An Historical Perspective On the Development of the Ecological Site Concept.

The concept of site “a piece of land with specific features” has a long history in natural resource management.  In the early 1900s, forest managers employed a site concept focused primarily on the influence of a specific set of climate and soil factors on forest production, in particular on the selection of appropriate species for planting after burns and timber harvest.  A key element of the concept also included the temporal pattern of species replacement to insure proper initial stocking.  In the early 1940s, pioneering range scientists adapted the concept, again with an emphasis on the ability of edaphic and climatic factors to support sustainable yield of forage.  However, the emphasis in rangeland applications had shifted to grass species composition in an undisturbed state (climax) as the basis for separation of sites.  A new view of ecological dynamics of plant communities, to one dominated by multiple equilibrium potential, requires a reconsideration of the factors for organizing units of the landscape.  Rather than a characteristic plant community, ecological dynamics provide a more appropriate criteria for grouping land units.  Within a specified climatic regime, soil properties are the best predictor of dynamics in response to changes in management.  The shift from climax vegetation to soil properties as an organizing basis for delineating landscape components will likely require reconsideration of the design of ecological sites.