黄土丘陵区不同坡度下土壤有机碳流失规律研究

Soil Organic Carbon Loss Under Different Slope Gradients in Loess Hilly Region

通过野外径流小区观测与采样分析,研究了自然降雨条件下坡度对土壤有机碳流失的影响。结果表明:在黄土丘陵区,随着坡度增加(10°～30°),其侵蚀强度(A)变化趋势为:A20°>A30°>A15°>A10°>A25°,表明在20°和25°之间存在着临界坡度;土壤有机碳流失的变化趋势与侵蚀强度一致,可见有机碳流失主要受侵蚀强度的影响。土壤侵蚀造成了泥沙中有机碳的富集,其平均富集比为2.27～3.74,且富集比随着侵蚀强度和坡度增大而减小。土壤有机碳流失程度与降雨特征值PI30呈幂函数关系。减少地表径流和土壤侵蚀是降低土壤有机碳流失的关键。

Based on field runoff plots observation and sample analysis,the effect of slope gradient on soil organic carbon loss was studied under natural rainfall conditions in loess hilly region.The results showed that with slope gradient increasing（from10° to 30°）,the changing trend of soil erosion intensity（A）was A20°〉A30°〉A15°〉A10°〉A25°,suggesting that slope gradient between 20° and 25° was a critical degree ranger to exist.Soil organic carbon loss was mainly influenced by soil erosion intensity,appearing the same trend as did soil erosion intensity with increasing slope gradient.Soil erosion results in organic carbon enrichment in sediment.Average enrichment ratios of five runoff plots varied from 2.27 to 3.74,and decreased with increasing erosion intensity and slope gradient.Soil organic carbon loss was a power function with rainfall erosiveness index（PI30）.The decrease of surface runoff and soil erosion is the key to reduce soil organic carbon loss.