红壤有机碳流失特征及其与泥沙径流流失量的定量关系

通过野外微型径流小区模拟降雨试验,对坡面小区尺度水力侵蚀过程中物理运移土壤有机碳的规律进行研究。结果表明:2 m×5 m径流小区持续降雨30 min后,大雨强(1.64 mm min-1)和小雨强(0.58 mm min-1)降雨条件下泥沙携带流失的有机碳总量分别为56.09 g和3.18 g,溶解于径流流失的有机碳总量分别为13.55 g和2.81 g。降雨强度和持续时间对有机碳流失的过程特征有显著影响。降雨强度越大,泥沙携带及溶解于径流的有机碳流失速率和总量也越大。大雨强泥沙有机碳富集比在产流发生后的18min内大于1,随后降至1以下。小雨强泥沙有机碳富集比始终小于1。大雨强径流有机碳浓度与径流量呈立方关系,小雨强有机碳流失量随径流量增加呈线性递增趋势;大雨强泥沙有机碳含量与泥沙量之间具有明显的立方关系。

Characteristics of loss of organic carbon in red soil and their quantitative relationships with sediment and runoff generation

Through plot-scaled field rainfall simulation experiments, effects of water erosion on transportation of soil organic carbon on a slope were analyzed. Results show that after 30 minutes of rainfall, the total sediment-associated loss of organic carbon was 56.09 g and 3.18 g, respectively, and the total runoff-associated loss of organic carbon was 13.55 g and 2.81 g from a plot 2m?5 m in size. Intensity and duration of rainfalls had significant effects on the process of soil organic carbon loss. The higher the rainfall intensity, the quicker and the more organic carbon was lost with sediment and runoff. In the initial 18 minutes of runoff triggered by rainfall of high intensity, the organic carbon enrichment ratio (ERsoc) of the sediment is higher than 1, and afterwards it dropped below 1, while throughout the rainfall event low in intensity it remained below 1. In the former case a cubic regression relationship was observed between concentration of soil organic carbon in runoff and volume of the runoff, and an S-shaped curve appeared demonstrating a rising trend of organic carbon loss with volume of the runoff, whereas in the latter, the runoff loss of organic carbon rose with the volume of runoff volume, showing a power function relationship. During the rainfall event high in intensity, the concentration of organic carbon in sediment was related to volume of the sediment, showing an obvious cubic relationship.