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

Characteristics and influencing factors for soil active organic carbon and nitrogen in abandoned cultivated lands in Minqin oasis

【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（3a）后0～20cm土层土壤MBC、MBN、POC、PON和ROC分配比例高于常规耕地（0a）,并和其他弃耕地构成显著差异（P〈0.05）.20～40cm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（3a）.【结论】弃耕有利于土壤活性有机碳、氮在0～20cm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.

【Objective】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 biomass nitrogen（MBN）,particulate organic carbon（POC）,particulate organic nitrogen（PON）and easily oxidized 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,PONand ROCpresented significant stratification after cultivated land being abandoned.The distribution ratio of MBC,MBN,POC,PON and ROCat 0~20cm soil depth were higher than that of cultivated land（0a）after being abandoned short-term（3a）,and significantly differed from others（P〈0.05）.At 20~40cm 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 MBCand 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 longterm-abandoned land than cultivated land and short-term-abandoned land（3a）.【Conclusion】Abandoned cultivation was in favor of formation and accumulation of active organic carbon and nitrogen at 0~20cm depth,meanwhile could improve the distribution ratio of active organic carbon and nitrogen and increase organic matter oxidation stability and particularly obvious in deeper soil.