干旱区绿洲-荒漠过渡带蒸散发及其驱动机制

doi:10.7522/j.issn.1000-694X.2025.00344

摘要/Abstract

摘要：

蒸散发是西北干旱区绿洲-荒漠过渡带水量平衡的重要分量，深入理解蒸散发过程及其驱动机制对保护该过渡带植被稳定具有重要科学价值。利用涡动相关、小气候、植被动态等观测数据，基于陆表下垫面与大气之间水汽传输的物理过程，定量解析了河西走廊中部临泽绿洲与其外围荒漠之间过渡带蒸散发的能量驱动和水汽传导控制效力。结果表明降水事件和植被动态变化显著缓解了下垫面水分胁迫，下垫面与大气之间高度耦合（解耦系数0.14），平衡分量和胁迫分量分别贡献了蒸散发的65%和35%，表面导度在控制该过渡带蒸散发速率中占据绝对主导地位，能够解释近70%的蒸散发变化。全年累积蒸散发量（218 mm）超过降水量（89 mm）约129 mm，表明地下水在维系该过渡带植被生长中起着关键作用，保持合理的地下水位对保护过渡带植被至关重要。

关键词: 蒸散发, 表面导度, 解耦系数, 水量平衡, 地下水

Abstract:

Evapotranspiration is large enough to be a very important component of water budget in the desert-oasis ecotone in arid regions. A better understanding of the evapotranspiration processes and its driving mechanisms is of insightful significance for protecting the stability of vegetation in the ecotone. Here within a physically based framework describing vapor transfer between the underlying surface and atmosphere， the controls of energy and vapor transfer on evapotranspiration over the underlying surface are determined quantitatively from observations of eddy covariance， micrometeorology， and vegetation dynamics. Rainfall events and vegetation dynamics relieved significantly water stress of the underlying surface， even so， the underlying surface was highly coupled with atmosphere given small decoupling coefficient （e.g.， 0.14）. The equilibrium and imposed components contributed 65% and 35% of the gross evapotranspiration， respectively. Surface conductance exerted an overwhelming control of evapotranspiration rate， which can explain nearly 70% of the variation in daily evapotranspiration. The annual accumulated evapotranspiration （i.e.， 218 mm） exceeded the corresponding precipitation （i.e.， 89 mm） by around 129 mm， suggesting that groundwater plays a pivotal role in sustaining vegetation growth in the ecotone， and keeping groundwater level fluctuating within a narrow range of values is consequently a high priority for conserving vegetation in this ecotone.

Key words: evapotranspiration, surface conductance, decoupling coefficient, water budget, groundwater

中图分类号:

P426.2

吉喜斌, 金博文, 赵文玥, 周海, 陈锐, 李东生, 赵丽雯, 赵文智. 干旱区绿洲-荒漠过渡带蒸散发及其驱动机制[J]. 中国沙漠, 2026, 46(1): 74-82.

Xibin Ji, Bowen Jin, Wenyue Zhao, Hai Zhou, Rui Chen, Dongsheng Li, Liwen Zhao, Wenzhi Zhao. Evapotranspiration and its driving mechanism of an oasis-desert ecotone ecosystem in arid regions[J]. Journal of Desert Research, 2026, 46(1): 74-82.

图/表 5

图1 研究区位置

Fig.1 Location of the study site

图2 荒漠-绿洲过渡带日蒸散发量（ET）、降水量（P）和叶面积指数（LAI）变化

Fig.2 Variation in daily evapotranspiration （ET）， precipitation （P）， and leaf area index （LAI） in the desert-oasis ecotone

图3 植被生长季日蒸散发量与主要环境驱动因子和表面导度的关系注：ET为日蒸散发量；Rn为净辐射；VPD为饱和水汽压差；θ为土壤体积含水量；Ep为日潜在蒸散发；gs为表面导度。黑粗直线表示日蒸散发量与各日均环境因子和表面导度的线性拟合（P<0.05）

Fig.3 Interrelations between daily evapotranspiration and key driving environmental factors and surface conductance during the growth season of vegetation （ET， Rn， VPD， θ， Ep， gs denote daily evapotranspiration， mean daytime net radiation， vapor pressure deficit， soil moisture， potential evapotranspiration， surface conductance， respectively； the bold black lines represent linear regression line between daily evapotranspiration and environmental factors and surface conductance （P<0.05））

图4 生长季空气动力学导度（ga）、表面导度（gs）和解耦系数（Ω）日均值

Fig.4 Daily average aerodynamic conductance （ga）， surface conductance （gs）， and decoupling coefficient （Ω） during the growth seasons

图5 生长季日均平衡潜热（λEeq）、胁迫潜热（λEimp）与潜热中的平衡分量（ΩλEeq）、胁迫分量（（1-Ω） λEimp）

Fig.5 Daily average equilibrium （λEeq）， imposed latent heat （λEimp）， and the equilibrium （ΩλEeq）， imposed （（1-Ω） λEimp） components of latent heat during the growth season

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