民勤绿洲弃耕地土壤活性有机碳和氮变化特征及影响因素

摘要

[Obj ective]The aim of this study was to understand the changes of active organic carbon and nitrogen of different soil layers after arable land abandoned in Minqin oasis.[Method]Based on the field investigation and laboratory analysis,the content of soil microbial biomass carbon(MBC),microbial bio-mass nitrogen(MBN),particulate organic carbon(POC),particulate organic nitrogen(PON)and easily oxi-dized carbon(ROC)were measured in abandoned cultivated lands in different years taking cultivated land as control in the Minqin oasis,northwest China.[Result]MBC,MBN,POC,PON and ROC presented signifi-cant stratification after cultivated land being abandoned.The distribution ratio of MBC,MBN,POC,PON and ROC at 0~20 cm soil depth were higher than that of cultivated land (0 a)after being abandoned short-term (3 a),and significantly differed from others (P<0.05).At 20~40 cm soil depth,the difference in the distribution ratio of POC,PON and ROC were not significantly between abandoned lands and cultivated land,but that of MBC and MBN differed significantly (P<0.05).The coefficient of oxidation stability (Kos)in deeper soil was significantly higher than that of surface and it was significantly higher in long-term-abandoned land than cultivated land and short-term-abandoned land (3 a).[Conclusion]Abandoned cultivation was in favor of formation and accumulation of active organic carbon and nitrogen at 0~20 cm depth,meanwhile could improve the distribution ratio of active organic carbon and nitrogen and increase or-ganic matter oxidation stability and particularly obvious in deeper soil.%【目的】了解民勤绿洲弃耕地不同土层土壤活性有机碳、氮演变特征．【方法】以民勤绿洲区不同年限弃耕地为研究对象，以常规耕地为参照，通过野外调查取样和室内测试分析，测定土壤微生物量碳（MBC）、微生物量氮（MBN）、颗粒有机碳（POC）、颗粒有机氮（PON）、易氧化碳（ROC）含量．【结果】弃耕后土壤活性有机碳、氮含量呈现明显的分层现象，短期弃耕（3 a）后0～20 cm土层土壤MBC、MBN、POC、PON和ROC分配比例高于常规耕地（0 a），并和其他弃耕地构成显著差异（P＜0．05）．20～40 cm土层，弃耕地土壤POC、PON和ROC分配比例和常规耕地差异不显著，但是MBC和MBN的分配比例和常规耕地差异显著（P＜0．05）．深层土壤氧化稳定系数（Kos）明显高于表层土壤，而且长期弃耕地Kos值显著高于常规耕地和短期弃耕地（3 a）．【结论】弃耕有利于土壤活性有机碳、氮在0～20 cm土层中的形成和累积，而且该土层中活性有机质的分配比例也明显高于常规耕地，弃耕能提高土壤有机质的氧化稳定性，深层土壤表现的尤为突出．