中文摘要：

【目的】团聚体是土壤重要的物理属性,也是土壤有机碳的主要固存场所。研究长期不同施肥对洞庭湖平原红壤性水稻土团聚体数量、稳定性、分形特征及其有机碳含量及分布的影响,为区域双季稻田施肥管理提供理论依据。【方法】以国家稻田土壤肥力与施肥效应长期试验为平台（1986—2013）,运用湿筛法获得不同粒级水稳性团聚体,分析对照（不施肥,CK）、单施氮磷钾肥（NPK）、低量有机肥与氮磷钾肥配施（LOM,有机肥氮比例为30%）和高量有机肥与氮磷钾肥配施（HOM,有机肥氮比例为60%）4种处理影响下耕作层（0—20 cm）土壤粒径〉0.25 mm的水稳性团聚体数量（WR0.25）、平均重量直径（MWD）、几何平均直径（GMD）、分形维数（D）及其有机碳含量与分布的变化特征。【结果】除粒径〉5 mm的土壤团聚体外,水稳性团聚体含量和团聚体对土壤有机碳的贡献率均随团聚体粒径减小呈现逐渐增加的趋势,而团聚体有机碳含量则呈现逐渐降低的变化趋势,其变化特征在不同处理间表现一致。长期不同施肥对2—5 mm和0.5—2 mm团聚体含量影响最大,与对照相比,施肥处理中上述两粒级团聚体含量分别增加35.5%—64.5%和6.2%—14.7%。施肥后团聚体的WR0.25、MWD、GMD分别增加8.6%—12.5%、7.1%—15.1%、13.7%—28.4%,而D值降低2.3%—3.5%,说明长期施肥增强团聚体稳定性,改善团聚体结构。单施氮磷钾肥和氮磷钾肥配施有机肥均可显著提高各粒级团聚体中有机碳含量（P〈0.05）,并始终表现出HOM强于LOM、LOM强于NPK的处理效应,与对照相比,HOM处理各级团聚体中有机碳含量较对照提高了22.1%—36.6%。水稳性大团聚体是土壤有机碳的主要载体,不同处理间〉0.25 mm团聚体中有机碳的分量占土壤有机碳的比例表现出HOM（83.5%）〉LOM（81.6%）〉NPK（79.2%）〉CK（69.9%）的顺序。施肥各处理均可显著提高?

英文摘要：

[Objective] As an important soil physical attribute, soil aggregates are the major site for soil organic carbon sequestration, so the impacts of long-term fertilization on aggregates characteristics and organic carbon distribution in a reddish paddy soil were studied in Dongting Lake Plain, China, which can provide a theoretical evidence for fertilization management in double cropping rice area. [Method] Undisturbed soil samples at 0-20 cm layer were collected from a 27 years （1986-2013） field experiment, which was established in the Hanshou county in Hunan province. The experiment included 4 treatments： CK （without fertilization）, NPK （N, P, K fertilizer application）, LOM （combined application of NPK and 30% organic manure fertilizers）, HOM（combined application of NPK and 60% organic manure fertilizers）. All soils were separated into five aggregate-size classes （〉5 mm, 2-5 mm, 0.5-5 mm, 0.25-0.5 mm and 〈0.25 mm） by wet sieving method and the macro aggregates fractions （〉0.25 ram） were chosen for results analysis. The amount, mean weight diameter, geometric mean diameter, fractal dimension of water-stable aggregates which denoted by WRo.25, MWD, GMD and D were exampled, separately. The aggregate-associated organic carbon was also measured. [Result] In addition to the size group of 〉5 mm, along with decreasing of particle sizes, the proportion of water-stable aggregates and the contribution rate of aggregates fractions to soil organic carbon （SOC） in the treatments increased, while the water-stable aggregate-associated organic carbon presented an opposite trend. Both the proportion of aggregates in the 2-5 mm and 0.5-2 mm size fractions were significantly increased under fertilization treatments when compared to CK treatment and the increasing rate was up to 35.5%-64.5% and 6.2%-14.7%, respectively. Fertilizer application also increased the value of WR0.25, MWD, and GMD of aggregates by 8.6%-12.5%, 7.1%-15.1%, and 13.7%-28.4%, respectively. As for the fractal dimension, it