Topsoil and Mulch Effects on Plant Species and Community Responses of Revegetated Mined Land

Abstract

Replacement of topsoil and the use of mulches for soil stabilization have become important components of mined land reclamation plans in the western United States. Four topsoil depths (0,20, 40, and 60 cm) and 2 mulch methods [crimped straw and standing barley (Hordeurn vulgare I,. Otis) stubble] were investigated on uranium mined land in Wyoming. Although 20 cm of topsoil provided initial benefits to stand establishment, after 4 growing seasons, 48 cm of topsoil was required to improve seeded grass growth over that found in non-topsoiled plots. Forty centimeters annual and biennial forbs (nonseeded species). Barley stubble mulch resulted in significantly (P = 0.05) higher biomass of seeded grass species than did crimped straw mulch when at least 40 cm of topsoil was present. Despite a decline in energy demand in the early part of this decade, coal and uranium mining continues to disturb hundreds of hectares in Wyoming each year. Reclamation of these lands must be a prime consideration in mining if productive rangeland is not to be lost. The application of topsoil and use of mulches as temporary site stabilizers have become important components of many surface mine reclamation programs. Questions remain, however, as to the amount of topsoil required for sustained site productivity and the type of mulch best suited to particular reclamation needs. Regulations at both federal and state levels now require salvage and redistribution of topsoil on mined areas. Numerous studies have shown that depth of reapplied topsoil and topsoil plus subsoil significantly influence aboveground plant production (Power et al. 1979, Schuman et al. 1984, Schuman and Power 1981), root growth (McGinnies and Nicholas 1980), and soil water relationships (Power et al. 1981, Schuman et al. 1980) on mined land. Quality of topsoil and spoil materials, climatic factors, seeded plant species requirements, and concurrent reclamation practices all appear to influence the optimal topsoil depth for a given area. Widespread use of mulches on mined sites has been based upon findings that mulches provide needed soil stabilization (Jones et al. 1969, Meyer et al. 1970), promote water conservation (Hopkins 1954, Winterlin et al. 1958, Dudeck et al. 1970), and often shorten the time needed for adequate plant establishment (Farmer et al. 1974, Aldon 1978). At present, straw and hay mulches are most commonly used in the Northern Great Plains. A number of studies have also evaluated the suitability of various annual species as temporary stabilizers (Sindelar et al. 1973, Dollhopf and Majerus 1975, DePuit et al. 1978). Further interest in stubble mulching has been promoted by the findings of Schuman’et al. (1980). Stubble mulching has been reported to result in equal or greater establishment of perennial grasses than has straw mulch and at 75 to 95% of the cost. This study was conducted to evaluate vegetation responses on Authors are research associate, Natural Resource Ecology Laboratory, Colorado State University, Fort Collins 80523 (former graduate assistant, Range Management Division. University of Wyoming, Laramie 8207 I); soil scientist, USDA, Agricultural Research Service, 8408 Hildreth Road, Cheyenne, Wyo. 82009; and assistant professor, Range Management Division, University of Wyoming, Laramie, Wyo. 82071. This research is a contribution from the USDA Agricultural Research Service and the Wyoming Agricultural Experiment Station. Published as Journal Article Series paper JA 1298, Wyoming Agricultural Experiment Station. Manuscript accepted August 23, 1984. seeded uranium mined lands to varied topsoil depth and mulch