Improving the Accuracy of Rangeland Conservation Plans with Raster Soil and Ecological Site Maps: Implications for Management.

Using traditional mapping techniques, soil scientists have produced high quality interpretive maps for land owners and managers for many decades.   Unfortunately in areas where rangeland is the primary interpretive focus, soil map units frequently consist of multiple soil and/or non-soil components that are correlated to more than one ecological site.  Vector-based ecological site maps based on the dominant soil component do not accurately depict the location, spatial distribution, and total area of individual component soils and ecological sites within heterogeneous landscapes.  Furthermore, assigning a single ecological site to a soil map unit based on the dominant condition disregards the minor components, which often vary greatly in their forage production potential.  Forage inventories guided by dominant condition are subject to error.  As a result, conservation plans with grazing management recommendations based solely on this representation of soil map units will also have limited accuracy, including inaccurate stocking rate suggestions.  However, the increasing availability of remotely sensed elevation and imagery data coupled with innovative soil-landscape modeling technology allows a more accurate portrayal of soil patterns with gridded data sets.  Based on their relationships to slope gradient, photo darkness, gypsum index, and wetness index, ArcSIE software predicted the distribution pattern of 7 individual soil components and rock outcrop on the Culberson Gypsum Plain in West Texas.  The published soil survey was composed of 8 map units, all but one of which were multi-component.  The soil components were correlated to 5 different ecological sites with estimated productivity ranging from 120 to >9000 kg/ha.  The location, spatial pattern, and forage production of ecological sites as depicted by vector and raster maps will be evaluated.  Conservation planners were able to overcome some of the limitations of vector-based soil-ecological site maps by using raster-based maps of soils and ecological sites.  Implications for conservation planning, grazing management, and estimating composition of individual map unit delineations will be discussed.