三种温带草原类型生物多样性和生态系统功能对气候变化的敏感性

Convincing projection of the dynamics of terrestrial biosphere under climate change scenarios depends on to what extent and how climate change influences biodiversity and ecosystem functioning in the future. A field manipulative experiment has been set up by excavating 54 soil monoliths from three types of temperate grasslands (desert steppe, typical steppe, meadow steppe) along a natural precipitation gradient in the Mongolia Plateau of northern China since 2013. Two factors of nocturnal warming and increasing/decreasing precipitation were included to simulate climate change scenarios in northern China. Six treatments were included in the field manipulative experiment: control, nocturnal warming, increased precipitation, decreased precipitation, nocturnal warming plus increased precipitation, nocturnal warming plus decreased precipitation. Multiple variables from plant to soil microbes to fauna and from leaf to ecosystem levels are monitored to test the effects of climate change on biodiversity, ecosystem functioning, and biodiversity-ecosystem functioning relationships of the 3 grassland types in the temperate steppe as well as to reveal the underlying mechanisms for maintaining the relationship between biodiversity and ecosystem functioning. The results will facilitate the parameterization and validation for regional-scale model simulation and prediction of the long-term dynamics of biodiversity and ecosystem functioning under climate change scenarios. The research findings will have significant implications for the sustainable and adaptive management of the temperate steppe in northern China.

气候变化在多大程度上以及如何影响陆地生物多样性和生态系统功能是限制准确预测陆地生态系统未来动态变化的主要不确定性来源。本项目拟在我国北方干旱和半干旱区、沿自然降雨梯度选择三种温带草原类型(荒漠草原、典型草原和草甸草原)，采用土块移植和野外控制实验相结合方法，参照我国北方的气候变暖特征和降水格局变化，开展生物多样性和生态系统功能响应夜间增温和增减降雨敏感性的研究。实验处理包括对照、夜间增温、增加30%降水量、减少30%降水量、夜间增温和增加30%降水量、夜间增温和减少30%降水量。通过监测植物、微生物、土壤动物多度和类群的改变，以及生态系统碳、氮、水循环变化，探讨气候变化对温带草原生物多样性-生态系统功能关系的影响，从区域尺度上揭示生物多样性的生态系统功能维持机理，为陆地生物多样性和生态系统功能的预测模型提供参数估计和模型验证，同时为在未来气候变化情景下的我国温带草原适应性管理提供决策支持。

以我国北方沿着自然降雨梯度上的三类温带草原(荒漠草原、典型草原和草甸草原)为研究对象，参照我国北方的气候变暖和降水格局变化特征，采用土块移植和野外控制实验相结合的方法，通过监测植物和微生物群落组成和结构以及生态系统碳、氮、水循环变化，探讨气候变化对温带草原生物多样性-生态系统功能关系的影响及其潜在机制。本项目自2015年开始执行以来，围绕上述科学目标，取得以下重要研究进展和发现：(1) 夜间增温对三类草原始花期的影响存在差异：夜间增温提前荒漠和典型草原始花期，而推迟草甸草原始花期。减少和增加降水分别推迟和提前三类草原始花期。进一步的分析表明，气候变化情景下，三类草原始花期的改变主要受植物生长的调控，其次受环境因子调控。(2)三类草原始花期对减少和增加降水的敏感性是对称的，并且增温通过对土壤水分有效性和NDVI的调控提高荒漠草原始花期的降水敏感性。(3)在任何一种处理下均发现，草甸草原净生态系统初级生产力(NEP)最低，而荒漠草原NEP最高，这一发现挑战了植物生长随着降雨量的增加而提高的传统认知，并且强调了目前的IPCC预测模型在模拟气候变化情境下温带草原碳汇能力的精度方面仍需要提高。本研究从区域尺度上提高了以往关于环境因子调控对气候变化响应的理解，揭示了温带草原生态系统的碳汇维持机制，并为在未来气候变化情境下的我国温带草原适应性管理提供数据支持和决策依据。