發(fā)布時(shí)間：2018-05-08 08:45

  本文選題：地表粗糙度 + 入滲過程�。� 參考：《西北農(nóng)林科技大學(xué)》2017年博士論文

【摘要】：黃土高原是我國(guó)坡耕地的主要分布區(qū)之一。由于降雨集中、坡度大、土壤抗侵蝕性弱及人們耕作管理活動(dòng)等因素,該區(qū)也是水土流失主要的策源地。坡耕地嚴(yán)重水土流失,導(dǎo)致土壤及養(yǎng)分流失,降低土壤肥力和土地生產(chǎn)力,流失養(yǎng)分造成水體富營(yíng)養(yǎng)化。坡耕地經(jīng)耕作管理后形成的高低起伏、凹凸不平的微地形,稱之為地表粗糙度,其特征與坡面土壤侵蝕密切相關(guān)。研究坡耕地地表粗糙度對(duì)入滲、產(chǎn)匯流過程及養(yǎng)分流失的特征,有助于探明地表粗糙度對(duì)土壤侵蝕機(jī)理的影響以及為坡耕地水土流失治理提供科技支撐。因此,本研究在系統(tǒng)總結(jié)國(guó)內(nèi)外相關(guān)研究資料基礎(chǔ)上,以點(diǎn)種、鋤耕、等高耕作和犁耕等4種耕作措施形成的地表粗糙度為研究對(duì)象,并以平整直線坡為對(duì)照組,采用室內(nèi)外人工模擬降雨試驗(yàn)的方法,觀測(cè)了不同耕作方式下粗糙坡面微地形特征,以及對(duì)入滲、產(chǎn)流產(chǎn)沙與養(yǎng)分流失及泥沙顆粒機(jī)械組成特征等。獲取了以下主要結(jié)論。(1)通過三維激光掃描儀獲取耕作后粗糙坡面高程模型(DEM),利用Arc GIS分別提取了微地形坡度與坡向因子。分析表明相對(duì)于平整坡面,粗糙坡面微地形坡度分在范圍為0°-80°之間。其中,點(diǎn)種坡面微地形坡度主要集中在10°-15°、20°-40°范圍內(nèi),其臨界坡度分別為20°;同樣地,鋤耕坡面微地形坡度主要集中在10°-15°、20°-40°范圍內(nèi),其臨界坡度分別為20°;犁耕坡面微地形坡度主要集中在5°-30°,其臨界坡度為15°。等高耕作坡面微地形坡度主要集中在5°-30°,其臨界坡度為30°。隨著坡面坡度的增加,小于臨界坡度的柵格數(shù)隨坡面坡度的增大而減少,而大于臨界坡度的柵格數(shù)增加。另外,點(diǎn)種、鋤耕、等高耕作和犁耕坡面微地形坡向柵格數(shù)主要以南、西南或東南為主,即與試驗(yàn)徑流小區(qū)出流口方向一致。同時(shí)隨坡面坡度增加,粗糙坡面微地形南、西南或東南坡向的柵格數(shù)逐漸增加,而其他坡向的柵格數(shù)逐漸減小。(2)通過室內(nèi)人工模擬降雨試驗(yàn),利用土壤水分實(shí)時(shí)監(jiān)測(cè)技術(shù)獲取微地形特征點(diǎn)(凸處、凹處、平整處)、微坡面(cm~2)與平整坡面(m~2)的土壤含水量變化過程。研究結(jié)果表明粗糙坡面上凸處、洼處、平整處等在降雨過程中洼處穩(wěn)定土壤含水量高于凸處與平整處。可見,低洼處具有蓄積、促進(jìn)降水入滲的能力。另外不同深度的土壤水分變化趨勢(shì)表明降雨過程中粗糙坡面土壤水分活動(dòng)層為0-15cm,而平整坡面為0-10cm,進(jìn)一步說明粗糙度促進(jìn)坡面降水入滲深度。同時(shí)粗糙坡面上微坡面(cm~2)與平整坡面(m~2)的土壤水分變化過程相類似,這表明了微坡面與平整坡面產(chǎn)流方式一致。與平整坡面不同的是,粗糙坡面上微坡面產(chǎn)生的薄層徑流匯集在低洼處,從而延遲了坡面初始產(chǎn)流時(shí)間。(3)通過室內(nèi)人工模擬降雨試驗(yàn),粗糙坡面與平整坡面產(chǎn)流點(diǎn)位沿徑流方向的分布范圍分別為12-181 cm、42-180cm之間。同時(shí)兩處理坡面產(chǎn)流點(diǎn)位沿徑流方向上的變異系數(shù)分別為34.4%-52.1%、15.5%-31.1%。研究表明粗糙坡面產(chǎn)流點(diǎn)位較平整坡面在坡面空間分布更為分散。通過徑流小區(qū)人工模擬降雨試驗(yàn),可以看出相比于平整坡面,地表粗糙度具有推遲坡面初始產(chǎn)流時(shí)間的效應(yīng)。但是推遲產(chǎn)流效應(yīng)隨著坡度、雨強(qiáng)的增大而逐漸減弱。預(yù)測(cè)初始產(chǎn)流時(shí)間與實(shí)測(cè)初始產(chǎn)流時(shí)間比值為2.2%-36.2%,表明地表粗糙度影響坡面初始產(chǎn)流時(shí)間的主導(dǎo)過程為通過增加入滲的間接作用,從而確定了地表粗糙度延遲坡面初始產(chǎn)流主導(dǎo)作用。(4)通過三維激光掃描儀獲取降雨后各粗糙坡面高程模型(DEM),利用Arc GIS提取坡面匯流流向、匯流密度等特征。結(jié)果表明在平整坡面匯流方向均為連續(xù)沿坡面向下流動(dòng),匯流密度值為13.08-17.06 m/m~2之間。且隨著降雨強(qiáng)度、坡度的增大而增大。粗糙坡面匯流流向多變,增加了匯流的蜿蜒度,匯流密度較小,其值為6.85-11.44 m/m~2之間。相比于平整坡面,粗糙坡面匯流密度降低了31.7-51.5%。另外,由坡面徑流系數(shù)變化過程可知,粗糙坡面的徑流系數(shù)均少于平整坡面。將坡面匯流流向、匯流密度結(jié)合坡面徑流系數(shù)變化過程可知地表粗糙度通過蓄積水分,促進(jìn)降水入滲和增加坡面匯流流向多樣,降低匯流密度,從而造成坡面徑流連通性降低,徑流系數(shù)減少。但是隨著降雨強(qiáng)度、坡度增加,地表粗糙度聚集坡面徑流,有利于坡面徑流連通的作用,導(dǎo)致粗糙坡面與平整坡面的徑流系數(shù)差異逐漸減少。因此,該結(jié)果為解釋地表粗糙度對(duì)坡面徑流連通的影響提供依據(jù)。(5)通過室內(nèi)人工模擬降雨試驗(yàn),對(duì)比研究3種粗糙坡面處理分別為凸地、凹地和平整坡面上產(chǎn)流產(chǎn)沙、泥沙顆粒機(jī)械組成及其隨徑流和泥沙流失的可溶態(tài)和吸附態(tài)養(yǎng)分流失過程。結(jié)果表明總體而言,粗糙坡面可溶態(tài)養(yǎng)分流失量為凸地洼地平整坡;吸附態(tài)養(yǎng)分流失量為凸地平整坡洼地。徑流中養(yǎng)分流失主要以吸附態(tài)為主,可溶態(tài)養(yǎng)分流失總量與坡面總產(chǎn)流量呈冪函數(shù)關(guān)系,吸附態(tài)氮流失總量與總產(chǎn)沙量呈冪函數(shù)關(guān)系,吸附態(tài)磷流失總量與總產(chǎn)沙量呈線性正相關(guān)關(guān)系。同時(shí)泥沙顆粒中粘粒含量為洼地凸地平整坡,相對(duì)于試驗(yàn)原土,具有明顯的富集特征。粉粒、沙粒含量大小為凸地平整坡洼地。產(chǎn)沙過程中粘粒部分逐漸減少,粉粒和沙粒部分含量逐漸增加,隨著降雨歷時(shí)進(jìn)行,泥沙顆粒組成趨近于原土壤,進(jìn)一步闡明了粗糙度對(duì)坡面泥沙顆粒的侵蝕、搬運(yùn)與沉積過程的影響。另外,吸附態(tài)氮、磷與泥沙顆粒中粘粒富集率(Er)、中值粒徑(d50)、比表面積(SSA)成相關(guān)性,因此,粗糙坡面中吸附態(tài)養(yǎng)分流失差異主要受泥沙顆粒分布特征影響。
