采用野外调查测定、野外定位研究和室内分析相结合的方法,在黑河中游山前平原区选择邻近相同海拔和土壤类型的退耕(退耕1 a、5 a、10 a)造林地为研究对象,研究了山前平原区退耕地不同退耕年限的土壤碳动态,结果表明:退耕1 a、退耕5 a、退耕10 a和退耕造林地的土壤有机碳含量变化分别为16.89 gC/kg,8.24 gC/kg,8.56gC/kg和9.98 gC/kg,平均土壤有机碳密度分别为8.05 kg/m2,4.78 kg/m2,5.02 kg/m2和6.52 kg/m2.平均土壤有机碳周转时间分别为23 a,25 a,26 a和33 a;不同植被类型土壤CO2通量依次为退耕1 a土壤530.8 gC/(m2·a);退耕5 a土壤316.9 gC/(m2·a);退耕10 a土壤266.1 gc/(m2·a);退耕地造林(杨树林)286.9 gC/(m2·a).同一类型退耕地中,土壤有机碳含量和土壤碳密度随土壤深度增加而降低,而土壤有机碳周转时间则随深度增加而增大.%The paired plots with the same elevation and the soil type of the abandoned farmland ( 1 year after restored, 5 years after restored and 10 years after restored of the abandoned farmland) were selected as study objects in plain before mountain in middle part of Heihe River,Zhangye of Gansu, northwestern China. Based on the field survey, field orientation study and laboratory analyze and by means of comparison of difference of storage of organic carbon among different years after restored. The result indicate that the soil organic carbon (SOC) content for the 1 year after restored, 5 years after restored and 10 years after restored of the abandoned farmland and plantation of Populous is 16.89 gC/kg, 8.24 gC/kg,8.56 gC/kg and 9.98 gC/kg, respectively; the mean SOC density was 8.05 kg/m2, 4.78 kg/m2, 5.02 kg/m2 and 6.52 kg/m2, respectively; and the mean SOC turnover time was 23,25, 26 and 33 years, respectively. The soil surface CO2 flux for cropland, plantation of Populous and rangeland was 530.8 gC/(m2·a), 316.9 gC/(m2·a), 266.1 gC/(m2·a) and 286.9 gC/(m2·a), respectively. The SOC content and the SOC density decreased with soil depth in specific vegetation types, where the SOC turnover time increased with soil depth.
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