【摘要】 基于西双版纳野生兰科植物实测分布点及其立地海拔、坡度、坡向、年均温、植被覆盖度、植被数据,采用CCA排序法探索了环境因子对物种组成和丰富度的影响,偏CCA计算了各环境因子对物种组成的总效应和净效应,GLM回归模型拟合了物种丰富度对环境因子的响应。结果表明:海拔、坡度、坡向、年均温、植被覆盖度、植被6个环境因子共解释了物种组成变异的2%,其中,植被、海拔、年均温、植被覆盖度、坡向5个环境因子对物种组成的净效应达显著水平(P<0.05),但其作用强度依次减小。GLM拟合结果显示,物种丰富度与环境因子存在3种显著(P<0.05)关系:物种丰富度沿植被方向(热带季雨林>亚热带常绿阔叶林>热带雨林/暧性针叶林>热性竹林及其它等自然植被)依次递增;物种丰富度沿年均地表温度的梯度单调递减;物种丰富度沿海拔梯度变化小,呈微弱的单峰关系。更多还原

【Abstract】 This study assessed the impact of environmental variables on species composition and richness of the wild orchids in Xishuangbanna,based on GPS-positioned points of occurrence and corresponding attributives of altitude,slope,aspect,mean annual ground surface temperature( MT),fractional vegetation cover( FVC),and vegetation. This paper also detected the relationship between species composition and environmental variables by canonical correspondence analysis( CCA),calculate the gross and net effects on species composition for each environmental variable by partial CCA,and generalized linear model( GLM) to fit the response of species richness to each environmental variable. The results showed that the selected environmental variables explained 2% of the total variation in species composition,among which the net effects of vegetation,altitude,MT,FVC on species composition were significant( P< 0. 05),but their effect intensities decreased successively. GLM fitting revealed that there were three significant( P < 0. 05) types of relationship between the species richness and environmental variables:1) species richness was increasing along the vegetation types from the tropical monsoon forest,subtropical evergreen broadleaved forest,tropical rainforest,warm coniferous forest,bamboo forest,down to other natural vegetation; 2) species richness was decreasing with the mean annual ground surface temperature;3) species richness was decreasing with altitudinal gradient,and had gentle hump-shaped relationship with the altitude.更多还原