Testing the 'two water worlds' hypothesis under variable preferential flow conditions

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dc.contributor.authorRadolinski, Jesseen
dc.contributor.authorPangle, Lukeen
dc.contributor.authorKlaus, Julianen
dc.contributor.authorStewart, Ryan D.en
dc.contributor.departmentSchool of Plant and Environmental Sciencesen
dc.date.accessioned2021-07-26T13:38:11Zen
dc.date.available2021-07-26T13:38:11Zen
dc.date.issued2021-06en
dc.description.abstractWidespread observations of ecohydrological separation are interpreted by suggesting that water flowing through highly conductive soil pores resists mixing with matrix storage over periods of days to months (i.e., two 'water worlds' exist). These interpretations imply that heterogeneous flow can produce ecohydrological separation in soils, yet little mechanistic evidence exists to explain this phenomenon. We quantified the separation between mobile water moving through preferential flow paths versus less mobile water remaining in the soil matrix after free-drainage to identify the amount of preferential flow necessary to maintain a two water world's scenario. Soil columns of varying macropore structure were subjected to simulated rainfall of increasing rainfall intensity (26 mm h(-1), 60 mm h(-1), and 110 mm h(-1)) whose stable isotope signatures oscillated around known baseline values. Prior to rainfall, soil matrix water delta H-2 nearly matched the known value used to initially wet the pore space whereas soil delta O-18 deviated from this value by up to 3.4 parts per thousand, suggesting that soils may strongly fractionate O-18. All treatments had up to 100% mixing between rain and matrix water under the lowest (26 mm h(-1)) and medium (60 mm h(-1)) rainfall intensities. The highest rainfall intensity (110 mm h(-1)), however, reduced mixing of rain and matrix water for all treatments and produced significantly different preferential flow estimates between columns with intact soil structure compared to columns with reduced soil structure. Further, artificially limiting exchange between preferential flow paths and matrix water reduced bypass flow under the most intense rainfall. We show that (1) precipitation offset metrics such as lc-excess and d-excess may yield questionable interpretations when used to identify ecohydrological separation, (2) distinct domain separation may require extreme rainfall intensities and (3) domain exchange is an important component of macropore flow.en
dc.description.notesFunding for this work was provided in part by the Virginia Agricultural Experiment Station and the Hatch Program of the National Institute of Food and Agriculture, USDA (1007839). We would like to thank Aaron Cleveland for his help and hard work conducting this experiment. Thanks to Matthias Sprenger for initial criticism and discussion which helped improve the manuscript. Thanks to Kevin McGuire for the motivational discussions regarding mixing and preferential flow calculations with stable isotopes, all of which influenced the structure of this study. Thank you, Kelly Peeler and Durelle Scott, for help with liquid isotope analysis. We thank the two anonymous reviewers for their valuable and detailed comments.en
dc.description.sponsorshipVirginia Agricultural Experiment Station; Hatch Program of the National Institute of Food and Agriculture, USDA [1007839]en
dc.description.versionPublished versionen
dc.format.mimetypeapplication/pdfen
dc.identifier.doihttps://doi.org/10.1002/hyp.14252en
dc.identifier.eissn1099-1085en
dc.identifier.issn0885-6087en
dc.identifier.issue6en
dc.identifier.othere14252en
dc.identifier.urihttp://hdl.handle.net/10919/104396en
dc.identifier.volume35en
dc.language.isoenen
dc.rightsCreative Commons Attribution 4.0 Internationalen
dc.rights.urihttp://creativecommons.org/licenses/by/4.0/en
dc.subjectecohydrological separationen
dc.subjectmacroporesen
dc.subjectpreferential flowen
dc.subjectsoil structureen
dc.subjectstable isotopesen
dc.subjecttwo water worldsen
dc.titleTesting the 'two water worlds' hypothesis under variable preferential flow conditionsen
dc.title.serialHydrological Processesen
dc.typeArticle - Refereeden
dc.type.dcmitypeTexten
dc.type.dcmitypeStillImageen

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