Methods for determining soil water repellency on field‐moist samples

Dekker, L.W.; Ritsema, C.J.; Oostindie, K.; Moore, Demie; Wesseling, J.G.

doi:10.1029/2008wr007070

Cited by 90 publications

(85 citation statements)

References 60 publications

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“…At each sample point, soil water repellency was quantified using the WDPT test (Dekker, Ritsema, Oostindie, Moore, & Wesseling, ) and minidisk infiltrometer (Robichaud, Lewis, & Ashmun, ). Prior to the drop and infiltration tests, the soil surface was cleaned of any loose leaf and duff materials, thus exposing either the upper ash layer (burned sites) or the organic horizon (unburned sites).…”

Section: Methodssupporting

confidence: 88%

Effect of soil water‐repellent layer depth on post‐wildfire hydrological processes

Chen

McGuire

Stewart

2019

Hydrological Processes

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Soil water repellency induced by wildfires can alter hydraulic properties and hydrologic processes; however, the persistence and vertical position (i.e., depth) of water‐repellent layers can vary between systems and fires, with limited understanding of how those variations affect infiltration processes. This study occurred in two forested locations in the south‐central Appalachian Mountains that experienced wildfires in late 2016: Mount Pleasant Wildfire Refuge, Virginia, and Chimney Rock State Park, North Carolina. In each location, sites were selected to represent unburned conditions and low to moderate burn intensities. At each site, we measured the soil water repellency at the surface (ash layer or O horizon) and ~2 cm below the surface (A horizon) using the water drop penetration time method (n = 10–14). Soil water content was also measured over the upper 10 cm of the soil (n = 10), and infiltration tests were conducted using a tension infiltrometer (n = 6–8). The results showed that soil repellency was highest in the surface layer at the Mount Pleasant location and was highest in the subsurface layer at the Chimney Rock location. Soil water content was lower in unburned soil than in burned soil, especially for measurements taken immediately postfire, with soil water content negatively correlated with water repellency. Water repellency in the surface layer significantly reduced relative infiltration rates (estimated as differences between initial and steady‐state rates), whereas subsurface water repellency did not affect relative infiltration. As a result, water repellency persisted longer in sites with surface as opposed to subsurface water repellency. Finally, differences between burned and unburned sites showed that although the wildfires increased the occurrence of water repellency, they did not alter the underlying relationship between relative infiltration and water repellency of the surface soil.

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Section: Methodssupporting

confidence: 88%

Effect of soil water‐repellent layer depth on post‐wildfire hydrological processes

Chen

McGuire

Stewart

2019

Hydrological Processes

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“…The occurrence of repellent layers within the profile was evaluated by calculating the mean percentage of repellent drops (Category 1 and above) following Dekker et al (). Similar patterns of WR occurred with increasing depth between soils (Figure ) and surface WR existed in both soils.…”

Section: Resultsmentioning

confidence: 99%

Does fire alter soil water repellency in subtropical coastal sandy environments?

White

Lockington

Gibbes

2016

Hydrological Processes

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Irregular wetting, water repellency, and preferential flow are well‐documented properties of coastal sandy podzols, though little is known about the effect of fire on unsaturated zone processes in this environment. This study investigates water repellency at and below the soil surface in two coastal sandy podzols following bushfire. Water drop penetration time tests were applied to burned and unburned soils at a high dune field site in South East Queensland, Australia. It was found that the mean water drop penetration time of the burned soil was four times that of the unburned soil, but both soils were largely non‐repellent. Post‐fire repellency peaked below the surface in a patchy layer, in contrast to the laterally extensive layer reported in other studies, and high organic matter content in the soil did not appear to significantly influence repellency post‐burn. Non‐parametric statistics were used to quantify the high spatial variability in water repellency, which was ultimately insufficiently captured by atypically large (n = 1000 drop) datasets. This study confirms the presence of naturally occurring repellency and patchy infiltration in sandy soils while demonstrating that conclusively describing the influence of fire is challenging in a soil with heterogeneous infiltration characteristics. With respect to this uncertainty, it appears that fire does not increase soil water repellency such that infiltration and runoff processes due to fire‐induced water repellency would differ post‐burn.

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“…The WDPT measurements were performed on field-moist samples immediately after assessment of the wet weights of the samples. In this way the so-called "actual soil water repellency" is measured (Dekker and Ritsema, 1994;Dekker et al, 2009). …”

Section: Water Drop Penetration Time (Wdpt) Testmentioning

confidence: 99%

Impacts of grass removal on wetting and actual water repellency in a sandy soil

Oostindie

Dekker

Wesseling

et al. 2016

Journal of Hydrology and Hydromechanics

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Soil water content and actual water repellency were assessed for soil profiles at two sites in a bare and grasscovered plot of a sand pasture, to investigate the impact of the grass removal on both properties. The soil of the plots was sampled six times in vertical transects to a depth of 33 cm between 23 May and 7 October 2002. On each sampling date the soil water contents were measured and the persistence of actual water repellency was determined of field-moist samples. Considerably higher soil water contents were found in the bare versus the grass-covered plots. These alterations are caused by differences between evaporation and transpiration rates across the plots. Noteworthy are the often excessive differences in soil water content at depths of 10 to 30 cm between the bare and grass-covered plots. These differences are a consequence of water uptake by the roots in the grass-covered plots. The water storage in the upper 19 cm of the bare soil was at least two times greater than in the grass-covered soil during dry periods. A major part of the soil profile in the grass-covered plots exhibited extreme water repellency to a depth of 19 cm on all sampling dates, while the soil profile of the bare plots was completely wettable on eight of the twelve sampling dates. Significant differences in persistence of actual water repellency were found between the grass-covered and bare plots.

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Methods for determining soil water repellency on field‐moist samples

Cited by 90 publications

References 60 publications

Effect of soil water‐repellent layer depth on post‐wildfire hydrological processes

Effect of soil water‐repellent layer depth on post‐wildfire hydrological processes

Does fire alter soil water repellency in subtropical coastal sandy environments?

Impacts of grass removal on wetting and actual water repellency in a sandy soil

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