Vadose Zone Journal

Journal: Vadose Zone Journal

Abbreviation

Vadose Zone J.

Publisher

SSSA

ISSN

1539-1663

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Publications1 - 10 of 29

Soil Hydraulic Modeling Outcomes with Four Parameterization Methods: Comparing Soil Description and Inverse Estimation Approaches
Graham, Scott L.; Srinivasan, M.S.; Faulkner, Nathalie; et al. (2018)
Vadose Zone Journal
Different methods for parameterizing soil hydraulic models can lead to substantially varied predictions of soil–plant–atmosphere water fluxes. This study investigated, for a heterogeneous stony soil, four methods of soil hydraulic parameterization: (i) use of a pedotransfer function with a four-layer soil profile based on detailed soil physical and textural description; (ii) use of a pedotransfer function with a single-layer soil description; (iii) inverse estimation from soil moisture data; and (iv) inverse estimation from lysimeter drainage. Soil drainage, volumetric water content, and evapotranspiration were each modeled using HYDRUS-1D for an irrigated pasture in New Zealand during the time period 1 July 2011 to 15 Mar. 2014. The first 15 mo were used for model spin-up and inverse parameter estimation, while the remainder of the study period was used as a validation period, during which model results were compared against field data. Predictions from each model parameterization were compared with field-measured fluxes from lysimeter, soil moisture sensors, and eddy covariance to determine the approach most appropriate for our site and application. The parameters estimated inversely from field data improved the modeling of soil drainage, leading to total drainage within 5 to 7% of the measured volume and prediction of 35 to 80% more drainage peaks than parameterizations based on detailed soil physical description. While all methods underpredicted evapotranspiration by 18 to 30% compared with eddy covariance, improvement in drainage estimates with inverse estimation from field data led to decreased capability for modeling evapotranspiration. We suggest this approach for application in other settings to select the most appropriate parameterization approach for a given soil hydraulic model application.
Beech Forest Density Control on the Dominant Water Flow Types in Andic Soils
Capuliak, Jozef; Pichler, Viliam; Fluehler, Hannes; et al. (2010)
Vadose Zone Journal
Compressibility of Undisturbed Silt Loam Soil—Measurements and Simulations
Berli, Markus; Casini, Francesca; Attinger, Werner; et al. (2015)
Vadose Zone Journal
Insights from Independent Evapotranspiration Estimates for Closing the Energy Balance
Wohlfahrt, Georg; Irschick, Christoph; Thalinger, Bettina; et al. (2010)
Vadose Zone Journal
Unstable Infiltration Experiments in Dry Porous Media
Cremer, Clemens J.M.; Schuetz, C.; Neuweiler, Insa; et al. (2017)
Vadose Zone Journal
Micro push-pull tests for investigation of small-scale processes in unsaturated porous media
Knecht, Kajsa; Nowack, Bernd; Schulin, Rainer; et al. (2013)
Vadose Zone Journal
The micro push–pull test (μPPT) was recently developed for the in situ study of chemical and microbiological reactions in water‐saturated porous media at the millimeter scale. In a μPPT, a test solution containing reactants and nonreactive tracers is injected into a porous medium using suction cups and then re‐extracted from the same location. We adapted the μPPT method to unsaturated conditions and tested it against numerical simulations. Experiments were performed using sand packs in thin‐slab chambers as a model porous medium. We injected ~250 μL of a test solution containing either Br− or Acid Red 1 as the nonreactive tracer into the sand pack, followed by slow extraction of ~750 μL of solution from the same location. Extraction was feasible for applied capillary pressure heads in the range of 0 to 24 cm H₂O (corresponding water saturation of 1 to 0.34). To obtain spatially resolved information on water saturation and migration of injected test solutions in sand packs, visible light transmission combined with image analysis was used. Relative mass recoveries of injected tracers ranged from 56 to 99%. Extraction breakthrough curves of the tracers were successfully simulated considering advection, dispersion, and molecular diffusion without fitting any parameters. Experimental and numerical results showed that the μPPT method is a promising technique to study small‐scale behavior of solutes (e.g., ligands, biodegradable solutes, etc.) in unsaturated soils under in situ conditions.
In Situ Quantification of Atmospheric Methane Oxidation in Near-Surface Soils
Nauer, Philipp A.; Schroth, Martin Herbert (2010)
Vadose Zone Journal
The turnover of greenhouse gases in soils is largely mediated by the activity of microorganisms. In situ quantification of these processes is important to improve estimates on global budgets for many greenhouse gases, including CH₄ In this study, we assessed the utility of a modified version of the gas push–pull test (GPPT) to derive in situ apparent first‐order rate coefficients for atmospheric CH₄ oxidation in near‐surface soil. An ordinary GPPT consists of the controlled injection and subsequent extraction of reactants (i.e., CH₄ and O₂) and tracer gases (e.g., Ar, Ne, or He) into and out of the vadose zone at a location of interest. In the modified GPPT, injection and extraction takes place inside a cylinder previously placed in the soil and temporarily closed at the top. Using numerical simulations and tests in a laboratory sand tank, we found gas recovery to remain low (3–17%) and decrease with decreasing injection–extraction depth during ordinary GPPTs of∼1‐h duration. Under similar test conditions, modified GPPTs resulted in high gas recovery (64–90%) of all gases used. This allowed the modified GPPTs to be prolonged up to 12 h in simulations and 6 h in laboratory experiments, while gas recovery still remained substantial (19–57%). The modified GPPT was successfully applied to quantify atmospheric CH₄ oxidation in situ in a sandy soil in Zurich, Switzerland. Calculated first‐order rate coefficients ranged from 0.7 to 1.6 h⁻¹and agreed with literature values and estimates derived from a diffusion–consumption model fitted to CH₄ concentration profiles. Our modification extends the applicability of GPPTs to study microbially mediated gas turnover in near‐surface soils.
A Network of Terrestrial Environmental Observatories in Germany
Zacharias, Steffen; Bogena, Heye; Samaniego, Luis; et al. (2011)
Vadose Zone Journal
Multicompartment and multiscale long‐term observation and research are important prerequisites to tackling the scientific challenges resulting from climate and global change. Long‐term monitoring programs are cost intensive and require high analytical standards, however, and the gain of knowledge often requires longer observation times. Nevertheless, several environmental research networks have been established in recent years, focusing on the impact of climate and land use change on terrestrial ecosystems. From 2008 onward, a network of Terrestrial Environmental Observatories (TERENO) has been established in Germany as an interdisciplinary research program that aims to observe and explore the long‐term ecological, social, and economic impacts of global change at the regional level. State‐of‐the‐art methods from the field of environmental monitoring, geophysics, and remote sensing will be used to record and analyze states and fluxes for different environmental compartments from groundwater through the vadose zone, surface water, and biosphere, up to the lower atmosphere.
Dynamics of Fluid Interfaces and Flow and Transport across Material Interfaces in Porous Media - Modeling and Observations
Lehmann, Peter; Neuweiler, Insa; Vanderborght, Jan; et al. (2012)
Vadose Zone Journal
Mechanics and Energetics of Soil Penetration by Earthworms and Plant Roots: Higher Rates Cost More
Ruiz, Siul; Schymanski, Stan; Or, Dani (2017)
Vadose Zone Journal

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