Journal
WATER RESOURCES RESEARCH
Volume 54, Issue 6, Pages 4009-4027Publisher
AMER GEOPHYSICAL UNION
DOI: 10.1029/2017WR021006
Keywords
hydraulic redistribution; water use; semiarid
Categories
Funding
- NSF [EAR 1417444, EAR 1417101, EAR 1331906, ACI 1261582,, EAR 1331408]
- Marie Curie International Outgoing Fellowship within the 7th European Community Framework Programme, DIESEL project [625988]
- Water, Environmental, and Energy Solutions (WEES) initiative at the University of Arizona Institute of the Environment
- University of Arizona Office of the Vice President of Research
- Philecology Foundation of Ft. Worth, Texas
- Department of Energy's Office of Science
- Directorate For Geosciences
- Division Of Earth Sciences [1417444] Funding Source: National Science Foundation
- Division Of Earth Sciences
- Directorate For Geosciences [1417101] Funding Source: National Science Foundation
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A major challenge in critical zone science is to understand and predict the interaction between above-ground and below-ground ecohydrologic processes. One process that facilitates this connection is hydraulic redistribution, a phenomenon by which roots serve as preferential pathways for water movement from wet to dry soil layers. We use a multilayer canopy model in conjunction with experimental data to quantify the influence of hydraulic redistribution on ecohydrologic processes in order to characterize the competitive and facilitative interaction between mesquite trees and bunchgrasses in a semiarid savanna. Both measured and simulated results show that hydraulic descent dominates during the wet monsoon season, whereas hydraulic lift occurs between precipitation events. For 2015 year-long simulation, we find about 17% of precipitation is absorbed as soil moisture, with the rest of the precipitation returning to the atmosphere as evapotranspiration. In the wet season, 13% of precipitation is transferred to deep soil (>1.5 m) through roots, and in the dry season, 9% of this redistributed water is then transported back to shallow soil depths (<0.5 m). Assuming water supplied through hydraulic redistribution is well-mixed with moisture transported directly through the soil matrix and supports vegetation evapotranspiration, hydraulic redistribution supports 47% of mesquite transpiration and 9% of understory transpiration. Through modeling and experimental synthesis, this study demonstrates that in semiarid savanna ecosystems, mesquite exhibits a competitive advantage over understory bunchgrass through hydraulic redistribution. This analysis evaluates the relationship between two coexisting vegetation types that could be expanded to multiple vegetation species sharing resources in an ecosystem.
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