[Abstract]:The Loess Plateau is one of the main distribution areas of Sloping Farmland in China. Due to the concentration of rainfall, the high slope, the weak soil erosion resistance and the management activities of people, the area is also the main source of soil erosion. The serious soil erosion of the sloping farmland leads to the loss of soil and nutrients, the lowering of soil fertility and the productivity of land, and the loss of nutrients caused by water. The high and low undulating and uneven terrain formed by the management of sloping cultivated land, which is called the surface roughness, is closely related to the soil erosion of the slope. The study of the surface roughness of the sloping land on infiltration, the process of runoff production and the loss of nutrients will help to explore the effect of the surface roughness on the soil erosion mechanism. As well as providing scientific and technical support for soil and water erosion control in sloping land, based on the systematic summary of relevant research data at home and abroad, the research object is the surface roughness formed by 4 kinds of tillage measures, such as seed planting, hoeing ploughing, high tillage and plow tillage, and using the flat straight slope as the control group, the indoor and outdoor simulated rainfall experiments are adopted. The characteristics of the rough slope micro topography under different tillage methods, the infiltration, the runoff and sediment, the loss of nutrient and the mechanical composition of sediment particles were observed. The following main conclusions were obtained. (1) the elevation model of the rough slope after cultivation (DEM) was obtained by the three-dimensional laser scanner, and the slope and slope of the micro topography were extracted by using the Arc GIS. Factor analysis shows that the gradient of the rough slope of the rough slope is divided in the range of 0 -80 degrees relative to the flat slope. Among them, the gradient slope of the slope surface is mainly concentrated in the range of 10 -15 and 20 -40 degrees, and the critical slope is 20 degrees respectively. Similarly, the slope degree of the sloping surface is mainly concentrated in the range of 10 degrees -15 and 20 -40. The degree of the gradient of the plough slope is mainly concentrated at 5 -30 degrees, and its critical slope is 15 degrees. The slope degree of the slope is mainly concentrated at 5 -30 degrees, and the critical slope is 30 degrees. With the increase of the slope, the number of grids less than the critical slope decreases with the increase of the slope, but the number of grids larger than the critical slope increases. In addition, the number of grid grids in high tillage and ploughing slope surface is mainly South, southwest or southeast, which is the same as the outlet direction of the experimental runoff plot. At the same time, with the increase of the