阿拉善高原风沙过程与绿洲生态修复

Alax Plateau, a unique arid desert system, has been a research hotspot of eco-hydrology and aeolian processes. Staggered with denuded hills, fluvial plain, terminal lakes, blown out depressions, pebble gobi, sand dunes, river delta oasis and desert steppe, the study area is characterized by varying geographical units, multi land surface agents, and complex interaction of natural and social factors. Due to aridification and ecological degeneration, wind erosion, aeolian transport and land desertification are integrated as the most prominent land surface processes. In this project, the rate of land surface erosion and landforms sculptured by wind will be investigated by in situ observation. Regional, seasonal and directional variations of aeolian sand transport will be studied through observation on sand transporting winds, and sand transport rate. The source of sand deserts, wind regime of different dune types and spatial variations of the dune sand properties will be determined through sampling analysis, experiments and wind field measurements. The interaction mechanism between desert vegetation and aeolian process will be elaborated by investigating plant growth, community succession and abiotic habitats. Blown sand encroachment to oasis ecosystem will be analysed through RS multi-stage image interpretation and field survey. The project will be helpful to understand the aeolian processes, aeolian landform development, and has importance in oasis protection and regional sustainable development.

阿拉善高原干旱荒漠景观独具特色，是生态水文和风沙过程研究的重点区域。区内剥蚀丘陵、冲积平原、终端湖泊、风蚀洼地、砾石戈壁、流动沙丘、灌丛草原与荒漠绿洲交错分布，具有景观类型多样、地表多营力过程耦合与多要素互馈特征。干旱化与生态退化使风蚀、风沙搬运与沉积成为区域的关键地表过程。本项目通过野外观测，研究黑河下游冲湖积平原的地表风蚀速率和风蚀形态发育；通过起沙风、输沙率观测，研究风沙输移的区域性、季节性与方向性规律；通过流场观测与采样分析，研究沙丘发育的动力背景以及风沙物质的空间分异；通过植被生长、群落演替和生境调查，揭示荒漠植被与风沙过程的互馈机制；通过多期遥感解译和实地调查，分析流沙对绿洲生态系统的侵害过程。本项目有助于增强对阿拉善高原风沙过程、风成地貌发育的理解，对绿洲生态修复和区域可持续发展具有重要现实意义。

1..项目的背景.阿拉善高原干旱荒漠景观独具特色。具有景观类型多样、地表多营力耦合与复杂的人与自然互馈作用特征。风蚀、风沙搬运与沉积为关键地表过程。.2..研究方法与内容.对风蚀速率、风沙形态和风沙输移过程进行了野外观测；采样分析了沙丘沙的空间分异；调查了沙丘移动和荒漠植被群落演替；实验研究了荒漠植被与风沙过程的互馈机制；调查分析了风沙对绿洲系统的侵害过程。.3..重要结果.（1）植物固沙的间距效应。植物具有防风固沙作用，在背风侧发育风影沙丘。实验发现，灌木株高、株距和风况共同控制风影沙丘发育。在临界株距（0.5-0.7H）下，单独的风影沙丘合并成大的抛物线状沙丘，固沙能力提高4-5倍。本结果对固沙林合理配置具有重要意义（JGR，2018）。.（2）风沙的空气动力粒径分布。跃移层细沙和极细沙的相对含量与风速呈负相关，中粗沙的相对含量与风速呈正相关，沙粒平均粒径随高度的增加而减小，随风速的增加而增大，反映了风对沙粒的分选搬运机制（Sedimentology,2019）。.（3）不同地表的沙尘暴易发性。用沙尘暴和强风频率比值来量化沙尘暴易发性。沙漠和农田地区的沙尘暴易发性比草地、戈壁及盐壳地表高10-20倍，定量反映了土地利用和土地退化对干旱地区沙尘暴发生的影响（Atmospheric Research, 2020）。.（4）东亚沙尘暴的环境效应。2017年起源于蒙古戈壁的一次强沙尘暴造成中日韩约500个城市空气质量恶化，东亚大陆和北太平洋降尘分别为20.4Tg和5.3Tg，沙尘7天后抵达北美大陆(ACP,2018)。.4..关键数据及科学意义.共采集分析了800多个戈壁和沙漠沉积物样品，通过样地观测获得了干涸湖床的风蚀速率数据，通过观测获得了地表温湿度、风速、风向、沙粒数和沙粒动能的200余万条数据，还获得了大量实验和野外调查数据，对理解风沙过程具有重要意义。