基于功能性状及系统发育的亚高寒草甸群落构建

Exploring the community assembly of subalpine meadow communities based on functional traits and community phylogeny

为了解甘南藏族自治州亚高寒草甸植物群落在坡向梯度上的构建机制,该文选取5个坡向的样地,构建了植物群落系统发育树,测定了各坡向土壤环境因子和植物叶片的功能性状,检验了叶片功能性状的系统发育信号。结果表明:坡向变化对土壤含水量、土壤养分含量影响显著。大部分植物的叶片特征在不同坡向的差异显著,叶片干物质含量在南坡、西南坡较高,比叶面积和叶片氮、磷含量在北坡和西北坡较高。叶片的磷含量具有微弱的系统发育信号,而叶片干物质含量、比叶面积、叶片的氮含量均没表现出显著的系统发育信号。从南坡到北坡,群落的系统发育结构由发散到聚集。生境过滤作用是南坡、西南坡群落构建的驱动因素,种间竞争是北坡和西北坡群落构建的主要驱动力。西坡系统发育指数相反,其构建机制比较复杂,可能是几种机制共同作用的结果。

Aims The community assembly has been a prominent issue in community ecology. This work was intended to explore the mechanisms of the species coexistence and biodiversity in communities. Our objective was to explore the mechanisms of community assembly in subalpine meadow plant communities along slope gradients in Gannan Tibetan Autonomous Prefecture, Gansu Province, Northwest China. Methods We selected five slope-oriented plots to construct a super-tree representing the species pool. We sur- veyed the leaf functional traits and soil environmental factors in different slopes. Then we tested the phylogenetic signal of leaf dry matter content （LDMC）, specific leaf area （SLA）, leaf nitrogen content （LNC） and leaf phospho- rus content （LPC）. Important findings The changes of slope aspect had significant influence on soil water content （SWC） and soil nutrient content. Most of the plants leaf functional traits had significant difference along different slope aspects. The LDMC was higher in south and southwest slope than north slope, while SLA, LNC and LPC were relatively high in north and northwest slope. The LPC showed feeble phylogenetic signal, while LDMC, SLA, LNC did not have a significant phylogenetic signal. With changes in the slope aspect from south to north, community phyloge- netic structure shifted from over-dispersion to clustered dispersion. In south and southwest slope, habitat filtering was the driving force for community assembly. Interspecific competition was the main driving factor for commu- nity assembly in north and northwest slope aspects. But in west slope, two indices showed contrary consequence. This means the process of community assembly in west slope was more complicated and its phylogenetic index may be the result of several mechanisms working together.