@article{33fd15cd1ac540ccbac166c934f60251,
title = "Phenological assessment of transpiration: The stem-temp approach for determining start and end of season",
abstract = "Field-based assessment of transpiration phenology in boreal tree species is a significant challenge. Here we develop an objective approach that uses stem radius change and its correlation with sapwood temperature to determine the timing of phenological changes in transpiration in mixed evergreen species. We test the stem-temp approach using a five year stem-radius dataset from black spruce (Picea mariana) and jack pine (Pinus banksiana) trees in Saskatchewan (2016–2020). We further compare transpiration phenological transition dates from this approach with tower-based phenological assessment from green chromatic coordinate derived from phenocam images, eddy-covariance-derived evapotranspiration and carbon uptake, tower-based measurements of solar-induced chlorophyll fluorescence and snowmelt timing. The stem-temp approach identified the start and end of four key transpiration phenological phases: (i) the end of temperature-driven cycles indicating the start of biological activity, (ii) the onset of stem rehydration, (iii) the onset of transpiration, and (iv) the end of transpiration-driven cycles. The proposed method is thus useful for characterizing the timing of changes in transpiration phenology and provides information about distinct processes that cannot be assessed with canopy-level phenological measurements alone.",
keywords = "Carbon uptake onset, Green chromatic coordinate, Snowmelt, Spring onset, Stem diurnal cycle, Stem radius change, Stem-temp approach, Transpiration phenology",
author = "Nehemy, {Magali F.} and Zoe Pierrat and Jason Maillet and Richardson, {Andrew D.} and Jochen Stutz and Bruce Johnson and Warren Helgason and Barr, {Alan G.} and Laroque, {Colin P.} and McDonnell, {Jeffrey J.}",
note = "Funding Information: The dendrometer data from the study is currently available at the Federated Research Data Repository: doi.org/10.20383/102.0367 (Nehemy et al. 2021) under Creative Commons Attribution (CC BY 4.0) licence. The phenocamera images and Gcc data are available at PhenoCam Network: phenocam.sr.unh.edu. SIFrelative data archiving is available on Zenodo: 10.5281/zenodo.5884643 (Pierrat and Stutz, 2022). We thank the colleagues and undergraduate students that assisted with field work and instrument repairs. We are grateful for the help of (alphabetically) Gary Beckhusen, Megan Horachek, Tiara Jackle, Taylor Kosokowsky, Owen Laroque, Rafaella Mayrinck, Ben Nykiforuk, Christoforos Pappas, Nia Perron, Beckett Stark, Inge Verbeek, and Scott Wood. This research was supported by the American Geophysical Union – Horton Research Grant 2019 awarded to Magali F. Nehemy, an NSERC CREATE in Water Security and an NSERC Discovery Grant to Jeffrey J. McDonnell. The BERMS meteorological and flux measurements were supported by the Global Institute of Water Security, University of Saskatchewan and the Changing Cold Regions Network. We thank T. Andy Black, Rachhpal Jassal and Zoran Nesic, U.B.C. for the OBS flux data from 2016 to 2018. We acknowledge the support for the PhenoCam Network through National Science Foundation's Macrosystems Biology program (awards EF-1065029 and EF-1702697). PhotoSpec data collection and processing efforts were supported by NASA's Earth Science Division IDS (awards 80NSSC17K0108 at UCLA, 80NSS- C17K0110 at JPL) and ABoVE programs (award 80NSSC19M0130). A portion of this research was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration. This material is also based upon work supported by the National Science Foundation Graduate Research Fellowship (Grant No. DGE-1650604 and DGE-2034835). Any opinion, findings, and conclusions or recommendations expressed in this material are those of the authors(s) and do not necessarily reflect the views of the National Science Foundation. Funding Information: We thank the colleagues and undergraduate students that assisted with field work and instrument repairs. We are grateful for the help of (alphabetically) Gary Beckhusen, Megan Horachek, Tiara Jackle, Taylor Kosokowsky, Owen Laroque, Rafaella Mayrinck, Ben Nykiforuk, Christoforos Pappas, Nia Perron, Beckett Stark, Inge Verbeek, and Scott Wood. This research was supported by the American Geophysical Union – Horton Research Grant 2019 awarded to Magali F. Nehemy, an NSERC CREATE in Water Security and an NSERC Discovery Grant to Jeffrey J. McDonnell. The BERMS meteorological and flux measurements were supported by the Global Institute of Water Security, University of Saskatchewan and the Changing Cold Regions Network. We thank T. Andy Black, Rachhpal Jassal and Zoran Nesic, U.B.C., for the OBS flux data from 2016 to 2018. We acknowledge the support for the PhenoCam Network through National Science Foundation's Macrosystems Biology program (awards EF-1065029 and EF-1702697 ). PhotoSpec data collection and processing efforts were supported by NASA{\textquoteright}s Earth Science Division IDS (awards 80NSSC17K0108 at UCLA , 80NSS- C17K0110 at JPL) and ABoVE programs (award 80NSSC19M0130 ). A portion of this research was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration. This material is also based upon work supported by the National Science Foundation Graduate Research Fellowship (Grant No. DGE-1650604 and DGE-2034835 ). Any opinion, findings, and conclusions or recommendations expressed in this material are those of the authors(s) and do not necessarily reflect the views of the National Science Foundation. Publisher Copyright: {\textcopyright} 2023 Elsevier B.V.",
year = "2023",
month = mar,
day = "15",
doi = "10.1016/j.agrformet.2023.109319",
language = "English (US)",
volume = "331",
journal = "Agricultural and Forest Meteorology",
issn = "0168-1923",
publisher = "Elsevier",
}