本文選題：黃土丘陵區(qū) + 降雨　； 參考：《西北農(nóng)林科技大學(xué)》2017年碩士論文

【摘要】：陜北黃土丘陵區(qū)人工林地存在大規(guī)模的土壤干化現(xiàn)象,隨著林草植被建設(shè)的快速發(fā)展,長期造林過程中不合理的植被選擇和栽植密度致使林地土壤干化問題愈發(fā)嚴(yán)重。土壤干化問題的防治與修復(fù),因此也成為生態(tài)學(xué)科與土壤學(xué)科十分關(guān)注的熱點(diǎn)問題。該地區(qū)地形地貌特殊,不具備灌溉條件,加之當(dāng)?shù)氐叵滤癫剌^深,降雨成為干化土壤水分修復(fù)的唯一來源。為了探索降雨條件下林地干化土壤的水分入滲及遷移規(guī)律,本文利用野外地下10m大型土柱模擬棗林地土壤干層,通過長期定位監(jiān)測,探討不同降雨類型、不同生育時期下的干化土壤水分入滲、遷移規(guī)律,并進(jìn)一步利用Hydrus-1D模型進(jìn)行模擬預(yù)測,對當(dāng)?shù)貤椓滞寥浪值目茖W(xué)管理與改善具有重要的理論和實(shí)踐意義。主要得出以下結(jié)論:(1)獨(dú)立降雨與間歇降雨下的土壤水分入滲、遷移規(guī)律不同。獨(dú)立降雨條件下,土壤水分的入滲、遷移深度除了受降雨量、氣象因子等影響明顯外,還與降雨強(qiáng)度、初始土壤含水率有關(guān),降雨強(qiáng)度越大、初始土壤含水率越高,水分的入滲深度及遷移深度也越大;間歇降雨較獨(dú)立降雨具有更強(qiáng)的入滲、遷移規(guī)律,間歇降雨中前次降雨為后次降雨提高了土壤含水率,后次降雨在前次降雨的基礎(chǔ)上發(fā)生,幾次降雨交互對土壤水分的入滲、遷移產(chǎn)生促進(jìn)作用。相同降雨量下,其入滲深度較獨(dú)立降雨可提高100%~160%;遷移深度可提高91%~197%。(2)水分在土壤垂向運(yùn)輸中具有剖面特征,從地表向下依次表現(xiàn)為:蒸滲層、過渡層和入滲層。生育期內(nèi)三個土層深度分別為:0~60cm、60~120cm、120~220cm,休眠期依次為:0~100cm、100~140cm、140~240cm。其中,蒸滲層土壤水分受降水、蒸發(fā)作用影響最大,在生育期和休眠期內(nèi)該層次土壤儲水量均與降水量表現(xiàn)出較強(qiáng)的一致性,二者呈線性變化:W生=0.2332P+81.25(R2=0.41),W休=0.7011P+133.24(R2=0.66);過渡層受蒸發(fā)作用影響有所減弱,該層土壤儲水量僅呈微弱波動,在生育期內(nèi)表現(xiàn)為土壤水分入滲大于蒸發(fā),休眠期為蒸發(fā)大于入滲;入滲層則不受蒸發(fā)作用影響,土壤水分不斷向深層入滲補(bǔ)給,土壤儲水量隨時間推移而不斷增加。(3)生育期月平均蒸發(fā)耗水量為40.1mm,蒸發(fā)耗水系數(shù)基本維持在0.87左右,平均每月降水量約87.0%用以蒸發(fā)消耗,13.0%用于入滲補(bǔ)給土壤;休眠期月平均蒸發(fā)耗水量為24.7mm,土壤蒸發(fā)耗水系數(shù)高達(dá)5.1,該時期蒸發(fā)損失量79.4%來自降水,20.6%來自土壤儲水量,因此休眠期是土壤水分損失的重要階段。(4)黃土丘陵區(qū)并非所有降雨都能夠?qū)ν寥浪钟杏绊憽?014.8.1~2016.12.31間降雨次數(shù)與降雨量的有效率分別為21.3%、62.6%;土壤水分的垂直運(yùn)輸具有滯后性,且分帶特征明顯,試驗(yàn)觀測期間,有效降雨對干化土壤,的水分修復(fù)深度介于350~400cm。(5)Hydrus-1D模型對于模擬土柱土壤水分的模擬值與實(shí)測值吻合程度良好。利用Hydrus-1D模型建立典型平水年條件下的土壤水分運(yùn)移深度模擬,估算出600cm深度的土壤干層得到修復(fù)大致需要8~9年的時間,并進(jìn)而擬合出土壤水分運(yùn)移深度的時效性方程,證實(shí)了土壤干層的水分修復(fù)是一個長期、緩慢的過程。
[Abstract]:In the loess hilly area of Northern Shaanxi, there are large-scale soil dryness in the artificial forestland. With the rapid development of the construction of forest and grass vegetation, the unreasonable vegetation selection and planting density in the long period of afforestation have caused the problem of soil dryness in woodland more serious. The prevention and repair of soil dry problems have also become the ecological subject and soil discipline. In order to explore the law of water infiltration and migration of dry soil under rainfall conditions, this paper uses 10m large soil column in the field to simulate the soil dry of jujube woodland. Layer, through long-term location monitoring, we discuss the different rainfall types, the water infiltration and migration of dry soil under different growth periods, and further use the Hydrus-1D model to simulate and predict the soil moisture in the local jujube forest. It is of great theoretical and practical significance to the scientific management and improvement of soil moisture in the local jujube forest. The following conclusions are drawn as follows: (1) independent rainfall and The soil moisture infiltration under intermittent rainfall is different. Under the condition of independent rainfall, the infiltration of soil moisture, the depth of migration is obviously related to rainfall intensity, the initial soil moisture content, and the greater the rainfall intensity, the higher the soil moisture content in the initial soil, the more depth of water infiltration