PRELIMINARY GIS STUDY OF THE TERROIR OF THE WISCONSIN LEDGE AMERICAN VITICULTURAL AREA

The Wisconsin Ledge American Viticultural Area (AVA) encompasses 2.4 million acres in northeastern Wisconsin and contains over a dozen wineries with more under development. Wisconsin's grape growing tradition goes back to the 1840's when Hungarian nobleman Agoston Haraszthy planted a vineyard. The Wisconsin Ledge is named after the prominent geomorphologic feature known as the Niagara Escarpment. Grape growers have had success growing hybrid grapes that were developed to withstand the often harsh Wisconsin winters. White hybrids include: St. Pepin, La Crescent, Frontenac Blanc, Brianna, and Louise Swenson. Red hybrids include: Frontenac, Frontenac Gris, Marechal Foch, Marquette, and Petite Pearl. A preliminary GIS analysis of climate, topographic, geologic and soil data helps to define the Wisconsin Ledge's terroir. The geology is dominated by the limestones that comprise the Niagara Escarpment along with glacial till that was deposited during the last period of glaciation. Elevation of the Wisconsin Ledge ranges from 571 to 1,312 feet above sea level with an average of 833 feet. Annual precipitation varies from 28 to 36 inches/year with most of the vineyards being the areas of lowest precipitation. Growing degree days (GDD) are a good measure of the viability of a region to successfully grow grapes and the Wisconsin Ledge GDD ranges from 1,947 to 2,426 (50º F base). Average daily temperature for the region ranges from 42-47º F and is influenced not only by the slightly higher elevation of the region, but also from the microclimate created by Lake Michigan that moderates temperatures keeping winter minimums and summer maximums slightly higher and lower, respectively. Soils in the region are characterized by well drained loams with the sandier loams in the southern portions and more clay, sand and gravel-rich loams in the north due to the glacial till. Slopes in this region are generally low with an average slope of 2º and an overall mean aspect (downslope direction) of 169.7º, which corresponds to southerly facing slopes. Characterization of the Wisconsin Ledge's terroir allows for a better understanding of the regions viability for expanding its grape production both in terms of where to plant new vineyards but also identifying which grape variety would be the best suited for the new vineyard.