荒漠草原沙漠化植物群落及土壤物理变化

沙漠化是草地退化最严重的形式之一。以空间代替时间的方法,通过对宁夏中北部荒漠草原沙漠化过程中植物群落特征和土壤物理特性的研究,探讨草地植物群落与土壤物理特性对沙漠化的响应机制。结果表明:(1)潜在沙漠化阶段草地以牛枝子、猪毛蒿、中亚白草为优势种,轻度沙漠化阶段草地以中亚白草、苦豆子为优势种,中度沙漠化阶段草地以狗尾草、虫实为优势种,重度沙漠化阶段草地以沙米、赖草、狗尾草为优势种,极度沙漠化阶段草地以沙米为优势种。(2)随着沙漠化程度的加剧草地植物群落生物量、Shannon-Wiener指数、丰富度指数、盖度均呈降低趋势,但轻度沙漠化阶段草地植被生物量比潜在沙漠化增加了23%。(3)草地沙漠化导致土壤容重和土壤粗砂粒含量增加,而土壤水分,土壤细砂粒和粘粉粒含量降低。荒漠草原沙漠化导致了土壤环境和植被明显退化,草地生产力明显降低。

Changes in the plant community and soil physical properties during grassland desertification of steppes

Characteristics and soil physical properties of plant communities undergoing desertification in steppes located in north central Ningxia, China were studied. The investigation was carried out to probe the responses of plant communities and changes in soil physical properties that occur during desertification of steppes. It was found that the dominant species in steppes with potential for desertification were Lespedeza potaninii, Artemisia scoparia Walds, and Pennisetum centrasiaticum. In steppes subjected to only light desertification, Pennisetum centrasiaticum and Sophora alopecuroides were dominant. The species Utricularia australis and Corispermum hyssopifolium were dominant in steppes experiencing moderate desertification. In steppes subjected to severe desertification, Agriophyllum squarrosum, Aneurolepidium dasystachys and Utricularia australis were dominant, and in steppes with extremely severe desertification Agriophyllum squarrosum was dominant. When such grasslands experienced intensifying desertification, their biomass, Shannon-Wiener index, richness index, and ground cover tended to decline. The biomass of grasslands suffering light desertification was 23% higher than that of grasslands with potential for desertification. As desertification proceeded, the soil bulk density and coarse sand content of grasslands increased but their soil moisture and clay-silt content tended to decrease most significantly. The desertification of grasslands caused the soil to form a coarse texture and thus increase its bulk weight, with the consequence that soil moisture and silt content tended to decrease. As desertification intensified, these changes made the soil more susceptible to erosion, so that, directly or indirectly, the productivity of such grasslands inevitably must decrease. Therefore, the desertification of steppes involves progressively less retention of moisture and fine soil particles, leading to desiccation and erosion of the soil, changes in plant species, and inevitable loss of productivity.