青藏高原东南部森林群落生态位特征与物种多样性的影响因素

Niche characteristics and diversity influencing factors of forest community on the southeastern Qinghai-Tibet Plateau

青藏高原东南部的东喜马拉雅地区和横断山区是全球生物多样性热点区,也是青藏高原重要的生态安全屏障区,但对该区域森林群落的生态位特征以及多样性相关研究较少。收集和整理了分布于青藏高原东南部的乔木植物及其科属特征,并分析主要优势物种的生态位特征以及森林群落多样性的影响因素。采用“Levins”方法计算优势物种的生态位宽度和生态位重叠值;随后,使用方差比率法、χ^(2)检验、Association coefficient联结系数和Ochiai指数等方法分析了种间联结性;最后,使用方差分解方法计算了每个环境因素对植物多样性的解释率。研究结果表明:(1)位于东喜马拉雅地区和横断山区森林群落共有植物42科71属119种,物种组成主要以松科(17种)、杜鹃花科(10种)、桦木科(9种)、无患子科(8种)和樟科(6种)为主;(2)该地区所有种植物生态位重叠值较低(平均值为0.027),并且生态位重叠值为0的种对数最多,说明森林群落整体竞争较小,处于一个相对稳定的状态;(3)生态位宽度值由高到低的物种依次为:冷杉、杜鹃、云南铁杉、川西云杉、落叶松、黄背栎、高山栎、花楸、石栎和云南松,这10种植物在森林群落占据优势地位;(4)种间关联结果显示方差比率大于1,说明森林群落中物种间存在较强的正关联,群落内各个物种占据的不同生态位,合理地利用各种资源;(5)年均温和坡向被认为是影响该地区森林群落物种多样性最关键的两个环境因子;(6)森林群落在年均温为7—11℃的地区和半阳坡的地形中,群落植物多样性最高。

The East Himalaya-Hengduan Mountains in the southeastern part of the Qinghai-Tibetan Plateau is a global biodiversity hotspot,but little has been reported on the botanical diversity and ecological niche characteristics of forest community in this region.We collected and compiled a list of s arborescent plants distributed and their family characteristics in the southeastern Qinghai-Tibet Plateau,and analysed the ecological niche characteristics of the major dominant species as well as the factors influencing the diversity of the forest communities.In our study,the “Levins” method was used to calculate the niche width and niche overlap value of dominant species;subsequently,the interspecific connectivity was analysed using the variance ratio method,χ~2 test,Association coefficient and Ochiai index;and,finally,the rate of explanation of plant diversity by each environmental factor was calculated using the variance decomposition method.The results of the study showed that:(1) the forest community in the East Himalaya-Hengduan Mountains consisted of 119 species in 42 families and 71 genera,and the species composition was mainly dominated by Pinaceae(17 species),Rhododendron(10 species),Betulaceae(9 species),Sapindaceae(8 species),and Camphoraceae(6 species);(2) the overlap of ecological niches of all plants in this region was low(mean 0.027) and ecological niches overlap values of most species pairs with were zero,which indicated that the forest community was little competition and in a relatively stable state;(3) The top 10 species in terms of niche width were,in order:Abies fabri,Rhododendron simsii,Tsuga dumosa,Picea likiangensis,Larix gmelinii,Quercus guyavifolia,Quercus semecarpifolia,Sorbus pohuashanensis,Lithocarpus glaber,and Pinus yunnanensis,and 10 species dominate the forest community;(4) the results of the inter-species associations show that the variance ratio is greater than 1,indicating that there is a strong positive association between species in the forest community,and that the different ecological niches occupied by each species in the community make rational use of various resources.(5) the mean annual temperature and slope direction were considered to be the two most critical environmental factors that affected plant diversity in the region;(6) the communities have the highest community plant diversity in intervals with mean annual temperatures of 7—11℃ and in terrain with semi-sunny slopes.