@article{3f4e6c72ff0e43a3b623df41c476f22b,
title = "Seasonal variation in the canopy color of temperate evergreen conifer forests",
abstract = "Evergreen conifer forests are the most prevalent land cover type in North America. Seasonal changes in the color of evergreen forest canopies have been documented with near-surface remote sensing, but the physiological mechanisms underlying these changes, and the implications for photosynthetic uptake, have not been fully elucidated. Here, we integrate on-the-ground phenological observations, leaf-level physiological measurements, near surface hyperspectral remote sensing and digital camera imagery, tower-based CO2 flux measurements, and a predictive model to simulate seasonal canopy color dynamics. We show that seasonal changes in canopy color occur independently of new leaf production, but track changes in chlorophyll fluorescence, the photochemical reflectance index, and leaf pigmentation. We demonstrate that at winter-dormant sites, seasonal changes in canopy color can be used to predict the onset of canopy-level photosynthesis in spring, and its cessation in autumn. Finally, we parameterize a simple temperature-based model to predict the seasonal cycle of canopy greenness, and we show that the model successfully simulates interannual variation in the timing of changes in canopy color. These results provide mechanistic insight into the factors driving seasonal changes in evergreen canopy color and provide opportunities to monitor and model seasonal variation in photosynthetic activity using color-based vegetation indices.",
keywords = "AmeriFlux, PRI, PhenoCam, evergreen conifer, phenology, seasonality, xanthophyll",
author = "Bijan Seyednasrollah and Bowling, {David R.} and Rui Cheng and Logan, {Barry A.} and Magney, {Troy S.} and Christian Frankenberg and Yang, {Julia C.} and Young, {Adam M.} and Koen Hufkens and Arain, {M. Altaf} and Black, {T. Andrew} and Blanken, {Peter D.} and Rosvel Bracho and Rachhpal Jassal and Hollinger, {David Y.} and Law, {Beverly E.} and Zoran Nesic and Richardson, {Andrew D.}",
note = "Funding Information: This is a product of the IMGG workshop held in Flagstaff, AZ, in May 2019. ADR and DRB thank J. Page, J. White, and D. Evans for inspiration. ADR acknowledges support from the National Science Foundation, through the Macrosystems Biology (awards EF‐1065029 and EF‐1702697) and Long‐Term Ecological Research (award DEB‐1832210) programs. DRB acknowledges support from the NASA Carbon Monitoring Systems (awards NNX16AP33G and 80NSSC20K0010) and ABoVE (80NSSC19M0130) programs, and the National Science Foundation, through the Macrosystems Biology and NEON‐Enabled Science program (DEB‐1926090). Thanks to flux tower scientists for hosting the PhenoCams and providing flux and met data, and to many agencies for funding the flux towers. PhenoCam acknowledgments for individual sites are presented in Supporting Information. Needle pigments were quantified by Sophia Lopez, who held a Langbein Research Fellowship (Bowdoin College), with Jaret Reblin{\textquoteright}s support. The authors declare no conflict of interest. Funding Information: This is a product of the IMGG workshop held in Flagstaff, AZ, in May 2019. ADR and DRB thank J. Page, J. White, and D. Evans for inspiration. ADR acknowledges support from the National Science Foundation, through the Macrosystems Biology (awards EF-1065029 and EF-1702697) and Long-Term Ecological Research (award DEB-1832210) programs. DRB acknowledges support from the NASA Carbon Monitoring Systems (awards NNX16AP33G and 80NSSC20K0010) and ABoVE (80NSSC19M0130) programs, and the National Science Foundation, through the Macrosystems Biology and NEON-Enabled Science program (DEB-1926090). Thanks to flux tower scientists for hosting the PhenoCams and providing flux and met data, and to many agencies for funding the flux towers. PhenoCam acknowledgments for individual sites are presented in Supporting Information. Needle pigments were quantified by Sophia Lopez, who held a Langbein Research Fellowship (Bowdoin College), with Jaret Reblin{\textquoteright}s support. The authors declare no conflict of interest. Publisher Copyright: {\textcopyright} 2020 The Authors New Phytologist {\textcopyright} 2020 New Phytologist Foundation",
year = "2021",
month = mar,
doi = "10.1111/nph.17046",
language = "English (US)",
volume = "229",
pages = "2586--2600",
journal = "New Phytologist",
issn = "0028-646X",
publisher = "Wiley-Blackwell",
number = "5",
}