Abstract:

[Objective] Interspecific covariation plays a fundamental role in maintaining species coexistence, optimizing resource use, and promoting vegetation stability in communities. Forest communities distributed across the Danxia landforms of northern Guizhou serve as an ecological barrier in the middle and upper reaches of the Yangtze River. This study aims to reveal the theoretical mechanisms by which forest communities attain stability through interspecific covariation across different structural layers in the region. [Methods] This study focused on a typical evergreen broad-leaved forest in the Changqiangou region of the Xishui National Nature Reserve in northern Guizhou. Community plots were established for field surveys to assess species niches, interspecific covariation, and community stability across vertical layers using niche breadth indices (B_(S), B_(L)), the niche overlap index (O_ij), the variance ratio method (VR), the χ² test, and Spearman's rank correlation test. [Results] The results indicated that Cunninghamia lanceolata had the highest importance value in the arbor layer, while Chimonobambusa utilis and Dryopteris erythrosora dominated the shrub and herb layers, respectively. These predominant species also exhibited relatively large niche breadth values, underscoring their dominance within their corresponding vertical layers. The proportion of species pairs with niche overlap values (O_ij ≥ 0.5) decreased from the arbor layer (70.53%) to the shrub (43.68%) and herb layers (30.00%), suggesting a gradual decline in interspecific competition along the vertical gradient. Interspecific covariation and correlation were stronger in the arbor and shrub layers than in the herb layer. Specifically, the arbor and shrub layers exhibited significant positive overall covariation. whereas the herb layer showed only a non-significant positive trends, indicating that positive interspecific interactions were more pronounced in the arbor and shrub layers. Euclidean distances to the community stability point were quantified 21.5 and 24.2 for the arbor and shrub layers, respectively, whereas the herb layer had the largest distance, at 24.6, reflecting higher relative stability in the arbor and shrub layers and the lowest stability in the herb layer. [Conclusion] These results demonstrate that interspecific covariation and stability decrease progressively from the arbor to the shrub and herb layers, that the arbor and shrub layers exhibit strong competition while maintaining high stability, and that robust positive interspecific interactions facilitate community evolution. The findings of this study provide a reference for the sustainable management of forests in nature reserves.

Key words: Danxia landform, forest communities, niche, interspecific covariation, stability

摘要：

【目的】种间协变可维持群落物种共存、优化资源利用和促进植被稳定性。贵州黔北丹霞地貌分布的森林群落在长江中上游发挥着生态屏障功能，本研究旨在揭示该区域森林群落在不同结构层次上如何实现种间协变以维持群落稳定性。【方法】本研究通过贵州习水国家级自然保护区长嵌沟片区典型的常绿阔叶林为对象，设置群落样地调查，利用生态位宽度指数（B_(S)、B_(L)）、生态位重叠指数（O_ij）、方差比率法（R）、χ²检验和Spearman秩相关检验法，按群落垂直结构层次研究物种生态位、种间相互作用和群落稳定性。【结果】森林群落乔灌草3个层次重要值最高的分别是杉木（Cunninghamia lanceolata）、金佛山方竹（Chimonobambusa utilis）和红盖鳞毛蕨（Dryopteris erythrosora），生态位宽度值也较大，表明这几个物种是各自层次的优势种。群落不同结构层次O_ij≥0.50的种对占比乔木层为70.53%、灌木层为43.68%和草本层为30.00%，表明乔灌草层种间竞争依次降低。乔木层和灌木层的种间协变和相关性强于草本层，乔灌层总体协变表现出显著正关联，而草本层为不显著正关联，表明乔木层和灌木层种间正协同作用较强。乔灌草各层次群落稳定点欧氏距离分别为21.5、24.2和24.6，说明乔灌层相对稳定性较高，而草本层稳定性最低。【结论】森林群落种间协变和稳定性随乔灌草层次改变逐渐降低，乔木层和灌木层种间竞争作用强而稳定性高，种间正相互作用明显而促进群落演化。研究结果可为自然保护区森林可持续管理提供参考。

关键词: 丹霞地貌, 森林群落, 生态位, 种间协变, 稳定性