黄土丘陵区林地干化土壤水分入渗及迁移规律研究

发布时间：2018-05-16 02:39

本文选题：黄土丘陵区 + 降雨　；参考：《西北农林科技大学》2017年硕士论文

【摘要】：陕北黄土丘陵区人工林地存在大规模的土壤干化现象,随着林草植被建设的快速发展,长期造林过程中不合理的植被选择和栽植密度致使林地土壤干化问题愈发严重。土壤干化问题的防治与修复,因此也成为生态学科与土壤学科十分关注的热点问题。该地区地形地貌特殊,不具备灌溉条件,加之当地地下水埋藏较深,降雨成为干化土壤水分修复的唯一来源。为了探索降雨条件下林地干化土壤的水分入渗及迁移规律,本文利用野外地下10m大型土柱模拟枣林地土壤干层,通过长期定位监测,探讨不同降雨类型、不同生育时期下的干化土壤水分入渗、迁移规律,并进一步利用Hydrus-1D模型进行模拟预测,对当地枣林土壤水分的科学管理与改善具有重要的理论和实践意义。主要得出以下结论:(1)独立降雨与间歇降雨下的土壤水分入渗、迁移规律不同。独立降雨条件下,土壤水分的入渗、迁移深度除了受降雨量、气象因子等影响明显外,还与降雨强度、初始土壤含水率有关,降雨强度越大、初始土壤含水率越高,水分的入渗深度及迁移深度也越大;间歇降雨较独立降雨具有更强的入渗、迁移规律,间歇降雨中前次降雨为后次降雨提高了土壤含水率,后次降雨在前次降雨的基础上发生,几次降雨交互对土壤水分的入渗、迁移产生促进作用。相同降雨量下,其入渗深度较独立降雨可提高100%~160%;迁移深度可提高91%~197%。(2)水分在土壤垂向运输中具有剖面特征,从地表向下依次表现为:蒸渗层、过渡层和入渗层。生育期内三个土层深度分别为:0~60cm、60~120cm、120~220cm,休眠期依次为:0~100cm、100~140cm、140~240cm。其中,蒸渗层土壤水分受降水、蒸发作用影响最大,在生育期和休眠期内该层次土壤储水量均与降水量表现出较强的一致性,二者呈线性变化:W生=0.2332P+81.25(R2=0.41),W休=0.7011P+133.24(R2=0.66);过渡层受蒸发作用影响有所减弱,该层土壤储水量仅呈微弱波动,在生育期内表现为土壤水分入渗大于蒸发,休眠期为蒸发大于入渗;入渗层则不受蒸发作用影响,土壤水分不断向深层入渗补给,土壤储水量随时间推移而不断增加。(3)生育期月平均蒸发耗水量为40.1mm,蒸发耗水系数基本维持在0.87左右,平均每月降水量约87.0%用以蒸发消耗,13.0%用于入渗补给土壤;休眠期月平均蒸发耗水量为24.7mm,土壤蒸发耗水系数高达5.1,该时期蒸发损失量79.4%来自降水,20.6%来自土壤储水量,因此休眠期是土壤水分损失的重要阶段。(4)黄土丘陵区并非所有降雨都能够对土壤水分有影响。2014.8.1~2016.12.31间降雨次数与降雨量的有效率分别为21.3%、62.6%;土壤水分的垂直运输具有滞后性,且分带特征明显,试验观测期间,有效降雨对干化土壤,的水分修复深度介于350~400cm。(5)Hydrus-1D模型对于模拟土柱土壤水分的模拟值与实测值吻合程度良好。利用Hydrus-1D模型建立典型平水年条件下的土壤水分运移深度模拟,估算出600cm深度的土壤干层得到修复大致需要8~9年的时间,并进而拟合出土壤水分运移深度的时效性方程,证实了土壤干层的水分修复是一个长期、缓慢的过程。
[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.

【学位授予单位】：西北农林科技大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：S714

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