Variability of a Fragiochrept with windthrow microtopography in North central Wisconsin

The variability of an Aquic Fragiochrept in Taylor County, Wisconsin, was studied on 5- by 10m grid points at two sites (100 by 70m) that have windthrow microtopography. The effect of the general slope of each research site was accounted for in the analysis of the windthrow microtopography. The soils were developed in a silt loam eolian deposit over a dense sediment-flow deposit, which was underlain by dense basal till. The surface microtopography and depth to the fragipan and mottling were measured at each grid point. The thickness of the A, E, and B horizons were measured where they were present. Old logging roads and wet depressions not associated with knolls were also recorded. The depth of the fragipan was significantly greater on knolls than on cradles and areas undisturbed by windthrows. The fragipan was found at a significantly shallower depth on old logging roads, wet depression areas, and cradles when compared with the areas not affected by these features. A set of microtopographic modifiers is proposed that could be used to more appropriately distinguish among map units in windthrow-affected areas. The recognition and incorporation of information on microtopography is considered essential for refining the specificity and utility of soils information for forest-management interpretations. -Authors