Sul Ross State University

An Ecological Classification of Davis Mountain State Park

by Rick Voldseth and Lynn Loomis

The Davis Mountains are located in far-west Texas, in the region known as the Trans-Pecos. In 1933 Davis Mountains State Park was established in the foothills near Fort Davis, Texas.

The park lies at elevations above 1525 m. Total relief is almost 200 m. Long slopes with gradients steeper than 30 percent typify the hillsides/mountainsides.

Aspect is important. Bedrock consists of Tertiary aged rhyolitic tuffs and lava flows.

The area has cool, moist summers and mild, dry winters. Mean annual precipitation is about 48 cm; mean annual temperature is about 14.5⁰ C.

Oak-juniper woodlands and mid-grass prairies characterize the vegetation cover.

Texas Parks and Wildlife managers will develop a natural resource management plan for Davis Mountains State Park (DMSP) and require detailed information on the soil and other park resources. By conducting an Order 2 Soil survey and developing a site-level Ecological Land Classification (ELC), information on the land resources of DMSP can be provided in a useful, ecological context.

This can be accomplished by application of the Soil-Landscape Paradigm with considerable focus on the landforms. The methods that define soil survey (legend building, mapping, transecting) are fundamentally rooted in this model. The methods used for soil survey can be modified for simultaneous collection of data and additional detail, on landform, bedrock geology and vegetation that is needed to develop an ELC.

This project is designed to investigate the relationships among landform, bedrock geology, soil bodies and vegetation in DMSP and to develop interpretations and maps based upon these relationships at a scale of 1:12,000. This will be achieved through the development of an ELC based on the framework suggested by Driscoll (1984).

Within the framework, we will utilize the following existing component classification systems: "Soil Taxonomy: A Basic System of Soil Classification for Making and Interpreting Soil Surveys" (Soil Survey Staff, 1999); "The National Vegetation Classification System" (The Nature Conservancy, 1998); "A Manual for Describing NSSL Soil-Sampling Sites; Terms and Concepts for Identifying Physiographic Position and other Sampling Site Descriptors; draft version 1.0" (Peterson, 1990) along with "A Geomorphic Classification System" (USDA Forest Service, 1998).

This project is cooperatively funded by Texas Parks and Wildlife Department, Sul Ross State University and the Houston Livestock Show and Rodeo.