不同砾石存在形式红壤坡面侵蚀特征的比较

On the erosion characteristics of red soil slope with different gravel existence forms

我国南方红壤丘陵区是仅次于黄土高原的严重水土流失区域,土壤中砾石的存在将对整个水文循环产生影响,现有的研究主要集中在砾石覆盖与产流产沙关系等方面,而降雨强度和坡度对不同砾石存在形式土壤侵蚀的影响研究较少。为研究红壤坡面在不同砾石存在形式下侵蚀特征的差异,作者利用室内人工模拟降雨,结合曹娥江上游地区降雨及坡地特点,研究不同降雨强度和坡度条件下,无砾石(砾石含量0%)、覆盖5%砾石和嵌套5%砾石红壤坡面的侵蚀过程,比较各坡面降雨产流时间、径流率、产流过程、产沙强度等特征。结果表明:1)各研究坡面在10°、15°、20°和25°4个坡度的产流时间均表现出随降雨强度增加而缩短,径流总量和次降雨产沙量均随着降雨强度的增加而增加。2)降雨强度为120 mm/h时,无砾石和覆盖5%砾石坡面在4个坡度的径流率随时间变化过程较接近,而坡度10°嵌套5%砾石坡面的径流率远低于其他3个坡度的。3)各研究坡面在2个降雨强度和4个坡度下,覆盖5%砾石和嵌套5%砾石红壤坡面径流总量、次降雨产沙量均小于无砾石坡面。4)在较小降雨侵蚀力作用下,嵌套于坡面的砾石可以增加地表入渗,阻碍坡面侵蚀;而在较大降雨侵蚀力作用下,由于嵌套砾石坡面裸露土壤相对于覆盖砾石坡面多,从而坡面侵蚀量较高。该研究为非均质土壤坡面水土过程研究、土壤侵蚀预报、坡面水文模型应用等提供基础数据。

[Background]Red soil hilly region in southern China is the area of serious soil erosion second only to the Loess Plateau.The presence of gravel in soil affects the hydrological cycle.Most of the existing studies mainly focus on gravel cover and soil erosion,while the effects of rainfall intensity and slope on soil erosion in different gravel forms are seldom studied.[Methods]In order to study the difference of erosion characteristics of red soil slope with different gravel forms,the erosion processes of red soil slope with no gravel(gravel content 0%),5%gravel-mulching and 5%gravel-embedded red soil slope were studied under 2 rainfall intensities(60 mm/h and 120 mm/h)and 4 slope gradients(10°,15°,20°and 25°),based on the indoor artificial rainfall simulation and combined with rainfall and slope characteristics in the upper reaches of Cao e River of Zhejiang province.Characteristics such as the rainfall runoff generation time,runoff rate,runoff generation process,and sediment yield intensity were compared.[Results]1)The runoff generation time of 4 slope gradients decreased with rainfall intensity increasing.The total runoff and the amount of sediment yield increased with rainfall intensity increasing.2)The runoff rate of 4 slope gradients of no gravel and 5%gravel-mulching slopes was approximate when the rainfall intensity was 120 mm/h.Compared with other 3 slope gradients,the runoff rate of 5%gravel-embedded slopes with slope 10°was much lower.3)With 2 rainfall intensities and 4 slope gradients,the total runoff and the amount of sediment yield of 5%gravel-mulching and 5%gravel-embedded slopes were lower than those of the no gravel slopes.4)For all slopes,the maximum of sediment yield intensity was found with the slope gradient 25°.When the rainfall intensity was 120 mm/h,the peak value of sediment yield intensity appeared in 25 minutes;and when the rainfall intensity was 60 mm/h,the peak value of sediment yield intensity appeared in 35 minutes.[Conclusions]Gravel-mulching soils are more effective than gravel-embedded soils in inhibiting the formation of surface soil rills,increasing the roughness of rills and reducing the runoff rate of rills under rainfall intensities 120 mm/h.This study provides basic data for quantifying soil and water processes on heterogeneous soil slopes,prediction of soil erosion and application of hydrological models on slopes.