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Climate sensitivity of water use by riparian woodlands at landscape scales
Hydrological Processes ( IF 3.2 ) Pub Date : 2020-10-15 , DOI: 10.1002/hyp.13942
Marc Mayes 1 , Kelly K. Caylor 1, 2, 3 , Michael Bliss Singer 1, 4, 5 , John C. Stella 6 , Dar Roberts 6 , Pamela Nagler 7
Affiliation  

Semi‐arid riparian woodlands face threats from increasing extractive water demand and climate change in dryland landscapes worldwide. Improved landscape‐scale understanding of riparian woodland water use (evapotranspiration, ET) and its sensitivity to climate variables is needed to strategically manage water resources, as well as to create successful ecosystem conservation and restoration plans for potential climate futures. In this work, we assess the spatial and temporal variability of Cottonwood (Populus fremontii)‐Willow (Salix gooddingii) riparian gallery woodland ET and its relationships to vegetation structure and climate variables for 80 km of the San Pedro River corridor in southeastern Arizona, USA, between 2014 and 2019. We use a novel combination of publicly available remote sensing, climate and hydrological datasets: cloud‐based Landsat thermal remote sensing data products for ET (Google Earth Engine EEFlux), Landsat multispectral imagery and field data‐based calibrations to vegetation structure (leaf‐area index, LAI), and open‐source climate and hydrological data. We show that at landscape scales, daily ET rates (6–10 mm day−1) and growing season ET totals (400–1,400 mm) matched rates of published field data, and modelled reach‐scale average LAI (0.80–1.70) matched lower ranges of published field data. Over 6 years, the spatial variability of total growing season ET (CV = 0.18) exceeded that of temporal variability (CV = 0.10), indicating the importance of reach‐scale vegetation and hydrological conditions for controlling ET dynamics. Responses of ET to climate differed between perennial and intermittent‐flow stream reaches. At perennial‐flow reaches, ET correlated significantly with temperature, whilst at intermittent‐flow sites ET correlated significantly with rainfall and stream discharge. Amongst reaches studied in detail, we found positive but differing logarithmic relationships between LAI and ET. By documenting patterns of high spatial variability of ET at basin scales, these results underscore the importance of accurately accounting for differences in woodland vegetation structure and hydrological conditions for assessing water‐use requirements. Results also suggest that the climate sensitivity of ET may be used as a remote indicator of subsurface water resources relative to vegetation demand, and an indicator for informing conservation management priorities.

中文翻译:

河岸带林地的用水对气候的敏感性

半干旱河岸林地面临着全球干旱地区景观中不断增加的采水需求和气候变化的威胁。为了从战略上管理水资源,以及为潜在的气候未来制定成功的生态系统保护和恢复计划,需要提高对河岸林地用水(蒸散量,ET)及其对气候变量敏感性的景观尺度理解。在这项工作中,我们评估了杨木(杨杨)-杨柳(柳柳)的时空变异性。)河岸廊林地ET及其与植被结构和气候变量之间的关系,在2014年至2019年之间,位于美国亚利桑那州东南部的圣佩德罗河走廊,距离为80公里(美国),2014年至2019年。用于ET的基于云的Landsat热遥感数据产品(Google Earth Engine EEFlux),针对植被结构的Landsat多光谱图像和基于现场数据的校准(叶面积指数,LAI)以及开源气候和水文数据。我们显示,在景观尺度上,每日ET速率(6-10毫米天-1)和生长季的ET总量(400–1,400 mm)与已发布的田间数据的速率匹配,而建模的覆盖规模平均LAI(0.80–1.70)与已发布的田间数据的较低范围匹配。在过去的6年中,总生长期ET的空间变异性(CV = 0.18)超过了时间变异性(CV = 0.10),这表明了达到尺度的植被和水文条件对于控制ET动态的重要性。多年生和间歇性径流河段之间,ET对气候的响应有所不同。在常年水流到达时,ET与温度显着相关,而在间歇水流站点,ET与降雨和溪流显着相关。在详细研究的河段中,我们发现LAI和ET之间存在正但不同的对数关系。通过记录流域尺度上ET的高空间变异性模式,这些结果强调了准确评估林地植被结构和水文条件差异以评估用水需求的重要性。结果还表明,ET的气候敏感性可以用作与植被需求相关的地下水资源的远程指标,也可以作为告知保护管理重点的指标。
更新日期:2020-12-10
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