陕北黄土丘陵区枣林休眠期土壤水分与温度特征研究

发布时间：2019-07-08 11:59

【摘要】：陕北黄土丘陵区属于典型的半干旱气候区,降雨量较少且蒸发强烈,土壤水分长期处于亏缺状态。本文以黄土丘陵区枣林地和裸地为研究对象,在研究其全年土壤水分及温度变化特征的前提下,探讨其在枣林休眠期的土壤水分及温度变化特征,并通过连续定位监测裸地与覆膜条件下的浅层土壤水分及土壤温度,探讨土壤浅层的水分迁移规律及其缘由,评价覆膜措施在枣林休眠期的土壤保墒效果,对修复和治理黄土高原规模化林草地土壤干化具有借鉴作用。同时利用hydrus-1D模型对裸地及覆膜条件下的浅层土壤水分及温度进行模拟,为不同年份休眠期的覆膜保墒措施提供理论基础。主要得出以下结论:(1)枣林地1000cm土层内土壤水分在全年的变化可分为三层:易变层(0-250cm)、难变层(250-750cm)和稳定层(750-1000cm),其中易变层土壤水分变化范围为6.39%-12.83%,土壤储水量变化于148-235mm,难变层土壤储水量变化于391-460mm,稳定层土壤储水量变化于240-268mm。随着土层深度的增加,深层土壤储水量不断增加且水分的季节性变幅迅速减小,另外深层土壤水分的变化较浅层土壤具有一定的滞后性。(2)枣林休眠期土壤水分损失主要发生在浅层土壤,其中裸地和枣林地50cm土层土壤水分损失量占全部损失量的47.5%和52.8%,而50-340cm土壤水分损失量占全部损失量的34.5%和35.2%,340-1000cm土壤水分损失量占全部损失量的18%、12%。水分消耗主要来自土壤的自然蒸发,10月份土壤水分为休眠期最高值,10月初到土壤发生冻结前,土壤水分下降速度较快,土壤发生冻结后,地表冻结蒸发减小,深层土壤温度较浅层土壤温度高,土壤未冻水随着土壤中热量的传输而发生转移,深层土壤水分向地表迁移,浅层土壤水分呈上升趋势,持续至土壤解冻,土壤水分开始下降。历经整个休眠期,0-60cm土层土壤水分均值由11.4%降至8.93%,60~200cm土层土壤水分在休眠期基本处于稳定,均值为7.03%。(3)土壤中的温度梯度是导致土壤水分运移变化的一个重要因素,而土壤的热量主要来自于太阳辐射,太阳辐射对土壤温度的影响达到土层以下50cm深度。在晴天,裸地土壤温度表现出正弦趋势的昼夜变化特征,随着土层深度的增加,土壤温度最值出现的时间较上层土壤滞后,同时,土壤温度的日振幅值也在减小。在两种覆膜条件下,土壤温度日最大值和日最小值出现的时间均较裸地滞后,其中黑色覆膜又滞后于白色覆膜。土壤温度日最大值白色覆膜裸地黑色覆膜,而日最小值黑色覆膜白色覆膜裸地。另外,裸地及覆膜条件下各个土层地温与气温呈显著的线性关系,且随着土层深度的增加,相关性逐渐减弱。(4)枣林生长期降雨较少时,随着土壤温度的不断升高,土壤水分呈下降趋势,覆膜措施可有效抑制土壤水分的蒸发损失,土壤水分蒸发损失平均速度裸地白色覆膜黑色覆膜。枣林休眠期土壤未冻结阶段,土壤水分较低,降雨量较少,土壤水分蒸发对土壤温度的敏感性减弱,土壤温度与土壤水分均呈下降趋势,其中水分下降速度裸地白色覆膜黑色覆膜,裸地0-50cm土层土壤储水量减少7.34mm,白色覆膜和黑色覆膜0-50cm土层土壤储水量分别减少4.85mm和4.02mm。(5)hydrus-1D模型对裸地及黑色薄膜覆盖下的土壤水分及温度的模拟结果与实测值吻合良好,为土壤水分运移模式的分析和不同年份枣林休眠期的覆膜保墒措施提供了理论基础。
[Abstract]:The loess hilly region of northern Shaanxi is a typical semi-arid climate region, with less rainfall and strong evaporation, and the soil moisture is in a deficit condition for a long time. Based on the study of the characteristics of soil moisture and temperature in the whole year, the soil moisture and the temperature change of the jujube forest in the period of the jujube forest were studied in this paper, based on the study of the characteristics of soil moisture and temperature in the hilly region of the Loess Plateau. The soil moisture and soil temperature under the condition of the bare land and the coating film were monitored by continuous positioning, and the water migration law and the cause of the soil shallow layer were discussed, and the effect of the film-coating on the soil moisture retention in the period of the jujube forest was evaluated. The soil drying of the large-scale forest grassland in the loess plateau is of reference to the restoration and treatment of the loess plateau. At the same time, using the hydro-1D model to simulate the shallow soil moisture and temperature under the bare and covered conditions, the paper provides a theoretical basis for the film-covered protection measures in different years. The results are as follows: (1) The change of soil moisture in the 1000cm soil layer of the jujube forest in the whole year can be divided into three layers: the variable layer (0-250cm), the difficult-to-change layer (250-750 cm) and the stable layer (750-1000cm), wherein the variation range of the water content of the variable layer is 6.39-12.83%, and the water storage capacity of the soil is changed to 148-235 mm, The water storage capacity of the hard-changing soil layer varied from 391 to 460 mm, and the water storage capacity of the stable layer varied from 240 to 268 mm. With the increase of the depth of the soil layer, the water storage capacity of the deep soil is increasing, and the seasonal variation of the moisture is rapidly reduced, and the change of the deep soil moisture has a certain lag in the shallow soil. (2) The soil moisture loss in the period of the jujube