基于功能性状的中亚热带岩溶常绿落叶阔叶混交林物种多样性维持研究

理解植物功能性状和功能实体在森林群落的分布,有助于探讨物种丧失对森林生态系统功能、冗余和恢复力的影响。为了解脆弱的岩溶石山森林在应对生物多样性丧失的生态系统反馈,对桂林岩溶石山两块1hm²的常绿落叶阔叶混交林的木本植物数据进行了分析。包括基于功能性状计算功能多样性、构建功能实体计算功能冗余以及采用Pearson相关分析和Mantel检验评估物种多样性指标在生态系统的维持机制。结果显示:(1)青冈+大叶榉树群落的功能多样性指标均低于鱼骨木+青冈+圆叶乌桕群落,且两个群落间功能均匀度不相关(P ＞ 0.05),功能丰富度、功能离散度和Rao''s二次熵呈现极显著相关性(P ＜ 0.001),功能分散度呈现显著相关性(P ＜ 0.05)。(2)两个群落的物种丰富度与功能冗余指标表现出相似的线性关系,即物种丰富度与功能实体等级、功能冗余、功能超冗余呈正相关,与功能脆弱性呈负相关关系。(3)不同植物功能性状间、不同功能多样性指标间和不同功能冗余指标间的相关性较强,功能多样性指标和功能冗余指标间无显著相关性,但功能性状与功能多样性指标、功能性状与功能冗余指标均存在不同程度的相关性。而在功能实体与物种多样性指标的相关性方面,呈现出同物种丰富度与物种多样性指标相似的显著度。另外,物种多度与物种丰富度、功能分散度、功能离散度、Rao''s二次熵及功能脆弱性均显著相关。总之,在岩溶石山常绿落叶阔叶混交林中,高功能多样性的群落存在高功能冗余的现象,但功能多样性和功能冗余是相互独立的因素;物种丰富度高的群落所提供的保险效应无法抵消其生态系统的脆弱性。因此,不能仅通过保护物种丰富度来维持生态系统的特有功能,还应充分考虑多度对生态系统功能的贡献,以更有效地实现对岩溶石山森林生态系统的保护。

Maintenance of species diversity in evergreen deciduous broad-leaved mixed forest of karst hills in central subtropical region based on functional traits

Understanding the distribution of plant functional traits and functional entities in forest communities can contribute to exploring how species loss impact on forest ecosystem function, redundancy, and resilience. To figure out the ecosystem performance of fragile karst hills forests in response to biodiversity loss, this study analyzed woody plant data from two 1hm² deciduous broad-leaved mixed forests which is located in the karst hills of Guilin. The analysis included calculating functional diversity based on functional traits, constructing functional entities for computing functional redundancy, and applying Pearson analysis and Mantel test to examine the maintenance mechanism of species diversity indicators in the ecosystems. The results showed that: (1) All the functional diversity indicator of Quercus glauca+Zelkova schneideriana community were lower than those of Psydrax dicocca+Quercus glauca+Triadica rotundifolia community, and the functional evenness was not correlation between two communities (P > 0.05). Additionally, the functional richness, functional dispersion and Rao''s quadratic entropy of the two communities showed highly significantly correlated (P < 0.001), and the functional divergence indicates showed significant correlation (P < 0.05). (2) The species richness and functional redundancy indices of the two communities exhibited similar linear relationship. Specifically, species richness was positively correlated with functional entities rank, functional redundancy, and functional over-redundancy, while species richness was negatively correlated with functional vulnerability. (3) There were strong correlations among different plant functional traits, different functional diversity indicators and different functional redundancy indicators, and no significant correlations between functional diversity indicators and functional redundancy indicators, but there were different degree of correlations between functional traits and functional diversity indicators, and between functional traits and functional redundancy indicators. It should not be ignored that the correlations between functional entities and species diversity indicators showed similar significance to species richness and species diversity indicators. In addition, species abundance was significantly correlated with species richness, functional divergence, functional dispersion, Rao''s quadratic entropy and functional vulnerability. In conclusion, in evergreen deciduous broad-leaved mixed forest of karst hills, communities with high functional diversity demonstrated highly functional redundancy, while functional diversity and functional redundancy were independent factors. Furthermore, it is noteworthy that the insurance effect provided by communities with high species richness could not fully offset the vulnerability of the ecosystem. To realize the conservation of forest ecosystems in karst hills more effectively, not only maintain the unique function of the ecosystem only by protecting the species richness, but also should fully consider the contribution of species abundance to the ecosystem function.