Evaluation of actual evapotranspiration measured by large‐scale weighing lysimeters in a humid alpine meadow, northeastern Qinghai‐Tibetan Plateau,Hydrological Processes

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Evaluation of actual evapotranspiration measured by large‐scale weighing lysimeters in a humid alpine meadow, northeastern Qinghai‐Tibetan Plateau
Hydrological Processes ( IF 2.8 ) Pub Date : 2021-01-20 , DOI: 10.1002/hyp.14051
Licong Dai _{1,

2,

3} , Ruiyu Fu ₄ , Xiaowei Guo _{1,

2} , Xun Ke _{1,

2,

3} , Yangong Du _{1,

2} , Fawei Zhang _{1,

2} , Yikang Li _{1,

2} , Dawen Qian _{1,

2} , Huakun Zhou _{1,

2} , Guangmin Cao _{1,

2}

Affiliation

The accurate estimation of evapotranspiration (ET) is essential for assessing water availability and requirements of regional‐scale terrestrial ecosystems, and for understanding the hydrological cycle in alpine ecosystems. In this study, two large‐scale weighing lysimeters were employed to estimate the magnitude and dynamics of actual evapotranspiration in a humid alpine Kobresia meadow from January 2018 to December 2019 on the northeastern Qinghai‐Tibetan Plateau (QTP). The results showed that daily ET_a averaged 2.24 ± 0.10 mm day ⁻¹ throughout the study period, with values of 3.89 ± 0.14 and 0.81 ± 0.06 mm day⁻¹ during the growing season and non‐growing season, respectively. The cumulative ET_a during the study period was 937.39 mm, exceeding precipitation (684.20 mm) received at the site during the same period by 37%, suggesting that almost all precipitation in the lysimeters was returned to the atmosphere by evapotranspiration. Furthermore, the cumulative ET_a (805.04 mm) was almost equal to the maximum potential evapotranspiration estimated by the FAO‐56 reference evapotranspiration (ET₀) (801.94 mm) during the growing season, but the cumulative ET_a (132.25 mm) was 113.72% less than the minimum equilibrium ET_eq) (282.86 mm) during the non‐growing season due to the limited surface moisture in frozen soil. The crop coefficient (K_c) also showed a distinct seasonal pattern, with a monthly average of 1.01 during the growing season. Structural equation model (SEM) and boosted regression tree (BRT) show that net radiation and air temperature were the most important factors affecting daily ET_a during the whole study period and growing season, but that non‐growing season ET_a was dominated by soil water content and net radiation. The daily K_c was dominated by net radiation. Furthermore, both ET_a and K_c were also affected by aboveground biomass.

中文翻译：

青藏高原东北部湿润高寒草甸大型蒸散蒸散仪测得的实际蒸散量的评估

准确估算蒸散量（ET）对于评估水的可获得性和区域规模陆地生态系统的需求，以及了解高山生态系统的水文循环至关重要。在这项研究中，使用了两个大型称重测力计来估算2018年1月至2019年12月在东北青藏高原（QTP）上的潮湿高寒嵩草草甸的实际蒸散量和动态。结果表明，每日ET_一个平均2.24±0.10毫米天^-1整个研究期间，具有3.89±0.14和0.81±0.06毫米日的值^-1分别在生长季节和非生长季节。累积ET_一研究期间的降水量为937.39毫米，比同期在该地点接收的降水量（684.20毫米）多了37％，这表明蒸散仪中几乎所有的降水量都通过蒸散返回了大气。此外，在生长季节，累积ET _a（805.04 mm）几乎等于FAO-56参考蒸散量（ET ₀）（801.94 mm）估算的最大潜在蒸散量，但累积ET _a（132.25 mm）为113.72。在非生长季节，由于冷冻土壤中的表层水分有限，因此比最小平衡ET _eq）（282.86 mm）低％。作物系数（K _c）还表现出明显的季节性模式，在生长季节每月平均为1.01。结构方程模型（SEM）和增强回归树（BRT）表明，净辐射和气温是在整个研究期间和整个生长季节影响每日ET _a的最重要因素，但非生长季节ET _a则以土壤为主水分和净辐射。每日K _c以净辐射为主。此外，ET _a和K _c都受到地上生物量的影响。

更新日期：2021-01-20

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