高寒草甸植物群落谱系结构与多样性格局

为了解青藏高原高寒草甸植物群落谱系结构及物种多样性在海拔梯度上的变化，以甘南藏族自治州的高寒草甸植物群落为对象，选取五个不同海拔的研究样地，进行野外群落学调查及环境因子的测量，计算净亲缘指数（net relatedness index，NRI）和最近亲缘指数（nearest taxon index，NTI）等，探讨了群落谱系结构与谱系多样性的海拔格局变化.结果表明：随海拔升高，土壤温度、含水量、土壤全氮及有机碳均呈现降低趋势.植物群落物种丰富度、Shannon-Weiner多样性指数及谱系α多样性随海拔升高均呈现单峰变化规律，即在海拔3500m处植物群落α多样性达到最大；谱系β多样性指数betaMPD随海拔增加呈升高趋势，反映物种聚集受到生境过滤的显著影响.低海拔（3000m）群落谱系发散（NRI<0，NTI<0），竞争排斥起到主要作用；中低海拔（3250m）和中海拔（3500m）处同时存在聚集（NRI>0，NTI>0）和发散（NRI<0，NTI<0）两种谱系结构，生境过滤和竞争排斥共同维持群落物种多样性；高海拔（3750m、4000m）群落谱系结构聚集（NRI>0，NTI>0），其驱动因素与物种趋同进化和生境过滤有关.多元回归分析显示，在不同海拔，土温和土壤含水量成为物种共存的主要影响因素.本研究揭示青藏高原高寒草甸海拔梯度植物群落谱系结构及多样性格局的变化，说明生态位过程是维持其群落多样性的重要机制.

Phylogenetic structure and diversity pattern of plant community in alpine meadow

In order to understand the changes of plant community phylogenetic structure and species diversity in alpine meadow of Qinghai Tibet Plateau, plant communities and environmental factors of alpine meadow were measured at five different altitudes, net relative index (NRI) and nearest taxon index (NTI) were calculated, and the changes of phylogenetic structure and phylogenetic diversity were discussed. The results showed that with the increase of altitude, soil temperature, soil water content, soil total nitrogen and organic carbon decreased. The number of richness, Shannon-Weiner index and phylogenetic diversity of plant community showed a "humped-back" relationship with the increase of altitude. Community species diversity reached the maximum at 3500m. The betaMPD increased with the increase of altitude, indicating that species aggregation was affected by habitat filtration. The low altitude (3000m) community had divergent (NRI < 0, NTI < 0), and competition exclusion played a major role; at lower altitude (3250m) and middle altitude (3500m), there were aggregation (NRI > 0, NTI > 0) and divergence (NRI < 0, NTI < 0), indicating that habitat filtration and competitive exclusion jointly maintained the species diversity of the community; community phylogenetic structure aggregation (NRI > 0, NTI > 0) at high altitude (3750m, 4000m) was related to species convergence evolution and habitat filtration. Multiple regression analysis showed that soil temperature and soil water content were the main influencing factors of species coexistence in different altitudes. This study reveal that the changes of plant community phylogenetic structure and diversity pattern of alpine meadow in Qinghai Tibet Plateau, indicating that niche process is an important mechanism to maintain the diversity of plant communities.