Foliar Nitrogen and Phosphorus Asymmetrically Predict the Thermal and Hydric Niches of Woody Plants in Eastern China

Understanding the formation mechanisms of plant hydrothermal niches is a core issue in ecology. This study focused on 362 woody plant species in eastern China to investigate the effects of leaf nitrogen (N), phosphorus (P), and their ratio (N/P) on hydrothermal niches and to assess the role of phylogenetic signals. Our results showed that all niche parameters exhibited significant yet varying strengths of phylogenetic signals, with thermal niche signals generally stronger than those of hydric niches. Leaf N and P were significantly correlated with thermal niche dimensions (e.g., breadth and lower limits), whereas leaf N/P and P primarily drove variation in hydric niche dimensions (e.g., breadth and upper limits). This study confirms the asymmetric and dimension-specific influences of leaf nutrients on hydrothermal niches, highlights the necessity of controlling for phylogenetic history in trait-niche research, and provides new perspectives for understanding plant environmental adaptation and evolution.