华南典型侵蚀区土壤有机碳流失机制模拟研究

Experimental Study on Soil Organic Carbon Loss in Red Soil Erosion under Different Simulated Rainfall Intensity and Slope Gradient

土壤侵蚀条件下的碳流失问题是目前全球碳循环研究中的新点,也是土壤侵蚀基础性研究中的弱点.目前对于土壤侵蚀的研究多侧重于侵蚀造成养分流失及土地退化方面,关于土壤侵蚀对碳循环的影响研究较少.针对华南红壤侵蚀区的碳流失问题,采用室内人工模拟降雨的方法,探讨了华南典型侵蚀区两种土壤类型（林地、弃耕荒地）的有机碳流失过程,主要取得以下一些成果,（1）土壤有机碳的流失主要以侵蚀泥沙为载体,两种土壤（林地、弃耕荒地）坡面的泥沙有机碳含量均表现出随降雨历时逐渐减小的趋势,但雨强和坡度对侵蚀泥沙中有机碳含量的影响没有明显规律;林地土壤坡面的侵蚀泥沙中有机碳含量明显高于弃耕荒地土壤坡面的侵蚀泥沙中有机碳含量.（2）林地土壤的泥沙有机碳富集比大于弃耕荒地的泥沙有机碳富集比,林地土壤有机碳富集比变化范围为0.99-1.65,而弃耕荒地土壤有机碳富集比变化范围为0.86-1.07;林地土壤的有机碳流失率大于弃耕荒地的有机碳流失率.林地土壤的有机碳流失率变化范围为1.6%-18.9%,弃耕荒地土壤的为2.2%-10.4%.土壤有机碳流失率随降雨雨强的增加而增大,坡度对土壤有机碳流失率的影响不显著.（3）土壤有机碳流失强度与侵蚀强度呈明显的线性正相关关系,试验条件下（不同地类土壤、雨强、坡度）土壤有机碳流失强度与侵蚀强度间的函数关系可表达为：y（SOC）=5.104x（Erosion）＋0.036（r2=0.984）.

Soil carbon loss in erosion is not only the one of new topics in global carbon cycle research, but also the key problem in soil physical study. Most previous studies focused on nutrient loss in soil erosion and land degeneration, but few attentions have been paid to soil carbon loss complaining with soil erosion. This study used simulated rainfall method to investigate the influences of soil type, rainfall intensity and slope gradient on soil organic carbon loss. The results showed that: (1) Soil organic carbon loss is major in losing with sediment and the content of soil organic carbon in sediment decrease with rainfall duration. There are no obvious relation between rainfall intensity and the content of soil organic carbon in sediment. The content of soil organic carbon in sediment from forest land treatment is greater than that from abandoned land treatment. (2) The enrichment ratio of soil organic carbon in sediment for forest land treatment is also higher than it for abandoned land treatment. For forest land treatment, the enrichment ratio of soil organic carbon in sediment ranges from 0.99 to 1.65. But for abandoned land treatment, it ranges from 0.86 to 1.07. The soil organic carbon loss rate of forest land treatment is greater than that abandoned land treatment. For forest land treatment it ranges from 1.6% to 18.9%, and 2.2% to 10.4% for abandoned land treatment. The soil organic carbon loss rate increases with rainfall intensity, but no obvious tendency can be found with increased slope gradient. And (3) there are lineally relationship between the soil organic carbon loss rate and soil erosion rate. The function of them under different soil type, rainfall intensity, and soil slope can be expressed as:y(SOC)=5.104x(Erosion)+0.036 (r2=0.984).