concentrations of 122 plant species in the Xilingol Grassland National Reserve (established in 1979), we addressed this issue by resampling plant leaves of the same 121 species in 2018, and compared the leaf N, P, and N:P ratio between the 2 years. We found that leaf N, P, and N:P ratio of the 121 species all exhibited large variation, with a magnitude of 4.5‐fold for N, 5.8‐fold for P, and 6.3‐fold for N:P ratio, respectively. However, the mean leaf N, P, and N:P ratio of the 121 species, as well as for each family, each life form and each habitat type, did not significantly change over 40 years (1979 vs. 2018), though a 2°C increase in annual mean temperature occurred. We identified that taxonomic difference was the primary driver for variations in leaf N, P, and N:P ratio in this grassland reserve, which is different from those on the regional and global scales. These results suggest that controls over leaf stoichiometry are likely scale‐dependent. Thus, using leaf stoichiometry to explain community assemblage and species distribution should take into account the scale‐dependent drivers. Plain Language Summary: Nitrogen (N) and phosphorus (P) are important elements in terrestrial biogeochemical cycles. Disentangling the controls over leaf N, P, and N:P ratio at different spatial scales (i.e., local, regional and global) is of great significance for understanding the N and P cycles in terrestrial ecosystems, especially in the face of current global changes. Previous studies have revealed some global‐ and regional‐scale controls over leaf N, P, and N:P ratio, but the local‐scale controls remain inconsistent. By a field investigation on leaf N, P, and N:P ratio of 121 species in a grassland reserve, we showed that leaf N, P, and N:P ratio all exhibited large variation. We identified that taxonomic difference was the primary driver for leaf N and P stoichiometry, different from the major drivers on a regional or a global scale. Moreover, a 2°C‐increase in temperature over 40 years (1979–2018) did not alter the leaf N, P, and N:P ratio of the same 121 plant species, suggesting that the current magnitude of global warming does not necessarily alter local‐scale leaf stoichiometry. Key Points: Taxonomic difference plays a critical role in driving local‐scale leaf N and P stoichiometryA 2°C increase in annual mean temperature over 40 years does not alter leaf N, P, and N:P ratioLocal‐scale controls over leaf stoichiometry are different from those on the regional and global scales [ABSTRACT FROM AUTHOR]