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Development of airflow pathways in heterogeneous unsaturated soil was studied for spatially and temporally varying soil moisture conditions using laboratory and numerical modeling methods. During rainfall periods the fraction of subsurface-originated airflow increased whereas fresh surface-originated airflow was dominant during rain-free periods.

Vadose Zone Journal February 01, 2013, Vol.12, vzj2011.0118. doi:https://doi.org/10.2136/vzj2011.0118

Data from drainage experiments were used to derive soil hydraulic parameters in a Bayesian framework using a Markov chain Monte Carlo sampling method. Prior to parameter identification with observed data the use of global sensitivity analysis facilitates identification of the necessary set of measurements for successful parameters estimation.

Vadose Zone Journal February 01, 2013, Vol.12, vzj2011.0150. doi:https://doi.org/10.2136/vzj2011.0150

To avoid adverse effects from treated urban wastewater used for irrigation, a sound irrigation policy based on real-time soil states is needed. In this work, a system assimilating embedded sensor datastreams into a hydrologic model to improve real-time soil state estimates is proposed and is examined with a wastewater reuse system in Palmdale, CA.

Vadose Zone Journal February 01, 2013, Vol.12, vzj2011.0176. doi:https://doi.org/10.2136/vzj2011.0176

A column experiment on infiltration through frozen soil was conducted. We observed three phases of infiltration. The duration of each phase increased with increasing initial soil water content at the time of freezing. The infiltration process was controlled by the volumetric ice content and thickness of the frozen layer.

Vadose Zone Journal February 01, 2013, Vol.12, vzj2011.0188. doi:https://doi.org/10.2136/vzj2011.0188

We develop an algorithm for estimating saturated hydraulic conductivity and van Genuchten parameters from a time-lapse vertical electrical conductivity profile beneath a managed aquifer recharge pond. We then derive a relationship that can be used for real-time estimation of in situ infiltration rates from one-dimensional electrical conductivity estimates.

Vadose Zone Journal February 01, 2013, Vol.12, vzj2011.0203. doi:https://doi.org/10.2136/vzj2011.0203

The three-dimensional root system architecture (RSA) of a lupin plant is constructed using two methods, an automated procedure based on a three-dimensional MRI image, and a semi-manual method based a 3D virtual reality system. The two results show some differences in connectivity of root segments, which affects the distributions of root water uptake and xylem pressures.

Vadose Zone Journal February 01, 2013, Vol.12, vzj2012.0019. doi:https://doi.org/10.2136/vzj2012.0019

Microbial and biochemical properties are very important indicators to assess soil quality. We investigated the impact of cerrado (CE), pine forest (PF), and no-tillage (NT) systems on microbial and biochemical indicators, finding lower indicators in the PF system and higher indicators in the NT system when compared to the CE system.

Vadose Zone Journal February 01, 2013, Vol.12, vzj2012.0027. doi:https://doi.org/10.2136/vzj2012.0027

Thermal conductivity and diffusivity were measured for different sands under varied water saturation and temperature. Data showed that the thermal properties increased noticeably for sample temperatures above 50°C. At sample temperatures between 30 and 50°C, changes in thermal properties were small.

Vadose Zone Journal February 01, 2013, Vol.12, vzj2012.0033. doi:https://doi.org/10.2136/vzj2012.0033

This study examines nitrate and nitrous oxide dynamics in deep (down to 5 m) alluvial gravel vadose zones, under a synthetic urine application and an adjacent control plot. Nitrous oxide levels and nitrate/bromide ratios suggest that denitrification occurred in the soil and subsoils, but was relatively minor in the deeper alluvial gravel vadose zone.

Vadose Zone Journal February 01, 2013, Vol.12, vzj2012.0038. doi:https://doi.org/10.2136/vzj2012.0038

We critically review the two main classes of frost heave models—capillary and frozen-fringe models. We describe recent developments in the field and highlight areas where new research is needed.

Vadose Zone Journal February 01, 2013, Vol.12, vzj2012.0049. doi:https://doi.org/10.2136/vzj2012.0049

Frost heave causes damage to roads, buildings, pipelines, and more, amounting to millions of dollars annually. This paper provides better understanding of the processes occurring in freezing soils and the fundamental cause of frost heaving. A Heave Index is formulated, quantifying the likelihood and magnitude of heave to occur at a certain location.

Vadose Zone Journal February 01, 2013, Vol.12, vzj2012.0051. doi:https://doi.org/10.2136/vzj2012.0051

The applicability of the sensible heat balance (SHB) concept for estimating soil freezing and thawing rates was tested in a numerical modeling study. Results indicated that the SHB method was suitable for estimating soil freezing and thawing rates at depths below 24 mm. Application of the method requires accurate estimates of soil thermal properties. Agronomy Dep., Iowa State Univ., Ames, IA 50011; Soil Science Dep., North Carolina State Univ., Raleigh, NC 27695 USDA-ARS, Northwest Watershed Research center, Boise, ID 83712

Vadose Zone Journal February 01, 2013, Vol.12, vzj2012.0053. doi:https://doi.org/10.2136/vzj2012.0053

Analyses of field observations and laboratory experiments indicate that observed rapid water table responses, manifested either as groundwater ridging for a shallow water table or the Lisse effect for a deep water table, are caused by the rapid introduction of additional energy into the capillary fringe from intense rainfall on the ground surface.

