松嫩碱化草甸土壤种子库对增温和降水变化的响应及机制

The responses and sensitivity of the grassland ecosystem and biodiversity to global climate changes is one of the critical scientific issues in biogeography and ecology. Soil seed bank is a critical life stage and the potential donator of biodiversity. Under the background of global climate changes, the aboveground plant diversity has been extensively reported. However, the sensitivity and response mechanisms of soil seed bank to climate changes have drawn little attention. It remains elusive whether and how the grassland ecosystem affects soil seed bank under the double pressure of climate changes and human activities. In this proposal, we chose Songnen grassland as the main study area. Based on plot investigation, transect plot investigation along the natural temperature and rainfall gradients, we will clarify the responses of soil seed bank to temperature and precipitation changes and will also investigate the formation and dispersal of seed rain, seed dormancy and germination by Situ-control, long-term located monitoring, and laboratory simulation experiments, so as to reveal the critical response processes of soil seed bank to climate changes. Furthermore, based on the above work, we will construct a response model that integrates the environmental factors and core ecological process. This program would aid better understanding the patterns and processes in response to climate changes in arid and semi-arid grassland ecosystem, as well as providing guidance for the vulnerable ecosystem management.

草地生态系统及其生物多样性对气候变化的响应及敏感性，是地理学和生态学关注的重要科学问题。土壤种子库作为植物的关键生活史阶段，是植物多样性的潜在提供者，是生物多样性的重要组成部分。目前草地系统地上植物多样性对气候变化的响应研究报道较多，对气候变化下地下土壤种子库格局和过程的响应及机制研究不足，而这是阐明气候变化对生态系统稳定性及生物多样性影响机制的重要内容。选择松嫩碱化草甸草原作为研究区，运用自然水热梯度样带调查和定位控制观测，阐明土壤种子库特征对水热格局的响应；应用原位控制、定位监测和室内模拟等方法，研究种子雨形成、散布和种子休眠萌发等对增温和降水格局变化的响应特征，揭示土壤种子库对水热变化响应的关键途径和过程，构建融合关键环境因子和核心生态过程的响应机制模型。项目将有助于深化干旱半干旱区草地生态系统格局和过程对全球变化的响应及机制的认识，为应对气候变化的脆弱性生态系统管理策略提供指导。

目前草地系统地上植物多样性对气候变化的响应研究报道较多，对气候变化下地下土壤种子库格局和过程的响应及机制研究不足，而这是阐明气候变化对生态系统稳定性及生物多样性影响机制的重要内容。本项目以松嫩苏打盐碱化草地为研究对象，对自然水、热、盐碱梯度样带的地上植被组成、种子库特征进行了调查和研究；并选择了羊草为研究对象，探讨了自然水热梯度下，羊草的结实率、结实量、穗部、散布动态等植冠种子库信息。通过水热模拟实验，探讨了土壤种子库的输出动态对增温、降雨量增加和减少、降雨频次的增加和减少等的响应，并阐明了松嫩苏打盐碱化条件下，影响种子库动态的重要机制。获得了如下研究结果和结论。.1. 松嫩苏打盐碱化草地在自然水、温度和盐碱梯度下，植物物种组成、物种丰富度均有显著的差异。通过面上调查，地上植被共发现159个物种，土壤种子库的共发现20个物种。随着盐碱程度的加剧和降水的减少，物种的地上植被和土壤种子库的数量减少，株高降低、多度和植被覆盖度均呈现降低的趋势..2. 探讨了增温2℃、5℃；降雨量增加50%、模拟多年平均降雨量和降雨量减少50%、以及降雨量相同条件下降水频率增加50%对土壤种子库的输出动态的影响。结果表明，增温、降雨及其互作对土壤种子库输出的物种组成和密度均具有显著的影响，且温度和降雨的改变种子库输出的物种也存在显著差异。.3. 明确了松嫩平原水分、温度和盐碱等生态因子对土壤种子库物种输出动态的影响机制。在NMDS分析中，土壤种子库组成与土壤的Na+、Cl-、RSC、碱化度、ESP、AP 的含量显著相关；而土壤的SO42-、pH、EC、SAR、SOC和AN则与土壤种子库没有显著的相关性；系统阐述了苏打盐碱土对种子萌发的影响，明确了土壤中的Na2CO3以及NaHCO3是抑制种子萌发的关键因素，突破了高pH是影响种子萌发的关键因素的传统认识。.项目实施期间，共发表（包括接受，待刊）学术论文10篇，其中SCI论文7篇，国内核心论文3篇。授权发明专利3项，受理发明专利3项，出版专著1部。.