亚热带常绿阔叶林栲树与薯豆不同龄级种群生态位特征

种群不同年龄组的生态位是种群资源利用随时间变化的一种重要形式。根据高度将植物种群分为乔木组、幼树组和幼苗组3个年龄梯度,对重庆缙云山自然保护区常绿阔叶林优势树种—栲树与薯豆生态位特征进行了比较研究。结果表明：(1)栲树与薯豆3个龄级的实际生态位宽度均较大,但资源利用能力都不强；它们的生态位宽度与资源利用能力随龄级增加而增大趋势很明显。(2)栲树与薯豆幼苗组生态位特化程度高,幼树组与乔木组生态位泛化程度不高。(3)薯豆乔木组、幼树组的生态位宽度和资源利用能力均大于栲树,但薯豆幼苗组生态位宽度和资源利用能力却比栲树小。(4)两个种群生态位重叠较高,资源性竞争激烈；生态位重叠随年龄增长而呈“V”字形,幼树组重叠值低与幼苗组的高竞争导致栲树中等龄级的缺失有关。

The Niche Characteristics of Castanopsis fargesii and Elaeocarpus japonicus at Different Age Groups in Sub-tropical Evergreen Broad-leaved Forest

The niche of age group of plant population is one important aspect of the resource utilization which changed with the time.According to the height of plant's individuals,the population was divided into three age gradients-tree group,sapling group and seedling group.The niche characteristics of different age groups of Castanopsis fargesii and Elaeocarpus japonicus were studied,which are the dominant plants in evergreen broad-leaved forest in Jinyunshan Nature Reserve,Chongqing.The results indicate:(1)The realized niche breadths of C.fargesii and E.japonicus at three age groups are rather wide while their resource utilization capacities are not strong.It is obviously that the niche breadths and resource capacities of the two species became wider or stronger when they grew up to the canopy.(2)The degree of niche speciation of C.fargesii and E.japonicus at seedling group are very high,while niche generation of the two species at tree group and sapling group are not high.(3)The niche breadths and resource utilization capacities of E.japonicus are larger than C.fargesii at tree group and sapling group except that of at seedling group.(4)The niche overlaps of C.fargesii and E.japonicus are large,which indicated that the resource competition of the two species was violent.The trend of niche overlap of the two species with age group likes V character.It means that the overlap is lowest at sapling group which would be involved in the deficiency of the middle age group of C.fargesii,which was resulted from the violent competition at seedling group.