基于坡面径流输沙模型的湘中红壤丘陵区土壤有机碳流失模拟研究

坡面径流是泥沙和土壤有机碳(soil organic carbon,SOC)流失的主要动力.本研究以典型湘中红壤丘陵区坡耕地(翻耕和免耕)为研究对象,通过野外径流小区模拟降雨试验,对已建立的以径流率为变量的对数线性回归坡面径流输沙模型进行修正,并结合泥沙中SOC的富集特性,建立湘中红壤丘陵区的坡面SOC流失模型.研究结果表明:坡面SOC流失模型能够有效地应用于湘中红壤丘陵区次降雨过程中坡面SOC流失的模拟中,且具有较好地模拟效果,SOC流失率模拟平均误差在30%左右,决定系数在0.85以上;同时模拟结果表明,泥沙和SOC流失过程在坡面径流侵蚀影响下呈现波动状态,表现为产流开始后10min泥沙和SOC流失呈增加趋势,其后在波动中逐渐趋于平稳;通过比较翻耕和免耕条件坡面径流输沙和SOC流失模型,结果显示侵蚀性降雨条件下,翻耕方式泥沙和SOC流失率大于免耕方式.非侵蚀性降雨条件下,翻耕方式泥沙和SOC流失状况与免耕方式一致.

Simulating Study of the Loss of Soil Organic Carbon Based on the Model of Sediment Transport by Slope Runoff in the Hilly Red Soil Region of Central Hunan Province

Plots were set up in typical hilly red soil region field (conventional tillage, CT and no tillage, NT) of central Hunan province. Simulated rainfall experiments were conducted to modify the built linear regression model in which the variable was the runoff rate of sediment delivery by runoff, and then, the model of SOC loss was established on the basis of the revised model and SOC enrichment characteristics of sediment. The results showed that the model of SOC loss could be effectively adapted to the simulation of SOC loss in hilly red soil region of central Hunan province during a rainfall event and could get a wonderful simulation result and accuracy. The mean error from the simulation of SOC loss rate was observed to be around 30% with the determination coefficient beyond 0.85 in CT and NT. In the meantime, the simulated results indicated that the process of the sediment and SOC loss revealed a fluctuant state under overland flow erosion. The sediment and SOC loss rate rose at the first stage of 0~10 min after runoff began and then kept a relatively stable tendency. Comparing the model of sediment transport by runoff and SOC loss in NT with that in CT,the results demonstrated that the sediment and SOC loss rate in CT were greater than that in NT under erosive rainfall. And the situation of sediment and SOC loss in CT were similar to that in NT under non-erosive rainfall.