中文摘要：

土壤中的生物是维持土壤质量的重要组分.采用稀释平板法,对固定沙地、半固定沙地和流动沙地的土壤微生物类群进行了研究.结果表明：芽孢型细菌、放线菌和霉菌各类群数量为：固定沙地〉半固定沙地〉流动沙地;不同类型沙地中微生物各类群数量垂直分布的基本趋势依次为：结皮层（固定沙地）〉0-15 cm〉30-45 cm〉75-90 cm,随土层的加深而递减;芽孢型细菌中的巨大芽孢杆菌和地衣芽孢杆菌占优势;放线菌中的95%以上是链霉菌属,其中白孢类群占优势;霉菌中的青霉和毛霉占优势;土壤微生物各类群数量与有机质含量、植被盖度、植物种类和凋落物的多少呈正向关系;从固定沙地到半固定沙地再到流动沙地的过程,是沙地微生物类群、植物群落和有机质丧失的过程,是沙漠化发生和发展的重要标志.

英文摘要：

The microorganism in soil is one of the most important components to maintain the soil quality. The different soil numbers of microorganism groups in different types of sandy land had different functions. Adopting the dilution of flat method measures the numbers of microorganism groups in the fixed sandy land, semi-fixed sandy land and shifting sandy land. The result suggested that the numbers of spore-forming bacteria, actinomycete and fungi are as follows fixed sandy land semi- fixed sandy land〉shifting sandy land. In the different types of sandy land,the numbers of all kinds of bacteria, actinomycete and fungi had a basic tendency at vertical distribution of soil： crust layer （fixed sandy land ）〉0-15 cm〉30-45 cm〉75-90 cm, and it decreases with increase of the soil depth;B, megaterium and B. licheniformis have an advantage in spore-forming bacteria; Albosporus groups have an advantage in actinomycete;Penicillium and Mucor have an advantage in fungi; The group numbers of soil microorganism intimate related with the contents of soil organism, plant covering rate, and kinds of plant. The numbers of all kinds of groups in soil microorganism had positive correlation with organism contents, the plant covering rate, the kinds of plant, something which wither and fall, they were： fixed sandy land〉semi- fixed sandy land〉shifting sandy land; From fixed sandy land to semi-fixed sandy land to shifting sandy land, it is a course that the numbers of soil microorganism groups,groups of plants and organism lost, and it is also a course and sign to development of sandy desertification.