Environmental Factors Related to Medusahead Distribution

Abstract

Sites particularly susceptible to medusahead invasion in the more arid portions of Idaho were either those with well-developed soil profiles, particularly those with high clay content either at or near the surface; or those occupying topographic positions that received additional run-off from adjacent sites. In more mesic climates moderately well developed soils appeared as highly susceptible as the well-developed soils. Conversely, soils with little profile development, particularly those which were well drained, remained dominated by cheatgrass in early seral stages regardless of whether they were in the more arid or mesic areas. The nature of the surface geology as it influenced the soil texture derived therefrom was a valuable aid to identifying sites susceptible to medusahead. Maintaining a good stand of perennial vegetation appeared the best barrier to medusahead invasion into susceptible soils.