湖泊沉积记录的黄土高原小流域近千年土壤侵蚀与气候变化关系研究

Global climate change has an important impact on soil erosion, and the study of the relationship between soil erosion and climate change is one of the important frontiers issues of soil erosion. Most studies suggest that global warming will exacerbate the severity of soil erosion, but its basic mechanisms and driving factors have not been well understood. .In this project, we will reconstruct the history of soil erosion intensity and climate change during the last millennium based on preliminary work, recorded by 210Pb, 137Cs and AMS14C well-dated lake sediments from the China Loess Plateau, such as Lake Chaonaqiu, Lake Gonghai and Lake Maying. Furthermore, this project will research the relationship between soil erosion intensity and climate change in small lake basin during the last millennium, based on a comprehensively comparison of climate change reconstructed in lake sediments itself and other credible archives and meteorological data, and then reveal the relationship between soil erosion intensity and climate change in lake basin during the last millennium, trying to find out the history of regional soil erosion in characteristic period (such as MWP, LIA and CWP), find the historical similarity for the current soil erosion extent, and then primarily reveal the mechanisms and driving factors of soil erosion intensity influenced by climate change.

全球气候变化对土壤侵蚀产生重要影响，研究土壤侵蚀与气候变化之间的关系是土壤侵蚀学科的重要前沿领域之一。多数研究认为全球气候变暖会加剧土壤侵蚀严重程度，而其基本机理和驱动因素尚不清楚。本项目拟在前期工作基础上，选择黄土高原典型湖泊（如朝那湫、宁武公海和马营海）为研究对象，开展小流域近千年土壤侵蚀与气候变化关系研究。通过210Pb、137Cs以及AMS14C等多种年代学方案，建立准确可靠的年代学模型；综合开展多代用指标研究，建立近千年高分辨率土壤侵蚀强度变化（代用指标）时间序列以及气候变化（代用指标）序列。通过土壤侵蚀强度变化序列与气候记录的对比分析，揭示湖泊小流域近千年土壤侵蚀强度与气候变化之间的关系，试图查明特征时期（如中世纪暖期、小冰期和当前暖期）黄土高原区域土壤侵蚀变化历史，以及为当前土壤侵蚀寻找历史相似形，初步释译气候变化对土壤侵蚀强度的可能影响机理和驱动因素。

全球气候变化对土壤侵蚀产生重要影响，研究土壤侵蚀与气候变化之间的关系是土壤侵蚀学科的重要前沿领域之一。本项目选择黄土高原典型湖泊（如朝那湫、宁武公海和马营海）为研究对象，通过210Pb、137Cs以及AMS14C等多种年代学方案，结合多代用指标，建立小流域高分辨率土壤侵蚀与气候变化历史，揭示湖泊小流域土壤侵蚀强度与气候变化之间的关系。试图为当前土壤侵蚀寻找历史相似形，初步释译气候变化对土壤侵蚀强度的可能影响机理和驱动因素。本项目目前以朝那湫为研究对象，初步取得下列结果和认识：..（1）气候偏干期，朝那湫流域植被覆盖度低，土壤侵蚀增强，沉积物粒度偏粗；反之，在气候偏湿期，植被覆盖度高，土壤侵蚀减弱，沉积物粒度偏细。近300年来，朝那湫沉积物粒度序列记录到四次强侵蚀事件，分别发生在约公元1770A.D.前后、1835 A.D.前后、1875 A.D.前后和1970 A.D.前后，这四次强侵蚀事件发生在十年/数十年尺度干旱时段内。.（2）在古环境研究中，湖泊沉积物磁化率的环境指示意义通常被解释为: 磁化率升高指示流域内侵蚀和径流搬运能力增强，间接反映降水较多，气候湿润; 磁化率降低指示流域内侵蚀和径流搬运能力减弱，间接反映降水较少，气候干旱。我们的研究结果揭示了湖泊沉积物磁化率不同以往研究的特殊环境指示意义：磁化率升高指示流域内侵蚀和径流搬运能力减弱，反映降水较多，气候湿润； 磁化率降低指示流域内侵蚀和径流搬运能力增强，反映降水较少，气候干旱。