中文摘要：

【目的】依托8年长期（2005~2012）固定道定位试验,研究不同耕作方式对土壤有机碳、土壤微生物量、土壤酶活性在0—90 cm土层的分布特征,为优化中国西北干旱区的耕作方式提供理论依据。【方法】试验包括固定道垄作（PRB）、固定道平作（PFT）与传统耕作（CT）三种耕作模式下的土壤有机碳土壤总有机碳（TOC）、颗粒有机碳（POC）、土壤微生物量碳（MBC）、土壤微生物量氮（MBN）、土壤微生物量磷（MBP）、蔗糖酶、过氧化氢酶、脲酶及小麦产量进行了测定和分析。【结果】在0—90 cm土层,不同耕作方式下的TOC、POC、MBC、MBN、MBP、蔗糖酶活性、脲酶活性均随着土层的增加呈下降趋势,过氧化氢酶活性呈先下降后增大的分布特征;在0—60 cm,固定道保护性耕作能够显著增加心土层作物生长带土壤有机碳储量,有机碳储量大小为PRB〉PFT〉CT;PRB、PFT较CT可以显著增加0—10 cm作物生长带TOC、POC、MBC、MBN、MBP含量、蔗糖酶、脲酶活性,其大小为PRB〉PFT〉CT;耕作方式对过氧化氢酶活性影响不显著;TOC、POC、MBC、MBN、MBP、蔗糖酶活性、脲酶活性、过氧化氢酶活性之间均达到了显著或极显著相关。【结论】PRB较PFT、CT能够提高耕作层（0—10 cm）土壤有机碳含量、土壤微生物量、土壤酶活性,增加作物产量,增大0—60 cm土层有机碳储量,耕作方式（PRB、PFT及CT）对10 cm以下土层土壤环境改善作用不明显。

英文摘要：

【Objectives】An eight consecutive year（ 2005- 2012） field experiment was conducted to evaluate tillage practices on soil organic carbon,microbial biomass and soil enzyme activity and their distributions in 0-90 cm depth of soils in arid northwestern China,to which would provide a theoretical basis for better choosing tillage practices. 【Methods】The treatments include permanent raised bed（ PRB）,zero tillage with control traffic on flat field（ PFT） and conventional tillage（ CT）,and the total soil organic carbon（ TOC）,particulate organic carbon（ POC）,microbial biomass carbon（ MBC）,microbial biomass nitrogen（ MBN）,microbial biomass phosphorus（ MBP）,enzymatic activities（ invertase,urease and catalase） and grain yield of spring wheat were measured.【Results】The contents of TOC,POC,MBC,MBN and MBP and the activities of invertase and urease were declined with increasing depth（ 0- 90 cm） in the PRB,PFT and CT treatments,and the catalase activity was decreased first and then increased. In the whole 0-60 cm soil depth,the SOC storage was the highest under PRB,followed by the PFT and CT treatments in crop growth areas. The activities of enzymes（ invertase and urease） and the contents of TOC,POC,MBC,MBN and MBP in the upper layer（ 0-10 cm） in the plots tilled by PRB and PFT were higher than those in the plots tilled by CT. There were significant and extremely significant correlations among TOC,POC,MBC,MBN,MBP and enzyme activities（ invertase,urease and catalase）,while the catalase activity was not significantly affected by the three tillage modalities. 【Conclusions】The PRB and PFT treatments could improve the contents of soil organic carbon,microbial biomass,soil enzyme activities and the grain yield,and the sequestration of carbon in the whole profile of 60 cm under the PRB treatment was greater than that under the CT and PFT treatments. Beneath 10 cm,there was no significantly improvement in soil environment for the PRB and PFT treatments compare with the