Vadose Zone Journal February 01, 2013, Vol.12, vzj2012.0054. doi:https://doi.org/10.2136/vzj2012.0054

Three types of urban waste composts were tested for their effect on water and solute transport in a cultivated silt loam bare Albeluvisol. Compost addition was found to increase water retention in the topsoil by 0.015 to 0.03 cm3 cm−3. Bromide leaching was larger in compost-amended plots than in the control due to smaller soil water evaporation.

Vadose Zone Journal February 01, 2013, Vol.12, vzj2012.0056. doi:https://doi.org/10.2136/vzj2012.0056

The effect of freeze-thaw cycles on the unfrozen water content in cohesive soils was examined. The freeze-thaw effect on the unfrozen water content in bentonites is not statistically significant. The unfrozen water content was found to be best correlated to the specific surface area and the clay content as measured by the laser diffraction method.

Vadose Zone Journal February 01, 2013, Vol.12, vzj2012.0057. doi:https://doi.org/10.2136/vzj2012.0057

Snow augmentation experiments conducted over two consecutive seasons found that inter-annual variability in the timing of snow accumulation had a greater impact on soil temperatures than changes in snow depth. Thus, predicting the response of permafrost to climate change will be sensitive to both the magnitude and timing of autumn snowfall.

Vadose Zone Journal February 01, 2013, Vol.12, vzj2012.0058. doi:https://doi.org/10.2136/vzj2012.0058

The grazed site with lower vegetation/snow cover and larger thermal conductivity had greater freezing rates and larger soil temperature fluctuations. Winter precipitation was 15% of the annual water balance for the ungrazed site, but only 11% for the grazed site. Spring snowmelt infiltration was critical in seasonal water and energy balances.

Vadose Zone Journal February 01, 2013, Vol.12, vzj2012.0059. doi:https://doi.org/10.2136/vzj2012.0059

TDR is a standard tool for measurement of water content in unfrozen soils. Empirical TDR calibration relationships derived for unfrozen soils are not directly transferable to frozen soils. In this work, dielectric mixing models are used to explore factors affecting the dielectric permittivity and TDR measurement of liquid water in frozen soils.

Vadose Zone Journal February 01, 2013, Vol.12, vzj2012.0060. doi:https://doi.org/10.2136/vzj2012.0060

Using antifreeze liquid and a common K(h)-based hydraulic equation, an apparent impedance parameter Ωa was experimentally determined for the air-filled porosity of unsaturated frozen soil. Ωa is about 4 ranging from 0.5 to 6.5 as a function of matric potential. Results of the experimental method may be useful in estimating snowmelt infiltration.

Vadose Zone Journal February 01, 2013, Vol.12, vzj2012.0061. doi:https://doi.org/10.2136/vzj2012.0061

Remote monitoring of freeze-thaw transition of arctic soils using the complex resistivity method was simulated in column studies. Our results revealed the sensitivity of this method to freeze-thaw transition and its potential for monitoring freeze-thaw processes in the arctic region that are critical to global carbon cycle and climate change.

Vadose Zone Journal February 01, 2013, Vol.12, vzj2012.0062. doi:https://doi.org/10.2136/vzj2012.0062

The method of determination of the fractal dimension based on particle size distribution (PSD) derived from the laser diffraction method is analysed. Discussion is provided on the impact of the PSD determination methodology on the derived fractal dimension, and the possibility for characterization of soil by a single fractal approach.

Vadose Zone Journal February 01, 2013, Vol.12, vzj2012.0064. doi:https://doi.org/10.2136/vzj2012.0064

Thermal degradation of some rock glaciers in the Turtmann valley (CH) has accelerated recently, causing unusual thermokarst features to develop, with surface creep rates exceeding 3 m/a. A multidisciplinary research project was started to investigate the internal thermal, mechanical, and hydrological interactions affecting this response. The creep velocities with depth show some seasonal dependency.

Vadose Zone Journal February 01, 2013, Vol.12, vzj2012.0067. doi:https://doi.org/10.2136/vzj2012.0067

We introduce a new design for direct-push electrical resistivity probes, as well as document an inversion procedure for processing the data. We demonstrate the effectiveness of these probes at an artificial recharge site in Watsonville, CA. The data from these probes lends new insight into processes governing infiltration at the site.

Vadose Zone Journal February 01, 2013, Vol.12, vzj2012.0073. doi:https://doi.org/10.2136/vzj2012.0073

Soil water content and temperature were measured in shallow soil under no-tillage and fall plowing systems over 10 winters. Data analysis shows differences in soil freezing characteristics (SFC) between tillage treatments that changed over the 10-yr period. Analysis of hysteresis in SFC suggested it may be more apparent than mechanistically real.

