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题名: 黑河中游绿洲-荒漠过渡带水分运移过程研究
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.
内容类型: 学位论文
URI标识: http://ir.rcees.ac.cn/handle/311016/34367
Appears in Collections:环境化学与生态毒理学国家重点实验室_学位论文
城市与区域生态国家重点实验室_学位论文

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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.
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