Long-Term Effectiveness of Revegetation at the Tuba City, Arizona Uranium Mill Tailings Disposal Site

Abstract

Revegetation is a reclamation method used to stabilize land that has been disturbed (i.e. Uranium contamination) by mining in an effort to establish a sustainable plant community. During 1986-88, large amounts of topsoil were removed at the site adjacent to the Tuba City disposal cell to remove windblown contaminated soil and construct the Uranium disposal cell. Re-establishing a sustainable plant community is critical to minimizing dust emissions, controlling erosion, and improving rangeland condition, and enhancing evapotranspiration. The objective of this study was to evaluate the long-term effectiveness of revegetation efforts by 1) comparing plant species composition and abundance on the reclaimed area and native rangeland protected from grazing, 2) current rangeland condition by comparing plant communities on grazed and protected native rangeland 3) differences in soil fertility, particle size distribution, and morphology that could be influencing vegetation differences in the three areas, 4) landscape-scale evapotranspiration rates and effects on groundwater recharge in the three plant communities, and 5) the value of using relatively undisturbed Legacy Management parcels as reference areas. Plant cover in the revegetated area was greater in 2014 (24%) than in 1998 (15%); however, plant species composition and diversity in the revegetated area and in the reference area remained markedly different. The effectiveness of revegetation is improving, but given the extended amount of time the improvement is not matching the protected area’s percent cover. The reference area showed highest cover during the early cool-season. However, the grazed area possessed the highest plant species composition and highest foliar cover in the late warm-season. The vegetation relevé estimate and foliar cover statistics show the revegetated area (24%) was significantly less than the surrounding vegetation (35%), even after 26 years since original revegetation. These results are critical in assisting Legacy Management to identify environmentally sustainable methods for the continuous management of this site and others in the area.