土壤风蚀量随残茬高度的变化规律研究

在内蒙古自治区武川县建立农田土壤风蚀试验区,采用内蒙古农业大学研制的移动式风蚀风洞和旋风分离式集沙仪,直接在农田上观测不同残茬高度条件下的农田风蚀土壤损失情况。试验结果表明:土壤风蚀量和扬起沙尘的高度随风速的增加而增加,随着作物秸秆残茬高度的增加而降低,且输沙量与高度变化符合指数函数关系,土壤颗粒主要集中在近地表层内运动。保护性耕作可明显地提高启沙风速,减少农田土壤损失,当秸秆高度为30 cm时,风蚀量仅为传统耕地的1/4左右。     

作物残茬覆盖对农田土壤风蚀的影响

为定量评价干旱半干旱地区农田土壤抗风蚀效果,采用移动式风洞及其配套测试系统对内蒙古武川县上秃亥乡农田地表进行了原位测试研究。结果表明,不同风速下土壤风蚀量随作物残茬盖度的增加呈指数规律减少;40%以上残茬盖度可明显提高土壤颗粒起动风速并减少风蚀量;当风速为14~18 m/s时,地表作物残茬盖度为60%~80%具有较好的抗风蚀效果。     

农田耕作方式与土壤风蚀强度关系的风洞模拟实验

以土壤风蚀严重的河北坝上康保县为研究区,采用风洞试验的技术手段,对农田耕作方式与土壤风蚀强度的关系进行研究。结果表明,农田留茬与翻耕、农田垄向及农作物残茬高度的差异对土壤风蚀强度有较大影响。垄向平行主风向的风蚀强度大于垄向垂直主风向的风蚀强度。风速越大,垄向不同造成的风蚀强度的差异越大,尤其是当风速≥15m/s时,风蚀强度的差异表现得较为明显;风蚀强度与留茬高度呈负相关;翻耕地的风蚀强度大于任何留茬地的风蚀强度;风蚀强度与风速变化呈现出指数函数变化规律。因此,农田垄向垂直主风向、作物收获后不进行翻耕、留有适度茬高、优先种植残茬硬度较大的莜麦作物,这样的耕作方式可有效降低土壤风蚀强度,缓解河北坝上地区农田土壤风蚀状况。     

旱地保护性耕作土壤风蚀模型研究

在分析国外风蚀模型资料的基础上,建立了适用于保护性耕作的风蚀模型。该模型以小时为步长,根据气象数据、地表土壤水分、秸秆残茬覆盖率及地表粗糙度,模拟不同耕作体系下农田土壤风蚀流失量情况;针对保护性耕作的特点,考虑到残茬覆盖对土壤含水量和地表粗糙度的影响;通过田间风蚀测定数据的验证,证明所建立的保护性耕作风蚀模型的模拟值与实测值比较吻合。     

小麦留茬对陕北农田风蚀影响的室内风洞模拟

作为风蚀区主要保护性耕作措施之一,秸秆留茬覆盖可以通过增加地表粗糙度(Z0)减少近地表风速和侵蚀动力,并缩短风蚀颗粒的搬运距离和搬运高度,从而减少地表风蚀量.本研究采用室内模拟风洞实验,测定并分析了陕北2种主要土壤类型(风沙土和黄绵土)在4个风速、3种小麦留茬高度和2种留茬行距处理下土壤风蚀强度和在0～60 cm风洞断...     

土壤风蚀量随风速的变化规律研究

使用野外风洞作为风蚀研究的试验手段,通过农田土壤、沙及生土的风洞试验研究发现,农田土壤的风蚀量随风速呈指数函数变化,沙及生土的风蚀量随风速呈幂函数变化。试验研究还表明,农田土壤的风蚀量与表土层(3cm)的含水量呈显著负相关,沙的风蚀量与含水量的相关性不显著。风蚀导致土壤中的细颗粒成分大量损失,这是土壤颗粒粗化的原因所在。     

保护性耕作农田风沙流空间分布规律研究

为了解保护性耕作农田风沙流的空间分布规律,对保护性耕作农田进行了野外风洞原位风蚀测试.结果表明:保护性耕作农田在不同风速下各高度的风沙流水平分布符合三次多项式规律,经过27行残茬、5.5 m的水平距离风沙流基本达到了平衡稳定状态;在垂直方向上风沙流分布符合高阶多项式规律,具有与砾石戈壁地表输沙量垂直分布极为相似的"象鼻"效应.试验还发现保护性耕作农田风沙流主要活动在近地表40 cm高度以下范围,占到风蚀物总质量的90%左右.     

