青海湖流域高寒草甸壤中流水分来源研究
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摘要
通过对青海湖流域高寒草甸壤中流水分来源进行研究,以期揭示青海湖流域高寒草甸系统壤中流的产流机制。收集了大气降水、土壤水和壤中流中δ~(18)O和δD及实测降水数据,对比分析了大气降水、土壤水和壤中流的氢氧同位素特征,并使用了二源线性混合模型对壤中流进行了产流来源计算。结果表明:青海湖高寒草甸分布区大气降水线(LMWL)的斜率和截距均高于全球大气降水线(GMWL),降水较多的月份δ~(18)O、d-excess值较低;壤中流的水分来源与地形及其土壤深度密切相关,具体表现为:(1)壤中流在坡下土壤上层(0—40cm)和下层(40—80cm)产流氢氧同位素值相对聚集,并具有较明显的蒸发富集特征,表明该部分壤中流多源于降雨前储存于土壤中的水分,雨前土壤水对于壤中流在坡下土壤上层(0—40cm)和下层(40—80cm)产流的平均贡献率为85.88%和83.48%;(2)坡中壤中流水分来源因土壤深度而异,雨前土壤水对壤中流在坡中土壤下层(40—80cm)产流的平均贡献率为57.59%,表明大气降水和雨前土壤水贡献相当;壤中流在坡中土壤上层(0—40cm)产流与当地大气降水的季节变动基本一致,雨前土壤水对该层壤中流产流的平均贡献率为39.90%,表明其主要受到大气降水的驱动,与坡中金露梅灌丛根系和土壤孔隙分布有关。同时,随着雨前含水量、降水量和降水特征的不同,雨前土壤水和大气降水对于壤中流的贡献特征也会发生变化。
Based on the study about the water sources of subsurface flow in alpine meadow of the Qinghai Lake basin,the mechanism of subsurface flow generation in alpine meadow system of the Qinghai Lake basin was expected to be revealed.This paper collected δ~(18)O andδD of atmospheric precipitation,soil water and subsurface flow,as well as the observed atmospheric precipitation data,to make a comparative analysis of hydrogen and oxygen isotopic characteristics of atmospheric precipitation,soil water and of subsurface flow,and used the second source linear mixed models to calculate the water sources of subsurface flow.The results showed that the slope(8.72)and intercept(25.09)of LMWL(local meteoric water line)were evidently larger than those of GMWL(global meteoric water line);the relatively lower d-excess values and δ~(18)O were observed in months with small precipitation amount;the sources of subsurface flow were closely related to topography and soil depth,and the specific performances were as follows:(1)The hydrogen and oxygen isotope values of subsurface flow relatively aggregated in the upper layer(0—40cm)and lower layer(40—80cm)of downslope soil,and showed obvious characteristics of evaporation and enrichment,which indicated that this part of the subsurface flow mostly came from the water that stored in soil before the rain,and the average contribution rates of the soil water before rain for subsurface flow in the upper layer(0—40cm)and lower layer(40—80cm)of downslope soil were 85.88% and 83.48%,respectively;(2)The water sources of middleslope subsurface flow varied with the soil depth,and the average contribution rate of the soil water before rain for subsurface flow inthe lower layer(40—80cm)of soil was 57.59%,which indicated that the contributions of atmospheric precipitation and soil water before rain were equal.The seasonal changes ofδ~(18)O andδD of middleslope subsurface flow in the upper layer(0—40cm)of soil were similar with those of the atmospheric precipitation,and the average contribution rate of the soil water before rain for subsurface flow in the lower layer(40—80cm)of soil was only 39.90%,indicating that it was mainly driven by atmospheric precipitation,which was related with soil porosity distribution and the roots of Potentilla fruticosa in the middleslope.Meanwhile,the contribution rate of the soil water before rain and atmospheric precipitation for subsurface flow would change with the soil water content before rain,precipitation amount and precipitation characteristics.
Based on the study about the water sources of subsurface flow in alpine meadow of the Qinghai Lake basin,the mechanism of subsurface flow generation in alpine meadow system of the Qinghai Lake basin was expected to be revealed.This paper collected δ~(18)O andδD of atmospheric precipitation,soil water and subsurface flow,as well as the observed atmospheric precipitation data,to make a comparative analysis of hydrogen and oxygen isotopic characteristics of atmospheric precipitation,soil water and of subsurface flow,and used the second source linear mixed models to calculate the water sources of subsurface flow.The results showed that the slope(8.72)and intercept(25.09)of LMWL(local meteoric water line)were evidently larger than those of GMWL(global meteoric water line);the relatively lower d-excess values and δ~(18)O were observed in months with small precipitation amount;the sources of subsurface flow were closely related to topography and soil depth,and the specific performances were as follows:(1)The hydrogen and oxygen isotope values of subsurface flow relatively aggregated in the upper layer(0—40cm)and lower layer(40—80cm)of downslope soil,and showed obvious characteristics of evaporation and enrichment,which indicated that this part of the subsurface flow mostly came from the water that stored in soil before the rain,and the average contribution rates of the soil water before rain for subsurface flow in the upper layer(0—40cm)and lower layer(40—80cm)of downslope soil were 85.88% and 83.48%,respectively;(2)The water sources of middleslope subsurface flow varied with the soil depth,and the average contribution rate of the soil water before rain for subsurface flow inthe lower layer(40—80cm)of soil was 57.59%,which indicated that the contributions of atmospheric precipitation and soil water before rain were equal.The seasonal changes ofδ~(18)O andδD of middleslope subsurface flow in the upper layer(0—40cm)of soil were similar with those of the atmospheric precipitation,and the average contribution rate of the soil water before rain for subsurface flow in the lower layer(40—80cm)of soil was only 39.90%,indicating that it was mainly driven by atmospheric precipitation,which was related with soil porosity distribution and the roots of Potentilla fruticosa in the middleslope.Meanwhile,the contribution rate of the soil water before rain and atmospheric precipitation for subsurface flow would change with the soil water content before rain,precipitation amount and precipitation characteristics.
