双面蒸发条件下沟岸地土壤水分时空分布特征

发布时间：2018-04-02 15:37

本文选题：双面蒸发　切入点：沟岸地　出处：《西北农林科技大学》2015年硕士论文

【摘要】：黄土高原是我国水土流失最严重的地区,也是水资源最为缺乏的地区之一,因而水资源成为该区生态恢复的关键因子。由于沟壑密度较大,切沟沟壁的侧面蒸发和土壤表面蒸发使得土壤水分蒸发强烈,该区的土壤水分条件进一步恶化。本文在野外调查和定位监测的基础上,研究了受到双面蒸发影响强烈的沟岸地土壤水分时空分布规律,得到如下结论：(1)沟岸地四个试验小区中的土壤水分含量整体较差,其大小顺序为柠条林地除去柠条后的裸地草地除去长芒草的裸地。双侧面蒸发条件下且东侧水分亏损比西侧更严重。沟壁的侧面蒸发作用致使沟岸地土壤水分整体较低,大部分接近萎蔫含水量,侧面蒸发作用对距沟壁距离为20 cm处土壤水分的影响最为显著,致使其含水量达到萎蔫含水量以下,其作用强度随距离增加而减弱。在双侧面蒸发条件下,水分横向分布与单侧面蒸发条件下土壤水分分布规律一致,东侧水分比西侧亏缺更严重。沟岸地各土层土壤储水量与距沟壁距离呈二次函数关系,二次多项式可以用于描述沟岸地土壤储水量的分布特征。由于沟岸地土壤水分情况较差,土壤含水量整体较低,各土层土壤含水量的均为弱变异,并且与其方差的线性相关性不显著。(2)沟岸地土壤在各深度的储水量变化趋势与降雨的变化趋势大体一致,即降雨量的增加的月份土壤储水量也较高。0-2 m土层土壤储水量的变化较剧烈,随着土层深度的增加受到降雨的影响减小,土壤储水量随时间的变化随之减小。横向来看,在受到降雨影响较大的0-2 m土层中,变化最强烈的的为除去长芒草的裸地,在该土层中各小区变异系数的大小顺序为：柠条林地除去柠条后的裸地草地除去长芒草的裸地,在3-4 m土层,各小区的变异系数大小顺序也满足这个关系。从图中也可以看出土壤沟岸地土壤在3m以下土层的变化较表层小,但也表现出随降雨量的变化而变化的趋势。各小区土壤水分的变异系数最小的土层为0-1 m,变异系数均小于20%,属于弱变异。而变异系数最大的土层为3-4 m,从时间上来看,雨季的土壤水分分布的变异系数较大,而旱季的较小。(3)距离沟壁2m范围内,土壤水分干湿交替强烈,土壤粘粒含量与土壤水分时间稳定性的相关性不显著。对于沟岸地土壤水分的时间稳定性,本文运用相对差分法发现则MRD的大小顺序为草地柠条裸地,分别为12.43%18.84%10.79%,同样的,SDRD的极差大小则为柠条草地裸地,分别为8.82%8.58%7.96%。KL和GL中0-1m和3-4 m土层中的极干点出现在距离沟壁较远的测点,而4m以上土层的极湿点则出现在距离沟壁较近处,但极干点不一定总是出现在距离沟壁较近的位置,这说明距离沟壁较近处不一定是测定范围内土壤水分最低的点,而是干湿交替最强烈的的点。SDRD和MRD与土壤粘粒含量的相关性不显著。(4)距沟壁距离的增加,20-80 cm土层土壤有机质呈降低趋势,而在表层则呈先减小后增加趋势。在双侧面蒸发条件下水分状况较好的沟岸地西侧有机质含量大于水分含量相对较差的东侧。双侧面蒸发条件下土壤速效钾的含量分布无显著差异,在单侧面蒸发条件下,距沟壁2m处0-20 cm土层土壤速效钾含量较高,其他土层无显著差异。(5)通过蒸发槽对三种边界条件下蒸发过程的模拟试验可以发现,侧面蒸发的蒸发量低于表面蒸发,双面蒸发的蒸发量高于表面蒸发。如果考虑降雨因素,双面蒸发对土壤水分的影响变得尤为显著。侧面蒸发的蒸发速率略小于表面蒸发,而双面蒸发的蒸发速率则明显大于表面蒸发。双面蒸发和侧面蒸发的蒸发量与表面蒸发的蒸发量的比值有先增加后降低,而后又出现增加的趋势。表面蒸发和侧面蒸发的蒸发量与双面蒸发存在显著的线性关系,可表示为：EA3=0.556EA1+0.489Ea2,.,在本实验中,温度对三种界面下的蒸发的蒸发量有显著相关性,降雨量和空气湿度对土壤储水量的变化量相关性显著；土壤储水量的值与温度和平均湿度相关性显著。
[Abstract]:The Loess Plateau is the most serious area of soil erosion in China, is also one of the regions most lack of water resources, and water resources become the key factor of ecological restoration in the area. Because of gully density, gully wall surface evaporation and soil evaporation makes the soil water evaporation, soil water conditions in the region further deterioration. Based on field investigation and monitoring on the studied by double evaporation strong gully land soil moisture distribution, we get the following conclusions: (1) the overall poor soil moisture content in the four experimental plots in the gully land, the size of the order for the removal of Caragana forest after bare grassland removal of Caragana long grass vegetation. Double side evaporation conditions and the water loss is more serious than west side. Evaporation trench wall soil water ditch bank is low, most close to Wilting moisture, evaporation from the side of the trench wall distance effect at 20 cm soil moisture is the most significant, the water content reached below the wilting point, its intensity decreases with increasing distance. In double side evaporation conditions, consistent distribution of soil moisture distribution and one side water evaporation conditions on the eastern side, water is more serious than the deficit. Gully land soil water storage with the distance from the trench wall distance is quadratic function relationship, two polynomial can be used to describe the distribution characteristics of gully land soil water storage. Due to poor gully land soil moisture, soil moisture content is low, the soil moisture of soil the water was weak and variation, linear correlation and variance is not significant. (2) the ditch bank soil roughly the same trend in the change trend of the water storage depth and rainfall, the rainfall increased month The change of soil water storage was also higher in.0-2 m soil water storage of soil is high, with the increase of soil depth under the influence of rainfall decreases, changes of