广西大明山亚热带森林树木功能性状与功能多样性的海拔格局及其影响因素

Tree functional traits and functional diversity of subtropical forests and their environmental drivers along an altitude gradient in Daming Mountain in Guangxi

关键词:  树木功能性状，功能多样性，环境因子，海拔，大明山

Key words:  tree functional traits, functional diversity, environmental factor, altitude, Daming Mountain

摘要:

掌握植物功能性状与功能多样性的空间格局及其影响机制，对理解生态系统功能以及制定生物多样性保护策略具有重要价值。该研究在广西大明山300~1 400 m的8个海拔段建立了24个森林监测样地，在开展群落调查和树木功能性状测定基础上，分析了亚热带森林8种植物功能性状和4种功能多样性指数的海拔变化格局及其影响因素。结果表明：（1）随着海拔升高，树木叶厚度与叶干物质含量显著增加，叶面积、比叶面积、叶片碳含量、叶片氮含量及叶片含水率则显著下降，叶片磷含量无显著变化。（2）功能丰富度和功能离散度沿海拔呈驼峰型变化，功能均匀度先降低后升高，Rao二次熵指数则单调递增。（3）冗余分析表明，海拔和土壤全钾是影响功能性状空间格局的主要因素，而与海拔相关的土壤温湿度及土壤全磷含量是功能多样性的关键影响因子。该研究为理解山地树木对环境变化的适应策略及森林生态系统管理提供了科学依据。

Abstract:

Understanding spatial patterns of plant functional traits and functional diversity, and the mechanisms that drive them, is essential for interpreting ecosystem functioning and for designing biodiversity conservation strategies. However, patterns of tree functional traits and functional diversity along altitude gradients in mountain forests, and the environmental drivers behind those patterns, remain poorly understood. By establishing 24 forest monitoring plots across eight altitudinal ranges (300–1 400 m) in the subtropical montane forest of Daming Mountain, Guangxi, South China, this study analyzed the altitudinal variation in eight tree functional traits and four functional diversity indices using community survey and trait measurement data, and evaluated their key environmental determinants. The results were as follows: (1) With increasing altitude, leaf thickness and leaf dry matter content increased significantly, while leaf area, specific leaf area, leaf carbon content, leaf nitrogen content, and leaf water content decreased significantly. In contrast, leaf phosphorus content displayed no clear altitudinal trend. Specific leaf area was strongly negatively correlated with leaf dry matter content and significantly positively correlated with both leaf nitrogen and leaf phosphorus contents. Leaf nitrogen and leaf phosphorus contents were significantly positively correlated, while leaf phosphorus content was negatively correlated with leaf carbon content. (2) Functional richness and functional divergence displayed unimodal (hump-shaped) patterns along the altitude gradient. Functional evenness declined initially and then increased, whereas Rao’s quadratic entropy increased monotonically with altitude. (3) Redundancy analysis indicated that altitude and soil total potassium were the main factors explaining spatial variation in functional traits, accounting for 29.6% and 12.8% of the variation, respectively. For functional diversity, altitude-associated soil temperature and soil total phosphorus were key drivers; soil temperature alone explained the largest share of variation (36.0%), followed by soil total phosphorus (7.9%) and soil moisture (7.6%). This study reveals that leaf structural traits exhibit stronger altitudinal adaptation than nutrient-related traits, whereas functional diversity is more responsive to soil nutrients and microclimate than plant traits. These findings advance our understanding of tree adaptive strategies in montane forests and provide insights for ecosystem management. We recommend prioritizing conservation of mid-altitude diversity hotspots in Daming Mountain, as well as managing soil phosphorus and potassium availability to support the restoration of degraded forests.