Site 4 represents soil region scale, i.e., the i+3 level. The soil region is located on the Arlington Agricultural Research Station, University of Wisconsin-Madison, and was 100-ha in size. Soil data were derived from the Map Unit Interpretation Database (MUIR) with a scale of 1:15,840. Soil map units were Plano silt loam (0 to 2 % and 2 to 6 % slope) - fine-silty, mixed, mesic Typic Argiudolls; Ringwood silt loam (1 to 6 % and 6 to 12 % slope) - fine-loamy, mixed, mesic Typic Argiudolls; Joy silt loam (0 to 4 % slope) - fine-silty, mixed, mesic Aquic Hapludolls; Ossian silt loam (0 to 3 % slope) - fine-silty, mixed, mesic Typic Haplaquolls; Saybrook silt loam (2 to 6 % slope) - fine-silty, mixed, mesic Typic Argiudolls; and Rotamer loam (2 to 6 % and 12 to 20 % slope) - fine-loamy, mixed, mesic Typic Argiudolls. All soil map units have in common that soils are formed in silty sediment and the underlying glacial till, however, thickness of silt is very different. Land use was alfalfa, corn and oats.
We used a DEM with horizontal resolution of 4-m and vertical resolution error of +/- 0.5 m derived by an analysis of aerial photographs. Original scale of the photos was 1:20,000, which were scanned at a pixel size of 30 mm resulting in 1-m pixel. Based on a stereo-pair analysis, a point elevation model was created with 4-m grid spacing, which was interpolated to produce a DEM (Environmental Remote Sensing Center and Environmental Engineering Department of the University of Wisconsin-Madison, internal communication). Elevations ranged from 321.2 to 328.5 m above sea level.