南亚热带森林常见种和偶见种的功能多样性特征

群落特征可能取决于物种在功能实体功能特征的独特组合（FE）中的分布。了解这些分布是保护生物多样性和维持生态系统功能的基础。鼎湖山南亚热带常绿阔叶林群落物种丰富，根据物种的多度来区分常见种（每hm²超过一个个体）和偶见种（每hm²少于一个个体）。基于功能实体，分别计算功能实体数量、功能冗余度、功能脆弱度和功能过度冗余度来描述每个样方中常见种和偶见种的功能多样性。采用Wilcoxon检验检测常见种和偶见种功能性状的差异，通过线性回归分析常见种和偶见种的功能多样性与物种数量的关系，采用冗余分析（RDA）影响常见种和偶见种的功能多样性的环境因子。研究结果表明：（1）鼎湖山南亚热带常绿阔叶林群落中功能性状在常见种和偶见种间差异显著。（2）群落中数量较低的偶见种保持着较高比例的功能实体数量。功能实体数量、功能冗余度与常见种和偶见种数量显著正相关，功能过度冗余度与偶见种数量显著正相关，功能脆弱度与常见种和偶见种的物种数量呈显著负相关。（3）海拔是影响常见种功能多样性最关键的地形因子，凹凸度是影响偶见种功能多样性最关键的地形因子。土壤含水量是影响常见种功能多样性最关键的土壤因子，速效钾是影响偶见种功能多样性最关键的环境因子。研究结果表明，尽管物种丰富的热带森林具有较高的功能冗余，但其提供的保险效应不能抵消生态系统的功能脆弱性。减少具有独特功能实体和偶见种的损失是避免热带森林生态系统功能损失的有效和必要的方法。

Influencing factors of functional redundancy and functional vulnerability of common and occasional species in south Asian tropical forests

Many community characteristics depend upon the distribution of species among functional entities (unique combinations of functional traits). Understanding these distributions is fundamental to conserve biodiversity and maintain ecosystem functions. We distinguish between common species (more than one individual per hectare) and rare species (less than one individual per hectare) based on species richness in the southern subtropical evergreen broad-leaved forest community of Dinghushan, Guangdong Province. In this study, based on functional entities, the number of functional entities, functional redundancy, functional vulnerability, and functional over-redundancy were calculated separately to describe the functional diversity of common and rare species. Wilcoxon test method was used to detect the differences in functional traits among common and rare species. Linear regression was used to analyze the relationship between the functional diversity of common and rare species and the number of species. RDA(Redundancy Analysis) was used to analyze the environmental factors affecting the functional diversity of common and rare species. The results showed that:(1) There were significant differences in functional traits among common and rare species of the subtropical evergreen broad-leaved forest in Dinghushan. (2) The lower number of rare species in the community maintained a higher proportion of the number of functional entities. The number of functional entities was significantly and positively correlated with the number of common and rare species, and the number of functional entities increased much more rapidly with the number of rare species than with the number of common species, suggesting that communities with high abundance are less sensitive to species loss. The functional redundancy was significantly and positively correlated with the number of species of common and rare species, suggesting that southern subtropical forests with high species numbers are more resistant to disturbance. The functional over-redundancy was significantly and positively correlated with the number of rare species, indicating that rare species have a higher density of species in their functional entities. The functional vulnerability was significantly negatively correlated with the number of species of common and rare species, indicating that species-rich communities moderately reduced potentially functional vulnerability, but the degree of vulnerability remained higher in species-rich communities. (3) Elevation was a significant topographic factor affecting functional diversity of common species, and relief was a significant topographic factor affecting functional diversity of rare species. Soil water content was a significant soil factor affecting the functional diversity of common species, and fast-acting potassium was a significant environmental factor affecting the functional diversity of rare species. Our results highlighted that although species-rich tropical forests had high probability of functional redundancy, the insurance effect provided by that could not offset functional vulnerability in the ecosystems. Reducing loss of species with unique trait combinations and occasional species is an effective and necessary way to avoid the loss of functions in tropical forest ecosystems.