藏北高寒草地土壤有机碳库时空动态及对气候变化的响应

A large amount of C could be sequestrated in the soil of the Tibetan Plateau for a long period because of its cold and relatively humid climate.Tibetan Plateau has high climate change sensitivity. Hence, minor changes in soil C stock will have significant effects on atmospheric CO2 concentration. In this study, a soil organic carbon (SOC) database based on soil inventory and soil survey will be established. Using the database, we will analyze spatial pattern of SOC and its effect factor. In addition, relations between SOC distribution and grazing intensity will be studied, which mechanism will be explained. Century, a soil organic matter model, will be improved by adding soil freeze/thaw modular, and its accuracy also will be evaluated. Through input of grazing intensity based on remote sensing retrieval together with climate and soil texture, Century model will be used to simulate SOC variation under climate change and anthropogenic activities in past 30 years. BIOME4-Century model will be developed on the basis of coupling function of BIOME4 and Century, which will be driven to simulate SOC trend under the future climate change and anthropogenic. This study of the estimated effect of climate change on SOC in alpine grassland addresses an important issue in terrestrial carbon cycle research and can provide useful inputs for environmental policy making.The study can be helpful to support decision-maker to reduce anthropogenic emissions of C and prolong SOC sequestration time.

受青藏高原独特环境的作用，高寒草地土壤中固存了大量的有机碳且对气候变化十分敏感，气候较小的变化就可能对土壤有机碳产生较大的影响。项目以藏北高原高寒草地土壤有机碳为主要研究对象，通过建立不同时期土壤有机碳数据库，分析高寒草地土壤有机碳的空间分布特征及环境因子的控制作用，通过建立不同放牧梯度序列，分析放牧活动对土壤有机碳的影响程度。基于对Century模型冻融模块的改进，并结合野外调查和遥感反演方法，建立过去30年连续的藏北高寒草地土壤有机碳数据序列，研究高寒草地土壤碳储量的时空变化，定量评估气候变化和放牧活动对土壤有机碳储量的影响。把BIOME4模型与Century模型进行功能耦合，以典型浓度路径(RCPs)气候数据为驱动，模拟未来气候变化和人类活动共同作用下土壤碳储量的变化趋势。项目成果是认识高寒草地固碳速率和潜力重要科学基础。

藏北地区生态环境脆弱，探讨气候变化下土壤有机碳对冻融作用的响应，可为藏北地区生态系统功能提升和畜牧业可持续发展提供科学依据和数据支撑。本研究基于气候插值数据、未来情景数据、野外采样、模拟数据等，分析藏北地区土壤有机碳密度时空变化特征；对CENTURY模型进行冻融过程的耦合，分析冻融作用对藏北地区土壤有机碳密度的影响，进一步分析冻融作用下藏北地区土壤有机碳密度变化趋势。藏北地区高寒草甸0~50 cm土层深度的土壤有机碳密度约为高寒草原的3倍，分别为5.10 kg•C•m-2和1.78 kg•C•m-2；随着土层的加深，土壤有机碳密度逐渐减小。近55年来，藏北地区土壤有机碳密度呈减小趋势，减小速率为0.872 g•C•m-2•yr-1，高寒草甸草原减小速率最大，高寒荒漠最小。在空间上，土壤有机碳密度从东南到西北为逐渐减小趋势。考虑气候变化冻融过程影响下， 2016~2050年不同情景下不同植被类型土壤有机碳密度均呈减小趋势，其中RCP8.5情景下减小趋势最大。冻融作用对藏北地区土壤有机碳分解先为抑制作用后逐渐转为增强作用。