Geographic Analysis of Viticulture Potential in Virginia
First, to delineate regions across Virginia that had greater or lesser viticulture potential from a physical and climatological basis, weather station data were collected for minimum winter temperatures, maximum summer temperatures, precipitation, length of growing season, and day versus night temperature differentials. In addition, elevation and slope models were constructed to complement the climatic variables in identifying areas that contained factors most conducive to grape production. To validate this regional assessment, the history of fruit industries within the state are outlined geographically to display the evolution of the fruit industries, and to establish the factors which have shaped the current fruit landscape.
Secondly, at the local scale, a Geographic Information System (GIS) approach was used to identify sites at the county scale that had greater or lesser viticulture potential from a physical basis. Composite maps, constructed by individual counties in the state, were produced from a series of physical databases. The individual databases (sources and resolution in parentheses) included land-use (Virginia Gap Analysis; 30meter2 resolution), slope, aspect, and elevation (USGS 1:24,000 Digital Elevation Model; 30meter2), and soils data (USGS Digital Line Graph (DLG-3)). Each physical feature layer was given a numerical classification, then all layers were combined to produce a 0 to 100 scale in the final, composite image.
Given this model of potential vineyard suitability, existing fruit operations in select counties were geo-located on each feature layer using a Global Positioning System (GPS: 1-2meter accuracy). Actual data on occurrences of frosts, minimum winter temperatures, and other site variables were collected from these fruit operations and surrounding weather stations as a sample to validate the model. A strong correlation between areas containing characteristics of current fruit acreage--namely apple--and sites high in potential for viticulture according to the model.
Studying the history of geographic distribution of apple and grape industries across the state reinforces the regional assessment of viticulture potential, formulated by the climatic and topographic analysis. Employment of GIS approach at the local site scale was shown to be an effective tool for site selection at the local scale with certain caveats. In addition, the evaluation procedure integrating GIS and GPS technologies allows us to visually assess the distribution pattern of each of the factors employed individually; and, in turn, physically identify and locate areas of viticulture potential created from the combination of those factors.
- Masters Theses