引文
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[19]伊万娟,李小雁,崔步礼,等.青海湖流域气候变化及其对湖水位的影响[J].干旱气象,2010,28(4):375-383.
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[21]Scholl M A,Shanley J B,Murphy S F,et al.Stable-isotope and solute-chemistry approaches to flow characterization in a forested tropical watershed,Luquillo Mountains,Puerto Rico[J].Applied Geochemistry,2015,63(1):484-497.
[22]张英虎,牛健植,朱蔚利,等.森林生态系统林木根系对优先流的影响[J].生态学报,2015,35(6):1788-1797.
[23]王锐,刘文兆,宋献方.黄土塬区土壤水分运动的氢氧稳定同位素特征研究[J].水土保持学报,2014,28(3):134-137.
[2]Mueller M H,Alaoui A,Kuells C,et al.Tracking water pathways in steep hillslopes byδ18 O depth profiles of soil water[J].Journal of Hydrology,2014,519(1):340-352.
[3]郑海金,胡建民,黄鹏飞,等.红壤坡耕地地表径流与壤中流氮磷流失比较[J].水土保持学报,2014,28(6):41-45.
[4]谢颂华,涂安国,莫明浩,等.自然降雨事件下红壤坡地壤中流产流过程特征分析[J].水科学进展,2015,26(4):526-534.
[5]丁文峰,李勉.不同坡面植被空间布局对坡沟系统产流产沙影响的实验[J].地理研究,2010,29(10):1870-1878.
[6]卢修元,魏新平,王君勤.土壤容重对溶质迁移过程的影响[J].水土保持通报,2013,33(2):26-29.
[7]谢小立,尹春梅,陈洪松,等.基于环境同位素的红壤坡地水分运移研究[J].水土保持通报,2012,32(3):1-6.
[8]Boulet A K,Prats S A,Malvar M C,et al.Surface and subsurface flow in eucalyptus plantations in north-central Portugal[J].Journal of Hydrology and Hydromechanics,2015,63(3):197-204.
[9]鲁春霞,谢高地,肖玉,等.青藏高原生态系统服务功能的价值评估[J].生态学报,2005,24(12):2749-2755.
[10]周笃珺,马海州,山发寿,等.青海湖流域及周边地区的草地资源与生态保护[J].资源科学,2006,28(3):94-101.
[11]李婧,杜岩功,张法伟,等.草毡表层演化对高寒草甸水源涵养功能的影响[J].草地学报,2012,20(5):836-841.
[12]张思毅.青海湖流域典型生态系统地表能量收支与蒸散发研究[D].北京:北京师范大学,2014.
[13]Robinson D A,Binley A,Crook N,et al.Advancing process-based watershed hydrological research using near-surface geophysics:A vision for,and review of electrical and magnetic geophysical methods[J].Hydrological Processes,2008,22(18):3604-3635.
[14]Dusek J,Vogel T,Sanda M.Hillslope hydrograph analysis using synthetic and natural oxygen-18signatures[J].Journal of Hydrology,2012,475(12):415-427.
[15]Cui B L,Li X Y.Characteristics of stable isotopes and hydrochemistry of river water in the Qinghai Lake Basin,northeast Qinghai-Tibet Plateau,China[J].Environmental Earth Sciences,2014,73(8):4251-4263.
[16]赵国琴,李小雁,吴华武,等.青海湖流域具鳞水柏枝植物水分利用氢同位素示踪研究[J].植物生态学报,2013,37(12):1091-1100.
[17]吴华武,李小雁,赵国琴,等.青海湖流域降水和河水中δ18 O和δD变化特征[J].自然资源学报,2014,29(9):1552-1564.
[18]Cui B L,Li X Y.Runoff processes in the Qinghai Lake Basin,Northeast Qinghai-Tibet Plateau,China:Insights from stable isotope and hydrochemistry[J].Quaternary International,2015,380(1):123-132.
[19]伊万娟,李小雁,崔步礼,等.青海湖流域气候变化及其对湖水位的影响[J].干旱气象,2010,28(4):375-383.
[20]Zeng C,Wang Q,Fan J.Effect of initial water content on vertical line-source infiltration characteristics of soil[J].Transactions of the Chinese Society of Agricultural Engineering,2010,26(1):24-30.
[21]Scholl M A,Shanley J B,Murphy S F,et al.Stable-isotope and solute-chemistry approaches to flow characterization in a forested tropical watershed,Luquillo Mountains,Puerto Rico[J].Applied Geochemistry,2015,63(1):484-497.
[22]张英虎,牛健植,朱蔚利,等.森林生态系统林木根系对优先流的影响[J].生态学报,2015,35(6):1788-1797.
[23]王锐,刘文兆,宋献方.黄土塬区土壤水分运动的氢氧稳定同位素特征研究[J].水土保持学报,2014,28(3):134-137.