Wednesday, 9 November 2005 - 9:00 AM
280-1

A New Approach to Soilscape Quantification.

Blake Ketchum and Alan Busacca. Department of Crops and Soils, Washington State University, @201 Johnson Hall, Pullman, WA 99164-6420

Intense variations in soil horizon sequences of Spodosols result from treethrow, lateral transport of soil components, and dependence of soil properties upon microtopographic features. These limit the applicability of the classical pedon and soil-landscape concepts to watershed containing Spodosols. To overcome this limitation, we precisely measured horizon volume, horizon distribution and horizon variability, by a new set of methods, and we related these properties to environmental factors. We used these relationships to identify patterns and drivers of eluviation and illuviation in a podzolized 0th order watershed in Baraga County, Michigan. The volumes and spatial distribution of eluvial horizons correlate significantly with flow area and slope, greater volumes are generally associated with steeper, west-facing parts of the landscape. The volume of the Bhs horizon is significantly correlated with the wetter landscape positions, whereas Ortstein layers and the Bs2 horizon have greater volumes in higher parts of the landscape.

We then mapped elemental fluxes due to weathering and soil development using intensive field sampling and an elemental mass balance. Greater losses were generally associated with wetter landscape areas. We inferred lateral fluxes of water and soil components from spatial patterns of eluviation and illuviation in the watershed. We found that Si losses were greatest losses of all elements, averaging 372 kg/m2 land area. The soils lost an average 9.9 kg/m2 land area of Al; Fe, Ca and P were retained in the system. Greater soil carbon facilitated elemental losses. The morphology and distribution of spodic tongues showed the most statistically significant correlation with the spatial distribution and magnitude of mass fluxes of all the environmental and morphologic variables that we quantified in this landscape. The research suggests that Spodosol morphology may be useful in modeling mass transport in these soils.


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