Zettl, J. D., Barbour, S. L., Huang, M., Si, B. C. and Leskiw, L. A. 2011. Influence of textural layering on field capacity of coarse soils. Can. J. Soil Sci. 91: 133–147. The current method of designing reclamation covers for land disturbed by oil sands mining in northern Alberta, Canada, relies on an estimate of the field capacity (FC) of both natural soils and reclamation soil prescriptions. The objective of this research was to examine the influence of layered, textural heterogeneity on FC. Field testing was performed on seven natural sites with coarse-textured soils that support a range of ecosite classes. Double-ring infiltration and drainage tests with real time monitoring of water content were undertaken along with test pit excavation and detailed profile sampling. The measured water storage at FC following drainage demonstrated that higher water storage at FC values are associated with increased textural heterogeneity, and these sites reflected more productive ecosite class. Rigorous, physically based modeling illustrated that a texturally heterogeneous site can have water storage at FC within 1 m profile that is between 110 to 330 mm higher than a homogeneous profile with the same average texture. These higher values of water storage at FC in texturally heterogeneous sites could account for the differences in observed ecosite productivity. This work highlights the importance of textural layering in designing reclamation covers in coarse-textured soils to maximize FC.

Huang, M., Barbour, S. L., Elshorbagy, A., Zettl, J. D. and Si, B. C. 2011. Infiltration and drainage processes in multi-layered coarse soils. Can. J. Soil Sci. 91: 169–183. Infiltration and drainage processes in multi-layered soils are complicated by contrasting hydraulic properties. The objective of this study was to evaluate the performances of the hysteretic and non-hysteretic models to simulate the infiltration and drainage processes from three different natural soil profiles containing as many as 20 texturally different layers. Hydraulic properties were estimated from soil textures using pedotransfer functions and were calibrated and validated using measured water contents during infiltration and drainage phases, respectively. The results supported the use of the Arya-Paris pedotransfer function to estimate the wetting curve when contact angles are incorporated. The unique Kozeny-Carmen equation parameter was evaluated by optimizing the estimated saturated hydraulic conductivity. The calibrated numerical model (Hydrus-1D) accurately simulated soil water content profiles and water volumes during the infiltration and drainage phases. The mean error of prediction (MEP) between the measured and estimated soil water contents varied from –0.030 to 0.010 cm3 cm−3, and the standard deviation of prediction (SDP) from 0.003 to 0.057 cm3 cm−3. The simulation was improved for more heterogeneous soil profiles when hysteresis was taken into account. The measured and simulated results indicated that the soil profile with vertical heterogeneity in soil texture can store more water than the similar textured vertically homogeneous soils under drained conditions.

[1] Seven high-resolution (0.3-0.6 m depth intervals), 1-D vertical profiles of the d 2 H of pore water were collected across a 300 km 2 study area in southern Saskatchewan, Canada, to define the vertical controls on solute transport in a >120 m thick, two-layered aquitard system. The 1-D profiles were augmented with an existing d 2 H profile collected from a previous study. The surficial aquitard in the area consists of Quaternary deposits (either glacial till or lacustrine deposits; 13 to 128 m thick) underlain by an upper Cretaceous claystone aquitard (80-110 m thick). The shape of the individual d 2 H profiles and associated 1-D transport modeling suggest diffusion is the regionally dominant vertical transport mechanism across the aquitards. The profile shape is controlled by the thickness of the Quaternary deposit and the d 2 H value at the upper boundary, which coincides with the depth of the water table. The upper boundary d 2 H value varies considerably across the area (À149% to À101%), perhaps due to differences in local hydrological conditions (e.g., slope, aspect, infiltration) across the landscape. Modeling of all profiles shows the timing for till deposition and the timing of climate change during the Holocene are consistent across the area ($30 ka and 7-10 ka before the present, respectively), corroborating other studies. This study provides insights into the hydrogeologic controls on solute transport in an aquitard system and associated geologic and climatic changes for a prairie region over the past 30 ka, and improves our understanding of initial and time-dependent transport boundary conditions for the study of aquitards.

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The reestablishment of productive forests over mining waste and overburden is a primary reclamation goal in oil sands mining in Northern Alberta, Canada. Soil water conditions in coarse‐textured soils can be limiting to forest growth. The objective of this study was to evaluate the effect that textural variability may have on plant‐available water and concomitant forest productivity on coarse‐textured reclamation soils. The ecophysiological and biogeochemical processes model, Biome‐BGC (Thornton et al., Agricultural and Forest Meteorology 113: 185–222, 2002), was employed to simulate forest dynamics. The water flow sub‐model in Biome‐BGC was replaced by a field‐validated physically based formulation for transient unsaturated water flow. The modified model was assessed using validated physiological parameters, and model predictions were compared with measurements of aboveground biomass dynamics for jack pine (Pinus banksiana Lamb), white spruce [Picea glauca (Moench) Voss], and trembling aspen (Populus tremuloides Michx.). The modified Biome‐BGC model was then used to evaluate the response of leaf area index and net primary production to available water holding capacity on texturally variable, coarse‐textured soils. The results indicate that textural variability could increase the available water holding capacity within a 1‐m profile of coarse‐textured soil by 8 to 16 mm. This enhanced available water holding capacity could increase forest leaf area index by 0·3 to 0·8 and net primary production by 14–30% depending on the specific soil texture and tree species. Copyright © 2012 John Wiley & Sons, Ltd.