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基于稳定同位素的塔河典型植物水分来源和蒸散发组分分割研究
王勇
Subtype硕士
Thesis Advisor赵成义
2018-06-01
Degree Grantor中国科学院大学
Place of Conferral新疆乌鲁木齐
Degree Discipline理学硕士
Keyword稳定氢氧同位素 水分来源 蒸散发 植物蒸腾 土壤蒸发 Hydrogen And Oxygen Stable Isotopes Source Of Water Evapotranspiration Plant Transpiration Soil Evaporation
Abstract

蒸散发是陆地生态系统水分耗散的重要途径,与陆地植被总生态系统生产量密切相关。干旱区陆地生态系统水文过程的动态变化取决于植物水分利用和植物水分利用效率。 识别地表植被水分来源, 明确地表生态系统中非生产性(裸地蒸发)与生产性水分损失(蒸腾)的相对量,是探明干旱地区水分耗散过程的关键。本文结合相关气象资料和实测数据,研究了塔里木河流域降水 δD 和 δ18O 时空变化特征, 分析了大气降水同位素分馏特征和影响因素;结合当地大气水线特征,对不同林龄胡杨和柽柳的蒸腾进行了水源分割, 定量确定了蒸腾耗水的来源。利用蒸腾和蒸发同位素特征不同对不同地下水埋深地表蒸散发组分进行水文分割,并结合水量平衡方法验证了同位素方法分割结果; 结合植物生长指标测定以及同位素特征值定量识别不同地下水埋深地表蒸散发及其组分的耗水来源。主要研究结果如下:(1) 塔里木河流域地区大气降水线方程(LMWL)为 δD=6.9218O+5.58(n=38,R2=0.94),斜率和截距分别为 6.98 和 5.58,均显著低于全球、全国以及新疆地区大气水线。该地区大气降水同位素特征具有明显的年际变化和月际变化,呈现出 5-6 月份低, 7-8 月份高的特点, δ2H 和 δ18O 的变化过程基本一致。 塔里木河流域降水 δ18O 和 δD 与空气温度存在正相关关系, 温度效应较为明显, 相关方 程 分 别 为 : δ18O=0.78T-17.88 (R2=0.35, n=38) 和 δD=5.46T-119.03(R2=0.36,n=34)。大气降水的氘盈余变化范围为-15.23‰~24.24‰,均值为 8.25‰,小于全球降水线方程的截距 10,氘盈余变化范围较大说明大气降水水汽来源区湿度和蒸发非平衡分馏程度变化大。(2) 研究区植物水和土壤水的降水偏离值分别为-8.57 和-6.88, 与地下水的降水偏离程度(-1.89) 存在显著差异(P<0.05), 表明大气降水补给各水源过程中会发生生态水分分离现象, 存在两个不均一、不完全混合的水源库, 分别维持植物需水耗水和地下水补给。 不同林龄胡杨和柽柳水分利用来源存在差异,吸水层位随林龄增加而加深。胡杨幼苗和成熟木主要利用 0-60cm 浅层土壤水,利用比例达到 53.4%,平均吸水深度为 33.77cm;成熟胡杨和柽柳幼苗可能存在水分竞争关系, 二者主要水分来源均为 30-100cm 土壤水和地下水, 具体利用比例略有差异,平均吸水深度分别为 65.71cm 和 46.54cm;成熟柽柳则主要利用深层土壤水和地下水, 利用比例达到 61.9%。无论在幼苗阶段或成熟阶段,柽柳水分利用层位均低于胡杨, 对干旱环境的适应性更强。(3) 整个试验阶段胡杨的蒸腾量随地下水埋深增加而增加, 且占地表蒸散量的比重不断增加,最大值达到 77.55%, 蒸散量达到最大值 62.62mm。当地下水埋深浅于 100cm 时, 土壤蒸发比重较高, 植物水分耗散仅来源于表层土壤,可消耗量小, 使得土壤蒸发成为浅地下水埋深条件下主要的水分耗散形式, 胡杨蒸腾占地表蒸散的比重低于或近似于 50%,地表耗水以土壤蒸发为主;当地下水埋深低于 100cm 时,地表水分耗散形式以植物蒸腾为主。 柽柳蒸腾量在 100cm 地下水埋深处达到最大值,且后期蒸腾量远高于前期。试验前期,柽柳的蒸腾蒸散比重(mt/me) 均低于 50%, 各地下水埋深下柽柳地表蒸散发以土壤蒸发的形式为主;试验后期, 当地下水埋深低于 100cm 时, 地表耗水以植物蒸腾为主。与胡杨相比, 试验前期柽柳地表蒸散发量低于胡杨,且蒸腾量较小, mt/met 的值较低。

