珠江源头区植被恢复过程中不同地类土壤有机碳和全氮分布特征

Distribution Characteristics of Soil Organic Carbon and Total Nitrogen of Different Restoration Land in Vegetation Restoration Process at the Pearl River Headstream

为揭示植被恢复过程中不同地类土壤有机碳和氮素积累状况及差异特征,分析了珠江源头区典型流域占马地不同退化地类(灌木林地、疏林地、耕地及荒草地)恢复治理后土壤剖面有机碳和全氮含量、密度及其变化情况。结果表明,植被恢复16a后,6种恢复地类土壤有机碳及全氮的累积量从高到低的顺序均为:荒草地、云南松疏林地、滇青冈林地、萌生栎类灌丛、板栗林地、坡耕地,剖面垂直分布具有明显的层次性,随着土层深度的增加而减少,说明试验区土壤有机碳和全氮含量“表聚作用”明显,且整个试验区土壤有机碳和全氮含量相对分布比较均匀;不同恢复地类的土壤有机碳密度和全氮密度差别较大,且在同一恢复地类土壤中,单位深度土壤各土层平均有机碳密度均以表层土(0~20 cm)最大,且随土壤深度的增加而减少;试验区有机质分解较为容易、氮素矿质化作用明显,各恢复地类土壤C/N水平相对较低,介于3.92~9.67 g/kg之间,除坡耕地土壤碳氮比呈“Ⅴ”型外,其他5个样地土壤碳氮比大小均随土层深度增加而降低;试验区6种恢复地类0~20 cm土壤有机碳密度在2.09~3.91 kg/m 2之间,低于我国森林土壤0~20 cm土壤平均碳密度4.24 kg/m 2。

Taking the Zhanmadi small watershed in the typical watershed of Pearl river basin as the experimental area,the organic carbon and total nitrogen content,density and distribution characteristics of the soils in different degraded land types(shrub forest land,sparse forest land,cultivated land and grassland)were determined.The results showed that after restoration of remediation,the trends of soil organic carbon and total nitrogen content in six restoration land were:desert grassland,Pinus yunnanensis forest,Cyclobalanopsis glaucoides forest,sprouted sapling shrub,chestnut forest land,and slope farmland,The vertical distribution of the profile has obvious stratification,which decreases with the increase of soil depth,indicating that the soil organic carbon and total nitrogen content in the experimental area is“exposed”,and the relative distribution of soil organic carbon and total nitrogen in the whole experimental area is relatively uniform;Under different restoration measures,soil organic carbon density and total nitrogen density are different.In the same restoration soil,the average organic carbon density of each soil layer per unit depth is the largest in topsoil(0~20 cm),decrease with the increase of soil depth;The organic matter decomposition in the test area is easier,the nitrogen mineralization is obvious,and the soil C/N level of each restored forest land is relatively low,ranging from 3.92 to 9.67 g/kg.In addition,except for the soil carbon-nitrogen ratio of slope farmland,the soil carbon-nitrogen ratio of the other five plots decreased with the depth of the soil layer;For 0~20 cm soil organic of 6 kinds of restored forest land in the experimental area,the carbon density is between 2.09 and 3.91 kg/m 2,which is lower than the average carbon density of 4.20 kg/m 2 in China.