湿热河谷芭蕉群落优势物种空间分布格局与竞争对称性研究

Spatial distribution pattern and competitive symmetry of dominant species in Musa sp. community in the hot and humid river valley

竞争关系的对称性是塑造植物物种空间分布格局和影响物种共存重要机制之一,对其开展研究不仅对于揭示植物群落构建机制具有重要意义,也有助于解析群落演替的驱动力。在贵州赤水湿热河谷内的芭蕉群落中建设固定样地,对1989棵植物个体进行空间定位和物种识别并记录胸径等个体属性。采用对数相关函数和标记变异系数分析(marked variogram)等空间统计方法检测优势种的空间分布格局和竞争对称性,结果如下:(1)芭蕉(Musa sp.),粗糠柴(M.philippensis),粗叶木(L.chinensis),川钓樟(L.pulcherrima),红果黄肉楠(A.cupularis)等5种优势种均表现为小尺度下的种内聚集分布,其中芭蕉主要采用克隆繁殖,其重要值达33.6%,且种内聚集度最大。(2)芭蕉种群在5 m尺度下呈现出显著的种内对称性竞争,这一竞争过程减少了种群自疏作用并推动种内聚集分布格局的形成,增加了该种群在森林中的生存力。(3)芭蕉与其余4种优势种之间的不对称竞争过程导致了种间负关联。结果表明,不同优势种在种间竞争对称性上的差异说明了植物种群繁殖和扩散方式是群落构建的重要影响因素之一,相比于有性繁殖过程,采用无性克隆繁殖的植物个体可通过种内对称竞争机制来减少自疏以增加种群生存力,并通过与相邻异种个体的不对称竞争过程来提升种群获取有限资源的能力,进而成为演替中的优势个体。研究结果可为今后制定植物物种多样性保护政策提供科学参考。

The symmetry of competitive relations is one of the important mechanisms affecting plant biodiversity. Its research is of great significance not only to reveal the plant community assembly mechanism, but also to explain the driving factor of community succession. A plot was established for investigation in the hot and humid river valley of Chishui city, Guizhou province. The 1989 individual plants with diameter at breast height(DBH) over 1 cm were spatially located and identified at the species level. Attributes of individual plants such as diameter at breast height size and tree height also were recorded by investigation. The spatially statistical methods including pair-correlation function(PCF) based on inter-individual distances and marked variogram function(MVF) based on individual diameter at breast height were used to detect the spatial distribution pattern and potential competitive relationship of dominant species. The analysis showed that(1) the spatial distribution patterns of the five dominant species(Musa sp., M. philippensis, L. chinensis, L. pulcherrima, and A. cupularis) showed an aggregated distribution at a small scale. The importance value of Musa sp. in the constructive species reached 33.6% and the spatial aggregation was the largest.(2) The population of Musa sp. showed significant intra-specific symmetric competition at the 5 m scale. This competition process reduced the intensity of the population′s self-thinning and promoted intraspecific aggregation distribution patterns, and increased the viability of the population in the forest.(3) The asymmetric competition process between Musa sp. and other four dominant species resulted in negative interspecific associations. The differences in the symmetry of interspecific competition among different dominant species indicated that the mode of plant population reproduction and diffusion was one of the important factors affecting the process of assembly pattern and competition. Compared with the sexual reproduction process, the clonal propagation of plant individuals could reduce self-thinning to increase population viability through intraspecies symmetric competition mechanism. In addition, it could also enhance the ability of the population to obtain limited resources through asymmetric competition with neighboring heterogeneous individuals, and eventually become the dominant tree in the process of interspecies asymmetric competition. Therefore, it is suggested that in the future, we should strengthen the relevant basic research on the spatial distribution pattern and competition relationship of plants with clonal propagation, and deeply understand the relationship between asymmetric competition process and biodiversity loss during forest secondary succession. The results can provide a scientific reference for formulating plant species diversity protection policies.