黑河中游绿洲-荒漠过渡带水分运移过程研究
文献类型：学位论文
| 作者 | 沈亲 |
| 学位类别 | 博士 |
| 答辩日期 | 2015-05 |
| 授予单位 | 中国科学院研究生院 |
| 授予地点 | 北京 |
| 导师 | 傅伯杰 |
| 关键词 | 绿洲荒漠过渡带 土壤水分 植被蒸腾 水文联系 地下水 黑河流域，oasis - desert ecotone, soil water, plant transpiration, hydrological relations, groundwater, Heihe River Basin |
| 其他题名 | Water transport research in an oasis-desert ecotone of the middle of Heihe River Basin, China |
| 学位专业 | 生态学 |
| 中文摘要 | 水资源在干旱内陆河流域绿洲 -荒漠生态系统的发展与稳定发挥了重要作用。由于不合理开发利用，水资源短缺导致一系列生态环境恶化问题。水资源利用的改变，会引起水文循环过程的变化，最终导致生态系统的退化。土壤水和植物耗水是土壤-植物-大气连统体的关键因子，是生态水文过程中的主要变量，了解土壤水动态变化与植物耗水规律，有助于了解干旱区绿洲生态系统水分循环过程，为水资源合理利用以及绿洲农业生态系统的稳定和可持续发展提供科学依据。本文选取黑河中游绿洲-荒漠过渡带典型景观格局农田-防护林-荒漠作为研究对象，分析土壤水分动态变化特征和各景观单元中植被用水特征，揭示不同景观单元之间水文联系，对于黑河绿洲-荒漠生态系统管理和水资源分配具有重要理论和实践意义。 在玉米地-甘肃杨防护林-荒漠柠条相邻的样地中均匀布设土壤水分监测样点，在防护林中选取 8棵代表性甘肃杨，用热扩散法测定树干液流速率，同时，在各景观单元中各布设一口地下水位观测井，测定地下水位埋深。基于2012-2014连续3年的观测数据，首先分析不同景观单元土壤水分动态变化特征，结合时间稳定性方法，确定各景观单元最能代表样地平均值的样点。其次，分析防护林树干液流和蒸腾规律及主要影响因子，揭示干旱和地下水位动态对防护林蒸腾的影响，确定防护林蒸腾的主要水分来源。最后，基于水量平衡原理，确定防护林从农田中吸取的水量，农田灌水对防护林蒸腾的影响距离，揭示防护林与农田的水文联系。主要结论如下： （1）农田-防护林-荒漠中各景观单元土壤含水量剖面分布出现明显的分层特征。上层 0-200cm土壤深度，土壤含水量表现为农田（10.19%）>防护林（7.46%）>荒漠（5.64%）。下层200-280cm土壤深度，土壤含水量表现为防护林（19.51%） >荒漠（18.31%） >农田（15.46%）。由于农田灌溉，上层含水量大于防护林和荒漠。深层，农田无根系分布，灌溉水通过渗漏补给地下水，而防护林和荒漠植物根系，通过“水力提升”作用吸收地下水，水分补给导致下层土壤水分含量高于农田。各景观单元，深层土壤含水量（240-280 cm）的变异系数均最小，表层 0-20 cm变异系数较大，而 160-240 cm土层变异系数最大。农田和防护林 0-160 cm土壤水分有明显的脉冲特征，农田土壤水分减少速率（0.45–0.70%/day）大于防护林（0.32–0.47%/day）。受到根系分布影响，以及土壤蒸发的深度，土壤含水量减少速率随着土壤深度的增加而降低，农田土壤水分减少速率大于防护林。较小田间尺度，用相对偏差获得代表性样地平均值较相对偏差标准差结果更理想。由于 160-240 cm受地下水和灌溉水共同作用影响，稳定性最差。各景观单元，不同土壤深度，代表性样点位置不一。 （2）树干液流日平均速率变化范围为 30.62±11.44~101.88±28.98kgm-2 h-1，并随树木胸径呈线性增加。树干液流速率日均值与太阳辐射、大气温度、相对湿度、水汽压亏缺、相对可提取含水量以及地下水位埋深有显著相关关系（p< 0.05），且相关性大小顺序依次为：太阳辐射>水汽压亏缺>大气温度>相对可提取含水量>地下水位埋深>相对湿度。回归分析结果表明，树干液流速率与太阳辐射和大气温度呈线性增加趋势，与相对湿度和地下水位埋深呈线性降低趋势，而与水汽压亏缺呈对数增加趋势，与相对可提取含水量 没有明确的定量关系。 （3）2012-2014年生长季（5.22-9.21），防护林日平均蒸腾量分别为4.82mm、4.95mm和4.71 mm，总蒸腾量分别为594 mm、609 mm和 574 mm。降雨不能显著增加林分蒸腾（paired t-test, p < 0.05），土壤水分的改变如灌溉可以显著增加冠层导度和蒸腾量（t-test, p < 0.05）。土壤水分状况可明显影响冠层导度对水汽压亏缺的敏感性，土壤水分状况越好，敏感性越高。地下水位波动方法计算的地下水蒸腾量（0.6-7.1 mm day-1）有显著线性相关关系（p<0.05），且地下水蒸腾量占干旱期防护林蒸腾量的 80%。 （4）农田灌溉产生的深层渗漏，引起地下水位的抬升，补给防护林和荒漠），与树干液流计算的防护林蒸腾量（1.1-6.5 mm day-1 底层土壤水分，各景观单元间通过地下水的运移发生水文联系。荒漠和防护林之间，没有明显的水分交换关系。防护林在农田中根系分布呈对数降低趋势，且集中在 160 cm以上。距防护林越远，农田中土壤贮水量越大。选取农田中不同位点，距防护林和农田交接处分别为13 m、5 m和1m，得到防护林根系吸收水分占农田灌溉和降雨量比值在 2012年分别为5.94%、10.21%和 26.47%，在 2013年分别为 0.77%、5.53%和 22.71%。农田灌溉对防护林蒸腾的影响距离为 8 m。 本文应用生态水文的方法分析探讨绿洲边缘的农田 -防护林-荒漠体系土壤水分动态变化以及植被用水特征及其水分来源，为绿洲生态系统稳定可持续发展提供基础理论意义，也为黑河流域农业水管理等水资源分配制度提供参考借鉴作用，有利于绿洲生态系统景观结构与格局的优化。 |
| 英文摘要 | Water resources play a critical role in the development of the oasis - desert ecosystem in arid inland river basin. Due to the unreasonable utilization, water shortages have led a series of ecological and environmental deterioration. oil water and plant water consumption are the key factors of the soil - plant - atmosphere continuum, and they are the main variables in the water process. The knowledge of soil water dynamics and plant water uses will be useful in the understanding of the hydrological processes of the oasis ecosystem in arid areas, providing scientific basis for the rational utilization of water resources as well as the stable and sustainable development of oasis agriculture ecosystem. This study considered the cropland-treebelt-desert system in the arid inland river basin as an entire continuum to investigate the soil water content variations and plant water use characteristics. The knowledge of the