桥山天然栎林树种多样性及生态位分析

利用陕北桥山林区典型天然栎林样地材料，对木本植物的多样性及生态位作了分析。结果表明：树种的多样性不甚丰富，乔木层小于灌木层，这是较差的水热条件所致；树种多样性随坡向而变化，其主导因子为土壤的水分条件；乔木树种中油松的生态位最宽，这是它能与栎类树种在一起形成混交林的原因所在，因此可在栎林改造中引进油松；乔木树种之间以油松与辽东栎和槲栎的生态位重叠值最大，但却能形成混交林，这主要是广泛重叠导致了种间竞争减弱的缘故。

An Analysis on the Diversity and Ecological Niche of Oak Forest in the Qiaoshan Area

The diversity and ecological niche of xylophyta were analyzed based on the information obtained from the sampling plot of natural oak forest in the Qiaoshan area, northern Shaanxi. The conclusions are as follows: 1.The diversity of tree variety is not rich, and the arbor strata is less then that of shrubr one, owing to the poor water and sunshine conditions. 2.The diversity of xylophyta changes with exposure, making the soil water as a limiting factor. 3.Pinus tabulaeformis possesses the broadest ecological niche among arbor species, which is the reason that it could form mixed forest with Qurecus species, therefore, could be introduced into oak forest in stand reform. 4.Though the value of the niche overlap between pine and oak among the arbor species form the biggest one, both of them could grow in the same stand very well, resulting from that the wider overlap makes species competition decrease.