降雨侵蚀因子和植被类型及覆盖度对坡耕地土壤侵蚀的影响

Effects of rainfall erosion factor, vegetation type and coverage on soil erosion of sloping farmland

为探讨降雨和植被对辽西褐土区农耕坡地土壤侵蚀的影响,2006-2010年采用坡面径流小区观测法研究了天然降雨条件下降雨侵蚀因子、植被覆盖度、植被类型对坡耕地地表径流量、土壤侵蚀量的影响。设5°和10°两个坡度水平,以甘薯和谷子为供试作物,2006-2007年对照区为天然荒草地,2008-2010年为裸坡地。结果表明,甘薯地径流量和侵蚀量与降雨量(R)、最大30 min雨强(I_(30))、R×I(平均雨强)、R×I_(30)正相关显著(P<0.05);裸坡地径流量与R、R×I_(30)正相关显著(P<0.05),侵蚀量与I_(30)、R×I_(30)正相关显著(P<0.05),与降雨量相关不显著(P>0.05)。甘薯地和裸坡地的径流量和侵蚀量与平均降雨强度正相关均不显著(P>0.05)。回归分析表明,降雨量主要影响径流量,最大30 min雨强主要影响侵蚀量。中、高雨强下,侵蚀量与径流量显著正相关(P<0.01)。甘薯地径流量和侵蚀量与植被覆盖度呈显著负指数关系(P<0.05)。5°坡耕地,不同植被类型侵蚀量为甘薯地>荒草地>谷子地;10°坡耕地,荒草地侵蚀量总体最少。多元回归分析表明,对土壤侵蚀的影响为地表径流>降雨侵蚀力(R×I_(30))>植被覆盖度。通过连续5 a坡面径流小区观测,初步探明降雨和植被对辽西褐土区农耕坡地土壤侵蚀的影响,可为该区坡耕地土壤侵蚀的有效防治提供一定的理论依据和技术支撑。

In order to discuss the effect of rainfall and vegetion on soil erosion of sloping farmland in cinnamon soil region in western Liaoning, the experiment was carried out under natural rainfall on artificial slope runoff plots from 2006 to 2010. The runoff plots with an interval of 1 m were designed according to the 20-year standard and each area was 60 m2. Slope factor was set as 5° and 10° respectively. Among 3 runoff plots built under the same slope, 2 plots were practiced by millet - sweet potato rotation, and another runoff plot was set as the control, which was the natural hillside field in 2006-2007 and bare slope （coverage 〈5%） in 2008-2010. Millet and sweet potato were planted as test crops by contour tillage and row spacing was 50 cm. The result showed that soil erosion in the sloping farmland mainly occurred between June and August, particularly in July. The surface runoff and erosion amount increased in accordance with the increasing of gradient and the effect of slope on erosion amount was greater than runoff with the slope increasing. When rainfall reached a certain intensity, soil erosion would occur. The experiment also showed that the surface runoff and erosion amount on sweet potato field had significantly positive relations with the rainfall （P〈0.01 for runoff, P〈0.05 for erosion amount）, the maximum 30-minute rainfall intensity （P〈0.01）, the rainfall erosivity （which was the product of the former 2 factors） （P〈0.01）, and the product of rainfall and average rainfall intensity （P〈0.01）; the runoff on bare soil field had significantly positive relations with the rainfall （P〈0.01 and P〈0.05 on 5° and 10° bare soil field, respectively）, and the rainfall erosivity （P〈0.01）; the erosion amount had significantly positive relations with the maximum 30-minute rainfall intensity （P〈0.05 and P〈0.01 on 5° and 10° bare soil field, respectively）, and the rainfall erosivity （P〈0.01）, but had not positively significant relation with rainfall. The surface runoff and erosion amount were mostly affected by the precipitation and the maximum 30-minute rainfall intensity respectively through regression analysis and the both had not positively significant relation with average rainfall intensity on sweet potato and bare soil field. Erosion amount had a relation of power function and a significantly positive correlation with surface runoff under medium and higher rainfall intensity （P〈0.01）. The surface runoff and erosion amount on sweet potato field had a significantly negative exponential function relation （P〈0.05）. The amount of soil erosion on sweet potato field was the largest, the following was millet field and that of wild grass ground was the least. Multi variance regression analysis revealed that the factors impacting the amount of soil erosion from high to low were surface runoff, rainfall erosivity, and vegetation coverage, and the effects of rainfall erosivity and vegetation coverage on soil erosion increased with the slope increasing. Vegetation cover was especially important to protect against soil erosion on sloping farmland in western Liaoning, and crop management would be paid more attention with the increasing of gradient. The effects of different factors such as rainfall and crop varieties on soil erosion on sloping farmland were preliminarily known after the 5-year experiment in this paper. The research provides theoretical basis and technical support for the effective prevention and treatment of soil erosion in the region.