Lateral flow thresholds for aspen forested hillslopes on the Western Boreal Plain, Alberta, Canada

Abstract

Abstract:To predict the long-term sustainability of water resources on the Boreal Plain region of northern Alberta, it is critical to understand when hillslopes generate runoff and connect with surface waters. The sub-humid climate (P Ä ET) and deep glacial sediments of this region result in large available soil storage capacity relative to moisture surpluses or deficits, leading to threshold-dependent rainfall-runoff relationships. Rainfall simulation experiments were conducted using large magnitude and high intensity applications to examine the thresholds in precipitation and soil moisture that are necessary to generate lateral flow from hillslope runoff plots representative of Luvisolic soils and an aspen canopy. Two adjacent plots (areas of 2Ð95 and 3Ð4 m 2 ) of contrasting antecedent moisture conditions were examined; one had tree root uptake excluded for two months to increase soil moisture content, while the second plot allowed tree uptake over the growing season resulting in drier soils. Vertical flow as drainage and soil moisture storage dominated the water balances of both plots. Greater lateral flow occurred from the plot with higher antecedent moisture content. Results indicate that a minimum of 15-20 mm of rainfall is required to generate lateral flow, and only after the soils have been wetted to a depth of 0Ð75 m (C-horizon). The depth and intensity of rainfall events that generated runoff >1 mm have return periods of 25 years or greater and, when combined with the need for wet antecendent conditions, indicate that lateral flow generation on these hillslopes will occur infrequently.

Microtopographical and canopy cover controls on moss carbon dioxide exchange in a western Boreal Plain peatland

“…The peatland-pond complexes are located on a topographical high glacial till moraine adjacent to an upland forested hill slope reaching a height of 7 m above the pond surface. The pond and peatlands are located in a recharge zone, and water tables typically grade away from the peatland into the adjacent hillslope (Ferone and Devito, 2004;Redding and Devito, 2008). There is some disturbance associated with access roads for oil drilling located outside the study peatland-pond complex, and seismic lines (where strips of vegetation are removed) occur through upland and peatland landscape units.…”

Terrain-Shape Indices for Modeling Soil Moisture Dynamics

“…High variability during wet periods was attributed to the combination of well-drained soils and steeply sloping terrain in Pennsylvania (Takagi and Lin, 2011). Moreover, studies have shown that hydrologic flowpaths change over time from vertical infiltration during wet-up to subsurface lateral flow at or near saturation causing redistribution of moisture across the landscape (Redding and Devito, 2008;Rains et al, 2006;Swarowsky et al, 2012).…”

Effects of harvesting and drought on CO2and H2O fluxes in an aspen-dominated western boreal plain forest: early chronosequence recovery

“…Soil temperature and heat storage in the upper 0.05 m were measured using a thermocouple probe (TCAV-L; Campbell Scientific Inc.) inserted at 0.025 and 0.075 m below the soil surface. Soil volumetric moisture content (VMC, %) (CS616 TDR; Campbell Scientific Inc.; calibrated for study-site soils) and soil temperatures (107B thermistors; Campbell Scientific Inc.) were recorded at depths of 0.01, 0.10, 0.30, 0.50, and 1.0 m below the litter fall horizon -mineral soil interface at each site (Redding and Devito 2008;Brown et al 2013). VMC data were corrected for soil bulk density and temperature.…”