forest is mainly in the shallow soil, in which the loss of soil moisture in the 50 cm soil layer of the bare land and the date forest accounts for 47.5% and 52.8% of the total loss, while the loss of soil moisture in the 50-340cm accounts for 34.5% and 35.2% of the total loss. The loss of soil moisture in 340-1000cm accounts for 18% and 12% of total loss. The water consumption mainly comes from the natural evaporation of the soil, and the soil moisture in October is the highest value of the soil, and before the freezing of the soil in the beginning of October, the soil moisture decreases rapidly, and after the soil is frozen, the surface freezing evaporation is reduced, and the deep soil temperature is higher than the shallow soil temperature, With the transfer of the heat in the soil, the soil moisture was transferred to the surface, and the soil moisture in the shallow layer was on the rise, and then the soil was unfrozen and the soil moisture began to decline. The mean value of soil moisture in the 0-60 cm soil layer decreased from 11.4% to 8.93% over the whole period, and the soil moisture in the 60 ~ 200 cm soil layer was basically stable in the period of time and the mean value was 7.03%. (3) The temperature gradient in the soil is an important factor leading to the change of soil moisture, and the heat of the soil mainly comes from the solar radiation, and the effect of the solar radiation on the soil temperature reaches the depth of 50 cm below the soil layer. In a sunny day, the temperature of the bare soil shows the diurnal variation of the sinusoidal trend. With the increase of the depth of the soil layer, the time of the soil temperature is lower than that of the upper soil, and the daily amplitude value of the soil temperature is also decreasing. Under the two film-coating conditions, the time of the maximum and daily minimum value of soil temperature was lower than that of the white film. The maximum value of the soil temperature is the black film of the white film, while the daily minimum of the black-coated white film is bare. In addition, there is a significant linear relationship between the ground temperature and the temperature of each soil layer under the condition of bare land and film, and the correlation is gradually weakened with the increase of the depth of the soil layer. (4) When the rainfall in the growing period of the jujube forest is small, with the rising of the soil temperature, the soil moisture shows a downward trend, and the film-coating measures can effectively inhibit the evaporation loss of the soil water, and the average speed of the water evaporation loss of the soil water is the bare white-coated black film. the soil moisture content is lower, the rainfall is less, the sensitivity of the soil moisture evaporation to the soil temperature is reduced, the soil temperature and the soil moisture are all down, The soil storage capacity of the bare ground 0-50 cm soil layer is reduced by 7.34 mm, and the soil storage capacity of the white film and the black-coated 0-50 cm soil layer is reduced by 4.85 mm and 4.02 mm, respectively. (5) The simulation results of the hydro-1D model on the soil moisture and temperature under the coverage of the bare and black films are in good agreement with the measured values, and provide a theoretical basis for the analysis of the soil water migration pattern and the film-covering and protection measures for the date of the date and the time of the date in different years.
【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】：2016
【分类号】：S152

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