The University of Arizona

Viewpoint: delineating ecological sites.

J.A. Creque, S.D. Bassett, N.E. West


Both the Society for Range Management's (1995) Task Group on Unity in Concepts and Terminology (UCT) and the Natural Resources Conservation Service (1997) have recommended use of the ecological site as the fundamental land unit for evaluation of rangeland condition and trend. While the ecological site concept may be relatively straightforward. in practice the spatial definition of ecological sites within a management unit can prove problematic. This paper presents the use of readily available digital information in a GIS frame-work to delineate ecological sites within a pinyon-juniper/sagebrush semi-desert dominated landscape in Central Utah. An existing model of pre-Euroamerican pinyon-juniper woodland dynamics was combined with the site classification to evaluate landscape dynamics. We also created a map of landscape pattern of potential utility to land managers. The mapping capabilities of GIS offer a simple and remarkably adaptable technique for visual modeling of landscape pattern to assist in meeting a wide array of land management objectives. However. the "objective" delineation of ecological sites must be recognized as being necessarily based on a priori user-selected criteria.


land classification;semi-desert scrub;landscape ecology;geographic information systems;texture;pinyon-juniper;semiarid grasslands;fire ecology;slope;range management;botanical composition;Utah

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