中文摘要：

对三江平原1973、1983、2003年3个时期的毛苔草群落的种类组成、频度组成及物种多样性进行分析，并进行了比较研究。结果表明：不同时期毛苔草群落的种类组成差异明显，1973—1983年，毛苔草群落的变化主要体现在物种地位的变化，1983—2003年主要表现为物种组成种类的变化；物种多样性特征的变化表现为1973—2003年，物种丰富度呈下降趋势，物种多样性、均匀性呈先增加而后下降的趋势，优势度与之相反，总体表现均为1973—1983年变化缓慢，而1983—2003年变化较大；物种频度图的分析表明，不同时期毛苔草群落的结构均处于稳定状态，但随着演替进行，群落中有分化和演替的趋势，并且以1983—2003年变化最为明显；通过分析初步认为，毛苔草群落物种组成的变化主要由水位的下降所引起，景观破碎化对物种多样性的影响值得进一步研究。

英文摘要：

The species composite and species frequency figure of Carex lasiocarpa community in Sanjiang Plain wetland in 1973,1983 and 2003 were analyzed. At the same time , the species diversity was measured by applying richness index （R） , Shannon - Winner index （H） , Pielou evenness index （E） , Simpson dominance index （D）. A comparison in the changes of species diversity for different ages was conducted. The results showed that there were obvious differences between species composition and species diversity of different ages. The changes of species status were represented from 1973 to 1983. From 1973 to 2003, species richness showed the trends of reduce, but the changes trend of Shannon -Winner diversity Pielou evenness, Simpson dominance were： 1983 〉 1973 〉2003. In a word, more conspicuous changes were taken on in later 20 years than former 10 years. The analysis of species frequency figure indicated that Carex lasiocarpa communities in different periods were in stable state, however, there were trends of vegetation degradation and succession. The decline of water level was considered the main cause of changes of species diversity. The effects of landscape fragmentation on species diversity need deep farther study.