华北农田冬绿肥覆盖的抗风蚀研究

研究华北农田不同冬绿肥覆盖对农田土壤风蚀损失量的防治效果,并确定其最佳覆盖模式。结果表明:冬绿肥覆盖与冬闲相比,地表覆盖度、粗糙度增大,表层含水率提高,有机碳含量增加,土壤物理稳定性指数上升;5种冬绿肥覆盖模式可以不同程度减小土壤风蚀,风蚀量由大到小依次为:冬闲>草木樨>黑麦草>冬油菜>二月兰>毛苕子;综合看,冬油菜、毛苕子和二月兰覆盖的抗风蚀能力较强;风蚀大小与地表覆盖度、粗糙度、土壤有机碳含量、物理稳定性指数相关系数较高,而与土壤含水量相关系数较小。     

河北坝上风蚀对农田土壤肥力水平影响研究

河北坝上地区风多风大,冬春季节降水少,使得大片农田长期处于强烈的风蚀之中.由于地表土壤养分的大量流失,农田土壤生产能力下降,导致荒漠化进程加剧.针对传统和保护性耕作农田土壤及风蚀物养分的变化,研究分析了土壤的风蚀和有机物及养分衰减的定量关系及其衰减的机理.结果表明:风蚀过程是农田土壤退化的重要路径,可以通过风蚀物中有机质和养分的含量估算农田土壤的有机质和养分的损失量.土壤风蚀过程中,保护性耕作比传统耕作可以减少风蚀量62.56%.有机质损失减少31.05%,全氮损失减少29.15%,全磷损失减少32.25%,全钾损失减少66.11%;有机质及养分主要集中在细微的土壤颗粒之中.风蚀对土壤营养物质及有机质的流失高于土壤的流失,风蚀是土壤退化的重要原因,恶化环境的同时造成了严重的经济损失.可以采用保护性耕作技术防止农田沙漠化和提高作物产量.     

耕作地表土块状况及其对近地表风场的影响

为深入理解非可蚀性土块吸收风能、降低侵蚀力的机制,利用野外风速资料,对半干旱区农田传统耕作模式下犁耕、耙耱及抹平等的地表土块大小、土壤表面粗糙度、近地表风速及空气动力学特征进行了研究。结果表明,犁耕后农田土块长、宽、高均在15 cm以上,盖度为27.67%,耙耱、抹平后土块大小和盖度显著降低,抹平地表土块盖度仅为2.13%;土块的破碎导致土壤表面粗糙度降低,近地表风速增大;与犁耕地表比较,耙耱后土壤表面粗糙度降低34%~64%,抹平后降低幅度甚至在90%以上;耙耱抹平后地表以上0.5 m高度内风速显著增大,空气动力学粗糙度由1.1 cm降低至0.05 cm,侵蚀力增强。因此认为,合理选择犁耕、耙耱和抹平的时间对农田风蚀防治有实际意义。     

Research on wind erosion processes and controlling factors based on wind tunnel test and 3D laser scanning technology

The study of wind erosion processes is of great importance to the prevention and control of soil wind erosion. In this study, three structurally intact soil samples were collected from the steppe of Inner Mongolia Autonomous Region, China and placed in a wind tunnel where they were subjected to six different wind speeds (10, 15, 17, 20, 25, and 30 m/s) to simulate wind erosion in the wind tunnel. After each test, the soil surfaces were scanned by a 3D laser scanner to create a high-resolution Digital Elevation Model (DEM), and the changes in wind erosion mass and microtopography were quantified. Based on this, we performed further analysis of wind erosion-controlling factors. The study results showed that the average measurement error between the 3D laser scanning method and weighing method was 6.23% for the three undisturbed soil samples. With increasing wind speed, the microtopography on the undisturbed soil surface first became smooth, and then fine stripes and pits gradually developed. In the initial stage of wind erosion processes, the ability of the soil to resist wind erosion was mainly affected by the soil hardness. In the late stage of wind erosion processes, the degree of soil erosion was mainly affected by soil organic matter and CaCO₃ content. The results of this study are expected to provide a theoretical basis for soil wind erosion control and promote the application of 3D laser scanners in wind erosion monitoring.     

