TY - JOUR
T1 - Remote measurement of canopy water content in giant sequoias (Sequoiadendron giganteum) during drought
AU - Martin, Roberta E.
AU - Asner, Gregory P.
AU - Francis, Emily
AU - Ambrose, Anthony
AU - Baxter, Wendy
AU - Das, Adrian J.
AU - Vaughn, Nicolas R.
AU - Paz-Kagan, Tarin
AU - Dawson, Todd
AU - Nydick, Koren
AU - Stephenson, Nathan L.
N1 - Funding Information:
This study was funded by the David and Lucile Packard Foundation , the U.S. National Park Service , and the U.S. Geological Survey ( USGS ) Ecosystems and Climate and Land Use Research and Development programs and the USGS Southwest Climate Science Center. The Carnegie Airborne Observatory has been made possible by grants and donations to G.P. Asner from the Avatar Alliance Foundation, Margaret A. Cargill Foundation , David and Lucile Packard Foundation , Gordon and Betty Moore Foundation , Grantham Foundation for the Protection of the Environment , W.M. Keck Foundation , John D. and Catherine T. MacArthur Foundation , Andrew Mellon Foundation, Mary Anne Nyburg Baker and G. Leonard Baker Jr, and William R. Hearst III. Any use of trade names is for descriptive purposes only and does not imply endorsement by the U.S. Government. We thank the reviewers for their helpful comments.
Funding Information:
This study was funded by the David and Lucile Packard Foundation, the U.S. National Park Service, and the U.S. Geological Survey (USGS) Ecosystems and Climate and Land Use Research and Development programs and the USGS Southwest Climate Science Center. The Carnegie Airborne Observatory has been made possible by grants and donations to G.P. Asner from the Avatar Alliance Foundation, Margaret A. Cargill Foundation, David and Lucile Packard Foundation, Gordon and Betty Moore Foundation, Grantham Foundation for the Protection of the Environment, W.M. Keck Foundation, John D. and Catherine T. MacArthur Foundation, Andrew Mellon Foundation, Mary Anne Nyburg Baker and G. Leonard Baker Jr, and William R. Hearst III. Any use of trade names is for descriptive purposes only and does not imply endorsement by the U.S. Government. We thank the reviewers for their helpful comments.
Publisher Copyright:
© 2017 Elsevier B.V.
PY - 2018/7/1
Y1 - 2018/7/1
N2 - California experienced severe drought from 2012 to 2016, and there were visible changes in the forest canopy throughout the State. In 2014, unprecedented foliage dieback was recorded in giant sequoia (Sequoiadendron giganteum) trees in Sequoia National Park, in the southern California Sierra Nevada mountains. Although visible changes in sequoia canopies can be recorded, biochemical and physiological responses to drought stress in giant sequoia canopies are not well understood. Ground-based measurements provide insight into the mechanisms of drought responses in trees, but are often limited to few individuals, especially in trees of tall stature such as giant sequoia. Recent studies demonstrate that remotely measured forest canopy water content (CWC) is a general indicator of canopy response to drought, but the underpinning leaf- to canopy-level causes of observed variation in CWC remain poorly understood. We combined field and airborne remote sensing measurements taken in 2015 and 2016 to assess the biophysical responses of giant sequoias to drought. In 49 study trees, CWC was related to leaf water potential, but not to the other foliar traits, suggesting that changes in CWC were made at whole-canopy rather than leaf scales. We found a non-random, spatially varying pattern in mapped CWC, with lower CWC values at lower elevation and along the outer edges of the groves. This pattern was also observed in empirical measurements of foliage dieback from the ground, and in mapped CWC across multiple sequoia groves in this region, supporting the hypothesis that drought stress is expressed in canopy-level changes in giant sequoias. The fact that we can clearly detect a relationship between CWC and foliage dieback, even without taking into account prior variability or new leaf growth, strongly suggests that remotely sensed CWC, and changes in CWC, are a useful measure of water stress in giant sequoia, and valuable for assessing and managing these iconic forests in drought.
AB - California experienced severe drought from 2012 to 2016, and there were visible changes in the forest canopy throughout the State. In 2014, unprecedented foliage dieback was recorded in giant sequoia (Sequoiadendron giganteum) trees in Sequoia National Park, in the southern California Sierra Nevada mountains. Although visible changes in sequoia canopies can be recorded, biochemical and physiological responses to drought stress in giant sequoia canopies are not well understood. Ground-based measurements provide insight into the mechanisms of drought responses in trees, but are often limited to few individuals, especially in trees of tall stature such as giant sequoia. Recent studies demonstrate that remotely measured forest canopy water content (CWC) is a general indicator of canopy response to drought, but the underpinning leaf- to canopy-level causes of observed variation in CWC remain poorly understood. We combined field and airborne remote sensing measurements taken in 2015 and 2016 to assess the biophysical responses of giant sequoias to drought. In 49 study trees, CWC was related to leaf water potential, but not to the other foliar traits, suggesting that changes in CWC were made at whole-canopy rather than leaf scales. We found a non-random, spatially varying pattern in mapped CWC, with lower CWC values at lower elevation and along the outer edges of the groves. This pattern was also observed in empirical measurements of foliage dieback from the ground, and in mapped CWC across multiple sequoia groves in this region, supporting the hypothesis that drought stress is expressed in canopy-level changes in giant sequoias. The fact that we can clearly detect a relationship between CWC and foliage dieback, even without taking into account prior variability or new leaf growth, strongly suggests that remotely sensed CWC, and changes in CWC, are a useful measure of water stress in giant sequoia, and valuable for assessing and managing these iconic forests in drought.
KW - California
KW - Carnegie Airborne Observatory
KW - Giant sequoia
KW - Sierra Nevada mountains
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U2 - 10.1016/j.foreco.2017.12.002
DO - 10.1016/j.foreco.2017.12.002
M3 - Article
AN - SCOPUS:85044758753
SN - 0378-1127
VL - 419-420
SP - 279
EP - 290
JO - Forest Ecology and Management
JF - Forest Ecology and Management
ER -