soil water storage decreased with time. The lateral view, under the influence of rainfall of 0-2 m soil layer, the most change for the removal of grass of the bare land. In the soil in the area of coefficient of variation of the order of Caragana forest and grass vegetation removal remove bare grassland after Caragana, in order of size 3-4 m soil layer, the coefficient of variation of each district also meet this relationship. It also can change soil gully land in the soil layer below 3M the surface, but also exhibit changes with changes in rainfall and trend. The soil moisture variation coefficient of minimum soil was 0-1 m, the coefficient of variation was less than 20%, the variation is weak. The soil maximum coefficient of variation was 3 -4 m, from the time point of view, the rainy season variation coefficient of soil water distribution is larger, while the dry season is small. (3) from the trench wall in the range of 2m, soil moisture wetting strong, no significant correlation between soil clay content and soil moisture time stability. For the time stability of soil moisture to ditch the shore, the relative difference is found in the order of MRD grassland of Caragana bare land, respectively 12.43%18.84%10.79%, SDRD of the same size range, Caragana grass bare land, respectively 0-1m 8.82%8.58%7.96%.KL and GL in very dry and 3-4 m soil layer appeared in the distance measuring point of trench wall far above 4m, and the soil the wet point appears in the distance from the trench wall near, but do not always appear in the distance from the trench wall near the position, the distance is not necessarily the trench wall near the measuring range of soil moisture in the lowest point, but dry Wet alternate the strongest point between.SDRD and MRD and soil clay content was not significant. (4) increased from the trench wall distance, 20-80 cm soil organic matter decreased, and the surface was first decreased and then increased trend. In the double side evaporation conditions better water status in the West Bank the content of organic matter is greater than the moisture content is relatively poor on the east side. The double side soil available potassium evaporation under the condition of no significant difference in the distribution, single side evaporation conditions, away from the trench wall 2m 0-20 cm soil available potassium content is high, the other soil had no significant difference. (5) through the simulation test of three evaporation process the boundary conditions of the evaporation tank can be found, the evaporation side evaporation below the surface evaporation, evaporation double evaporation than the surface evaporation. If considering rainfall factors, effects of double evaporation on soil moisture became more and more obvious side. The evaporation rate of evaporation is slightly less than the surface evaporation, and evaporation rate of evaporation is significantly greater than the double surface evaporation. The ratio of evaporation and surface evaporation evaporation and evaporation of the double side evaporation is first increased and then decreased, and then increased. There is a significant linear relationship between evaporation and double surface evaporation and evaporation the side surface evaporation, can be expressed as: EA3=0.556EA1+0.489Ea2. In this experiment, there was a significant correlation between the three kinds of interface of the evaporation temperature of evaporation, precipitation and air humidity on the soil water content significantly; significant correlation between soil water and temperature and humidity value.

【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】：2015
【分类号】：S152.7

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