hydrological relations between different land uses are essential for ecosystem management and water resources distribution in arid inland river basin. The volumetric soil water content was measured to 300 cm depth along a cropland-treebelt-desert site at the oasis-desert ecotone in the Heihe River Basin,China. Sap flow was measured by the thermal dissipation method on eight Gansu Poplar (Populus gansuensis) trees with different diameter at breast height, and water table depth was monitored in each land use over the three consecutive growing seasons (2012-2014). The objectives were to 1) study the soil water variations and choose the representative locations with the temporal stability of soil water content,which could represent the mean soil water content of each land use, 2) investigate the influences of meteorological factors, soil water and water table depth on sap flow of Gansu Poplar, evaluate the response of treebelt stand transpiration to drought and groundwater, and identify the roles of different water use sources of Gansu Poplar, 3)to calculate the water absorption of treebelt from the cropland according to the maize evapotranspiration and soil water variations by water balance method at different locations in the cropland away from the treeblet, and determine the effects of cropland irrigation on treeblet transpiration. The following conclusions could be summarized: (1) The vertical distribution of the mean soil water content could be mainly divided into two layers. The mean soil water content in the 0-200 cm layer was greater in the cropland (10.19%) than that in the treebelt (7.46%) and desert (5.64%)as a result of frequent irrigation events. However, the cropland had oticeably lower mean soil water content below 200 cm depth (15.46%), compared to treebelt (19.51%)and desert (18.31%) with deeper roots to suck up groundwater through hydraulic lift.The coefficient of variation was lowest at the depth of 240-280 cm, whereas, it was greatest at the depth of 160-240 cm due to the combine effects of irrigation and groundwater. The coefficient of variation was lower in the cropland than that in the treebelt and desert. The decline process in soil water content pulse of the cropland and treebelt after irrigation event could be well described by an exponential decay function, and the soil water loss rate was greater in the cropland (0.45–0.70%/day)than that in the treebelt (0.32–0.47%/day). The soil water loss rater decreased with the increase of soil depth because of the root distribution and soil evaporation. The temporal stability of soil water content spatial pattern showed that in small field scale,the mean relative difference analysis was better than standard deviation of relative differences analysis to obtain representative location. The soil water content at the depth of 160-240 cm was most unstable due to the comprehensive effect of irrigaiton and groundwater. No single location could represent the spatial mean soil water content of different soil layers simultaneously for each land use. (2) The sap flow density of individual sample trees showed significant differences (p< 0.01), with the value ranging from 30.62±11.44 to 101.88±28.98 kg m-2h-1. The mean sap flow density increased linearly with diameter at breast height.The evaluation of stand tranpiration could be obtained by the diameter at breast height. The mean sap flow density was significantly correlated with solar radiation, air temperature, relative humidity, vapor