Vadose Zone Journal February 01, 2013, Vol.12, vzj2012.0075. doi:https://doi.org/10.2136/vzj2012.0075

The unique experimental data of X-ray computed tomography and magnetic resonance were combined with three-dimensional numerical modeling to analyze the effect of air entrapment on steady state flow rate in two subsequent infiltration experiments. The change of the flow rate was explained by air entrapment in preferential flow regions.

Vadose Zone Journal February 01, 2013, Vol.12, vzj2012.0078. doi:https://doi.org/10.2136/vzj2012.0078

The potential for groundwater and plant contamination during the natural attenuation and phytoremediation of soil contaminated with volatile organic compounds was investigated. The addition of substrate during natural attenuation helped to reduce subsurface contamination and careful plant management should be considered during VOC phytoremediation.

Vadose Zone Journal February 01, 2013, Vol.12, vzj2012.0081. doi:https://doi.org/10.2136/vzj2012.0081

Time series of soil water content and matric head for disturbed desert soils were simulated with HYDRUS using direct, indirect, and inverse parameterization methods. Despite good reproduction of water content by all methods, the head was underestimated. It is argued this might be due to soil disturbance, insufficient data or sensor hysteresis.

Vadose Zone Journal February 01, 2013, Vol.12, vzj2012.0083. doi:https://doi.org/10.2136/vzj2012.0083

Micro push-pull tests, originally developed to assess chemical and microbial reactions in water-saturated porous media at the mm-scale, were adapted to unsaturated conditions. The new method was evaluated using experiments and numerical simulations, and yielded promising results in unsaturated soils over a range of capillary pressure heads.

Vadose Zone Journal February 01, 2013, Vol.12, vzj2012.0087. doi:https://doi.org/10.2136/vzj2012.0087

Wildfire can change how soils take in, store, and release water. This study examined differences in how burned and unburned plots on north versus south-facing slope aspects respond to rainfall. The largest wildfire impacts were litter/duff combustion on burned north-facing slopes versus soil-water retention reduction on burned south-facing slopes.

Vadose Zone Journal February 01, 2013, Vol.12, vzj2012.0089. doi:https://doi.org/10.2136/vzj2012.0089

Quantification of bacteria in vadose zone pore waters is difficult. Laboratory testing of stainless steel suction lysimeters for sampling bacteria in wastewater demonstrated the lysimeters are suitable for enumeration in many practical applications, provided the sampler limitations are understood.

Vadose Zone Journal February 01, 2013, Vol.12, vzj2012.0092. doi:https://doi.org/10.2136/vzj2012.0092

In this paper two different subsurface parameterizations are compared for posterior soil moisture estimation from traveltime observations of crosshole GPR. The discrete cosine transform provides the most adequate and efficient results and enables linking MCMC derived parameter uncertainty to model resolution.

Vadose Zone Journal February 01, 2013, Vol.12, vzj2012.0101. doi:https://doi.org/10.2136/vzj2012.0101

Soil columns were subjected to surface evaporation. Layered columns with silt at the surface had more evaporation than uniform columns. Water loss from columns with sand at the surface occurred primarily in the sand and not from the underlying silt layer, while columns with silt at the surface drew water from the underlying sand layers.

Vadose Zone Journal February 01, 2013, Vol.12, vzj2012.0108. doi:https://doi.org/10.2136/vzj2012.0108

The effectiveness of thermal remediation in the vadose zone was assessed by applying material flow analysis. This method enabled evaluation of the remediation performance and the overall contaminant emission into the environment, and provided an overview of contaminant flows in the soil-water-air compartment, both before and during remediation.

Vadose Zone Journal February 01, 2013, Vol.12, vzj2012.0113. doi:https://doi.org/10.2136/vzj2012.0113

Advanced numerical simulation models can potentially improve irrigation on and soil salinity management, but prediction uncertainties need to be quantified. In this study, prediction intervals generated by propagating soil parameter uncertainties tended to underestimate the range of tracer transport variability observed across large lysimeters.

Vadose Zone Journal February 01, 2013, Vol.12, vzj2012.0143. doi:https://doi.org/10.2136/vzj2012.0143

A dual-continuum model of soil-moisture dynamics that incorporates water uptake by plants via a mechanism driven by a difference in water potential is presented. The model is used to predict the root-mediated redistribution of water in a forest soil and compared with extensive field measurements.

Vadose Zone Journal February 01, 2013, Vol.12, vzj2012.0154. doi:https://doi.org/10.2136/vzj2012.0154

ERRATUM

Vadose Zone Journal February 01, 2013, Vol.12, vzj2011.0165er. doi:https://doi.org/10.2136/vzj2011.0165er

Book Reviews

Vadose Zone Journal February 01, 2013, Vol.12, vzj2012.0026br. doi:https://doi.org/10.2136/vzj2012.0026br
Vadose Zone Journal February 01, 2013, Vol.12, vzj2012.0181br. doi:https://doi.org/10.2136/vzj2012.0181br

Special Section: Frozen Soils

The guest editors introduce this issue’s special section devoted to frozen soils. Climate change and interest in modeling of these soils has sparked increased interest in frozen soils research.

Vadose Zone Journal February 01, 2013, Vol.12, vzj2013.01.0001. doi:https://doi.org/10.2136/vzj2013.01.0001
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