@article{6ebe7a5956704b7b98bcad5aae2b7fad,
title = "Characterizing the Fluxes and Age Distribution of Soil Water, Plant Water, and Deep Percolation in a Model Tropical Ecosystem",
abstract = "Recent field observations indicate that in many forest ecosystems, plants use water that may be isotopically distinct from soil water that ultimately contributes to streamflow. Such an assertion has been met with varied reactions. Of the outstanding questions, we examine whether ecohydrological separation of water between trees and streams results from a separation in time, or in space. Here we present results from a 9-month drought and rewetting experiment at the 26,700-m3 mesocosm, Biosphere 2-Tropical Rainforest biome. We test the null hypothesis that transpiration and groundwater recharge water are sampled from the same soil volume without preference for old nor young water. After a 10-week drought, we added 66 mm of labeled rainfall with 152‰ δ2H distributed over four events, followed by background rainfall (−60‰ δ2H) distributed over 13 events. Our results show that mean transit times through groundwater recharge and plant transpiration were markedly different: groundwater recharge was 2–7 times faster (~9 days) than transpired water (range 17–62 days). The “age” of transpired water showed strong dependence on species and was linked to the difference between midday leaf water potential and soil matric potential. Moreover, our results show that trees used soil water (89% ±6) and not the “more mobile” (represented by “zero tension” seepage) water (11% ±6). The finding, which rejects our null hypothesis, is novel in that this partitioning is established based on soil water residence times. Our study quantifies mean transit times for transpiration and seepage flows under dynamic conditions.",
keywords = "critical zone, ecohydrological separation, stable isotopes, tracer, transit times, two water worlds",
author = "Jaivime Evaristo and Minseok Kim and {van Haren}, Joost and Pangle, {Luke A.} and Harman, {Ciaran J.} and Troch, {Peter A.} and McDonnell, {Jeffrey J.}",
note = "Funding Information: Data used in the study can be obtained from HydroShare, https://doi.org/ 10.4211/hs.60fb3a408cac40cbb38b 8f559ef1fc5c. All cryogenically extracted water samples (soil and xylem) are archived in McDonnell Lab; contact J. Evaristo (evaristo@sas. upenn.edu) for information on access to archived samples. We thank the following undergraduate research assistants for their help during the predrought and drought stages of the experiment: Meghan McDonnell, Ietza Gonzalez Silva, Fatima Olmos Flores, and Daniel Espinosa Ruiz. We thank Maggie Heard, Sara Jane Harders, John Adams, Kim Land, and all staff and crew at Biosphere 2 for their invaluable support during the conduct of this experiment. Peter Troch acknowledges funding from the Agnese N. Haury Foundation. Finally, we thank Kim Janzen and Cody Millar in McDonnell Lab (University of Saskatchewan, SK, Canada) for the logistical and lab support and Gibson Lab (University of Victoria, BC, Canada) for the mass spectrometry analysis. J. Evaristo thanks Saskatchewan Innovation and Opportunity Scholarship (Government of Saskatchewan) and Graduate Research Fellowship (School of Environment and Sustainability) for the research funding. The overall funding for this project is from an NSERC Discovery Grant and Accelerator Award to J. J. M. Funding Information: Data used in the study can be obtained from HydroShare, https://doi.org/10.4211/hs.60fb3a408cac40cbb38b8f559ef1fc5c. All cryogenically extracted water samples (soil and xylem) are archived in McDonnell Lab; contact J. Evaristo (evaristo@sas.upenn.edu) for information on access to archived samples. We thank the following undergraduate research assistants for their help during the predrought and drought stages of the experiment: Meghan McDonnell, Ietza Gonzalez Silva, Fatima Olmos Flores, and Daniel Espinosa Ruiz. We thank Maggie Heard, Sara Jane Harders, John Adams, Kim Land, and all staff and crew at Biosphere 2 for their invaluable support during the conduct of this experiment. Peter Troch acknowledges funding from the Agnese N. Haury Foundation. Finally, we thank Kim Janzen and Cody Millar in McDonnell Lab (University of Saskatchewan, SK, Canada) for the logistical and lab support and Gibson Lab (University of Victoria, BC, Canada) for the mass spectrometry analysis. J. Evaristo thanks Saskatchewan Innovation and Opportunity Scholarship (Government of Saskatchewan) and Graduate Research Fellowship (School of Environment and Sustainability) for the research funding. The overall funding for this project is from an NSERC Discovery Grant and Accelerator Award to J.?J.?M. Publisher Copyright: {\textcopyright}2019. The Authors.",
year = "2019",
month = apr,
doi = "10.1029/2018WR023265",
language = "English (US)",
volume = "55",
pages = "3307--3327",
journal = "Water Resources Research",
issn = "0043-1397",
publisher = "American Geophysical Union",
number = "4",
}