TY - JOUR
T1 - Numerical simulations of hydraulic redistribution across climates
T2 - The role of the root hydraulic conductivities
AU - Quijano, Juan C.
AU - Kumar, Praveen
N1 - Funding Information:
This research has been funded by NSF grants ATM 0628687, EAR 0911205, CBET 12091102, EAR 1331906, and EAR 1417444. JQ was also supported by the Dissertation Completion Fellowship 2012 from the University of Illinois at Urbana Champaign. The data for this paper are available at the Ameriflux data system. We acknowledge the following Ameriflux sites and their principal investigators for their data records: Metolius Intermediate Pine (PI: Beverly Law), Blodgett Forest (PI: Allen Goldstein), Harvard Forest (PI: J. William Munger), Duke Forest Hardwoods (PI: Ram Oren), Howland Forest Main (PI: David Y. Hollinger), Morgan-Monroe State Forest (PI: Kimberly Novick), Willow Creek (PIs: Paul Bolstad and Ankur Desai), LBA Tapajós Km 67 (PIs: J. William Munger, Scott R. Saleska, and Steven C. Wofsy), and Austin Cary (PI: Timothy A. Martin). In addition, funding for Ameriflux data resources was provided by the U.S. Department of Energy''s Office of Science. We also would like to acknowledge the Oak Ridge National Laboratory (ORNL) Distributed Active Archive Center (DAAC), in particular the Large-Scale Biosphere-Atmosphere Experiment in the Amazon (LBA) project, for the continuous high-resolution frequency-domain reflectometry measurements of soil moisture to 10 m depth near each of the two towers located at the km 83 tower site (logged forest site) in the Tapajos National Forest in the state of Para, Brazil.
Publisher Copyright:
© 2015. American Geophysical Union. All Rights Reserved.
PY - 2015/10
Y1 - 2015/10
N2 - Hydraulic redistribution, a process by which vegetation roots redistribute soil moisture, has been recognized as an important mechanism impacting several processes that regulate plant water uptake, energy and water partitioning, and biogeochemical cycling. We analyze how the magnitude of hydraulic redistribution varies across ecosystems that are exposed to different climates and seasonal patterns of incoming shortwave radiation and precipitation. Numerical simulation studies are performed over 10 Ameriflux sites, which show that hydraulic redistribution predictions are significantly influenced by the specified root hydraulic conductivities. We performed sensitivity analyses by considering expected ranges of root conductivities based on previous experimental studies, and found contrasting patterns in energy-limited and water-limited ecosystems. In energy-limited ecosystems, there is a threshold above which high root conductivities enhance hydraulic redistribution with no increase in transpiration, while in water-limited ecosystems increase in root conductivities was always associated with enhancements in both transpiration and hydraulic redistribution. Further we found differences in the magnitude and seasonality of hydraulic redistribution and transpiration across different climates, regulated by interplay between precipitation and transpiration. The annual hydraulic redistribution to transpiration flux ratio (HR/Tr) was significant in Mediterranean climates (HR/Tr ≈ 30%), and in the tropical humid climates (HR/Tr ≈ 15%). However, in the continental climates hydraulic redistribution occurs only during sporadic precipitation events throughout the summer resulting in lower annual magnitudes (HR/Tr < 5%). These results provide more insights for suitable implementation of numerical models to capture belowground processes in eco-hydrology, and enhance our understanding about the variability of hydraulic redistribution across different climates.
AB - Hydraulic redistribution, a process by which vegetation roots redistribute soil moisture, has been recognized as an important mechanism impacting several processes that regulate plant water uptake, energy and water partitioning, and biogeochemical cycling. We analyze how the magnitude of hydraulic redistribution varies across ecosystems that are exposed to different climates and seasonal patterns of incoming shortwave radiation and precipitation. Numerical simulation studies are performed over 10 Ameriflux sites, which show that hydraulic redistribution predictions are significantly influenced by the specified root hydraulic conductivities. We performed sensitivity analyses by considering expected ranges of root conductivities based on previous experimental studies, and found contrasting patterns in energy-limited and water-limited ecosystems. In energy-limited ecosystems, there is a threshold above which high root conductivities enhance hydraulic redistribution with no increase in transpiration, while in water-limited ecosystems increase in root conductivities was always associated with enhancements in both transpiration and hydraulic redistribution. Further we found differences in the magnitude and seasonality of hydraulic redistribution and transpiration across different climates, regulated by interplay between precipitation and transpiration. The annual hydraulic redistribution to transpiration flux ratio (HR/Tr) was significant in Mediterranean climates (HR/Tr ≈ 30%), and in the tropical humid climates (HR/Tr ≈ 15%). However, in the continental climates hydraulic redistribution occurs only during sporadic precipitation events throughout the summer resulting in lower annual magnitudes (HR/Tr < 5%). These results provide more insights for suitable implementation of numerical models to capture belowground processes in eco-hydrology, and enhance our understanding about the variability of hydraulic redistribution across different climates.
KW - evapotranspiration
KW - hydraulic redistribution
KW - root uptake
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U2 - 10.1002/2014WR016509
DO - 10.1002/2014WR016509
M3 - Article
AN - SCOPUS:84956580993
SN - 0043-1397
VL - 51
SP - 8529
EP - 8550
JO - Water Resources Research
JF - Water Resources Research
IS - 10
ER -