Variation in characteristics of leaf functional traits of alpine vegetation in the Three-River Headwaters Region, China

Plant functional traits are adaptive traits formed by interactions between plants and the environment. Consid-ering the Three-River Headwaters Region as a case study, this study systematically analyzed the relationship between plant functional traits and environmental factors in cold regions. The results show that there were significant differences in plant functional traits among the different vegetation types (herbs, shrubs, and arbor plants). Leaf traits such as leaf area (LA), leaf length (LL), leaf width (LW), leaf circumference (LC), and shape coefficient (SC) showed the same trends among herbs, shrubs, and arbor plants. The correlation between leaf functional traits of plants in alpine regions shows that the unique growth mode of different plants and their degree of adaptation to alpine environments ultimately determine the leaf functional trait variations. Moreover, there was a negative correlation between soil temperature and the nitrogen balance index (NBI), chlorophyll content (Chl), flavonoid content (Flv), and SC, whereas there was a trend of first increasing and then decreasing relationship between soil temperature, LL (P < 0.05), and LC (P < 0.05). Similar to herb and shrub plants, arbor plants also showed significant differences in altitude in cold regions. There were significant negative correlations between altitude and NBI (P < 0.05), Chl (P < 0.05), Flv (P < 0.05), and anthocyanin content (P < 0.05), whereas LA (P < 0.05), LL (P < 0.05), and LC (P > 0.05) were significantly positively correlated with altitude. Conversely, there was no significant negative correlation between LW and altitude (P > 0.05). We conclude that climate factors play a decisive role in the distribution of plant functional traits at a global scale, whereas land use and disturbances play a major role at a regional scale, and topographic and soil factors determine the distribution of local characteristics.