中文摘要：

采用时空互代法，以典型侵蚀环境纸坊沟流域不同封禁年限的狼牙刺群落和杂灌群落为研究对象，选取放牧地和天然次生林为参照，分析了生态恢复过程中土壤微生物生物量、呼吸强度、代谢商及理化性质的演变特征。结果表明，封禁后土壤理化性质明显改善；微生物生物量随封禁年限的延长变化显著，阳坡随封禁年限增加土壤微生物生物量逐渐增加，25a后微生物生物量碳、氮、磷较封禁前分别增加252％、161％和174％，但显著低于天然侧柏林，仅为其39．O％、41_8％和53．7％；阴坡封禁前10年微生物生物量迅速增加，随后增加幅度减缓，呈波动式缓慢上升趋势；封禁25a后微生物生物量碳、氮、磷分别增加108％、93％和102％，但明显低于天然杂灌丛群落和辽东栎林，仅为辽东栎林的54．4％、49．1％和40．1％。土壤呼吸强度在封禁5a后增大明显，且随着年限增加逐渐上升，阳坡25a时达到最大值，而阴坡15a时达到最大值，随后开始有所下降，25a后降至最低点，但仍显著高于放牧地，相同封禁年限的土壤呼吸强度阴坡明显高于阳坡。qCO2随着封禁进程逐渐降低，25a后达到最低值。相关性分析显示微生物生物量碳、氮、磷、呼吸强度、qCO2与土壤养分和恢复年限相关性密切，达到显著（P〈0．05）或极显著水平（P〈0．01）。

英文摘要：

Vegetation restoration is a key measure to improve eco-environment in the Loess Plateau of China. To explore characteristics of the evolution of soil microbes after closure of hillsides for management of eroded hilly Loess Plateau, biomass and respiration of soil microbes and physico-chemical properties of the soils under natural shrubs （ Sophora davidii, mixed beskage ） different in history of the closure in Zhifanggou Catchment were studied systematically by means of substituting temporal serial with spatial serial. In addition, two pieces of grazing field and natural secondary forest （ Platycladus orientailis, Quercus liaotungensis）each were chosen as contrast. Results show that soil quality, including biomass, respiration and metabolic quotient of soil microbes and physical and chemical properties of the soil, was gradually improved along the chronosequence of vegetation restoration. Microbial biomass C, N and P （SMBC, SMBN and SMBP） increased remarkably after 5 years of closure and management and kept on increasing gradually with each passing year in the southern slope. After 25 years, they increased by 252%, 161% and 174%, respectively, as compared with that in the grazing field, but amounted only to 38.97%, 41.82% and 53.73% of that in the Platycladus orientailis land, respectively. The increase was found significant in the first 10 years of the measure in the northern slope, and afterwards it slowered down and even fluctuated. After 25 years they increased by 108%, 93% and 102%, respectively, as compared with the grazing field, but amounted only to 54.35%, 49.11% and 40.11% of that in the Quercus liaotungensis plot. Respiration of soil microbes increased remarkably after 5 years of closure and kept on with each passing year, peaking in the 25th year in the southern slope, but only in the 15th year, and then decreased in the following years and leveled off in the 25th year in the northern slope. Metabolic quotient （qCO2） declined with the history of closing and reached the lowest point in t