近景摄影测量技术在坡耕地土壤侵蚀速率研究中的应用

以5°,10°,20°的紫色土坡耕地为研究对象,分别进行5,10,15次强度的模拟耕作试验,在此基础上采用60L/min的流量进行3轮放水冲刷试验,采用近景摄影测量技术监测试验前后紫色土坡耕地小区的地形变化,通过生成高精度DEM数据计算土壤流失体积,并采用插钎法测量土层深度变化,验证近景摄影测量技术测定地形变化的准确度,进而推算不同坡度条件下的紫色土坡耕地耕作侵蚀速率和水力侵蚀速率。结果表明:(1)采用近景摄影测量技术能够准确监测地形变化,其测算结果与插钎法的结果比较接近,且通过计算土壤流失体积推算土壤侵蚀速率的方法比较可靠,精度较高;(2)紫色土坡耕地在坡度为5°,10°,20°条件下平均耕作侵蚀速率分别为69.85,131.45,155.34t/(hm2·tillage pass),耕作侵蚀速率随坡度增加呈增加趋势,随着耕作次数增加则呈逐渐减小的趋势;(3)紫色土坡耕地在坡度为5°,10°,20°条件下平均水力侵蚀速率分别为1 892.52,2 961.76,4 405.93t/(hm2·h),水力侵蚀速率与坡度呈正相关关系,与此同时,随着耕作强度的增加,水力侵蚀也呈逐渐增大的趋势,表明耕作侵蚀对水力侵蚀有加速作用。该研究为紫色土坡耕地耕作侵蚀和水力侵蚀交互作用下的土壤侵蚀研究提供技术支撑和数据基础。

Application of Close-range Photogrammetry Technology in the Study of Soil Erosion Rate on Slope Farmland

To determinate tillage erosion rate and hydraulic erosion rate of purple soil under different slope gradients, a series of simulated tillage experiments (5, 10, and 15 operation tillage) were conducted on 5°, 10°, and 20° slope farmlands, respectively. Then a series of scouring experiments with water discharge of 60 L/min were carried out on those slopes. Close-range photogrammetry technology was used to monitor the landform changes of purple slope farmland, and the high resolution digital elevation models (DEMs) were generated to calculate the net soil loss volume. Meanwhile, erosion pins were used to verify the accuracy of close-range photogrammetry technology by measuring the depth variation of soil layer, and the erosion rate and hydraulic erosion rate of purple slope farmland under different slope conditions were calculated. Results showed that the close-range photogrammetry technology was reliable and efficient to monitor landform changes and calculate the soil erosion rates. The calculated results of DEMs were similar to those of erosion pins. The average tillage erosion rates were 69.85, 131.45 and 155.34 t/(hm2·tillage pass) on 5°, 10° and 20° purple slope farmland, respectively, and tillage erosion rate showed an increase trend with the increasing of slope gradient, while it decreased with the increasing of tillage intensity. The average hydraulic erosion rates were 1 892.52, 2 961.76 and 4 405.93 t/(hm2·h) on 5°, 10° and 20° purple slope farmland, respectively. Hydraulic erosion rate was positively related to the slope gradient. Meanwhile, hydraulic erosion rate showed an increase trend with the increasing of tillage intensity, indicating that tillage erosion would accelerate the hydraulic erosion. These results could provide technical support and data foundation to the studies about soil erosion in purple slope farmland under tillage erosion and hydraulic erosion.