中文摘要：

通过对中国农牧交错带科尔沁沙质草甸土壤微生物数量的垂直分布及其季节动态的研究分析表明：（1）微生物总数、细菌和放线菌数量均表现出与降雨量同步的季节动态,即6月份较5月份有所减少,7月份增至最多,7月份以后微生物数量逐渐下降,真菌则表现出从5月份到8月份一直增加,9月份开始回落;（2）土壤微生物具有明显的垂直分布差异。细菌和放线菌的垂直分布表现出随土壤深度增加逐渐减少的趋势,真菌数量表层最高,20 cm以下变化不够规律;（3）土壤微生物的层化比率均大于2（5月份放线菌除外）;（4）不同土壤生态因子对微生物的影响不同,相同因子对不同微生物类群的影响也不相同。细菌受水分影响较大,真菌与地温的变化趋势相近,放线菌与水热条件的共同作用有关。土壤养分（有机碳和全氮）与微生物数量呈显著的正相关。

英文摘要：

Microbe plays a very important role in the procedure of material recycle and energy flow, and microbial ecology has become a very important discipline in the scientific research field, especially in arid and semi-arid areas. The main researches in Horqin Sand Land have been focused on vegetation, water use, soil physicochemical properties, etc. , and few have been on microbe. The paper was focused on the vertical distribution and seasonal dynamics of soil microbial numbers in sandy grassland of Horqin, Inner Mongolia, China. The samples were taken once a month from May to September,2007. The results showed great differences both in seasonal dynamics and vertical distribution. （ 1 ） The seasonal changes of the total microbial, bacteria and actinomyces number were closely related to rainfall variation in the period of May to September. It appeared that the numbers reduced from May to June, and increased to the peak in July, and then decreased gradually until to September. Fungi presented differently with bacteria and actinomyces. It was increasing since May and with a peak in August, then reduced to the least in September. （2） Microbial vertical distribution was obvious, which showed that bacteria and actinomyces number were abated as the soil depth increased. Fungi acted in a different way that the largest number was at the upper layer, and it was not in order at the lower layers. （ 3 ） Soil microbial stratification ratios are more than 2 except for actinomyces in May. （4） Different soil factors have different effects on microbe. Bacteria are greatly influenced by soil water content, while the seasonal variations of fungi are similar to those of temperature. Actinomyces is influenced by both soil water content and temperature. Microbial number shows significant positive correlation with soil nutrition, such as organic C and total N content.