slope gradient, the rough slope surface is south, the number of grid numbers in the south-west or South-East slopes gradually increases, while the number of other slopes gradually decreases. (2) Through the indoor simulated rainfall experiment, the soil moisture content change process of micro terrain feature points (convex, concave, flat), micro slope surface (cm~2) and flat slope surface (m~2) is obtained by the real-time monitoring technology of soil moisture. The results show that the soil moisture content in the rough slope surface, such as the convex place, the depression, the leveling place, and so on, is higher than that in the rainfall process. It is obvious that the low lying area has the capacity of accumulating and promoting the infiltration of precipitation. In addition, the trend of soil moisture change at different depths indicates that the soil moisture activity layer of the rough slope in the rainfall process is 0-15cm, while the flat slope is 0-10cm, which further indicates that the roughness promotes the infiltration depth of the slope surface and the micro slope surface (cm~) on the rough slope surface. 2) it is similar to the process of soil moisture change on the flat slope (m~2), which indicates that the slope surface and the flat slope are in the same way of runoff production. Different from the flat slope surface, the thin surface runoff produced on the surface of the rough slope is collected in the low-lying place, which delays the initial flow time between the slope surface. (3) the rough slope surface is simulated by indoor artificial rainfall experiment. The distribution of runoff point along the runoff direction is 12-181 cm and 42-180cm, respectively. At the same time, the variation coefficient of the flow point along the runoff direction is 34.4%-52.1%, respectively. The 15.5%-31.1%. study shows that the flow point position of the rough slope is more dispersed on the slope surface than the flat slope surface. Compared with the flat slope surface, it can be seen that the surface roughness has the effect of postponing the initial flow time of the slope, but the delayed yield effect gradually decreases with the increase of the gradient and the rainfall intensity. The ratio of the initial runoff time to the measured initial runoff time is 2.2% -36.2%, indicating that the surface roughness affects the initial runoff yield. The dominant process of time is to determine the initial flow leading role of the surface roughness delayed slope by increasing the indirect effect of infiltration. (4) the rough slope elevation model (DEM) after the rainfall is obtained by the three-dimensional laser scanner, and the flow direction and the density of the slope surface are extracted by Arc GIS. The flow density is between 13.08-17.06 m/m~2 and continuous slope along the slope. The flow density increases with the increase of rainfall intensity and slope. The flow direction of the rough slope is changeable, and the sinuous degree of the confluence is increased. The density of the confluence is less than that of 6.85-11.44 m/m~2. Compared with the flat slope, the density of the confluence of the rough slope is reduced by 31.7-51. 