Impact of hydraulic redistribution on multispecies vegetation water use in a semi-arid ecosystem: An experimental and modeling synthesis
Abstract
A key challenge in critical zone science is to understand and predict the interaction between aboveground and belowground ecohydrologic processes. One of the links that facilitates the interaction is hydraulic redistribution (HR), a phenomenon by which roots serve as preferential pathways for water movement from wet to dry soil layers. We use a multi-layer canopy model in conjunction with experimental data to examine the influence of HR on eco-hydrologic processes, such as transpiration, soil evaporation, and soil moisture, which characterize the competitive and facilitative dynamics between velvet mesquite and understory bunchgrass. Both measured and simulated results show that hydraulic descent (HD) dominates sap flux during the wet monsoon season, whereas hydraulic lift (HL) occurs between precipitation events. 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 (>2m) through mesquite roots, and in the dry season, 9% of this redistributed water is transported back to shallow soil depth (<0.5m). Assuming water supplied through HR is well-mixed with moisture transported directly through the soil matrix and supports vegetation evapotranspiration, HR supports about 47% of mesquite transpiration and 9% of understory transpiration. Through modeling and experimental synthesis, this study demonstrates that in the dry land ecosystem of southwestern U.S., Mesquite exhibits competitive advantage over understory bunchgrass through HR.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2017
- Bibcode:
- 2017AGUFM.H21M..03L
- Keywords:
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- 0426 Biosphere/atmosphere interactions;
- BIOGEOSCIENCES;
- 0476 Plant ecology;
- BIOGEOSCIENCES;
- 1630 Impacts of global change;
- GLOBAL CHANGE;
- 1813 Eco-hydrology;
- HYDROLOGY