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VINEYARD The suitability index rating is on a scale of 0 to 10, with 0 being unsuitable and 10 being the most suitable. The TSVS model can be tailored to specific grape vari- eties, and the suitability index can be weighted toward priority variables, such as growing degree-days or frost-free days. The model can also be used to pre- dict future vineyard site suitability based on climate change, by keying in anticipated temperature increases, for example. Regional TSVS models are now available for Lake and Mendocino counties in California. Models are also developed for specific American Viticultural Areas (AVAs), such as the Clear Lake and Red Hills in Lake County (and many others). Dr. Paul Skinner, founder and president of Terra Spase, said TSVS models can be developed using available data for virtually any U.S. grapegrowing region. He has also begun developing the concept interna- tionally, and is working with researchers in Poland, where there is interest in planting new vineyards in his- torical production areas. DATA DRIVEN SYSTEM The model integrates data from existing sources, including: topographic data and digital elevation models from the U.S. Geological Survey, soil survey data and maps from the U.S. Department of Agriculture Natu- ral Resources Conservation Service, and weather data from Prism Climate Group at Oregon State University, which sells data sets for the United States. More site- specific information can also be incorporated, such as weather data from local and privately owned weather stations, and soil data from onsite field sampling. Topographic properties include: elevation, slope (per- centage) and aspect (slope facing direction). Topograph- ic variables, such as slope and aspect, can be derived from available digital elevation models using geographic information system (GIS) software programs ArcGIS and Spatial Analyst. Soil properties to a depth of 60 centimeters (or a depth based on available data) include: soil surface texture, percentage of rock fragments (from 7.5 to 25 centimeters in diameter), pH, soil organic matter (per- AT A GLANCE The Terra Spase Vineyard Suitability model helps identify suitable sites for planting vineyards. The computer-based system uses soil, climate and topo- graphic data to generate maps that delineate locations with a suitability index of 0 to 10. Models and indexes can be developed for U.S. grape- growing regions, and tailored to specific varieties. The model can be used for long-term evaluation of vineyard sites based on estimated climate-change variables. WWW.VWM-ONLINE.COM This map shows historic growing degree-days in the Clear Lake AVA. The information can be used to determine suitable planting locations. Citing how the model can be applied in an area such as Lake County, where vineyard elevations range from 1,370 feet to more than 2,600 feet, Skinner explained, "The growing season is generally shorter with higher elevations. This is a big influence on what you can plant and where, and can relate to the availability of water needed for frost protection. This all comes out of the original data inputs for topography and elevation, and temperature data over the growing season that pro- vides minimum and maximum temperatures and grow- ing degree-days." The TSVS model and data can be used in several ways. The model provides a starting point for vineyard JULY - AUG 2012 VINEYARD & WINERY MANAGEMENT 49 centage of total content), soil depth to any restrictive layer, soil drainage, and available water capacity. Climate properties include: growing degree-days (GDD), based on monthly maximum and minimum temperatures during the growing season from April to October, and frost-free days (FFD). Weather and tem- perature data for the last 30 years are used as the basis for the model. Current land use (pasture, native grassland, orchard, etc.) is another factor usable in the model that can be weighted based on its influence on soil properties, and factors for site preparation and development.