川南坡地不同退耕模式对土壤腐殖质及团聚体碳和氮的影响

Soil Humus and Aggregate Carbon and Nitrogen in Slope Farmland with Different De-farming Patterns in Southern Sichuan Province

通过对川南坡地进行退耕试验,研究坡地退耕成慈竹林、杂交竹林、桤木+慈竹林和弃耕地对土壤腐殖质及团聚体碳和氮的影响。结果表明,坡地退耕5年后土壤腐殖质(胡敏酸、富里酸和胡敏素)、活性腐殖质(活性胡敏酸和活性富里酸)及团聚体碳和氮含量、胡敏酸与富里酸比值和胡敏酸E4/E6值,以及可浸提腐殖质(胡敏酸和富里酸)、活性腐殖质及>0.25mm各粒径团聚体碳和氮分配比例均增加,并呈现出慈竹林>杂交竹林>桤木+慈竹林>弃耕地>农耕地的变化规律。土壤团聚体有机碳(氮)含量及其分配比例随土壤团聚体粒径的增加呈现出"V"形变化,其最小值分别出现在2～1mm和0.5～0.25mm粒径。说明川南坡地退耕对增加土壤腐殖质及团聚体碳和氮含量、改善土壤肥力状况和促进土壤碳固定具有重要的作用和意义。

The contents of soil humus（including humic acid,fulvic acid and humin）,labile humus（including labile humic acid and fulvic acid） and aggregate carbon and nitrogen fractions were studied under slope farmland（CK） and its four de-farming patterns,including Neosinocalamus affinis plantation（NAP）,Bambusa pervariabilis×Dendrocalamopsis oldhami plantation（BDP）,Alnus crenastogyne＋Neosinocalamus affinis plantation（ANP） and abandoned farmland（AFL）.After 5 years＇ de-farming,all de-farming patterns of slope farmland showed higher contents of humic acid carbon（CHA） and nitrogen（NHA）,fulvic acid carbon（CFA） and nitrogen（NFA）,humin carbon（CHM） and nitrogen（NHM）,labile humic acid carbon（CLHA） and nitrogen（NLHA）,labile fulvic acid carbon（CLFA） and nitrogen（NLFA） and aggregate carbon and nitrogen,CHA/CFA ratio,E4/E6 ratio of humic acid,and higher proportions of CHA,CFA,CLHA,CLFA and 0.25 mm particle-sized aggregate carbon in total organic carbon and of NHA,NFA,NLHA,NLFA and 0.25 mm particle-sized aggregate nitrogen in total organic nitrogen,and those were followed the order of NAP BDP ANP AFL CK.The soil organic carbon（nitrogen） contents and distribution ratios in aggregates showed a ＂V＂ curve with the increment of aggregate size,and the lowest value was in 2~1 mm and 0.5~0.25 mm particle-size,respectively.It was suggested that slope farmland de-farming was important for increasing soil humus and aggregate carbon and nitrogen content,improving soil fertility and enhancing soil carbon sequestration in southern Sichuan province of China.