The Photochemical Reflectance Index (PRI) Captures the Ecohydrologic Sensitivity of a Semiarid Mixed Conifer Forest
AuthorYang, Julia C.
Magney, Troy S.
Knowles, John F.
Smith, William K.
Scott, Russell L.
Barron‐Gafford, Greg A.
AffiliationSchool of Geography and Development, University of Arizona
School of Natural Resources and the Environment, University of Arizona
Keywordseddy covariance flux
leaf gas exchange
proximal remote sensing
MetadataShow full item record
PublisherBlackwell Publishing Ltd
CitationYang, J. C., Magney, T. S., Yan, D., Knowles, J. F., Smith, W. K., Scott, R. L., & Barron‐Gafford, G. A. (2020). The photochemical reflectance index (PRI) captures the ecohydrologic sensitivity of a semiarid mixed conifer forest. Journal of Geophysical Research: Biogeosciences, 125(11), e2019JG005624.
Rights© 2020. American Geophysical Union. All Rights Reserved.
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AbstractAt the seasonal time scale, daily photochemical reflectance index (PRI) measurements track changes in photoprotective pigment pools as plants respond to seasonally variable environmental conditions. As such, remotely sensed PRI products present opportunities to study seasonal processes in evergreen conifer forests, where complex vegetation dynamics are difficult to capture due to small annual changes in chlorophyll content or leaf structure. Because PRI is tied explicitly to short- and long-term changes in photoprotective pigments that are responsible for regulating stress, we hypothesize that PRI by extension could serve as a proxy for stomatal response to seasonally changing hydroclimate, assuming plant functional responses to stress covary in space and time. To test this, we characterized PRI in a semiarid, montane mixed conifer forest in the Madrean sky islands of Arizona, USA, during the monsoon growing season subject to precipitation pulse dynamics. To determine the sensitivity of PRI to ecohydrologic variability and associated changes in gross primary productivity (GPP), canopy spectral measurements were coupled with eddy covariance CO2 flux and sap flow measurements. Seasonally, there was a significant relationship between PRI and sap flow velocity (R2 = 0.56), and multiple linear regression analysis demonstrated a PRI response to dynamic water and energy limitations in this system. We conclude that PRI has potential to serve as a proxy for forest functional response to seasonal ecohydrologic forcing. The coordination between photoprotective pigments and seasonal stomatal regulation demonstrated here could aid characterization of vegetation response to future changes in hydroclimate at increasing spatial scales. ©2020. American Geophysical Union. All Rights Reserved.
Note6 month embargo; first published online 27 October 2020
VersionFinal published version
SponsorsNational Science Foundation