水土流失治理措施对小流域土壤有机碳和全氮的影响

明确综合治理条件下小流域土壤有机碳(Soil organic carbon,SOC)和全氮(Total nitrogen,TN)的空间分布特征及其影响因素,对科学评价水土流失区土壤固碳潜力具有重要意义。以黄土高原丘陵沟壑区典型小流域(砖窑沟流域)为对象,基于流域内3种典型地貌类型(梁峁坡、沟坡、沟谷)和3种典型水土流失治理措施(水平梯田、林地和草地措施,坡耕地为对照),采集土壤样品737个,研究地貌类型和水土流失治理措施对小流域SOC和TN变化的影响。结果表明,同一地貌类型上,水平梯田、林地和草地措施的SOC和TN(0—10 cm土层)含量均显著高于坡耕地(P<0.1)。梁峁坡上,水平梯田、林地和草地措施条件下的SOC和TN含量较坡耕地依次提高了18%和24%、70%和59%、25%和21%;沟坡上,林地和草地措施的SOC和TN较坡耕地依次提高了76%和54%、25%和27%。同一治理措施在不同地貌类型间对0—10 cm土层SOC和TN的影响存在显著差异(P<0.1)。水平梯田条件下,沟谷的SOC和TN含量比峁坡提高了46%和43%;林地措施条件下,沟坡的SOC和TN含量比峁坡提高了18%和6%;草地措施条件下,沟坡的SOC和TN含量比峁坡提高了14%和18%。0—100 cm土层的SOC或TN在不同地貌类型或不同治理措施间的差异与土壤水分含量(Soil moisture,SM)的变化趋势基本一致,并且SOC或TN与SM呈指数关系y=aebx(y为SOC或TN,x为SM)。

Effects of soil erosion control measures on soil organic carbon and total nitrogen in a small watershed

It is significance of assessing soil organic carbon (SOC) and total nitrogen (TN) sequestration potential to understand dynamics of soil organic carbon (SOC) and total nitrogen (TN) at a small watershed with comprehensive measures in the loess region of China. Based on three topographic positions (Ridge slope, Gully slope, Valley bottom) and three control measures for soil erosion (Level terrace,Woodland measures,Grassland measures), 737 soil samples were collected to investigate effects of topographic positions and soil erosion control measures on soil organic carbon and total nitrogen at Zhuan Yaogou watershed in the hilly region of Loess Plateau. Under the similar topographic positions, SOC and TN (0-10 cm soil layer) in level terrace, woodland and grassland were significantly higher than those in cropland on sloping land (P<0.1). For the ridge slope, SOC and TN in level terrace, woodland and grassland were 18% and 24%, 70% and 59%, and 25% and 21% higher than that in cropland on sloping land, respectively; For the gully slope, SOC and TN in woodland and grassland were 76% and 54%, and 25% and 27% higher than that in cropland on sloping land, respectively. The similar control measures for soil erosion produced significant differences among topographic positions (P<0.1). In the 0-10 cm soil layer, For the level terrace measure, SOC and TN in valley bottom were 46% and 43% higher than those in the ridge slope; For the woodland measures, SOC and TN in the gully slope were 18% and 6% higher than those in the ridge slope; For the grassland measures, SOC and TN in the gully slope were 14% and 18% higher than those in the ridge slope. In the 0-100 cm soil depth, SOC or TN had the similar change characteristics with soil moisture among the topographic positions and the soil erosion control measures. An exponential relationships of y= ae^bx (y is SOC or TN and x is soil moisture) were developed between SOC (TN) and soil moisture at the small watershed.