鄱阳湖沿岸风沙地貌发育对环境变化的响应

Aeolian landforms are mainly distributed in inland and coastal regions. Its formation and evolution can respond to the environmental changes. Sand hills have developed on the shore of the Poyang Lake since the last glacial period. Coastal dunes and linear wind-eroded landforms, including blowouts and parabolic dunes in various shapes with distinct assemblages，occur on these sand hills, providing a good object to address the evolution of aeolian landforms in the humid East China dominated by the monsoon. This study will derive the formation age of aeolian landforms from the sedimentary ages given by OSL dating of aeolian sands. The type of aeolian landforms will be distinguished by the landform shape and its internal structure. At last the formation age sequence of aeolian landforms will be established, and the formation and transformation process of aeolian landforms in this humid area will be revealed. By comparing with other records, such as the paleoclimate, archaeology and vegetation revealed by pollen analysis, the formation age sequence will illustrate the response behavior of aeolian landforms to the environmental changes in this area.

风沙地貌主要分布在内陆干旱地区或沿岸地带，具有指示环境的作用。鄱阳湖的湖滨地带分布着末次冰期风沙堆积而形成的沙山，其上发育了年代、类型不同的沿岸沙丘（包括风蚀坑、抛物线形沙丘等）和线形风蚀地貌，为探讨季风湿润区的风沙地貌演变提供了条件。本项目拟通过光释光法测量风沙的沉积年龄来确定风沙地貌的形成年代，依据地貌形态、内部结构等确定风沙地貌的类型，最终建立风沙地貌发育的年代序列，进而揭示出鄱阳湖沿岸风沙地貌的形成过程以及不同类型的风沙地貌之间的转变关系。在此基础上，尝试利用孢粉重建古植被记录，再与已有的区域古气候、考古等记录对比，试图确定本区风沙地貌对环境变化的响应方式。

抛物线沙丘是风积地貌的重要类型，与其它类型的沙丘之间可以相互转化。位于华东地区的鄱阳湖湖滨堆积了末次冰期堆积的沙山，发育了季风湿润区罕见的风沙地貌。项目选取鄱阳湖西侧的沙岭、吉山和松门山这3座沙山为研究对象，在野外调查的基础上，利用1:10000的DEM测量了抛物线沙丘的形态，分析其空间分布的规律。利用7月、9月的高光谱遥感数据，计算了沙山的植被覆盖度。并采用光释光方法测量了抛物线沙丘的堆积年代。依据地形、水文、植被、风况等资料的对比研究发现：（1）沙岭、松门山不发育抛物线沙丘，原因在于松门山风蚀区的植被覆盖度过低（FVC基本小于30%），风沙活动强烈，导致风蚀坑占据主导，而沙岭被村庄与农田包围，缺乏抛物线沙丘存在的空间；（2）吉山发育了3种类型的抛物线沙丘，顺风向依次为type-A、type-B和type-C，其形成与高风能窄单峰的风况有关。type-A沙丘由槽形风蚀坑后楔形的坑后积沙转化而来，type-B沙丘则是type-A沙丘迁移后变形转化而来，type-C由低矮的沙堆上的风蚀坑转化而来；（3）沙源较多时形成复合的抛物线沙丘，而沙源较少时形成简单的抛物线沙丘；（4）抛物线沙丘的形成发生在0.25 ka以前，与文献记载的植被遭人为破坏导致沙山活化的年代接近。因此，人为破坏植被是湿润地区产生抛物线沙丘的触发因素。鄱阳湖湖滨抛物线沙丘的形成与演化模式，有助于加深对季风湿润区风沙地貌演化规律的认识。