Relation Between Ecological-Range Condition and Proportion of Soil-Surface Types

Abstract

Different kinds of A-horizon soil-surface types occur on loessmantled xerollic Orthids and Argids in the Intermountain area. Four soil-surface types were identified on sites with potential vegetation of Wyoming big sagebrush [Artemisia tridentata wyomingensis Beetle] and Thurber needlegrass [Stipa thurberiana Piper]. These surfaces occupy different microtopographic positions and have different morphologies and chemical and physical properties. This study relates differences in the cover of these soil-surface types to ecological-range condition on sites of similar potential. Proportion of the surface type found under shrub or bunchgrass cover varies with range condition. More of the surface associated with shrub cover is found on low condition sites because of greater sagebrush cover. More of the surface associated with bunchgrass cover is found on high condition sites because of greater grass cover. Proportion of the surface types found in the interspace between shrubs also varies with range condition. High condition sites have a greater cover of the soil surface associated with bunchgrass cover and of the soil surface with cryptogam-stabilized microrelief. Conversely, low condition sites have essentially none of the soil surface associated with bunchgrass cover but a large amount of the soil surface with little microrelief. Results are interpreted in terms of watershed stability and natural revegetation potential.