| Arid and semi-arid steppe region has always been the fragile ecological envi-ronment area, with open coal mining, damage to prairie land resources and ecological environment are becoming increasingly severe. In typical steppe region of Yimin opencast dump appears the biological soil crusts(BSCs) which is different from the original grassland landform, BSCs can re-allocation water resources, improve soil properties and affect the germination and growth of plants which has important sig-nificance for solving the problems of open-pit mine reclamation soil shortage, lack of water resources and less suitable species. Taking Yimin opencast mine as an example,the study investigates the coverage of BSCs, soil types, vegetation species composi-tion,functional composition and species diversity index,the soil samples were col-lected and the rainfall simulation experiment was done in laboratory which analyze the relationship among the succession of vegetation community with reclaimed soil development and the redistribution of rainfall. The main results are as follows:1.The effect of BSCs on reclaimed soil was obvious. (1)Effects on soil texture and soil bulk density are mainly concentrated in the 0?5cm topsoil. 2mm?0.05mm range of particles is the basic material for dump BSCs formation and development, with colonization and development of BSCs, coarse sand content reduced while the content of fine sand and silt increased; soil density is different in various crust type, among them the influence on soil bulk density by algae crust was more obvious than moss crust. (2)In addition to the pH value, other soil chemical properties are affected by biological soil crusts and the differences are significant. The influence degree of or-ganic matter, hydrolytic nitrogen, available phosphorus, available potassium by crusts can reach 20cm soil, total nitrogen accumulation degree can reach 10cm soil; The ac-cumulation ability of available phosphorus by algal crusts is higher than that of moss crusts and lichens crust.2.BSCs has a significant water holding capacity to topsoil. (1)When rainfall is low(5mm), in the short-term different types of crusts have significant water holding capacity while in a long-term it has differences: lichen crust < moss crust. (2)When the rainfall is high(lOmm), moss crust has obvious water holding capacity both in short and long-terms. BSCs has changed the infiltration of soil moisture due to its in-fluence on rainfall interception and effect on soil properties. The soil water retention capacity and infiltration, change of redistribution process forms a new water envi-ronment for soil-vegetation system in dumping site.3.With the increase of biological soil crusts coverage,dump natural invasive growth vegetation community important value, species diversity index shows differ-ent change patterns.(1)With the increase of the crust coverage, annual and biennial herbs(AB) important value gradually reduce,show a negative correlation; Important value of the perennial herb (PH) and the dominant species (guinea grass, Stipa grandis,DS) increase first and then decrease, which is a typical shrub encroachment phenom-enon.(2)With the increase of biological soil crusts coverage, Patrick species richness index (Pa), Shannon-Wiener diversity index (H'), Simpson diversity index (D), Pielou evenness index (Jp) first increase and then decrease, Shannon-Wiener diversity index(H'), Simpson diversity index (D) and Pielou evenness index (Jp) change slowly, Pat-rick species richness index (Pa) changes more obviously than the first three and af-fected more by the crust coverage. Affected by Biological soil crusts colonization and development, not only the vegetation functional community changes, the species di-versity also changes. In the artificial disturbance of open-pit mine dump, biological soil crusts become one of the important driving factors to vegetation succession. |
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