Because of the influence of global change and external disturbances,habitats of alpine meadows are trending toward aridification in the Qinghai-Tibetan Plateau.How would variation in habitat affect the eleva-tional pattern of species diversity? Nine sample plots were set along an elevational gradient in the Dongda Mountains in southeast Tibet.Ten 1 m×1 m sample quadrats were set in each sample plot,with five quadrats located in wet habitat and the others located in dry habitat.Species composition in each quadrat was investiga-ted.Species with a frequency lower than seven were defined as occasional species;otherwise,the species were common.For total occasional and common species,variation ofα,β,andγdiversity were respectively analyzed along the elevational gradient.β diversity was measured by the Cody index(βc),multiplicative partitioning (βw),and the slope of regression between similarity of species composition and distance(βslope).There were 160 seed plants recorded in these sample plots,among which,132 species were distributed in wet habitats and 107 species in dry habitats.For total and occasional species,αandγdiversity both decreased with elevational gain in wet habitats but increased in dry habitats.For common species,αandγdiversity both presented an increasing trend with elevational gain in wet and dry habitats.The elevational patterns ofβindexes were not consistent,βc andβwin wet habitats were higher than that in dry habitats,andβcandβwof occasional species was higher than that of common species.The elevational patterns of species diversity between wet and dry habitats were differ-ent,and diversity of occasional species had a high value,and will directly affect elevational patterns of species diversity.%受全球变化和外界干扰的影响,青藏高原高寒草甸生境趋向干旱化.生境变化对物种多样性的海拔分布格局有何影响?本研究以藏东南东达山作为研究地点,沿海拔梯度设置9个样地,在每个样地设置10个1 m×1 m样方,5个位于湿润生境,5个位于干旱生境,调查样方内的物种组成.将样方中频度≤7的物种确定为偶见种,反之为常见种,分析所有种、偶见种和常见种α、β和γ多样性沿海拔梯度的分布格局.以Cody指数(βC)、倍性分配法(βW)和物种组成相似性随海拔距离的衰减速率(βslope)3种方法测度β多样性.样地中共记录种子植物160种,其中湿润生境132种,干旱生境107种.湿润生境中,所有种和偶见种的α和γ多样性随海拔的增加而下降,而干旱生境中呈现为增加趋势;常见种α和γ多样性在两种生境中均随海拔的增加而略增加.3种β多样性指数的分布格局不一致,湿润生境中βC 和βW多样性高于干旱生境,偶见种βC 和βW 多样性高于常见种.高寒草甸湿润与干旱生境物种多样性的海拔分布格局不同,偶见种多样性高,直接影响物种多样性的海拔分布格局.
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