不同种植模式下坡耕地红壤团聚体有机碳矿化特征

Organic carbon mineralization characteristics of red soil aggregate fractions in sloping farmland with different planting patterns

为探讨不同种植模式下团聚体中有机碳转化和稳定的作用机制,以坡耕地红壤为研究对象,结合土壤团聚体组成及有机碳分布,通过室内有机碳矿化培养方法,并采用一级动力学方程拟合培养过程中CO2通量的动态变化,分析不同种植模式下团聚体有机碳矿化动态特征及其对土壤总矿化的贡献。结果表明:不同种植模式下土壤团聚体粒径均以>2 mm和2~0.25 mm为主,其总量在78%以上,玉米单作显著减少>2 mm团聚体的比例,但却显著增加<0.25 mm团聚体的比例。不同种植模式下<0.25 mm团聚体的有机碳含量显著高于全土、>2 mm团聚体和2~0.25 mm团聚体。全土中玉米大豆间作处理的土壤有机碳含量显著低于大豆单作处理,各粒径团聚体中有机碳含量在单作处理与对应的间作处理之间没有显著差异。不同种植模式下全土和团聚体中有机碳矿化作用的强弱表现为单作处理比对应的间作处理更强,并且大豆单作处理有机碳累积矿化量最高。不同种植模式下2~0.25 mm团聚体有机碳矿化速率最快,有机碳矿化作用最强,而<0.25 mm团聚体C0/SOC值(土壤有机碳矿化分解作用消耗土壤中有机碳的比例)较全土及其他两个粒径团聚体显著降低,更有利于土壤有机碳固存。>2 mm和2~0.25 mm团聚体对全土有机碳矿化的贡献最大。研究表明,大团聚体(>0.25 mm)在坡耕地红壤有机碳矿化中起重要作用,玉米大豆间作和玉米白萝卜间作在一定程度上可降低土壤有机碳矿化作用,增强土壤固碳能力。

To explore the mechanism of organic carbon transformation and stabilization with aggregate fractions under different planting patterns,the red soil of sloping farmland was selected as the research object,combined with soil aggregate composition and organic carbon distribution.Using the indoor organic carbon mineralization cultivation method,the first-order kinetic equation was used to fit the dynamic changes in the CO2 flux during the cultivation process,and the dynamic characteristics of aggregate organic carbon mineralization and its contribution to the total soil mineralization under different planting patterns were analyzed.The results showed that the particle size of soil aggregates were mainly>2 mm and 2~0.25 mm,the total amount of aggregates reached more than 78%.Corn(Zea mays)monoculture significantly reduced the proportion of>2 mm aggregates but significantly increased the proportion of<0.25 mm aggregates.The organic carbon content of<0.25 mm aggregates was significantly higher than that of bulk soils,>2 mm aggregates,and 2~0.25 mm aggregates under different planting patterns.The soil organic carbon(SOC)content of the corn-soybean(Glycine max)intercropping treatment in the bulk soils was significantly lower than that of the soybean single-cropping treatment.There was no significant difference between the organic carbon content of the aggregate fractions between monoculture treatment and the corresponding intercropping treatment.The mineralization of organic carbon in bulk soils and aggregates under different planting patterns revealed that it was stronger in monocultures than in intercropping,while the cumulative mineralization of organic carbon was the highest in soybean monoculture.The organic carbon turnover rate of 2~0.25 mm aggregates was the fastest and the organic carbon mineralization was the strongest,whereas the C0/SOC value(the proportion of SOC consumption by SOC mineralization and decomposition)of<0.25 mm aggregates was significantly lower than that of the bulk soils and the other two particle size aggregates,which was more conducive to SOC sequestration.The>2 mm and 2~0.25 mm aggregates contributed the most to total SOC mineralization.These results indicated that macroaggregates(>0.25 mm)play an important role in organic carbon mineralization in red soil of sloping farmland.Corn-soybean intercropping and corn-radish intercropping could reduce SOC mineralization and enhance soil carbon sequestration capacity to certain extent.