黄土和红壤坡面侵蚀差异及其与土壤性质的关系

为探究黄土和红壤侵蚀受雨强和坡度影响的差异及其与土壤性质的关系,通过测定分析黄土和红壤的各种理化性质,并分别对2种土壤在2个坡度(15°,20°)、2个雨强(60,90 mm/h)条件下开展4场降雨。结果表明:(1)与红壤相比,黄土的土壤颗粒更细,二者的毛管孔隙度、饱和含水量和田间持水量相差均在3%~6%以内,干筛时各粒级团聚体相差不大,但经湿筛破坏后二者团聚体差异较大,红壤的相对机械破碎指数(RMI)小于黄土,黄土有机质含量、阳离子交换量和络合态氧化物含量均高于红壤,无定形氧化物和游离氧化物则低于红壤;(2)同雨强、同坡度条件下,黄土产流时间均短于红壤,产流开始后,红壤比黄土先达到稳定径流率,不同雨强、坡度条件下,红壤稳定径流率为30~120 mL/s,黄土为100~220 mL/s,且在相同坡度、雨强范围内,红壤径流率变化层次分明,黄土则交错复杂;(3)红壤的产沙率和径流含沙率都较低,且多在产流几分钟即出现产沙率最大值,黄土产沙率则和径流率类似,在产流前期快速增长,10 min之后开始波动变化,再进入相对稳定产沙阶段,产沙率和径流含沙率随雨强和坡度的变化复杂;(4)不同土壤自身理化性质是影响坡面侵蚀的内在因素,与黄土相比,红壤的下渗能力更好,土壤抵抗径流剪切和剥蚀的能力更强,使得在同雨强、同坡度条件下红壤的侵蚀程度远低于黄土,规律性也更显著。

Difference of Slope Erosion Between Loess and Red Soil and Its Relationship with Soil Properties

In order to explore the difference of loess and red soil erosion affected by rainfall intensity and slope and its relationship with soil properties, various physical and chemical properties of loess and red soil were measured and analyzed, and four rainfall events were carried out on the two soils under two slope gradients (15°, 20°) and two rainfall intensity (60, 90 mm/h). The results showed that: (1) Compared with red soil, soil particles of loess were finer, and the differences in capillary porosity, saturated water content and field water holding capacity between loess and red soil were within 3% to 6%. There was no significant difference in the aggregates of each size of dry sieving, but the difference between the aggregates of the two was large after the destruction of wet sieving. The relative mechanical fragmentation index (RMI) of red soil was lower than that of loess. The organic matter content, cation exchange capacity and complex oxide content of loess were all higher than that of red soil, while amorphous oxide and free oxide were lower than that of red soil. (2) Under the same rainfall intensity and slope conditions, the runoff generation time of loess was shorter than red soil, after the start of runoff, red soil reached a stable runoff rate before loess. Under different rain intensity and slope conditions, the stable runoff rate of red soil ranged from 30 to 120 mL/s, while that of loess was between 100 to 220 mL/s. And within this range of slope and rain intensity, the runoff rate of red soil varied in distinct layers, while that of loess was staggered and complex. (3) The sediment yield and runoff sand content rate of red soil were both low, and the maximum sediment yield rate usually occurred within a few minutes of runoff. The sand yield rate of loess was similar to the runoff rate, it increased rapidly in the early stage of runoff, and then began to fluctuate after 10 minutes. When it entered the stage of relatively stable sediment yield, the sand yield rate and runoff sediment rate changed complicated with rainfall intensity and slope. (4) Different physical and chemical properties of soil were the internal factors affecting slope erosion. Compared with loess, red soil had better infiltration capacity and stronger resistance to runoff shear and denudation. The erosion degree of red soil under the same rainfall intensity and slope condition was much lower than that of loess, and the regularity was more obvious.