Latitudinal and climate effects on key plant traits in Chinese forest ecosystems

A long-standing goal of ecology and forest management is to understand the environmental controls of resource utilization strategy of plants along geographical gradients. However, the mechanisms that guide this phenomenon, especially along latitude gradients, remain unclear. Using key leaf functional trait data of 1185 species within 120 sites in Eastern and Western China, we quantified the relationships between plant traits, namely leaf area (LA), specific leaf area (SLA), leaf nitrogen content, leaf phosphorus content, leaf dry matter content (LDMC) and leaf delta 13C (d 13C) content, and local climate along the latitude in Eastern and Western China. Our results revealed that: (1) Plant traits showed a wide variation across the study locations in China. The variation in plant traits was strongly correlated with latitude. (2) In Eastern China, latitude alone explained 54% and 53% of the variation in N:P and leaf phosphorus content (Pmass (g/kg)), respectively. In Western China, latitude alone explained 75% of the variation in leaf area. In Eastern China, most plant traits are significantly correlated with each other. However, this phenomenon is not obvious in Western China. (3) Immediate climate factors (mean climate in the month when the leaf traits were sampled) contributes most to explaining functional traits related to leaf nutrients, such as leaf nitrogen content (Nmass (g/kg), Narea (g/cm2)), leaf phosphorus content (Pmass (g/kg), Parea (g/cm2)), and annual mean climate contributes more to explaining functional traits related to leaf survival strategies. (4) In Eastern China, immediate climate and annual mean climate variables can explain the variance of 39.2% and 41.3% of plant traits variation, respectively. In Western China, the effect size of corresponding factors are 23.4% and 25.2%, respectively.