Reclamation studies on oil shale lands in northwestern Colorado

Abstract

The overall objective of this project is to study the effects of various reclamation practices on above- and belowground ecosystem development associated with disturbed oil shale lands in northwestern Colorado. Plant growth media that are being used in field test plots include retorted shale, soil over retorted shale, subsoil materials, and surface disturbed topsoils, The project was initiated in June 1976 and is presently reporting on fourth-year data from both field and laboratory studies. The majority of research reported on within this report is being conducted on a 20-ha Intensive Study Site located near the focal points of oil shale activity in the Piceance Basin. The site is at an elevation of 2,042 m, receives approximately 30 to 35 cm of annual precipitation, and encompasses the plant communities most typical of the Piceance Basin. Some of the more significant results that are reported herein are (1) a soil cover of at least 61 cm in conjunction with a capillary barrier provided the best combination of treatments for the establishment of vegetation and a functional microbial community, (2) aboveground production values for native and introduced species mixtures are comparable after three growing seasons, (3) cover values for native species mixtures are generally greater than for introduced species mixtures, (4) native seed mixtures, in general, allow greater invasion to occur than introduced mixtures, (5) sewage sludge at relatively low rates appears to provide the most beneficial overall effect on plant growth of any fertilizer treatment tested, (6) cultural practices, such as irrigation, mulching, and fertilizing, have significant effects on both above- and belowground ecosystem development, (7) topsoil storage after 1.5 years does not appear to significantly affect general microbial activities but does reduce the mycorrhizal infection potential of the soil at shallow depths, (8) populations of mycorrhizal fungi are decreased on severely disturbed soils if a cover of vegetation is not established, (9) significant biological differences among ecotypes of important shrub species have been identified and will assist in selecting appropriate plant materials for reclamation, (10) a vegetation model is outlined which upon completion will enable the reclamation specialist to predict the plant species combinations best adapted to specific reclamation sites, and (11) synthetic strains of two important grass species are close to development which will provide superior plant materials for reclamation in the West.