茂兰喀斯特森林不同地形部位青冈种群结构与分布格局研究

Population structure and distribution pattern of Cyclobalanopsis glauca at different topographic sites in Maolan karst forest

关键词:  茂兰, 喀斯特森林, 青冈, 种群结构, 分布格局

Key words:  Maolan, karst forest, Cyclobalanopsis glauca, population structure, distribution pattern

摘要:

该研究以茂兰国家级喀斯特森林自然保护区不同地形部位(漏斗、坡地、槽谷)青冈种群为对象,采用立木级结构代替年龄结构的方法研究青冈种群结构,并绘制了种群的存活曲线,用方差/均值比率法(偏离指数C_X)、负二项参数(K)、丛生指数(I)、平均拥挤度(m^*)、聚块性指数(PAI)和聚集指数(C_a)等聚集度指标测定了青冈种群的分布格局,以评价该种群的结构特征与更新潜力。结果表明:三种地形部位中,青冈Ⅱ级幼树占绝对优势,其次是幼苗,中、大树占一定比例,存活曲线接近于Deevey Ⅲ型,种群具有较强的自我更新能力,表现为增长型种群; 三种地形部位青冈种群除槽谷有完整的径级结构外,漏斗和坡地的径级结构不完整,但均表现为幼苗数量少于幼树,幼树个体数量最多,中树和大树的数量最少,呈中间高而两端低的径级结构; 不同地形部位青冈种群分布格局为随机分布,分布格局在种群生长过程中发生变化,表现为随龄级的增加聚集程度减弱,从聚集型向随机型转变。其中,幼苗、幼树、小树多呈聚集分布,中树、大树多呈随机分布。该研究结果为茂兰自然保护区青冈种群的合理保护提供了科学依据。

Abstract:

Cyclobalanopsis glauca is one of the constructive species and dominant species in subtropical evergreen broad-leaved forest. C. glauca is also the dominant species in karst forest of Maolan National Reserve and plays an important role in the ecosystem. In order to reveal population dynamics of C. glauca, different topography sites(funnel, hillside, valley)in Maolan National Reserve were selected as the objects of research. The population structure was studied by the method of tree class structure instead of age structure, and survival curves of C. glauca was drawn. The distribution patterns of the population were measured by applying aggregate indices, including variance/mean ration(deviation index C_X), negative binomial parameter(K), clumping index(I), mean crowding index(m^*), patchiness index(PAI)and aggregation index(C_a). The population structure and renewal potential of C. glauca in Maolan National Reserve was evaluate. The results showed that Class Ⅱ saplings of C. glauca were absolute predominance, the seedlings were the second, and there were some adult individuals, the population had strong self-renewal capacity, characterized by a growing population. The survival curve tended to be type Deevey Ⅲ. Among three topography sites, there was complete diameter class structure of C. glauca in valley, but the diameter class structures were not complete in hillside and funnel. It showed that the number of seedlings were less than saplings, the number of saplings was the largest, the number of middle and large trees were the least, the diameter structure of C. glauca was high in the middle and low in both ends. The distribution pattern of C. glauca population showed random distribution at different topography sites, and changed from clump to random with the development of the population. It showed that seedlings and saplings were clump distribution, but middle size and large trees were random distribution. The population structure and distribution pattern of C. glauca among three topography sites are different. This study will provide scientific support for C. glauca protection and management in Maolan karst forest.