固沙植被区土壤质地与土壤微生物数量的关系

土壤微生物是荒漠生态系统的重要组分，参与成土过程与生物地球化学循环，其数量反映土壤质量，是判别退化生态系统恢复程度的重要指标。选取沙坡头固沙植被区土壤中的真菌、细菌、放线菌数量进行研究，分析了其时空分布、恢复特征及影响因子。结果表明：土壤微生物数量随固沙年限增加而增加，随土层深度增加而减少，夏秋季显著大于冬春季。三大类群微生物数量恢复曲线均呈现S型，在固沙植被建立18~24 a后恢复速率达到峰值，24~36 a后数量能够达到天然植被区的31.6%~83.7%。土壤微生物数量恢复过程主要受土壤细物质含量的影响，土壤pH是限制因子。土壤微生物对土壤状况与覆被变化敏感，能较早且敏感地指示生态系统功能的变化。

Recovery of Soil Microbe Quantities Dependent on Fine Particle Contents after Establishment of Sand-fixing Revegetation in Desert Region

As an important component of desert ecosystem, soil microbes participate in the processes of soil-forming and biogeochemical cycle. Soil microbe quantities reflecting soil quality is an important index which can be used to determine the recovery degree of degraded ecosystems. We studied the quantities of fungi, bacteria, and actinomycetes with a restoration chronosequence in Shapotou sand-binding revegetation area, and analyzed their temporal and spatial distributions, recovery characteristics and their impact factors. The results showed that soil microbe quantities increase with increasing age of revegetation and soil depth. In general, soil microbe quantities were higher in summer and autumn than those in spring and winter. The recovery processes of microbe quantities followed S shape curve that the recovery rates reached to the maximum 18 to 24 years after the establishment of sand-fixing vegetation, and the microbe quantities reached to 31.6% to 83.7% of the natural vegetation area 24 to 36 years after the establishment. The microbe recovery processes were primarily influenced by the fine particle contents of soil and limited by soil pH. The results meant that soil microbes were sensitive to soil conditions and vegetation cover, and their fluctuation could make an early and sensitive indication of the changes in ecosystem functions.