Digital Soil Mapping of Soil Properties As a Tool for Developing and Testing Ecological Site Concepts.

With the expansion of the NRCS ecological site effort, new and innovative approaches are needed to gather the data required for robust ecological site concept development. New and innovated approaches are also needed to predict sub-map unit ecological site variability, as such variability can significantly impact the effectiveness of land use treatments. While expert knowledge plays an important role in developing ecological site descriptions and estimating sub-map unit ecological site variability, existing soil data is often not sufficient to both refine ecological sites and predict sub-map unit ecological site variability.

We demonstrate a new method for generating the soil data needed for developing ecological site concepts and predicting sub-map unit ecological site variability based on raster predictive maps of soil properties over a 51,919 acre study area in San Juan County, Utah. Ecological site descriptions in this study area indicated that  Semidesert Sandy Loam (Wyoming big sagebrush) and Semidesert Sandy Loam (Fourwing saltbush) ecological sites were nearly identical in precipitation zones, landforms, soil textures, depths, and rock fragment percentages, but differed significantly in potential plant communities and response to management. Existing soil data did not allow a consistent difference between the two ecological sites to be identified. Raster based predictive maps of soil depth-to-bedrock provided evidence to distinguish between ecological sites and allowed predictions of sub-map unit ecological site variability. Refined ecological site concepts and sub-map unit spatial predictions are anticipated to help inform impending management actions to remove undesirable trees and replant sagebrush.