半干旱区沙地河流对其两侧沙丘格局及演变的影响研究

The pattern and morphological development of sand dunes at the riversides of modern rivers in sandy land of semi-arid region are closely related to characters of the valley such as its topography and direction. Choosing the Xar Moron River and its tributaries as the study area, and carry out topography measurement, remote sensing monitoring, observation of airflow and sediment discharge rate in some typical valleys’ cross sections. This research was conducted to analyze the relationship between the topography and directions of different valleys and the morphology, types, pattern, and evolvements of sand dune topographys on their banks, research on the influence of the change of valley topography on pattern evolution of sand dunes at the riverside, indicate near-surface aerodynamic process in different valleys’ cross sections, and discuss sandy land rivers’ influencing mechanisms of the development of sand dunes on their banks, which may deepen the recognition of mechanisms of land surface wind-river interaction process in semi-arid area and provide evidences consequently for the research of regional landscape response in the context of the changing global environment.

半干旱区沙地现代河流两岸沙丘的形态发育、分布格局与河谷形态、走向等特征密切相关。本项目以西拉木伦河流域为研究对象，开展河流地貌和风沙地貌的地形测量、遥感监测，明确河谷形态、走向与两侧沙丘地貌类型、格局及演变之间的关系，揭示河流地貌形态变化对两侧沙丘地貌格局及演变的影响机理；同时，开展典型河谷横断面气流与输沙率观测，分析典型河谷横断面近地表气流场结构及两岸沙丘动力过程，探讨河流地貌形态对气流的作用机制和对两岸风沙输移的影响机理。本研究将深化对半干旱区风力-河流交互作用地表过程机理的认识，为全球环境变化背景下区域景观响应研究提供依据。

科尔沁沙地地处农牧交错带，属气候变化和人类活动敏感区。该区河流两岸沙丘发育广泛，沙丘类型、格局因河谷走向和形态呈现明显的差异。近40a，该区风沙地貌覆盖面积呈减少趋势，年均变化率0.31%，体现在流动型沙丘面积减少、固定半固定类型沙丘面积增加；各类沙丘分维值相对变化不显著，位于1.07-1.10间，各沙丘处于相对稳定的演化过程中；沙丘沙物质组成优势粒径为细沙和中沙，平均粒径1.54~3.42Φ，属中等分选。科尔沁沙地风力、流水交互作用过程复杂，对地表景观塑造具有重要作用，这促使了科尔沁沙地不同河流两侧沙丘的形态特征、发育规模、空间格局表现一定的规律和差异特征；该区存在着河流为沙丘发育提供沙源、河流完全阻隔沙丘迁移、河流部分阻隔沙丘迁移、河谷影响其两侧沙丘发育类型、河谷影响其两侧沙丘发育规模、沙丘阻塞并迫使河流改道等6种风沙-流水作用关系。科尔沁沙地沙丘演化影响因素包括自然和经济因素。从统计学角度来讲，社会经济因素占主导地位，累计贡献率为64.26%，且其影响程度正逐年增加。通过开展沙丘格局特征研究，有助于深化对半干旱区风力-河流交互作用地表过程机理的认识，为全球环境变化背景下区域景观响应研究提供依据。