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极端干旱区胡杨根系吸水模型的构建
王玉阳
学位类型硕士
导师陈亚鹏
2017-05-01
学位授予单位中国科学院大学
学位授予地点新疆乌鲁木齐
学位专业理学硕士
关键词塔里木河下游 胡杨 根系分布 根系吸水模型 The lower reaches of Tarim River Populus euphratica root distribution root water uptake models
摘要Roots(mainly <=2 mm in diameter) are the pathway for soil water uptake by plants, the uptake of water by roots directly control the physiological activities of the whole plant.Root water uptake models provide a mathmatical tool for quantiatively understanding this process,which is the basis of studying the source and consumption of water of the plant, besides, it is also a crucial part of some ecohydrological research modules. So,the construction research of root water uptake models in extremely arid region can provide reference for quantitative study of water source of Populus euphratica, and it is helpful to understand the water use strategy of Populus euphratica. This research provides scientific basis for the protection and restoration of Populus euphratica in the lower reaches of Tarim River.This research selected desert riparian forest vegetation Populus euphratica at the lower reaches of Tarim River as the research object,we establish monitoring plot far away from the river and near the river respectively at Kumutuge.At each plot, two Populus euphratica were selected, we used neutron probe to detect the dynamic changes of soil water content in root zone , and cross section excavation for fine root sampling , at the same time, we combined with the relevant meteorological data, soil texture data etc.., based on the framework of Feddes model to construct the root water uptake model of Populus euphratica . The main results of the study as follows:1. At the same plot, the soil water content in the root zone of Populus euphratica had the same characteristics in the vertical direction, but there was considerable difference between different plot. Because of the little precipitation in the lower reaches of Tarim River, the soil water supply and the transpiration rate of plants almost did not change in a short period of time. Therefore, in this study, the overall trend of soil moisture in the root zone of Populus euphratica during the monitoring period (20 days) did not change significantly with time.2. There were no fine root growth at the soil surface, the fine roots of Populus euphratica in the river and far away from the river began to appear in 40cm and 80cm soil respectively. And fine roots showed a consistent distribution characteristics, that is, no fine roots at the surface, with the increase of soil depth showed a single peak pattern of the first increase and then decrease. In the horizontal direction, there was no significant change in the distribution of fine roots within the range of 6m from Populus euphratica trunk at the both site (P>0.05). In the vertical direction, the maximum root length density and fine root densely distribution area were more shallow than that of the river.3. The soil water content is the most important factor determining the distribution of fine roots in the lower reaches of Tarim River, the absence of fine roots in the soil surface is due to the coupling effect of low water content and high salt content. Because of the limitation of soil water and salt, the soil organic matter, available nitrogen and PH have little effect on the distribution of fine roots.4. The compensation water uptake process is weak in model simulation. After removing the compensation term, we adjusted the models at both sites and established the root water uptake models of Populus euphratica .That is :
其他摘要植物依靠根系(主要是直径<=2mm的细根)从土壤中吸收所需水分,根系吸水是植物水分运输系统的最初端,直接控制着整株植物的生理活动。根系吸水模型是用定量化手段研究植物根系吸水的数学模拟工具,是研究植物水分来源、耗水量的基础,同时也是一些生态水文研究模块的重要组成部分。因此,对极端干旱区胡杨根系吸水模型的构建研究,可为胡杨水分来源的定量化研究提供方法参考,并有助于理解荒漠河岸植物胡杨的水分利用策略,可为塔里木河下游胡杨林的保护和恢复提供科学依据。本研究选取塔里木河下游荒漠河岸林建群种胡杨为研究对象,在库木吐格断面河边和远离河道处各建立一胡杨监测样地,分别选取两棵生长较一致的胡杨,采用中子仪法监测胡杨根区土壤水分的动态变化特征、十字剖面开挖的方法进行细根取样,同时结合相关的气象数据、土壤质地等数据以Feddes模型框架为基础构建干旱区胡杨的根系吸水模型。主要结果如下:1. 在同一样地处,胡杨根区土壤水分在垂直方向上具有较一致的特征,而不同样地之间存在较大差异。由于塔里木河下游降水稀少,土壤水的补给情况、植物的蒸腾速率在较短时间段内几乎不发生变化,因此,在本研究中河边和远离河道处的胡杨根区土壤水分在监测期间(20天内)整体趋势随时间都未发生显著变化。2.无论是河边还是远离河道处,土壤表层均没有胡杨细根出现,河边和远离河道处胡杨细根分别在40cm和80cm深的土壤中开始出现;并且两处细根都呈现出一致的分布特征,即表层无细根,随着土壤深度的增加呈现出单峰型的先增加后减小的分布模式。在水平方向上,在距胡杨树主干6m范围内,两样地处胡杨细根分布量没有显著变化(P>0.05)。在垂直方向上,河边胡杨的最大根长密度和细根密集分布区域都比远离河道处浅。在160cm土壤深度以上,河边胡杨细根的分布量明显大于远离河道处(P<0.01),而在160cm以下两者趋于接近;而在水平方向上河边胡杨细根明显大于远离河道处(p<0.01)。3. 在塔里木河下游土壤水分含量是决定胡杨细根分布的最重要因素,土壤表层无细根出现正是由于表层土壤低含水量与高含盐量共同耦合作用造成的。在极端干旱区,由于表层土壤水盐的限制,使得土壤有机质、速效氮、PH对细根分布影响微弱。4、补偿吸水过程在模型模拟过程中表现微弱。去除补偿吸水项后,分别对远离河道处与河边的模型调参,将模型调参获得的不同最优参数分别带入对应的模型中。经验证得到远离河道处实测土与模拟土壤含水量拟合的决定系数R2为0.557,均方根误差RMSE为0.085,纳什效率系数为0.49;河边实测与模拟土壤含水量决定系数R2为0.551,均方根误差RMSE为0.064,纳什效率系数为0.481。模型模拟的效果尽管不是很好,但具有一定的说明性,具有一定的参考意义。经过调参检验修正后建立的胡杨根系吸水模型为,S1(z)和 S2(z)分别代表远离河道处和河边:
学科领域自然地理学
语种中文
文献类型学位论文
条目标识符http://ir.xjlas.org/handle/365004/14904
专题研究系统_荒漠环境研究室
作者单位中国科学院新疆生态与地理研究所
第一作者单位中国科学院新疆生态与地理研究所
推荐引用方式
GB/T 7714
王玉阳. 极端干旱区胡杨根系吸水模型的构建[D]. 新疆乌鲁木齐. 中国科学院大学,2017.
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