苔草沼泽物种多样性时空变化驱动机制探索：功能性状对环境梯度的响应

Across the distributional gradient of ecosystems, the functional traits of species may change in response to climatic and environmental differences. So exploring the contribution of environmental filtering evidenced by functional traits in the temporal and spatial changes of plant community is a research hotspot of current ecology. The formational mechanism of wetland vegetation zonation patterns and potential driving mechanisms of plant diversity change caused by wetland degradation is important focus of the current wetland science. In this study, field surveys of functional traits of Carex marshes along the latitudinal gradient (40o to 51o N latitude; six study wetlands from Dandong in Liaoning Province to Nanwenghe Nature Reserve in Da Hinggan Mountains) on regional scale (northeast China), and along the water level depth gradient ( from Carex lasiocarpa to C. appendiculata to C. appendiculata / Calamagrostis angustifolia )on the local scale were executed, and a database of functional traits of Carex marsh in northeast China will be created. On this basis, the changing trends of functional traits of species and community along the above-mentioned gradients, and the relationship between functional traits and the dominance (biomass) of species and community will be analyzed, the impacts of environmental factors (e.g. air temperature, water level depth and soil nutrients) and biological factors (inter-species and intra-species variation) on functional traits will be revealed. By using the control experiments of water depth and Nitrogen utilization, the response of functional traits of dominant species and the relationship between functional traits and dominance ( biomass) will be discussed，the relative impact of temperature, water depth and soil nitrogen utilization on the functional traits of dominant species will be revealed. Lastly, the simulation model will be established according to species distribution model, using key functional traits to predict species dominance and community type. The project will promote the study of global change ecology and biodiversity field, and will provide a scientific basis for the restoration and protection of the wetland ecosystem in the northeast china.

从功能性状出发探索环境过滤在植物群落时空变化中的作用是当前生态学研究的热点。湿地植被带状格局的形成机制和湿地退化引起的植物多样性变化的潜在机制是当前湿地科学研究的重要内容。控制着我国很大湿地区域的苔草沼泽远未得到应有的关注。本项目通过对区域尺度纬度梯度带（北纬40 至51 的6个纬度点）及局地尺度水深梯度带上苔草沼泽植被及功能性状的野外监测，分析上述梯度带上物种及群落水平的功能性状的变化规律及其与优势度的关系，揭示环境（气温、水深和土壤养分）和生物（种内和种间变异）因子对功能性状的影响；通过温度+水深+氮利用控制实验，探讨优势植物功能性状的响应、种内/种间变异及其与优势度的关系，揭示上述3因子对优势植物性状变异的相对影响；以物种分布模型为基础，建立关键性状对物种和群落预测的模拟模型。本项目将推动我国全球变化生态学与生物多样性领域的研究，为本区湿地生态系统的恢复与保护提供科学依据。

本项目研究工作完全按照研究计划进行，圆满完成了项目的预期研究目标。本项目完成了区域尺度（长白山—兴凯湖—三江平原—小兴安岭—大兴安岭纬度带）及局地尺度（每一个生物地理区内）的212个样点603个样方的植被调查及植物、土壤样品的采集，完成了室内植物比叶面积、叶片氮等性状及土壤养分的测试分析；完成了温度/水深/氮添加控制实验；完成了关键性状对控制因子的定量模拟预测分析。 .本研究取得进展如下：区域尺度上，物种丰富度表现出随纬度变化的单峰格局，株高、土壤有机质、水深及土壤总磷含量共解释了45%的变异。毛苔草群落物种丰富度表现出随纬度增加而降低的格局，而灰脉苔草及小叶章两个群落则未表现出纬度格局。毛苔草及小叶章群落主要受优势种高度的影响，分别解释18%及41%的变异；灰脉苔草的变异则主要由株高、土壤有机质和海拔共同决定，大约解释变异的55%；局地尺度上，两个苔草群落均表现出物种丰富度随水深增加而降低的格局，而小叶章群落的物种丰富度则未表现出随水深变化的明显规律；整体的物种丰富度表现为随水深变化的“钟型”格局。水深对两个苔草群落的物种丰富度有明显影响；而无因子对小叶章群落的物种丰富度显著影响。对4个优势种的水深梯度控制实验表明，小叶章的比叶面积和株高，甜茅的株高、比叶面积及叶面积， 漂筏的比叶面积和叶面积，毛果的株高、叶面积及比叶面积均对水深梯度明显响应；综合上述分析，株高和比叶面积可以作为关键性状进入下一步的分析。最后我们用GAM模型建立了关键性状与关键环境控制因子之间的定量关系。相关成果发表在Science of the total environment（2018）,Plos one (2016), Journal of vegetation science(2015)）及wetlands (2017) 等5篇SCI论文上，审稿人认为这些结果对全球湿地植被的多样性研究及三江平原湿地的保护和管理具有重要参考价值。