黑土区水稻土水稳性团聚体有机碳及其颗粒有机碳的分布特征

Distribution of Organic Carbon and Particulate Organic Carbon in Water-stable Aggregates of Paddy Soil in Black Soil Area

为研究黑土区水稻土水稳性团聚体有机碳及其颗粒有机碳含量和δ^(13) C值的分布特征,探讨黑土区水稻土水稳性团聚体有机碳及其颗粒有机碳的分布和稳定性,为该地区黑土的合理利用及土壤的合理培肥提供理论依据,以黑土区不同有机碳含量的水稻土为研究对象,利用湿筛法和物理分组技术分离提取各级团聚体及其颗粒有机物,采用^(13) C稳定同位素质谱技术分析有机碳含量及其δ^(13) C值。结果表明,黑土区水稻土以2~0.25mm团聚体为主,土壤有机碳主要富集在>0.25mm团聚体中,尤其是2~0.25mm团聚体中;团聚体有机碳的δ^(13) C值随团聚体粒级的减小而增大,>2mm和2~0.25mm团聚体中有机碳的δ^(13) C值均小于土壤有机碳的δ^(13) C值,具有碳截获或碳固定能力,而0.25~0.053mm和<0.053mm团聚体中有机碳的δ^(13) C值均大于土壤有机碳的δ^(13) C值,具有碳固持或稳定的能力;除B-2土样外,各土样均以2~0.25mm团聚体中的颗粒有机碳含量为最大,以0.25~0.053mm团聚体中的颗粒有机碳含量为最小,且该团聚体中颗粒有机碳含量与土壤有机碳含量呈显著正相关关系(r=0.917,P<0.01),表明微团聚体闭蓄态的颗粒有机碳对土壤有机碳的固持和稳定发挥重要作用。土壤颗粒有机碳及各级团聚体中颗粒有机碳的δ^(13) C值均小于土壤有机碳及各粒级团聚体中有机碳的δ^(13) C值,团聚体颗粒有机碳的δ^(13) C值也随团聚体粒级的减小而增大。因此,黑土区水稻土中>0.25mm的水稳性团聚体是有机碳的主要载体,团聚体颗粒有机碳作为活性碳库,较总有机碳更易反映黑土区水稻土有机碳的周转变化,其敏感性随团聚体粒级的增大而增强。

The objective of this study was to clarify the distribution of the mass and δ^13C values of organic carbon and particulate organic carbon in water-stable aggregates of paddy soil in black soil area, analyze the distribution and stability of aggregate organic carbon and particulate organic carbon, and provide theoretical basis for reasonable use and fertilization of black soil. Wet-sieving method and physical fractionation technique were used to separate soil aggregates and particulate organic carbon, and the content and δ^13C value of organic carbon were determined by stable isotope mass spectrometry technology. The results showed that 2 to 0.25 mm aggregate was the dominant aggregate fraction of paddy soil in black soil area, and organic carbon mainly concentrated in 〉0.25 mm aggregate fraction, especially in the 2 to 0.25 mm aggregates. δ^13C value of organic carbon in aggregates increased with the decrease of aggregates size, and δ^13C values of organic carbon in 〉2 mm and 2 to 0.25 mm aggregates were lower than those of soil organic carbon, which indicated that 〉2 mm and 2 to 0.25 mm aggregates could obtain or immobilize carbon, while the δ^13C values of organic carbon in 0.25 to 0. 053 mm and 〈0. 053 mm aggregates were higher than those of soil organic carbon, representing that these aggregates had the capability of carbon sequestration and immobilization. Except the B-2 soil samples, particulate organic carbon content was the highest in 2 to 0.25 mm aggregates, while it was the lowest in 0. 25 to 0. 053 mm aggregates, which was correlated with soil organic carbon content （r = 0. 917, P〈0. 01）, representing that occluded particulate organic carbon in microaggregate played an important role in sequestration and stabilization of organic carbon. The δ^13C values of particulate organic carbon in soil and aggregates were both lower than those of total organic carbon, and the δ^13C value of particulate organic carbon increased with the decrease of aggregate size. Therefore, organic carbon in 〉0.25 mm aggregate was the main carrier of organic carbon in paddy soil of black soil area, and particulate organic carbon of aggregates could reflect the organic carbon pool turnover of paddy soil in black soil area better as an active carbon pool, with its sensitivity increasing with the increase of aggregate size.