HR: 0800h
AN: H31D-0431    [Abstracts]
TI: Microenvironmental and Seasonal Variations in the Soil-Water Content of the Unsaturated Zone of a Sand Dune System at Pinery Provincial Park
AU: Webb, E A
EM: ewebb5@uwo.ca
AF: The University of Western Ontario, Department of Earth Sciences, Biological and Geological Sciences Building, London, ON N6A 5B7 Canada
AU: Ensign, K
EM: kl\_scott2002@yahoo.ca
AF: The University of Western Ontario, Department of Earth Sciences, Biological and Geological Sciences Building, London, ON N6A 5B7 Canada
AU: * Longstaffe, F J
EM: flongsta@uwo.ca
AF: The University of Western Ontario, Department of Earth Sciences, Biological and Geological Sciences Building, London, ON N6A 5B7 Canada
AB: The volumetric water contents of 1-2 m deep sand profiles were obtained monthly across the 250 m transition that contains the succession from unvegetated dune sands to C3 and C4 grass-dominated dunes to oak-savannah stabilized dunes at Pinery Provincial Park, south-western Ontario, Canada. The physical properties of the homogeneous sands are virtually identical at each profile. This consistency allows one to examine the relative influence of topography, degree of soil formation, vegetation type and abundance, forest canopy development, and seasonality on soil moisture contents in this rare, fragile and endangered ecosystem. The soils were all well drained, despite the frequent rain events that characterize this temperate-humid region. However, a less mobile fraction of water was retained in the soil for at least several months, even following large rain events. Soil water contents were too low to encourage preferential downslope flow; topography generally had little influence on soil moisture contents. The presence and type of vegetation had the greatest influence on soil moisture contents, both across the dune succession and vertically within the profiles. Grass roots facilitated deeper infiltration of precipitation relative to unvegetated dune soils. During the growing season, soil moisture contents were lowered significantly in the rooting zones of both the forested and dune-grass dominated profiles. The greatest differences in moisture content between forested and unforested areas occurred in the shallowest soil layers. Despite interception of rain by the oak canopy, water contents were higher in the forest soils. This behaviour reflects greater moisture retention by the organic-rich A-horizon and leaf litter layer typical of these more mature soils, and less evaporation from the cooler forest floor. Seasonal trends were dominated by the extent of soil water removal via transpiration, although these patterns were sometimes obscured by large precipitation events occurring a few days prior to sampling. Inter-site differences in moisture content were accentuated in the warmest summer months, when soils were subjected to the competing influences of increased evapotranspiration and periodic wetting events.
DE: 1818 Evapotranspiration
DE: 1851 Plant ecology
DE: 1854 Precipitation (3354)
DE: 1866 Soil moisture
DE: 1875 Unsaturated zone
SC: Hydrology [H]
MN: 2004 AGU Fall Meeting