【摘要】 在羊草群落中，未经火烧的部分具有较高的物种多样性，平均每平方米中有１６～２０种植物，占整个群落组成（３８～４７种）的４２％左右．同时，生物量、个体数量和群落学作用在各个物种间的分配也都达到了一种相对和谐的水平，反映出天然羊草群落具有较高的均匀度．由于火生态因子对草原生态系统的各个组成成分都具有一定的影响，打破了原有的平衡状态，致使群落的物种多样性、丰富度和均匀度发生一定的变化．一次火烧以后，在短时期内，通常会降低草原群落的多样性及均匀性水平，一般需要６年以上的时间才能达到正常状态．但在连年重复火烧的群落地段上，群落具有较高的物种多样性和均匀性．上述观测结果与火生态因子对羊草群落不同生活型的植物的影响和群落火烧演替规律是密切相关的．更多还原

【Abstract】 This research was made in Leymus chinesis and Stipa grandis steppe in the middle of NeiMongol.The results showed,in Leymus chinensis community,the natural unburned community had higher species diversity,there was 16￣20 species in one square metre,the whole community was made up of 38￣47 species.At the same time,the distribution of biomass,individual number and community rule to each species also reached a relative harmonious level,which illustrated that Leymus chinesis steppe community had formed a perfect and coordinate balance state.Because fire had certain influence on each composition of steppe ecosystem,which broke the original balance,the species diversity,richness and evenness of community finely appeared different changes under burning treatment.The levels of diversity and evenness of steppe community generally declined after once burning in short period,which could recovered to normal levels after more than six years.But the community plot with annual burning had higher diversity and evenness.更多还原