Response of Leaf Functional Traits of Quercus rehderiana Hand.-Mazz. to Elevation Gradient

Studying the response of plant leaf functional traits to elevation helps us understand plant adaptation to the environment and their distribution trends under global climate change. Currently, how plant leaf functional traits respond to elevation across different scales or among different species remains controversial. Quercus rehderiana Hand.-Mazz. is widely distributed across various altitude ranges in southwestern China, making it an ideal species to address this question. Therefore, this study established three 20 × 20 m quadrats at each of five altitude gradients (2000, 2200, 2400, 2600, and 2800 m). By measuring morphological and nutrient indicators in leaves from five individuals of Quercus rehderiana in each quadrat, we analyzed the response of leaf functional traits to elevation. The results showed that leaf thickness (LT), specific leaf area (SLA), phosphorus (P), potassium (K) concentrations, carbon phosphorus ratio (C:P ratio), and nitrogen phosphorus ratio (N:P ratio) of Quercus rehderiana varied significantly across different elevations. Regression analysis revealed that leaf area (LA), K concentration, and carbon nitrogen ratio (C:N ratio) decreased with increasing elevation, while LT and nitrogen (N) concentration increased. Correlation analysis indicated that LA was significantly negatively correlated with LT and leaf P concentration, but positively correlated with carbon (C) concentration and stoichiometric ratios (C:N, C:P, N:P). Leaf thickness (LT) was significantly negatively correlated with K and calcium (Ca) concentration. Specific leaf area (SLA) and K concentration were significantly negatively correlated with leaf dry matter content (LDMC). The leaves of Quercus rehderiana mainly adapt to different elevations through trade-offs among different morphological and chemical traits. These findings can support the conservation of germplasm resources and forest management.