Other Abstract

Evapotranspiration is an important part of the water balance of ecosystems, and itis also an important way for water dissipation in ecosystems. The dynamic changes inthe hydrological processes of the ecosystem in arid regions depend on the plant wateruse efficiency and the plant water use efficiency. Determining the source of moisturefor surface water dissipation and clarifying the relative amounts of non-productive(bare-ground evaporation) and productive-type water loss (transpiration) in naturalecosystems is the key to ascertaining the process of water dissipation in arid regionsand for better understanding. It is necessary to clarify the water use of plants and thelaws of surface water and groundwater dissipation, and to increase the utilization rateof water resources. In this paper, the transpiration of Populus euphratica and Tamarixramosissima water source segmentation to quantitatively identify the source oftranspiration water consumption. Transpiration and evaporation isotopes are used tohydrologically segment evapotranspiration components in different groundwaterdepths, and the results of isotope method segmentation are verified by combining waterbalance methods; combined with the determination of plant growth indexes andquantitative identification of different groundwater depths for the quantification ofisotope characteristics. The result is as follows:(1)The atmospheric precipitation line equation (LMWL) in the upper reaches ofthe Tarim River is δD=6.92δ18O+5.58 (N=38, R2=0.94), and the slope and intercept are6.98 and 5.58, respectively, both significantly lower than those of the wholeworld,country, as well as the atmospheric waterline of Xinjiang. It shows that watervapor is affected by the secondary evaporation fractionation during the process ofcondensation and precipitation falling to the ground. The isotope characteristics ofatmospheric precipitation in the region have obviously interannual and inter-monthlychanges, showing the low characteristics in May to June and high in July to August.The changes of δ2H and δ18O are basically consistent with the precipitation of δ18O andδD in the upper reaches of the Tarim River. There is a positive correlation between temperature and temperature effect. The correlation equations are: δ18O=0.78T-17.88(R2 = 0.35, n=38) and δD = 5.46T-119.03 (R2 = 0.36, n=34). The effect of precipitationis not significant. The mean value is 8.25‰, which is less than the intercept 10 of theglobal precipitation equation. The larger range of d-excess surplus shows that thehumidity and the non-equilibrium fractional fraction of evaporation in the atmosphericwater vapor source region vary greatly.(2) The precipitation deviations of plant water and soil water in the study area were-8.57 and -6.88, respectively, which were significantly different from the precipitationdepreciation (-1.89) of groundwater (P<0.05), indicating that the atmosphericprecipitation will be recharged in the course of various water sources. The phenomenonof ecological water separation occurs. There are two water pools that are nothomogeneously and incompletely mixed, which respectively maintain waterconsumption and groundwater recharge. There were differences in water use sources ofPopulus euphratica and Tamarix ramosissima at different ages, and the waterabsorption depth increased with the forest age increasing. Populus euphratica seedlingsand mature woods mainly use 0-60cm shallow soil water, and the utilization ratio is53.4%. The average water absorption depth is 33.77cm. There may be watercompetition relationship between the mature Populus euphratica and Tamarixramosissima seedlings, and the main source of both water is 30-100cm soil. For waterand groundwater, the specific utilization ratio is slightly different. The average waterabsorption depth is 65.71cm and 46.54cm respectively. For mature Tamarixramosissima, deep soil water and groundwater are mainly used, and the utilization ratioreaches 61.9%. No matter the seedling stage or mature stage, the water use layer ofTamarix ramosissima was lower than that of Populus euphratica and its adaptability toarid environment was stronger.(3) The transpiration of Populus euphratica increased with the increase ofgroundwater depth during the whole experiment period, and the proportion of surfaceevapotranspiration increased continuously. The maximum value reached 77.55%, andthe evapotranspiration reached a maximum of 62.62mm. When the depth ofgroundwater is shallower than 100cm, the surface soil strongly evaporates.The transpiration of plant water comes from the topsoil only, and the consumption is small,making the soil evaporation the main water dissipation form under shallowgroundwater depth conditions. The transpiration of the Populus euphratica accountsfor the surface evapotranspiration. The proportion is less than or close to 50%, and thesurface water consumption is mainly based on soil evaporation. When the groundwaterdepth is deeper than 100cm, the surface water dissipation pattern is mainly planttranspiration. The transpiration of Tamarix ramosissima reaches its maximum at thegroundwater depth of 100cm, and the transpiration is much higher than the previousperiod. At the early stage of the experiment, the mt/met of Tamarix ramosissima arebelow 50%, and the evapotranspiration of Tamarix ramosissima is mainly based on theform of soil evaporation at the depth of each groundwater. At the later stage of theexperiment, when the groundwater depth was less than 100cm, the surface waterconsumption was dominated by plant transpiration. Compared with Populus euphratica,the surface evapotranspiration of Tamarix ramosissima was lower than that of Populuseuphratica, and the transpiration was smaller and the mt/met value was lower.

Subject Area生态学
Language中文
Document Type学位论文
Identifierhttp://ir.xjlas.org/handle/365004/14995
Collection研究系统_荒漠环境研究室
Recommended Citation
GB/T 7714
王勇. 基于稳定同位素的塔河典型植物水分来源和蒸散发组分分割研究[D]. 新疆乌鲁木齐. 中国科学院大学,2018.
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