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Title: Interacting Effects of Leaf Water Potential and Biomass on Vegetation Optical Depth: Effects of LWP and Biomass on VOD

Abstract

Remotely sensed microwave observations of vegetation optical depth (VOD) have been widely used for examining vegetation responses to climate. Nevertheless, the relative impacts of phenological changes in leaf biomass and water stress on VOD have not been explicitly disentangled. In particular, determining whether leaf water potential (ψL) affects VOD may allow these data sets as a constraint for plant hydraulic models. Here we test the sensitivity of VOD to variations in ψL and present a conceptual framework that relates VOD to ψL and total biomass including leaves, whose dynamics are measured through leaf area index, and woody components. We used measurements of ψL from three sites across the US—a mixed deciduous forests in Indiana and Missouri and a piñon-juniper woodland in New Mexico—to validate the conceptual model. The temporal dynamics of X-band VOD were similar to those of the VOD signal estimated from the new conceptual model with observed ψL (R2 = 0.6–0.8). At the global scale, accounting for a combination of biomass and estimated ψL (based on satellite surface soil moisture data) increased correlations with VOD by ~ 15% and 30% compared to biomass and water potential, respectively. In wetter regions with denser and taller canopy heights, VOD hasmore » a higher correlation with leaf area index than with water stress and vice versa in drier regions. Our results demonstrate that variations in both phenology and ψL must be considered to accurately interpret the dynamics of VOD observations for ecological applications.« less

Authors:
ORCiD logo [1]; ORCiD logo [2]; ORCiD logo [3];  [4];  [4];  [5]; ORCiD logo [1]
  1. Department of Earth System Science, Stanford University, Stanford CA USA
  2. School of Natural Resources, University of Missouri, Columbia MO USA
  3. School of Public and Environmental Affairs, Indiana University-Bloomington, Bloomington IN USA
  4. Department of Biology, University of New Mexico, Albuquerque NM USA
  5. Pacific Northwest National Laboratory, Richland WA USA
Publication Date:
Research Org.:
Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
1430444
Report Number(s):
PNNL-SA-130914
Journal ID: ISSN 2169-8953; 830403000
DOE Contract Number:  
AC05-76RL01830
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Geophysical Research. Biogeosciences; Journal Volume: 122; Journal Issue: 11
Country of Publication:
United States
Language:
English

Citation Formats

Momen, Mostafa, Wood, Jeffrey D., Novick, Kimberly A., Pangle, Robert, Pockman, William T., McDowell, Nate G., and Konings, Alexandra G. Interacting Effects of Leaf Water Potential and Biomass on Vegetation Optical Depth: Effects of LWP and Biomass on VOD. United States: N. p., 2017. Web. doi:10.1002/2017JG004145.
Momen, Mostafa, Wood, Jeffrey D., Novick, Kimberly A., Pangle, Robert, Pockman, William T., McDowell, Nate G., & Konings, Alexandra G. Interacting Effects of Leaf Water Potential and Biomass on Vegetation Optical Depth: Effects of LWP and Biomass on VOD. United States. doi:10.1002/2017JG004145.
Momen, Mostafa, Wood, Jeffrey D., Novick, Kimberly A., Pangle, Robert, Pockman, William T., McDowell, Nate G., and Konings, Alexandra G. Wed . "Interacting Effects of Leaf Water Potential and Biomass on Vegetation Optical Depth: Effects of LWP and Biomass on VOD". United States. doi:10.1002/2017JG004145.
@article{osti_1430444,
title = {Interacting Effects of Leaf Water Potential and Biomass on Vegetation Optical Depth: Effects of LWP and Biomass on VOD},
author = {Momen, Mostafa and Wood, Jeffrey D. and Novick, Kimberly A. and Pangle, Robert and Pockman, William T. and McDowell, Nate G. and Konings, Alexandra G.},
abstractNote = {Remotely sensed microwave observations of vegetation optical depth (VOD) have been widely used for examining vegetation responses to climate. Nevertheless, the relative impacts of phenological changes in leaf biomass and water stress on VOD have not been explicitly disentangled. In particular, determining whether leaf water potential (ψL) affects VOD may allow these data sets as a constraint for plant hydraulic models. Here we test the sensitivity of VOD to variations in ψL and present a conceptual framework that relates VOD to ψL and total biomass including leaves, whose dynamics are measured through leaf area index, and woody components. We used measurements of ψL from three sites across the US—a mixed deciduous forests in Indiana and Missouri and a piñon-juniper woodland in New Mexico—to validate the conceptual model. The temporal dynamics of X-band VOD were similar to those of the VOD signal estimated from the new conceptual model with observed ψL (R2 = 0.6–0.8). At the global scale, accounting for a combination of biomass and estimated ψL (based on satellite surface soil moisture data) increased correlations with VOD by ~ 15% and 30% compared to biomass and water potential, respectively. In wetter regions with denser and taller canopy heights, VOD has a higher correlation with leaf area index than with water stress and vice versa in drier regions. Our results demonstrate that variations in both phenology and ψL must be considered to accurately interpret the dynamics of VOD observations for ecological applications.},
doi = {10.1002/2017JG004145},
journal = {Journal of Geophysical Research. Biogeosciences},
number = 11,
volume = 122,
place = {United States},
year = {Wed Nov 01 00:00:00 EDT 2017},
month = {Wed Nov 01 00:00:00 EDT 2017}
}