Data and Code for Patterns and drivers of plant CNP stoichiometry across a 3000 km aridity gradient

Leaf element stoichiometry is crucial for understanding nutrient dynamics and carbon (C) cycling in terrestrial ecosystems. However, the biogeographical patterns of leaf C, nitrogen (N), and phosphorus (P) content and their stoichiometric relationships along aridity gradients remain poorly understood, particularly regarding their driving factors. This study examined leaf C:N stoichiometry across a 3,000 km aridity gradient in China, encompassing 36 sampling sites representing forest, grassland, and desert ecosystems. We further investigated the relationships between leaf biochemical traits and environmental drivers. Results revealed that the mean leaf contents of C, N, and P at 588.29 ± 6.9, 19.11 ± 0.3, and 1.33 ± 0.03 g kg-1, respectively. The C:N, C:P, and N:P ratios were obtained as 32.43 ± 0.64, 480.65 ± 11.36, and 15.71 ± 0.4, respectively. The leaf C:N:P stoichiometry exhibited a pervasive nonlinear pattern, and a threshold of approximately 0.7 on an aridity index (AI). Below this threshold (AI < 0.7), the leaf C:P and N:P ratios decreased as AI increased, and N limitation became more evident. Conversely, these ratios increased above this threshold (AI > 0.7), indicating that P availability increasingly constrained plant growth. Furthermore, plants in arid regions (AI < 0.7) demonstrated strong stoichiometric homeostasis, suggesting effective physiological adaptation to environmental fluctuations. This homeostatic capacity substantially weakened in humid regions (AI > 0.7), where plants showed greater stoichiometric plasticity. These findings advance our understanding of spatial patterns in leaf nutrient stoichiometry and provide critical insights for modeling ecosystem nutrient cycling under global climate change scenarios.

叶片元素化学计量学（leaf element stoichiometry）对于解析陆地生态系统的养分动态与碳（C）循环过程至关重要。然而，沿干旱梯度分布的叶片碳、氮（N）、磷（P）含量及其化学计量关系的生物地理格局，尤其是其驱动机制，目前仍不甚明晰。本研究针对中国境内跨度达3000千米的干旱梯度展开叶片碳氮化学计量学分析，共设置涵盖森林、草原与荒漠生态系统的36个采样点位。我们进一步探究了叶片生化性状与环境驱动因子间的关联。研究结果表明，供试样品的叶片碳、氮、磷平均含量分别为588.29±6.9、19.11±0.3与1.33±0.03 g·kg⁻¹；碳氮比、碳磷比及氮磷比分别为32.43±0.64、480.65±11.36与15.71±0.4。叶片碳氮磷化学计量学呈现显著的非线性分布特征，且存在约0.7的干旱指数（aridity index, AI）阈值。当干旱指数低于该阈值（AI<0.7）时，叶片碳磷比与氮磷比随干旱指数升高而降低，氮限制效应愈发显著；反之，当干旱指数高于该阈值（AI>0.7）时，上述比值均呈上升趋势，表明磷素有效性对植物生长的约束作用持续增强。此外，干旱区域（AI<0.7）内的植物表现出较强的化学计量稳态性，提示其对环境波动具备高效的生理适应能力；而在湿润区域（AI>0.7），这种稳态能力大幅减弱，植物呈现出更强的化学计量可塑性。本研究成果深化了学界对叶片养分化学计量空间格局的认知，并为全球气候变化情景下的生态系统养分循环建模提供了关键理论依据。