Review on Developmental Characteristics and Ecological Functions of Soil Crust

Soil crust, distributing on arid and semi -arid areas, plays important roles in the ecological process of the system of soil-plant-vegetation. Based on large numbers of references, this paper reviewed the fruits and conclusions about soil crust researches in recent several decades, and some problems that need to be studied further also were summarized. The following results were found: 1) Biological soil crust and physical soil crust (two types of soil crust) usually occur together and affect each other in nature; however, few understandings on the relations between them and their multiple effects were known due to separate research for the two types crust artificially; 2) The development of soil crust shows temporal complexity and spatial variation obviously, and also its ecological effects have big differences in different regions or experimental conditions, even some contrary conclusions found; 3) Many researches in such areas as Loess Plateau and Black Soil Region have not been launched untill recent years, and it is necessitous that more studies should be developed to understand favorable or adverse effects of soil crust on soil erosion and its happening conditions and eco -hydrological processes in order to give an academic foundation to physical erosion modeling and effective using of soil crust resources.