pressure deficit, relative extractrable water and water table depth (p < 0.05). The order of the main environmental factors affecting the sap flow density were solar radiation > vapor pressure deficit > air temperature > relative extractrable water > water table depth > relative humidity. The mean sap flow density exhibited linear relationship with solar radiation and air temperature, and it increased logarithmically with vapor pressure deficit, whereas the water table depth and relative humidity had negative impact on sap flow. The relationship between sap flow and soil relative extractable water was implicit. (3) The mean stand transpiration was 4.82 mm (2012), 4.95 mm (2013) and 4.71 mm (2014). Total stand transpiration was 594 mm、609 mm和 574 mm during the growing periods from May 22 to September 21. Precipitation increased the stand transpiration but not statistically significant (paired t-test, p > 0.05). The recharge of soil water by irrigation caused stand transpiration and canopy conductance acceleration significantly (t-test, p < 0.05).Stand transpiration and canopy conductance increased by 27% and 31%, respectively, when soil water conditions changed from dry to wet. Canopy conductance decreased logarithmically with vapor pressure deficit, while there was no apparent relationship between canopy conductance and solar radiation. The sensitivity of canopy conductance to vapor pressure deficit decreased under dry soil conditions. Groundwater evapotranspiration, based on the water table fluctuation (WTF) method, was linearly correlated with stand transpiration (R2 = 0.71), and these two variables had similar variability. During the drought period, approximately 80% of total stand transpiration came fromgroundwater. (4)The hydrological relation in the lower soil layer among cropland-treebelt-desert was caused by groundwater recharge, as cropland irrigation raised up the groundwater level to replenish the deep soil layer. The hydrological relation between treebelt and desert was not apparent. The treebelt root extending to the cropland could be well described by a logarithmic decay function, and focused on the upper soil layer at the depth of 0-160 cm. With the increase of distance from the treebelt, soil water storage increased.Besides cipitation,irrigation and groundwater, the cropland irrigation was an important water source of shelter-belt,which could influence the tree transpiration within a threshold distance of about 8 m.The water absorped from the cropland accounted for cropland irrigation amount and precipitation were 5.94%、10.21% and 26.47% in 2012, and 5.85%、9.65% and 21.73% in 2013, respectively at different points from the edge of the cropland (1m,5m and 13 m). The application of ecohydrological method to analyze the soil water content dynamics and plant water use characteristics along the cropland – treebelt – desert landscape pattern at the edge of the desert - oasis system is very useful for the sustainable and stability development of the oasis agriculture ecosystem, and provides the basis theory for the water resources management of the Heihe River Basin, which is beneficial to the optimization of landscape structure and pattern of the oasis ecosystem. |
| 源URL | [http://ir.rcees.ac.cn/handle/311016/34367]  |
| 专题 | 生态环境研究中心_城市与区域生态国家重点实验室 生态环境研究中心_环境化学与生态毒理学国家重点实验室 |
| 推荐引用方式 GB/T 7714 | 沈亲. 黑河中游绿洲-荒漠过渡带水分运移过程研究[D]. 北京. 中国科学院研究生院. 2015. |
入库方式： OAI收割
来源：生态环境研究中心
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