@article{aa7b8569df3b446c92366ce0cf308fdc,
title = "Hydraulic redistribution buffers climate variability and regulates grass-tree interactions in a semiarid riparian savanna",
abstract = "Anticipating the ability of ecosystems to maintain functional integrity across predicted altered precipitation regimes remains a grand ecohydrological challenge. Overstory trees and understory grasses within semiarid savannas vary in their structure and sensitivity to environmental pressures, underscoring the need to examine the ecohydrological implications of this climatic variability. Whereas precipitation has long been recognized as a key driver of landscape ecohydrology, understanding a site's hydraulic redistribution regime (the balance in downward and upward movement of water and the seasonality of these bidirectional flows) may be equally important to understanding moisture availability to vegetation in these dryland ecosystems. As a result, we linked measures of ecosystem-scale carbon exchange, overstory tree sap flux and leaf-level gas exchange to understory whole-plot and leaf-level carbon and water exchange within intact and trenched plots (isolating trees from grasses) in a riparian savanna ecosystem. We maintained measurements across 2 years with distinct precipitation regimes. We found that interannual precipitation variability yielded a categorical shift in the directionality and magnitude of the hydraulic redistribution regime—even within this single site. Additionally, we found that connectivity between overstory trees and understory grasses through hydraulic redistribution created a short period of competition within an average rain year but that facilitation of understory function by overstory trees was much greater and lasted longer during drier years. Together, these findings suggest that hydraulic redistribution can serve as a hydrologic buffer against interannual precipitation variability. Given current climate projections of more variable precipitation within and across years, understanding how hydraulic redistribution regimes vary through time will greatly enhance our capacity to anticipate future ecohydrological function.",
keywords = "drylands, hydraulic lift, interannual variability, leaf gas exchange, mesquite (Prosopis velutina), photosynthesis, sap flow, woody plant encroachment",
author = "Barron-Gafford, {Greg A.} and Knowles, {John F.} and Sanchez-Ca{\~n}ete, {Enrique P.} and Minor, {Rebecca L.} and Esther Lee and Leland Sutter and Newton Tran and Patrick Murphy and Hamerlynck, {Erik P.} and Praveen Kumar and Scott, {Russell L.}",
note = "Funding Information: This project and data collection were supported by NSF Awards EAR 1417101, EAR 1417444, EAR 1331408, EAR 1331906 and ACI 1261582, as well as by a Marie Curie International Outgoing Fellowship within the 7th European Community Framework Programme, DIESEL project (No. 625988). Additional funding support was provided by the Water, Environmental, and Energy Solutions (WEES) initiative at the University of Arizona Institute of the Environment, the University of Arizona Office of the Vice President of Research and the Philecology Foundation of Ft. Worth, Texas. Funding for the continued operation of the AmeriFlux site is provided by Department of Energy's Office of Science and Department of Agriculture. All data used in this study are freely available by contacting the corresponding author. The authors wish to thank R. Bryant (USDA-ARS) for his careful operation and maintenance of the field measurement devices. EPSC was supported by the Marie Curie International Outgoing Fellowship within the 7th European Community Framework Programme, Division of Earth Sciences. Funding Information: This project and data collection were supported by NSF Awards EAR 1417101, EAR 1417444, EAR 1331408, EAR 1331906 and ACI 1261582, as well as by a Marie Curie International Outgoing Fellowship within the 7th European Community Framework Programme, DIESEL project (No. 625988). Additional funding support was provided by the Water, Environmental, and Energy Solutions (WEES) initiative at the University of Arizona Institute of the Environment, the University of Arizona Office of the Vice President of Research and the Philecology Foundation of Ft. Worth, Texas. Funding for the continued operation of the AmeriFlux site is provided by Department of Energy's Office of Science and Department of Agriculture. All data used in this study are freely available by contacting the corresponding author. The authors wish to thank R. Bryant (USDA‐ARS) for his careful operation and maintenance of the field measurement devices. EPSC was supported by the Marie Curie International Outgoing Fellowship within the 7th European Community Framework Programme, Division of Earth Sciences. Publisher Copyright: {\textcopyright} 2021 John Wiley & Sons, Ltd.",
year = "2021",
month = apr,
doi = "10.1002/eco.2271",
language = "English (US)",
volume = "14",
journal = "Ecohydrology",
issn = "1936-0584",
publisher = "John Wiley and Sons Ltd",
number = "3",
}