干旱半干旱区坡面覆被格局的水土流失效应研究进展

植被恢复与建设是控制水土流失的重要措施.在干旱半干旱地区,植被在空间上的分布呈现离散特征,在坡面上形成的裸地-植被镶嵌和植被条带分布等覆被格局对水土流失过程具有重要影响.覆被格局与水土流失关系研究是景观生态学格局与过程研究的重要内容.从植被斑块、坡面覆被格局对水土流失的影响与耦合覆被格局与水土流失的手段和方法三个方面对国内外相关研究进行总结分析.从中发现,植被类型、层次结构和形态特征是植被斑块尺度上影响径流泥沙的关键因素；不同覆被类型的产流产沙特征与覆被格局的准确描述是研究覆被格局水土流失效应的重要基础；坡面覆被格局对水土流失的影响关键在于其改变了径流泥沙运移和汇集的连续性,应重点关注径流泥沙源汇区的连通性和空间分布在水土流失中的作用；以坡面的精确覆被制图为基础,建立基于水土流失过程的覆被格局指数和耦合格局信息的径流与侵蚀模型是定量研究覆被格局影响的有效手段.今后应加强以下研究:以动态系统的观点研究覆被格局的变化对水土流失的影响,系统理解覆被格局与水土流失之间的相互联系与反馈机制,探讨两者间动态关系随尺度变化的规律性并发展尺度上推方法；构建过程意义明确且简单实用的格局指数,将覆被格局与水土流失过程有机联系起来；发展覆被格局的动态信息与产流产沙过程相结合的水文模型,加强对格局与径流泥沙反馈系统的耦合,建立真正意义上的覆被格局-水土流失过程耦合模型.

The effect of land cover pattern on hillslope soil and water loss in the arid and semi-arid region: a review

Vegetation restoration and construction play an important role in controlling soil and water loss. The spatial distribution of plant cover is scattered in arid and semi-arid region. The formed land cover patterns on hillslope such as bare soil-vegetation mosaic and banded vegetation pattern have great effect on runoff and soil erosion processes. The relationship between land cover pattern and soil loss is an important topic of pattern and process research in landscape ecology. We present a review of previous research from three aspects including the effects of vegetation patch and land cover pattern on runoff and soil erosion, and the way to account for land cover pattern and couple it with soil loss. Vegetation type, vegetation structure and vegetation morphology are the key factors of soil and water loss at the patch scale. Accurately understanding the runoff and sediment production characteristics of different land cover type and describing land cover pattern are two important bases to study the soil and water loss rules of land cover pattern on hillslope. The land cover pattern changes the continuity of runoff and sediment transport and convergence path. Thus, one should pay much more attention to the role of connectivity and distribution of runoff and sediment source and sink areas on hillslope in affecting soil and water loss. On the base of precise hillslope land cover mapping, developing pattern metrics involved soil loss processes and integrating land cover information in runoff and soil erosion models are two efficient approaches to quantitatively account for the effect of land cover pattern. There are several issues need further investigation in future. First, land cover pattern has a temporal variation which was ignored in most of previous studies. More studies are needed to investigate the influence of land cover pattern variation on soil and water loss from a systemic and dynamic view. Second, current studies on the interaction between land cover pattern and soil loss are mainly focused on the one-way effect analysis, e.g., impact of land cover pattern on soil loss. The feedbacks of soil loss processes to land cover pattern are ignored. Much more attention should be paid to understand the interactions and feedbacks between land cover pattern and soil loss. Third, scale is a universal appearance in ecological phenomenon. Investigating scale effect of the relationship between land cover pattern and soil loss and developing up-scaling methods are front and challenging topics. Fourth, much more simple and practical pattern metrics with physical mechanism should be developed to integrate land cover pattern and soil loss, and pattern metrics should be further applied to quantitatively indicate runoff and sediment yield. Finally, the variation of land cover pattern should be coupled with runoff and sediment production processes in hydrologic model. It can strengthen the ability of the model to account for the feedbacks between pattern and runoff and sediment. This is the key to establish the land cover pattern-soil loss process integrative model, which is very useful to provide scientific basis for protecting soil erosion and designing vegetation rehabilitation pattern in arid and semi-arid region.