Interactive effects of wind speed,vegetation coverage and soil moisture in controlling wind erosion in a temperate desert steppe,Inner Mongolia of China

The rapid desertification of grasslands in Inner Mongolia of China poses a significant ecological threaten to northern China. The combined effects of anthropogenic disturbances(e.g., overgrazing) and biophysical processes(e.g., soil erosion) have led to vegetation degradation and the consequent acceleration of regional desertification. Thus, mitigating the accelerated wind erosion, a cause and effect of grassland desertification, is critical for the sustainable management of grasslands. Here, a combination of mobile wind tunnel experiments and wind erosion model was used to explore the effects of different levels of vegetation coverage, soil moisture and wind speed on wind erosion at different positions of a slope inside an enclosed desert steppe in the Xilamuren grassland of Inner Mongolia. The results indicated a significant spatial difference in wind erosion intensities depending on the vegetation coverage, with a strong decreasing trend from the top to the base of the slope. Increasing vegetation coverage resulted in a rapid decrease in wind erosion as explained by a power function correlation. Vegetation coverage was found to be a dominant control on wind erosion by increasing the surface roughness and by lowering the threshold wind velocity for erosion. The critical vegetation coverage required for effectively controlling wind erosion was found to be higher than 60%. Further, the wind erosion rates were negatively correlated with surface soil moisture and the mass flux in aeolian sand transport increased with increasing wind speed. We developed a mathematical model of wind erosion based on the results of an orthogonal array design. The results from the model simulation indicated that the standardized regression coefficients of the main effects of the three factors(vegetation coverage, soil moisture and wind speed) on the mass flux in aeolian sand transport were in the following order: wind speedvegetation coveragesoil moisture. These three factors had different levels of interactive effects on the mass flux in aeolian sand transport. Our results will improve the understanding of the interactive effects of wind speed, vegetation coverage and soil moisture in controlling wind erosion in desert steppes, and will be helpful for the design of desertification control programs in future.     

20世纪90年代内蒙古自治区土地利用动态与风力侵蚀动态对比研究

内蒙古是我国风力侵蚀较为严重的地区之一,同时也是我国土地利用方式剧烈变化的地区之一。依据两期土地利用数据以及相应年代的土壤风力侵蚀数据,研究了20世纪90年代内蒙古自治区土地利用和风力侵蚀的静、动态格局。根据土地利用和风力侵蚀的空间分布及动态变化特点,设计了内蒙古土地利用—风力侵蚀动态区划,基于该区划详细讨论了内蒙古不同地区占主导地位的土地利用动态与风力侵蚀动态,由此揭示了两者之间存在的驱动——被驱动关系。研究发现,在过去10年里,内蒙古土地利用和风力侵蚀的基本格局没有太大变化,但风力侵蚀在总体上是增强了,而土地利用的变化主要反映为草地的退化和耕地的扩张。土地利用动态与风力侵蚀动态有着良好的时空对应关系草地的退化与耕地的扩张导致了显著的风力侵蚀增强,而草地的改善以及耕地的收缩对风力侵蚀的影响不是很大,这同时也表明了土地利用动态对风力侵蚀动态正、反向驱动力的不平衡性。     

An estimation method of soil wind erosion in Inner Mongolia of China based on geographic information system and remote sensing

