共和盆地巨型风蚀坑的发育对环境变化的响应

Mega-blowouts are the mainly geomorphic response to the dune reactivation in Gonghe Basin, Qinghai-Tibetan plateau. It has highly sensibility to environmental change and human activity, which were also the feedbacks of the regional aeolian activity to the short-term climate perturbation in arid alpine regions, include important environment signals. However, due to the complexity of the problem itself and the scarcity of individual case study, there are still some difficulties being existed to observe, model and predict for the mega-blowouts development process. The present proposal will conduct case study to detect the sedimentary structure and chronology of mega-blowouts, by means of combined modern detecting and dating methods, to verify the influence of sedimentary structure difference on the age and evolution processes of mega-blowouts. Though further analysis the role of the secondary airflow pattern to its shape forming and expansion. This research will reveal the feedback between the mega-blowout evolutions and regional climate change during the past centuries and its significance in dune reactivation process. The results can not only enhance our knowledge about the driving mechanics of the desertification in Qinghai-Tibetan plateau, but also provide meaningful strategies and suggestions to the combating and preventive measures on the desertification in alpine cold-arid regions. This research proposal has important theoretical and practical significance.

巨型风蚀坑作为青藏高原共和盆地沙丘再活化过程的主要地貌响应，对环境变化和人类活动具有极高的敏感性，也是区域风沙活动对高寒干旱区短期气候波动的反馈，承载着重要的环境信息。然而，受制于问题自身的复杂性和个体研究案例的稀缺性，对巨型风蚀坑发展过程的观测、模拟和预报均存在一定的困难。本项目拟利用现代测量技术和定年手段，对共和盆地巨型风蚀坑的沉积结构和形成年代进行准确探测和反演，探明下伏沉积基础差异对风蚀坑形成年代和演化过程的影响，进一步分析坑体内部次生流场结构对其形态塑造和扩张演化的加速作用，揭示高寒干旱区巨型风蚀坑的发育对过去百年尺度气候变化反馈及在沙丘再活化过程中的意义。研究结果不仅可以加深我们对青藏高原沙漠化驱动机制的认识，也可以对未来气候条件下高寒干旱区沙漠化的治理和预防措施提供有益的策略和建议，有着重要的理论和现实意义。

巨型风蚀坑的发育及演化对揭示高寒干旱区过去百年气候波动、反映沙丘的再活化过程具有重要意义。本项目运用无人机摄影测量及三维重构技术（UAVs-SfM）对巨型风蚀坑形态变化进行长序列的动态监测，并对不同演化阶段的巨型风蚀坑采用光释光测年（OSL）技术进行了准确定年；借助高精度探地雷达（GPR）对风蚀坑的沉积层理和发展过程做出了反演，结合定年结果对其年均扩张速率进行估算，探讨过去几百年来青藏高原东北缘高寒干旱区风沙活动对气候变化的响应及反馈过程；揭示了巨型风蚀坑的物质平衡及历史粉尘释放、现代风沙活动规律及影响因素，并尝试研发了一种对风蚀坑进行近自然修复与治理技术。重要结果如下：（1）风蚀坑尺度越大，其水平坍塌扩张速度越快，坑体内的蚀积格局也越复杂；（2）风蚀坑不同演化阶段内气流与形态的反馈关系存在差异，坑体越大气流分离越明显，二次流对坑壁的掏蚀越强烈；（3）巨型风蚀坑形成于大约~260年前，与小冰期的极端气候事件有密切的关系，其形成与演化大致经历四个主要阶段：孕育期、幼年期、青年期和成熟期；（4）巨型风蚀坑的固定-活化-再活化过程中的潜在粉尘排放量与风蚀坑的尺度基本呈正相关，共和盆地古沙丘活化引起的粉尘释放量可达到4182.63t/年，地表土壤有机碳损失量可达306.38t/年；（5）沙源供应影响共和盆地沙丘的发育过程，沙丘尺度在沙丘移动和变形规律中发挥重要作用；（6）龙羊峡库区近32年间潜在风沙入库量可达1.20×108 T，库区风沙输移受风况、气候、植被等多种因素共同影响。该项目促进了学术界对青藏高原巨型风蚀坑形成和演化过程的进一步认识，对未来气候变化条件下高寒干旱区沙漠化的治理和预防措施提供了基础数据，具有重要的理论和现实意义。