and the depth of migration. The intermittent rainfall has a stronger infiltration than the independent rainfall, the law of migration, the previous rainfall in the intermittent rain to increase the soil moisture content, the latter rainfall on the basis of the previous rainfall, the infiltration of soil water and the promotion of the migration of several rainfall. Under the same rainfall, the infiltration depth is more independent than rainfall. The migration depth can increase the depth of 91%~197%. (2) in the vertical transport of soil, which has the characteristics of profile in the vertical transport of soil. From the ground to the surface, the depth of water is shown in successively: the steaming layer, the transition layer and the infiltration layer. The depth of the three soil layers in the growth period is 0~60cm, 60~120cm, 120~220cm, respectively: 0~100cm, 100~140cm, 140~240cm., and the soil water of the steamed layer. The influence of precipitation and evaporation is the greatest. The soil water storage at this level in the growth period and the dormancy period shows a strong consistency with the precipitation. The two are linear changes: W =0.2332P+81.25 (R2=0.41) and W =0.7011P+133.24 (R2=0.66); the influence of evaporation on the transition layer is weakened, and the soil water storage in this layer is only slightly fluctuating. During the growth period, the soil moisture infiltration is greater than evaporation, the dormancy period is greater than the infiltration, the infiltration layer is not affected by the evaporation effect, the soil water is constantly replenishment to the deep infiltration, and the soil water storage is increasing with the time. (3) the average evaporation water consumption of the month of the fertility period is 40.1mm, and the coefficient of evaporation water consumption is basically maintained at about 0.87. The average monthly precipitation is about 87% for evaporation consumption and 13% for infiltration and recharge of soil; the average evaporation water consumption of the dormancy period is 24.7mm, the coefficient of soil evaporation water consumption is as high as 5.1. The evaporation loss of 79.4% comes from the precipitation, 20.6% comes from the soil water storage, so the dormancy period is an important stage of soil water loss. (4) the loess hilly area is not The effect of all rainfall on soil moisture is 21.3% and 62.6%, respectively. The vertical transport of soil moisture is 21.3%, 62.6%, and the vertical transport of soil moisture is lagging, and the characteristics of the zoning are obvious. During the experimental observation, the restoration depth of the effective rainfall to dry soil is between the 350~400cm. (5) Hydrus-1D model. The simulated values of soil moisture in the simulated soil column are in good agreement with the measured values. The Hydrus-1D model is used to simulate the soil moisture migration depth under the typical year condition. It is estimated that the soil dry layer of the 600cm depth is approximately 8~9 years, and then the aging equation of soil moisture migration depth is fitted. Soil moisture restoration is a long and slow process.

【學(xué)位授予單位】：西北農(nóng)林科技大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2017
【分類號】：S714

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