Near-saturated surface soil hydraulic properties under different land uses in the St Denis National Wildlife Area, Saskatchewan, Canada

摘要

Surface soil hydraulic properties are key factors controlling the partition of rainfall and snowmelt into runoff and soil water storage, and their knowledge is needed for sound land management. The objective of this study was to evaluate the effects of three land uses (native grass, brome grass and cultivated) on surface soil hydraulic properties under near-saturated conditions at the St Denis National Wildlife Area, Saskatchewan, Canada. For each land use, water infiltration rates were measured using double-ring and tension infiltrometers at -0.3, -0.7, -1.5 and -2.2 kPa pressure heads. Macroporosity and unsaturated hydraulic properties of the surface soil were estimated. Mean field-saturated hydraulic conductivity (K_(fs)), unsaturated hydraulic conductivity at -0.3 kPa pressure head, inverse capillary length scale (α) and water-conducting macroporosity were compared for different land uses. These parameters of the native grass and brome grass sites were significantly (p < 0.1) higher than that of the cultivated sites. At the -0.3 kPa pressure head, hydraulic conductivity of grasslands was two to three times greater than that of cultivated lands. Values of α were about two times and values of K_(fs) about four times greater in grasslands than in cultivated fields. Water-conducting macroporosity of grasslands and cultivated fields were 0.04% and 0.01% of the total soil volume, respectively. Over 90% of the total water flux at -0.06 kPa pressure head was transmitted through pores > 1.36 x 10~(-4) m in diameter in the three land uses. Land use modified near-saturated hydraulic properties of surface soil and consequently may alter the water balance of the area by changing the amount of surface runoff and soil water storage.