黄土丘陵区不同土地利用类型下深层土壤轻组有机碳剖面分布特征

Distribution of light fraction organic carbon under different land use types in the deep soil layer of hilly regions of the Loess Plateau,China

以黄土丘陵区林地(刺槐和柠条)、撂荒地及坡耕地3种土地利用类型为研究对象,以浅层土壤(0—100 cm)为对照,采用有机碳密度分组法对不同利用类型深层土壤(100—400 cm)轻组有机碳含量及其分配比例进行了研究。结果表明,1)3种土地利用类型土壤轻组有机碳含量及其分配比例随土壤深度的增加而显著下降,其含量的变化范围为0.09 1.76 g/kg,分配比例变化范围为4.19%32.24%;各利用类型下亚深层(100—200 cm)、深层(200—400 cm)土壤轻组有机碳含量为浅层的12.4%39.8%,分配比例为浅层的28.7%66.2%;随土层深度增加,轻组有机碳含量及其分配比例的降幅在不同土地利用类型下表现为刺槐林地>撂荒地>柠条林地>坡耕地;2)各土地利用类型下同一土层轻组有机碳含量及其分配比例不同,浅层、亚深层和深层土壤轻组有机碳含量及其分配比例表现为林地>撂荒地>坡耕地。3)退耕还林还草增加了浅层土壤轻组有机碳含量及其分配比例,却降低了亚深层、深层土壤轻组有机碳含量及其分配比例,即与浅层土壤相比,植被恢复相对增加了深层土壤有机碳的稳定性。

Taking the Robinia pseudoacacia woodlands, Caragana korshinskii shrublands, abandoned croplands, and slope croplands in hilly regions of the Loess Plateau as study objects , we investigated the contents and distribution ratios of soil light fraction organic carbon （ LFOC） in the deep soil layer （100-400 cm） under different land use types by using the method of relative density fractionation with the shallow soil layer （ 0-100 cm ） as the control .The results show that there are significantly declining trends in the content and distribution ratio of soil light fraction organic carbon along with the increase of soil depth under the studied land use types .The contents of soil light fraction organic carbon range from 0.09 to 1.76 g/kg, while the distribution ratios of soil light fraction organic carbon range from 4.19%to 32.24%.Under the three land use types , the contents and distribution ratios of soil light fraction organic carbon in the sub-deep soil（100-200 cm） and deep soil（200-400 cm） of that in the shallow layer（0-100 cm） range from 12.4%to 39.8%, 28.7%to 66.2%, respectively.The declining rates of the soil light fraction organic carbon contents and distribution ratios are Robinia pseudoacacia woodlands 〉abandoned croplands〉Caragana korshinskii shrublands 〉slope croplands .The contents and distribution ratios of soil light fraction organic carbon in the same soil layer among the three land use types are different .The contents and distribution ratios of soil light fraction organic carbon both are forestlands 〉abandoned croplands 〉slope lands in these three layers .Both the contents and distribution ratios of soil light fraction organic carbon are increased after the implementation of the Grain for Green project , while those in the sub-deep and deep soils of those in the shallow layer are reduced .Compared with the shallow soil layer , the stability of deep soil organic carbon is enhanced respectively in the process of revegetation .