TY - JOUR
T1 - Canopy Temperature Is Regulated by Ecosystem Structural Traits and Captures the Ecohydrologic Dynamics of a Semiarid Mixed Conifer Forest Site
AU - Javadian, Mostafa
AU - Smith, William K.
AU - Lee, Kangsan
AU - Knowles, John F.
AU - Scott, Russell L.
AU - Fisher, Joshua B.
AU - Moore, David J.P.
AU - van Leeuwen, Willem J.D.
AU - Barron-Gafford, Greg
AU - Behrangi, Ali
N1 - Funding Information:
Data collection and continued maintenance of the US‐MtB EC flux site was supported by NSF Earth Sciences awards EAR 1417101, EAR 1331408, and EAR 1331906. W. K. Smith was supported by funding from the DoD SERDP (RC18‐1322) and NASA SMAP (80NSSC20K1805). J. B. Fisher was supported in part by NASA ECOSTRESS. This work was also partly supported by the University of Arizona Earth Dynamics Observatory, funded by the office of Research, Innovation & Impact.
Publisher Copyright:
© 2022. American Geophysical Union. All Rights Reserved.
PY - 2022/2
Y1 - 2022/2
N2 - Plant canopy temperature (Tc) is partly regulated by evaporation and transpiration from the canopy surface and can be used to infer changes in stomatal regulation and vegetation water stress. In this study, we used a thermal Unmanned Aircraft Systems in conjunction with eddy covariance, sap flow, and spectral reflectance data to assess the diurnal characteristics of Tc and water stress status over a semiarid mixed conifer forest in Arizona, USA. Diurnal Tc dynamics were closely related to tree sap flow and changes in spectral reflectance associated with stomatal regulation. Consistent with previously reported deviations, we found that on average Tc was 1.8°C lower than the above canopy air temperature (Ta). However, the relationship between Tc and Ta varied significantly according to tree density and tree height classes, with taller and denser trees exhibiting relatively low |Tc-Ta| (2.4 and 2.1°C cooler canopies, respectively) compared to shorter and less-dense tree stands (1.7 and 1.5°C cooler canopies, respectively). We used these data to evaluate space-borne diurnal measurements of Tc and water stress from the ECOsystem Spaceborne Thermal Radiometer Experiment on Space Station (ECOSTRESS) mission. We found that ECOSTRESS observations of Tc accurately tracked seasonal shifts in diurnal surface temperatures and vegetation water stress, and that site-level observations of heterogeneity in forest composition and structure could be applied to separate the processes of canopy transpiration and soil evaporation within the ECOSTRESS footprint. This study demonstrates how proximal and satellite remote sensing approaches can be combined to reveal the diurnal and seasonally dynamic nature of Tc and water stress.
AB - Plant canopy temperature (Tc) is partly regulated by evaporation and transpiration from the canopy surface and can be used to infer changes in stomatal regulation and vegetation water stress. In this study, we used a thermal Unmanned Aircraft Systems in conjunction with eddy covariance, sap flow, and spectral reflectance data to assess the diurnal characteristics of Tc and water stress status over a semiarid mixed conifer forest in Arizona, USA. Diurnal Tc dynamics were closely related to tree sap flow and changes in spectral reflectance associated with stomatal regulation. Consistent with previously reported deviations, we found that on average Tc was 1.8°C lower than the above canopy air temperature (Ta). However, the relationship between Tc and Ta varied significantly according to tree density and tree height classes, with taller and denser trees exhibiting relatively low |Tc-Ta| (2.4 and 2.1°C cooler canopies, respectively) compared to shorter and less-dense tree stands (1.7 and 1.5°C cooler canopies, respectively). We used these data to evaluate space-borne diurnal measurements of Tc and water stress from the ECOsystem Spaceborne Thermal Radiometer Experiment on Space Station (ECOSTRESS) mission. We found that ECOSTRESS observations of Tc accurately tracked seasonal shifts in diurnal surface temperatures and vegetation water stress, and that site-level observations of heterogeneity in forest composition and structure could be applied to separate the processes of canopy transpiration and soil evaporation within the ECOSTRESS footprint. This study demonstrates how proximal and satellite remote sensing approaches can be combined to reveal the diurnal and seasonally dynamic nature of Tc and water stress.
KW - ECOSTRESS
KW - canopy temperature
KW - diurnal vegetation dynamics
KW - ecohydrologic dynamics
KW - semiarid mixed conifer forest
KW - thermal UAS
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U2 - 10.1029/2021JG006617
DO - 10.1029/2021JG006617
M3 - Article
AN - SCOPUS:85125144657
SN - 2169-8953
VL - 127
JO - Journal of Geophysical Research: Biogeosciences
JF - Journal of Geophysical Research: Biogeosciences
IS - 2
M1 - e2021JG006617
ER -