中文摘要：

利用陕北黄土丘陵区17个不同撂荒年限的群落样方数据，分析了撂荒演替中20个主要种的演替生态位宽度和生态位重叠指数．3种生态位宽度指数以Levin和Shannon-Wiener指数适用性较好，2种指数表明演替前期主要种的生态位宽度较窄．后期较宽；演替各阶段优势种生态位较宽．伴生种较窄。根据演替生态位重叠指数．利用种的极点排序和系统聚类法分析了种的演替生态学特性，结果表明．4种生态位重叠指数以Morisita和Pianka指数在演替生态位的研究中适用性较好。种的极点排序与种极点分析和实际观察结果基本一致，指示了种的生态对策连续统，说明种的演替方向和相对竞争能力；系统聚类中类内种的生态学特性基本一致．3类的划分结果表明第1类为定居优势种，位于演替序列前期；第2类为竞争优势种，位于演替后期；第3类为定居一竞争相对平衡种，位于演替中期。

英文摘要：

Succession niche breadth and overlap of 20 main species in 17 communities from land abandoned over a number of years were analyzed to compare three niche breadth and four overlap indices. The decision on the best choice indices, based on species characteristics using polar ordination and hierarchal cluster analysis are discussed. The results show that the Levin and Shannon--Wiener niche breadth indices are better than the Hurlbert index for more exact ecological explanations, i.e. the value of niche breadth of species in the early stages of a succession are greater than that of species in a later stage and the dominant species are greater than the companion species. PO using four overlap indices using Macauthor＇ s r-and K-selection continuum showed that species located on the left of the axes are r-selection, while those on the right are relatively K- selection. It also indicates species competition ability and succession direction, Morisita and Pianka overlap indices are better than percentage and Wanggang indices for cluster analysis--using the first two gives ecologically reasonable results. For example, if three groups are clustered, then the first group are open to colonization, because most species are in an early succession stage, the second are in a later stage of advantaged competition while the third are in a relatively stable community with a balance between colonization and competition.