古尔班通古特沙漠生物结皮中土壤微生物垂直分布特征

VERTICAL DISTRIBUTION PATTERNS OF SOIL MICROORGANISMS RELATING TO BIOLOGICAL CRUSTS IN THE GURBANTUNGGUT DESERT, XINJIANG

对新疆古尔班通古特沙漠主要沙丘类型--沙垄的不同部位、不同类型生物结皮中土壤微生物数量变化特征进行研究,结果表明:(1)微生物总数从垄顶至垄间低地呈递增趋势,在沙垄不同部位0～20 cm土层中的垂直分布有差异.(2)土壤微生物各类群数量垂直变化规律为:细菌数量在垄顶0～10 cm土层中递减,到10～20 cm有所回升;在迎风坡和背风坡的0～10 cm土层中递增,到10～20 cm有所下降;在垄间低地0～20 cm土层中呈递增趋势.放线菌数量在各部位均随土层加深而递减.真菌数量在垄顶和迎风坡0～20 cm土层中的垂直变化与细菌在垄顶的垂直变化一致,在垄间低地和背风坡,真菌数量均在2～5 cm土层中出现峰值,然后随土层加深递减.(3)微生物类群的组成表现为:细菌数量＞放线菌数量＞真菌数量.在垄间低地细菌所占微生物总数比例相对垄顶有所增加,而放线菌和真菌相应减少.(4)土壤微生物的数量变化特征与生物结皮的类型、分布以及土壤有机质含量等因子有一定相关性.

The Gurbantunggut Desert, located in the Junggar Basin in north Xinjiang with an area of 4.88×104 km2, is the second largest desert in China. Biological soil crust is widely spread and is ecologically important in this region. In this study, the quantities, distribution patterns and compositions of soil microorganisms in different types of biological crusts, geomorphic locations and soil layers of sand dune were examined. The results showed that: (1) The total number of microorganisms increased sharply from top of sand dune to interdune areas. The vertical distribution patterns of the microorganisms quantitatively varied with the deepening of soil layer at different terrain parts. (2) The quantities of bacteria, actinomyces and fungi were consistent with total quantity from top of sand dune to interdune areas. But the vertical distribution of each group quantitatively varied in different soil layers. The vertical distribution of bacteria quantitatively declined at 0~10 cm in depth and increased at 10~20 cm in depth at top of sand dune, which was reverse on slope of sand dune. At interdune areas, the vertical distribution of bacteria quantitatively increased with deepening of soil layer (0~20 cm). The variation of actinomyces' quantity was simple, which reduced at soil layer (0~20 cm) in each location of sand dune. The vertical variation of fungal quantity showed the same tendency as bacteria at the top and windward of sand dune in different soil layers. However, the tendency varied at bottom and leeward of sand dune, where the quantity of fungi reached the peak value at 2~5 cm in depth, and then declined at 5~20 cm in depth. (3) Among different soil microorganism groups, bacteria were predominant, actinomyces the next and fungi the least. The bacteria accounted for 90% of the total at interdune areas, but the proportions of actinomyces and fungi declined. (4) The composition, distribution and quantity of soil microorganisms might be influenced by landform, existence of biological soil crust and organic matter contents. Fig 5, Tab 1, Ref 34