半干旱区湿地植被群落结构与交错带的变化分析

以宁夏回族自治区盐池县四儿滩湿地为例,通过2005—2010年7—9月份的野外调查,以重要值为基础数据,采用丰富度指数﹑物种多样性指数﹑生态优势度指数对四儿滩湿地植被群落结构年际间的变化以及湿地湿生带、交错带、旱生带这3带之间植被群落结构的差异进行了对比分析,并研究了湿地—干草原交错带边缘效应。结果表明:(1)四儿滩湿地植被生长状态在2005—2007年呈现增长趋势,2008—2010年长势衰减,湿地出现退化情况。其中,2007年植被长势最好,2010年植被长势最差。(2)在湿地与干草原交错带中,出现明显的边缘效应。生态优势度(SP)、丰富度(R)和物种多样性(SW)均是交错带最大,其次是旱生带,湿生带最小。(3)铁路建设对湿地边缘靠近铁路的旱生带影响最大,而上游人工湖的建设对湿生带影响最大。(4)在四儿滩湿地,交错带的植被变化情况与降雨量密切相关。

Structure and Ecotone Variations of Wetland Vegetation Communities in Semi-arid Region

The edge effects of plant communities were investigated in a wetland-dry grassland ecosystem of Siertan wetland in Yanchi County,Ningxia Hui Autonomous Region.Based on the importance values,the indices of abundance,diversity and ecological dominance were calculated to analyze the changes and the major environmental factors of plant community structure among three strips and three lines in the ecosystem.The calculated indices show that the vegetations of the investigated area were growing well during the years from 2005 to 2007.However,the exuberant growth had been retarded from 2008 to 2010.Among these five years,the vegetation in 2007 exhibited the best growing condition,while that in 2010 showed the worst.The edge effect was amplified apparently in the community ecotone of wetland and arid grassland,where had the highest ecological dominance(SP),richness indices(R) and diversity(SW) indices.The dry zone was the most disturbed area by the railway construction.Observations indicated that the changes of vegetation growth in the ecotone were highly related to the amount and frequency of the precipitation.