Studies of wind erosion based on Geographic Information System(GIS) and Remote Sensing(RS) have not attracted sufficient attention because they are limited by natural and scientific factors.Few studies have been conducted to estimate the intensity of large-scale wind erosion in Inner Mongolia,China.In the present study,a new model based on five factors including the number of snow cover days,soil erodibility,aridity,vegetation index and wind field intensity was developed to quantitatively estimate the amount of wind erosion.The results showed that wind erosion widely existed in Inner Mongolia.It covers an area of approximately 90×104 km2,accounting for 80% of the study region.During 1985–2011,wind erosion has aggravated over the entire region of Inner Mongolia,which was indicated by enlarged zones of erosion at severe,intensive and mild levels.In Inner Mongolia,a distinct spatial differentiation of wind erosion intensity was noted.The distribution of change intensity exhibited a downward trend that decreased from severe increase in the southwest to mild decrease in the northeast of the region.Zones occupied by barren land or sparse vegetation showed the most severe erosion,followed by land occupied by open shrubbery.Grasslands would have the most dramatic potential for changes in the future because these areas showed the largest fluctuation range of change intensity.In addition,a significantly negative relation was noted between change intensity and land slope.The relation between soil type and change intensity differed with the content of Ca CO3 and the surface composition of sandy,loamy and clayey soils with particle sizes of 0–1 cm.The results have certain significance for understanding the mechanism and change process of wind erosion that has occurred during the study period.Therefore,the present study can provide a scientific basis for the prevention and treatment of wind erosion in Inner Mongolia.     

A field investigation of wind erosion in the farming–pastoral ecotone of northern China using a portable wind tunnel: a case study in Yanchi County

The farming–pastoral ecotone in northern China is an extremely fragile ecological zone where wind erosion of cropland and rangeland is easy to occur. In this study, using a portable wind tunnel as a wind simulator, we conducted field simulated wind erosion experiments combined with laboratory analysis to investigate wind erosion of soils in trampled rangeland, non-tilled cropland and tilled cropland in Yanchi County, China. The results showed that compared with rangeland, the cropland had a higher soil water holding capacity and lower soil bulk density. The wind erosion rate of trampled rangeland was much higher than those of non-tilled cropland and tilled cropland. For cropland, the wind erosion rate of the soil after tilling was surprisingly less than that of the soil before tilling. With increasing of wind speed, the volume mean diameter of the eroded sediment collected by the trough in the wind tunnel generally increased while the clay and silt content decreased for all soils. The temporal variation in wind erosion of the trampled rangeland indicated that particle entrainment and dust emission decreased exponentially with erosion time through the successive wind erosion events due to the exhaustion of erodible particles.     

Application of a new wind driving force model in soil wind erosion area of northern China

The shear stress generated by the wind on the land surface is the driving force that results in the wind erosion of the soil. It is an independent factor influencing soil wind erosion. The factors related to wind erosivity, known as submodels, mainly include the weather factor(WF) in revised wind erosion equation(RWEQ), the erosion submodel(ES) in wind erosion prediction system(WEPS), as well as the drift potential(DP) in wind energy environmental assessment. However, the essential factors of WF and ES contain wind, soil characteristics and surface coverings, which therefore results in the interdependence between WF or ES and other factors(e.g., soil erodible factor) in soil erosion models. Considering that DP is a relative indicator of the wind energy environment and does not have the value of expressing wind to induce shear stress on the surface. Therefore, a new factor is needed to express accurately wind erosivity. Based on the theoretical basis that the soil loss by wind erosion(Q) is proportional to the shear stress of the wind on the soil surface, a new model of wind driving force(WDF) was established, which expresses the potential capacity of wind to drive soil mass in per unit area and a period of time. Through the calculations in the typical area, the WDF, WF and DP are compared and analyzed from the theoretical basis, construction goal, problem-solving ability and typical area application; the spatial distribution of soil wind erosion intensity was concurrently compared with the spatial distributions of the WDF, WF and DP values in the typical area. The results indicate that the WDF is better to reflect the potential capacity of wind erosivity than WF and DP, and that the WDF model is a good model with universal applicability and can be logically incorporated into the soil wind erosion models.     

三种不同床面近地层湍流输送特征

为了深入理解土壤风蚀发生机制,利用风洞实验风速廓线资料,采用空气动力学方法,计算了干旱、半干旱地区不同类型地表近地层湍流输送随风速以及地表性质的变化特征.结果表明:地表越粗糙,风速越大,湍流输送越强,且湍流输送强度与地面粗糙元密度有关.