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不同土地利用方式下有机碳的含量和性质变化越来越受到人们的关注。以黄土高原南部高原沟壑区(长武地区)塬面上农田以及不同树龄的果园为对象,研究了土壤总有机碳、易氧化有机碳和难氧化有机碳含量,比较了不同利用方式下土壤有机碳的氧化稳定系数(Kos)和有机碳密度差异。结果显示,该区域果园表层土壤总有机碳的整体水平与农田相当,但果园总有机碳、易氧化有机碳随果园年限增长有降低的趋势。在土壤剖面中,总有机碳、易氧化有机碳及难氧化有机碳都随深度下降而下降的趋势;而Kos值随剖面深度和果园年限增长而呈升高的趋势。0～2 m土壤剖面有机碳储量从高到底顺序是:农田>新果园(小于5年果园)>盛果期果园(10～15年果园)>老果园(15年以上果园)。以农田为基准,在0～200 cm厚度土层中,新果园有机碳储量下降了6.1%,盛果期果园下降了9.3%,老果园有机碳储量下降了22.4%。说明随着果园年限的增长,土壤有机碳储量降低。
Different types of land use of organic carbon content and the nature of change more and more people’s attention. The contents of total organic carbon, readily oxidizable organic carbon and difficult-oxidation organic carbon in the farmland and orchards of different ages in the gullied-land upper plateau (Changwu region) in the southern Loess Plateau were compared. The soil organic matter Carbon oxidation stability (Kos) and organic carbon density differences. The results showed that the overall level of total organic carbon in surface soil of orchard was similar to that of farmland, but the total organic carbon and organic carbon in the orchard tended to decrease with the increase of orchard age. In the soil profiles, total organic carbon, readily oxidizable organic carbon and difficult-to-oxidize organic carbon tended to decrease with depth, while Kos values tended to increase with the increase of profile depth and orchard age. The order of organic carbon storage in 0-2 m soil profiles from top to bottom is: farmland> new orchard (less than 5 years) orchards> full orchard (10-15 years orchard)> old orchard (more than 15 years orchard). Based on cropland, organic carbon storage in new orchards decreased by 6.1% in 0 ~ 200 cm soil layer, decreased by 9.3% in orchards in full bloom and decreased by 22.4% in old orchards. As the orchard age increases, soil organic carbon storage decreased.