Effect of Sagebrush Control Methods and Seeding on Runoff and Erosion

Abstract

A large-plot (27 m2) rainfall simulator was used to examine the effects of controlling Wyoming big sagebrush (Artemisia tridentata ssp. wyomingensis) and seeding with crested wheatgrass (Agropyron desertorum) upon infiltration rates and soil erosion in central Nevada. A new parameter-runoff initiation frequency index (an estimate of frequency of occurrence in years that a natural storm will produce surface runoff at the site) was also used for making treatment comparisons. The runoff initiation index reflects a more comprehensive appraisal of hydrologic response on semiarid rangelands than does infiltration rate but sometimes results in a different assessment of treatment effects. Initially, all range improvement techniques reduced terminal infiltration rates and increased sediment yields. The magnitude of treatment effects varied in proportion to the degree of site disturbance: plowing/seeding caused the greatest impact, burning/seeding next, and spraying/seeding had only minimal effect. Treatments showed a steady trend toward recovery in a 2-year period. In terms of runoff initiation frequency, however, plowing/seeding had the least detrimental effect with burning/seeding and spraying/seeding having greater effect. Trends subsequent to treatment indicated watershed improvement of plowed/seeded areas and a decline in burned/seeded areas. These somewhat contradictory results are due to the runoff retention capability of furrows created by plowing and/or artificially seeding across the slope. Surface storage characteristics are incorporated in runoff initiation frequency indexing but not in infiltration rates alone.