模拟降雨对亚热带阔叶林土壤坡面产沙产流及养分流失的影响

Research on Runoff,Sediment and Nutrients Loss Characteristics on Soil Slope of Subtropical Evergreen Broad-leaved Forest Under Artificial Simulated Rainfall

采用人工降雨方法,研究了不同降雨强度和坡度对亚热带阔叶林土壤坡面产沙产流及养分流失的影响。结果表明:(1)在不同降雨强度下,初始产流时间随坡度的增加趋于提前,随降雨强度的增大产流时间提前,降雨强度对初始产流时间的影响大于坡度变化的影响。(2)在同一坡度条件下,产流强度和平均入渗强度随降雨强度的增加而增加;曲线拟合的结果表明产流强度随时间遵循幂函数变化规律,而坡面入渗强度随时间呈对数函数变化。(3)不同降雨强度下,径流量随降雨历时的变化趋势基本一致,径流量均随降雨历时呈"增加—稳定"趋势,在整个降雨过程中,径流量随坡度的增加而增加,相同坡度下,径流量随着降雨量的增加而增加;降雨初始时刻,坡度对径流量的影响较小,而在降雨后期,降雨强度和坡度对径流量的影响较大;产流率与径流量的变化趋势相反,随降雨历时呈"降低—稳定"趋势,在整个降雨过程中,土壤产流率随坡度的增加而降低,在相同坡度下,产流率随着降雨量的增加而增加。(4)侵蚀泥沙量的变化特征表现为坡度越大,坡面侵蚀泥沙的流失量越大;泥沙侵蚀量随降雨历时的增加而增加,在降雨10min左右达到峰值;在相同坡度和降雨历时下,泥沙侵蚀量随降雨强度的增加而增加;不同坡度下的侵蚀泥沙量在峰值前后与产流历时均呈乘幕函数变化,不同坡度下侵蚀泥沙养分含量与产流历时间的关系均可用幂函数表达。(5)不同坡度条件下,泥沙量与侵蚀泥沙中养分的含量均存在不同程度的正相关关系,其中坡度为15°,20°和25°时,侵蚀泥沙养分含量与泥沙流失量间的相关性明显优于坡度为5°和10°时,说明侵蚀泥沙量的增加会引起泥沙中各类养分含量的增加效应,而不同坡度下的全磷与侵蚀量没有显著的相关关系(P>0.05)。

Simulated rainfall experiments were conducted to investigate the research on soil and sediment yield and nutrients loss characteristics on soil slope of subtropical evergreen broad-leaved forest. The results showed that： （1） The runoff occurring time shortened with the increasing rainfall intensity and slope gradient, and the influence of rainfall intensity on runoff occurring time was greater than that of slope gradient. （2） For the same slope gradient, the runoff intensity and the average infiltration rate increased with the increasing rainfall intensity, and the temporal change of runoff intensity followed a power function and that of the average infiltration rate followed a logarithmic function. （3） The runoff amount first increased and then tended to be stable with the increasing rainfall duration, and increased with the increasing slope gradient. For the same slope gradient, the runoff amount increased with the increasing rainfall amount. Soil slope gradient had less influence on the runoff at rainfall initial moment, and rainfall intensity and slope gradient had the greater influence on the runoff. The runoff-yielding rate showed an opposite temporal variation with the runoff amount, which first decreased and then tended to be stable with the increasing rainfall duration. The runoff-yielding rate decreased with the increasing slope gradient. For the same slope gradient, the runoff amount increased with the increasing rainfall amount. （4） Slope sediment yield increased with the increasing slope gradient, and also increased with the increasing rainfall duration, which reached the maximum in the first 10 min of the rainfall. For the same slope gradient and rainfall duration, sediment yield increased with the increasing rainfall intensity. The slope sediment yield and nutrient loss followed a power function. （5） For different slope gradients, positive correlations existed between slope sediment yield and nutrient loss, and the correlation coefficients on the slopes of 15°, 20° and 25° were much better than on the slopes of 5° and 10°, while the total phosphorus had no correlation with slope sediment yield （P〉0.05）, which implied that the slope sediment yield could cause the increase of various kinds of nutrients in sediment.