多样性响应气候增温：海拔梯度与植食作用交互研究

How strong are climate warming-driven changes within alpine meadow, an area under increasing threat especially in developing countries such as China? Observations of plant community change and accompanying functional shift within mountain grasslands along elevational gradient in response to recent warming are scarce. Among potential factors confounding the influence of climate warming in grassland community dynamics are environmental heterogeneity such as soil nutrients variability and interspecific interactions especially plant-insect herbivores interactions. Disentangling the independent and combined effects of climate warming, environmental heterogeneity and interspecific interactions might help ecologists understanding the feedbacks and interactions among global warming. Moreover, rather than species richness and evenness, biodiversity measures including functional diversity and phylogenetic diversity produced new ecological insights into the projections of species loss under climate change. In this project, we plan to assess changes in plant community composition and aboveground biomass production under simulated climate warming using transparent open top chambers (OTCs) and insect-exclusion with insecticide in fully factorial field experiments within alpine meadow ecosystems along different elevational gradients in the Yulong mountain. We intend to calculate different biodiversity measures (richness, evenness, functional and phylogenetic diversity) to comprehensively reflect the changes in plant community composition under experimental treatments. We also plan to measure distinct environmental ingredients including soil water content, nutrient availabilities and meterological factors to assess the relative contributions to biodiversity and aboveground biomass production. The aims of the research are to: 1) investigate the independent and combined effects of experimental warming, environmental heterogeneity and herbivory on a majority of measures of plant diversity in alpine meadows of the Yulong mountain, 2) assess different biodiversity-productivity relationships associated with experimental warming, elevation and plant-insect herbivores interactions within alpine meadows of the Yulong mountain. Understanding these broad-scale trends will help identify geographic regions vulnerable to global warmings and hightlight future research priorities.

气候变暖威胁生物多样性及生态系统功能。本项目以玉龙雪山高山草甸生态系统为研究对象，在群落水平上结合随海拔梯度变化的环境差异以及植食昆虫的植食作用研究实验增温对于高山草甸生物多样性以及生态系统功能的影响。在考虑了环境梯度及植食作用对生物多样性和生态系统功能可能的影响之后，通过物种多样性、功能多样性以及系统发育多样性更加全面准确地反映实验增温对于生物多样性直接的影响；同时衡量高山草甸群落地上生物量在实验增温下的反应。本项目一方面可帮助理解气候增温下高山草甸生态系统的相互作用和反馈过程；另一方面可为全球气候变化背景下脆弱的高山草甸生态系统植物多样性保护和生态系统功能维持提供理论参考。

人为原因导致的全球变暖和空气氮添加威胁高山草甸生态系统的生物多样性和生态系统功能。然而，沿环境梯度全球变化如何影响群落构建机制以及生物多样性-生产力相互关系仍不清晰。为理解气候驱动因子对高山草甸可能影响，我们在云南玉龙雪山沿海拔梯度通过布置增温框（OTC）和喷施尿素分别模拟全球变暖和氮添加以研究高山草甸群落格局和多样性-生产力相互关系。我们采用新功能多样性方法（例如，结合系统发育和功能多样性）和扩展性状-梯度分析方法（例如，功能性状均值和范围）以描述驱动物种组合的生态机制。同时，通过一般线性混合模型比较不同维度的多样性指标（包括物种丰富度、均匀度、系统发育多样性和功能多样性）与群落地上生物量相互关系以探讨多样性-生产力最优模型并且比较分析气候变化对此模型可能影响以及各自效应大小。.研究结果表明实验增温倾向导致物种的快速丧失且在中间海拔特别强烈，但群落功能格局很大程度上不受实验处理影响。海拔梯度导致物种数量和功能多样性的降低且群落功能格局随海拔由低海拔过度扩散转换为高海拔随机分布。相比于实验处理间群落格局的一致性，实验处理对单功能性状表达（包括植株最大高度、比叶面积和叶片氮含量）影响更为明显，即实验增温倾向于增强功能性状的表达且增温效应强度依赖于海拔梯度。生物多样性-生产力最优模型为物种丰富度、系统发育多样性和单个功能性状（叶片氮含量，mg/g）组合。生物多样性，特别是系统发育多样性，在各情景下均表现强烈的正效应，但实验处理对多样性-生产力关系影响甚微。.本项目一方面揭示了气候变化下高山草甸群落组织构建的复杂性和环境依赖性，强调了功能多样性对于气候变化背景下群落多样性和结构预测的重要性；另一方面提供证据支持了单一多样性指标不能完全解释生态系统功能的共识，阐明了未来气候变化背景下生物多样性对于生态系统功能的重要性。