狭叶方竹伴生群落结构及优势种空间分布格局

Community structure and spatial distribution pattern of dominant species in Chimonobambusa angustifolia companion community

为探究狭叶方竹伴生群落结构特征及优势种空间分布格局,以3个狭叶方竹伴生群落(斗篷山、老山界、雷公山)为研究对象,采用样地法调查分析群落垂直结构、径级结构、高度级结构、物种重要值、优势种空间分布格局及其影响因素。结果表明:3个群落垂直结构明显,从上向下可分为乔木层、灌木层和草本层,层间植物不发达,仅少量藤本和附生草本。3个群落径级结构(DBH≥1 cm)呈倒“J”形,更新良好,群落平均胸径依次为老山界(16.02 cm)>雷公山(11.38 cm)>斗篷山(8.98 cm),群落密度则呈相反趋势。斗篷山、雷公山优势种径级结构呈倒“J”形,种群为增长型。老山界优势种径级结构呈单峰型,光叶水青冈种群为衰退型,多脉青冈和巴东栎种群存在衰退风险。随着群落演替,老山界群落优势种将逐步被替代。3个群落高度级结构总体呈倒“J”形,平均高度大小依次为斗篷山(8.14 m)>雷公山(6.87 m)>老山界(6.69 m)。不同群落优势种高度级结构存在差异,大多呈倒“J”形,单峰型次之。物种重要值在不同群落和群落不同层间存在差异,斗篷山、老山界和雷公山优势种重要值之和分别占乔木层重要值的47.58%、57.72%、25.81%。优势种空间分布格局小径级个体(DBH<10 cm)趋于均匀分布或集群分布,中径级(10 cm≤DBH<30 cm)和大径级(DBH≥30 cm)个体趋于均匀分布或随机分布。3个狭叶方竹伴生群落结构和优势种空间分布格局受多种生态因子的综合影响。群落演替时间和竞争排斥是影响群落结构的主导因子,扩散限制和竞争排斥是影响优势种空间分布格局的主导因子。

To explore the community structural characteristics and spatial distribution pattern of dominant species, three companion communities of Chimonobambusa angustifolia(Doupengshan, Laoshanjie, and Leigongshan) were selected as research objects, and the communities were investigated using quadrat method. The community vertical structure, diameter class structure, height class structure, species importance value, and spatial distribution pattern of dominant species were studied, and the factors affecting community structure and spatial distribution pattern were also analyzed. The results showed the following: the vertical structure of the three communities was clear, and it could be divided into three layers-tree layer, shrub layer and herb layer from the canopy to the ground. The interlayer plants were underdeveloped with few vines and epiphytes. The diameter class structure(DBH≥1 cm) of the three communities had an inverse "J" shape, indicating successful regeneration, and the average diameter was ranked as follows: Laoshanjie(16.02 cm)>Leigongshan(11.38 cm)>Doupengshan(8.98 cm), but the individual density showed the opposite trend. The diameter class structure of dominant species had an inverse "J" shape in Doupengshan and Leigongshan, implying that the population was a growing type. However, the diameter structure of dominant species had a unimodal type in Laoshanjie. The population of Fagus lucida was a declining type, and there was a degradation risk in the population of Cyclobalanopsis multinervis and Quercus engleriana. Dominant species of Laoshanjie will be replaced gradually by other plants with community succession. Overall, the height class structure of the communities was an inverse "J" shape, and the average height was ranked as follows: Doupengshan(8.14 m)>Leigongshan(6.87 m)>Laoshanjie(6.69 m). The height class structures of dominant species were different, and most were an inverse "J" shape, followed by unimodal type. The importance values of communities and layers were different, and the importance values of dominant species accounted for 47.58%, 57.72%, and 25.81% of the importance values of the tree layer in Doupengshan, Laoshanjie, and Leigongshan, respectively. The spatial distribution pattern of dominant species tended to be uniform or clumped in small size(DBH<10 cm), but it tended to be uniform or random in middle size(10 cm≤DBH<30 cm) and large size(DBH≥30 cm). This suggest that the community structure and spatial distribution pattern of dominant species in the three communities were comprehensively influenced by combined factors. Community succession time and competitive exclusion were the major factors affecting the community structure, whereas dispersal limitation and competitive exclusion were the major factors affecting the spatial distribution pattern of dominant species.