5%. also, from the change process of slope runoff coefficient, the runoff coefficient of the rough slope is less than that of the flat slope. The flow direction of the slope and the flow density combined with the change process of the slope runoff coefficient can be seen that the surface roughness is accumulated through accumulating water, which promotes precipitation infiltration and increases the flow direction of slope surface to various and reduces the density of confluence, thus causing the slope surface. The runoff connectivity is reduced and the runoff coefficient decreases. However, with the increase of rainfall intensity and the increase of slope, the surface roughness aggregates the runoff on the slope surface, which is beneficial to the function of the slope runoff connectivity, which leads to the decrease of the runoff coefficient between the rough slope and the flat slope. Therefore, this result provides the basis for explaining the influence of the surface roughness on the slope runoff connectivity. (5) through indoor simulated rainfall experiments, 3 kinds of rough slopes were treated to produce miscarriage sand, the mechanical composition of sediment particles and the loss of soluble and adsorbed nutrients with runoff and sediment loss. The results showed that in general, the dissoluble nutrient loss of the rough slope was convex DIWA. The amount of nutrient loss in runoff was mainly adsorbed state, the total amount of soluble nutrient loss and total runoff yield showed a power function relationship. The total amount of adsorbed nitrogen loss and total sediment yield showed a power function relationship, and the total amount of adsorbed phosphorus loss and total sediment yield showed linear positive correlation. At the same time, the content of clay particles is convex and leveling in the low-lying land, which has obvious enrichment characteristics compared with the test original soil. The size of grain and sand grain is a convex flat and whole slope depression. The content of clay particles gradually decreases and the content of grain and sand part increases gradually during the process of sediment production, and the composition of sediment particles is closer to the original soil as the rainfall goes on. Further clarifies the influence of roughness on the erosion, transport and deposition of sediment particles on the slope. In addition, the adsorption nitrogen, the concentration of clay particles in the phosphorus and sediment particles (Er), the median particle size (D50), and the specific surface area (SSA) are related. Therefore, the difference of the adsorption and shunt loss in the rough slope is mainly influenced by the distribution characteristics of sediment particles.

【學(xué)位授予單位】：西北農(nóng)林科技大學(xué)
【學(xué)位級(jí)別】：博士
【學(xué)位授予年份】：2017
【分類號(hào)】：S157

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