中文摘要：

为分析保护性耕作措施对旱作农田土壤活性有机碳的影响以及对土壤有机碳的敏感响应指标进行归纳总结,探讨适合西南丘陵区紫色土农田生态系统在保护性耕作下的有机碳分组方法和活性碳有效指标提供科学依据,进而为土壤固碳减排、提高土壤质量奠定理论基础。在重庆北碚西南大学试验农场对平作（traditional tillage,T）、垄作（ridge tillage,R）、平作＋秸秆覆盖（traditional tillage＋straw mulching,TS）和垄作＋秸秆覆盖（ridge tillage＋straw mulching,RS）4种处理下、西南紫色土丘陵区＂旱三熟＂种植模式下的土壤总有机碳（Total soil organic carbon,TOC）、颗粒有机碳（Particulate organic carbon,POC）、水溶性有机碳（Dissolved organic carbon,DOC）、易氧化有机碳（Readily oxidized organic carbon,ROC）、可矿化有机碳（Mineralized organic carbon,MOC）以及微生物量有机碳（Microbial biomass carbon,MBC）进行了测定和分析。结果表明,秸秆覆盖不仅增加了表层土壤的TOC,也有利于20cm以上的耕层TOC的增加,而垄作对TOC的影响很小。秸秆覆盖处理下各土层POC均显著高于传统耕作,而单纯的垄作处理对5cm以下土层的POC没有影响,却显著地降低了0-5cm土层POC含量。DOC含量随土层的加深逐渐降低,且不同处理的差异主要出现在表层0-5cm土壤中,5cm以下土壤的DOC含量不易受到耕作措施的影响。TS、RS与对照相比均显著提高0-5cm土层的ROC含量,R与T之间差异不显著,秸秆覆盖只对土壤表层ROC影响很大。T、R、TS、RS处理全年日均土壤呼吸分别为1.84,1.65,2.22,2.21μmol/（m2·s）,年土壤呼吸总量分别为696.31,624.41,840.12,836.33g/m2。与对照相比,垄作对土壤呼吸的影响不大,秸秆覆盖加速了土壤呼吸速率。秸秆覆盖处理显著提高了MBC含量,而垄作处理的影响不大。MBC与土壤呼吸速率呈显著正相关,R2介于0.756~0.919之间,P〈0.05。通过对土

英文摘要：

Effects of conservation tillage on soil active organic carbon in dry farmland was used for summarized sensitive indicators of soil organic carbon.It also provided scientific basis for organic carbon grouping method and searched effective indicator of activated carbon which was suitable for purple soil farmland in southwest hilly area.Meanwhile,there was theoretical basis for soil carbon sequestration and emission reduction and improving soil quality.The LI 6400-09 respiratory chamber was adopted in the experiment conducted in the experimental field in Southwest University in Beibei District of Chongqing.Total soil organic carbon,particulate organic carbon,dissolved organic carbon,reading oxidizable organic carbon,mineralized organiccarbon and microbial biomass carbon were measured in the triple intercropping system of wheat/maize/soybean.There were four treatments including T（traditional tillage）,R（ridge tillage）,TS（traditional tillage＋ straw mulching）and RS（ridge tillage ＋ straw mulching）,which were replicated for three times.Straw mulching not only increased the content of TOC in the soil surface,but also was conductive to TOC of20 cm soil layer.Ridge tillage had very little influence on TOC.In each soil layer,POC in straw mulching treatment was significantly higher than that of conventional tillage.R treatment had no effect on POC below5 cm soil layer,but significantly decreased POC in 0-5cm soil layer.The content of DOC decreased along with the depth of soil.The difference mainly occurred in 0-5cm soil layer among all the treatments.DOC was not easy to be affected by tillage measure below 5cm soil layer.Compared with the control,TS and RS were significantly improved the content of ROC in 0-5cm soil layer,but there was no significant difference between R and T.It had great effects on soil surface ROC by straw returning.The average daily soil respiration of T,R,TS and RS treatment were 1.84,1.65,2.22,2.21μmol/（m2·s）.Annual soil respiration amount were 696.31,624.41,840.12 and 836.33g/m