中文摘要：

以浅沟集水区为研究对象，分析了子午岭地区林地被开垦破坏15年后裸露地在不同侵蚀强度和侵蚀方式下的土壤养分流失和土壤微生物数量的变化。结果表明，林地开垦破坏后，土壤侵蚀加剧发展，侵蚀强度达159．7t／（hm^2·a），是林地土壤侵蚀量的上千倍。开垦破坏15年后，裸露地浅沟集水区不同地形部位表层土壤全氮、有机碳、速效磷和土壤微生物总数显著减少，同林地相比，依次分别减少37．9％～82．6％、42．7％～86．4％、24．2％～80．3％和31．8％～92．0％。在裸露地浅沟集水区梁坡随坡长的增加，表层土壤有机碳、全氮和速效磷含量及微生物总数呈显著的下降趋势，且沟槽的土壤各养分含量及微生物总数明显低于沟间。裸露地浅沟集水区土壤养分流失强度及微生物数量减少幅度在浅沟集水区的空间分布与土壤侵蚀方式和侵蚀强度相对应。林地开垦破坏15年后，土壤养分以有机碳流失最严重，其次分别为速效磷、全氮；微生物中的真菌减少幅度最大，细菌次之，放线菌减少幅度最小。

英文摘要：

This paper quantitative analyzed changes of soil nutrient and soil microbial quantity on different slope positions in a shallow gully catchment with bare-fallow land after 15 a of deforestation. Research results showed that following 15yr of deforestation, accelerated soil erosion was severe and erosion intensity reached 159.7 t/（hm^2·a）, which was more thousands times greater than those in the forested land total N, available P and soil microbial quantity greatly prio dec r to deforestation. Due to severe soil loss, topsoil organic C, reased. As compared to the forest land prior to deforestation, soil total N, organic C, available P and soil microbial quantity reduced by 37.9 %-82.6 %, 42.7 %-86.4 %, 24.2 % -80.3 %, and 31.8 %-92.0 %, respectively. As slope length increased on hillslope in a shallow gully catchment with bare - fallow land, soil total N, organic C, available P and soil microbial quantity markedly tended to decrease; soil nutrient contents in gully channels were greatly higher than those in gully slope. The spatial distribution in soil nutrient loss intensity and soil microbial quantity reduction rate was responded to soil erosion pattern and intensity in shallow gully catchments. After 15 yr of deforestation, the sequence of soil nutrient loss rate was total N 〉 organic C 〉 available P;the order of soil microbial quantity reduction rate was fungi 〉 bacterium 〉 actinomyces.