湘西北烤烟和玉米连作田土壤团聚体碳特征比较

选择湘西北烤烟和玉米连作两种典型耕地，分析不同粒径团聚体的有机碳差异及与土壤总有机碳及其活性组分的关系。结果表明，玉米及烤烟连作的土壤，较大的团聚体具有较高的有机碳含量；玉米田土壤有机碳主要储存于粒径>2 mm团聚体中，而烟田土壤有机碳主要储存于粒径>2 mm和2~0.25 mm的团聚体中；相较于烟田，玉米田土壤大团聚体具有较高的有机碳含量、固碳能力及有机碳贡献率；两种土壤均以粒径>2 mm团聚体有机碳对土壤总有机碳的响应最敏感；土壤易氧化有机碳（EOC）及颗粒有机碳（POC）均与粒径>2 mm和2~0.25 mm团聚体有机碳贡献率呈显著或极显著正相关。因此，山地烟区烤烟和玉米连作田土壤质量保育和退化修复工作均需提升大团聚体比例以提高其固碳能力。

Comparison of Organic Carbon Characteristics in Soil Aggregates of Maize and Tobacco Continuous Cropping Fields in Northwestern Hunan

The soils in maize and tobacco succession cropping fields in northwestern Hunan were sampled to analyze the differences of organic carbon in soil aggregates and their relationship with soil organic carbon and its active components. The results showed that, organic carbon contents in soil aggregates of maize and tobacco succession cropping fields increased with the increase of soil aggregate size. Soil organic carbon was mainly stored in >2 mm aggregates in corn succession cropping field (CSCF) and in >2 mm and 2-0.25 mm aggregates in tobacco succession cropping field (TSCF). Compared to TSCF, the soil aggregates of CSCF had higher organic carbon content, carbon sequestration capacity and contribution rates to soil organic carbon by 0.25-0.053 mm aggregates. In both soils, organic carbon of >2 mm soil aggregates were the most relevant to soil total organic carbon, meanwhile soil labile organic carbon (EOC) and particulate organic carbon (POC) showed significant or extremely significant positive correlation with the contribution rates to soil organic carbon by > 2 mm and 2-0.25 mm aggregates carbon. The results suggested that increasing the proportion of macro-aggregates and their carbon sequestration capacity favor to repair and improve soil quality in CSCF and TSCF in northwestern Hunan.