气候变暖对青藏高寒草地土壤碳组分及其稳定性的影响

Nowadays, most researches have proved that global climate temperature has been increasing apparently since 1900, and understanding the effect of climate warming on the structure and function of terrestrial ecosystems and its mechanism are therefore important scientific issues for global change study. Alpine meadow in Tibetan Plateau is predicted to be sensitive to changes in climate, and soil organic carbon (SOC) in the upper soil layer is enormous in the region. It is supposed that small changes in the SOC storage caused by warming scenarios in the future would exert obvious impact on the carbon balance of alpine meadow ecosystem. Therefore, understanding the responses of SOC compositions and decomposition process of SOC are essential to scientifically evaluate the effect of carbon sink or source in alpine meadow in Tibetan Plateau in the warming scenarios. Scientists can take three approaches to explore the underlying effect of climate warming on the SOC storage of alpine meadow in Tibetan Plateau. One is how SOC storage change with climate warming and its mechanisms. Second is how climate warming affluence the composition of SOM in alpine meadow in Tibetan Plateau, e.g. labile organic carbon, aggregates, and the structure of SOM. Third is how the decomposition process of SOC in soil and soil fractions vary with temperature, such as the decomposition rate of SOC, temperature sensitivity (Q10). In this study, we will use the long-term stimulating warming experiment in the field (Open-top Chambers, OTC), horizontal transect and vertical transect of alpine meadow in Tibetan Plateau, by analyzed changes in soil respiration, SOC storage, the composition of SOC, the structure of SOM, the decomposition rates of SOC and Q10 (incubation experiment), to adders above scientific issues, in view of the stability of SOC storage and the temperature sensitivity of SOM decomposition. Our results will provide new scientific foundation and insights to evaluate the soil carbon sequestration of alpine meadow in Tibetan Plateau and its adaptation management in the warming scenarios in the future.

气候变化对生态系统结构和功能的影响是当前全球变化研究的热点领域之一。青藏高寒草地表层土壤有机碳贮量巨大，在气候变暖情景下其土壤碳贮量的微弱变化就会对区域碳源汇功能产生重要影响。因此，科学地评估气候变暖对高寒草地土壤碳贮量的影响及其过程机理，需要考虑如下几个方面：1）土壤碳贮量变化及其机理？2）土壤碳组分变化及其机理（活性碳、团聚体和有机质结构）？3）土壤（组分）分解过程对温度变化的响应特征及其机理（分解速率和温度敏感性等）？本项目将利用模拟增温实验（OTC）、水平样带和垂直样带为基础平台的青藏高寒草地，采用原位控制实验+样带调查+室内培养的技术体系，从土壤呼吸、碳组分、有机质结构和土壤（组分）碳矿化及其温度敏感性相结合途径，重点从土壤碳稳定性及其分解的温度敏感性角度，综合研究气温升高对高寒草地土壤碳贮量及其稳定性的影响和机理，为准确评估气候变暖情景下高寒草地固碳效应及其适应性管理提供依据。

气候变化对生态系统结构和功能的影响是全球变化研究的热点领域。本项目利用西藏当雄模拟增温实验（OTC）、西藏高原从东到西水平草地样带和当雄垂直样带的基础实验平台，采用原位控制实验+样带调查+室内培养的技术体系，从土壤碳组分、土壤有机质结构和土壤（组分）碳矿化及其温度敏感性相结合途径，探讨气温升高对高寒草地土壤碳贮量及其稳定性的影响和机理。. 项目主要结果包括：1）发现要模拟升温情景下（气候变暖情景下），高寒草甸土壤将加强通过与土壤矿物联系的化学保护为主，是维持其土壤有机质稳定的主要机制；2）揭示了青藏高原沿海拔高度土壤有机碳含量、组成及团聚体稳定性特征和气候主导因素；3）发现在海拔大约4800－4950米达到最高，随后逐渐降低；因此，在未来探讨西藏高寒草甸土壤有机质含量与贮量对气候变化的响应与适应时，应充分考虑到土壤微团聚体与稳定烷基碳的垂直海拔高度的分异规律；4）发现青藏高原不同草地类型土壤有机质分解及其温度敏感性间存在显著差异，整体趋势表现为高寒草甸 (1.56) < 高寒草原 (1.88) < 高寒荒漠 (2.39)。5）外源性添加底物的C:N化学计量特征对土壤有机质分解的温度敏感性具有很强的调控作用；6）发现土壤有机质分解的温度敏感性在升温阶段显著低于降温阶段，考虑土壤有机质分解温度敏感性的不等效性对于准确预测高寒地区土壤有机质分解与气候的反馈作用具有重要的意义。7）发现温度敏感性整体表现为高寒湿地 (1.50)<小于高寒草甸 (1.83)；8）通过高强度室内控制实验，发现土壤碳氮矿化对降雨脉冲事件的响应及其不耦合现象，发展了微生物驱动模式下新的碳氮矿化响应机制。. 通过执行本项目，我们共发表了发表了SCI论文28篇（第一标9篇）、CSCD论文6篇（第一标注3篇）；其中，部分期刊发表在国际相关学科的主流期刊如：Soil Biology and Biochemistry、Global Change Biology、Global Ecology and Biogeography、Agriculture Ecosystem and Environment、Catena、Geoderma、Journal of Geophysical Research、Scientific Reports、生态学报、应用生态学报、自然资源学报等。