沙漠矿物风化程度与生态修复的互馈机制研究

Desertification is a major challenge today in the world. The critical steps in the desertification control are stabilizing the sand dune and promoting the vegetation development. A certain content of clay particles is essential for the vegetation development and the mineral weathering is an important source of the clay particles in the desert. The previous studies on the desert ecological restoration focus on the biological processes in the desertification, the weather-proof of vegetation in desert, soil crusts and so on. There are few researches on the role of mineral weathering on the desert ecological restoration, and the interaction mechanism between the mineral weathering and the vegetation restoration is not clear yet. This programme will pay more attention to the interaction mechanism between the mineral weathering and the desert ecological restoration by the field investigation and sampling, field experiment and observation. The studied area is located in Ulan Buh Desert and the main contents are the following: 1) the quantitative relation between the content of clay mineral and the mineral weathering degree; 2) the promoting impacts of the clay particles on the soil crusts; and 3) the impacts of the vegetation on the mineral weathering. The achievements of this programme will be helpful to comprehend the sand characteristics and its effects on the ecological restoration in Ulan Buh Desert, which will provide the theoretical and technical support for the desertification control in Ulan Buh Desert and the other similar desert area. Meanwhile, the outputs will also give consults to the present desertification control strategies in China.

沙漠化是当今世界面临的一项重大挑战，对沙漠的治理以稳定沙丘和促进植被发育为关键步骤，一定的粘性颗粒含量是沙漠植被发育的基础，而矿物风化是沙漠中粘性颗粒的重要来源。以往对沙漠生态修复的研究主要集中在沙漠化的生物学过程、沙漠地表结皮对生态修复的影响以及沙漠植被的抗蚀作用等方面，对矿物风化在沙漠生态修复中的作用这一机理问题研究较少，矿物风化与植被修复间的响应关系尚不明确。本项目以乌兰布和沙漠为研究区域，通过野外考察和采样、野外试验和监测等方法，研究矿物风化与沙漠生态修复的互馈机制。主要研究内容包括：①矿物风化程度与粘性颗粒含量的定量关系；②粘性颗粒含量对沙漠地表结皮的促发机制；③植被修复对沙漠泥沙矿物风化程度的反馈效应。研究成果将有助于认清乌兰布和沙漠的矿物风化特征及其对沙漠生态修复的影响和作用，为乌兰布和沙漠及其它沙漠地区的治理和修复提供理论和技术支撑，也为新时期我国的沙漠防治战略提供参考。

本项目以乌兰布和沙漠为研究对象，通过对流动沙丘、半固定沙丘和固定沙丘进行采样，分析了沙漠颗粒的粒径组成、矿物成分、风化程度及与生态修复的互馈关系，并通过野外和室内试验研究了粘性颗粒含量对地表结皮的促发作用。结果表明：沙漠40~60cm的底层沙和20~40cm的中层沙级配分布特征基本相似，0~20cm的表层沙小于0.1mm和0.01mm的颗粒含量明显较高；表层、中层和底层沙的中值粒径分别为0.203mm、0.215mm和0.224mm，粘性矿物含量垂向分布特征表现为表层＞中层＞底层，分别为4.52%、4.24%和3.82%，粘性矿物含量与中值粒径之间存在着较好的相关关系，粘性矿物颗粒含量越高则细颗粒越多，样本的中值粒径越小；风化程度与粘性矿物含量之间存在较好的相关关系，风化程度越高，粘性矿物含量也越高，各类型沙丘表层风化程度高于中层和底层，固定沙丘表层的风化程度略高于流动沙丘和半固定沙丘；野外结皮发育试验中，试验区域II所处的外部环境较区域I稳定，其整体结皮发育率达到76.8%，高于区域I的62.9%，区域I内部中心区域受到粘土障的二次保护，其结皮发育率达到91.2%，远高于其他区域，表明外部环境越稳定、粘性颗粒被保护的越好，地表结皮发育率越高；室内结皮发育试验表明，在粘性颗粒缺失的条件下，即使有稳定的外部环境及较好的降水条件，地表结皮也很难发育；粘性矿物含量与植被盖度之间具有良好的关系，植被盖度由4%增加至18%时，粘性矿物含量增加速率较快，之后增加速率减小，增加趋势趋于平缓；矿物风化程度随生态修复的时间逐渐增加，即生态修复的时间越长，所在区域的风化程度也越高。项目建立了植被覆盖度、植被修复时间与矿物风化程度之间的关系，阐明了沙漠矿物风化程度与生态修复的互馈关系。研究成果为深入认识沙漠地区矿物风化与生态修复的关系提供了支撑，为沙漠地区的生态修复提供了理论依据与科学支撑。