Reclamation Of A Limestone Quarry To A Natural Plant Community

Abstract

Reclamation of thousands of limestone quarries around the world is challenged by an extremely limiting environment, including steep slopes, high calcium carbonate substrates with low nutrients and low water holding capacity. These issues were addressed at the Exshaw quarry in the Rocky Mountains of southern Alberta. Reintroduction of key components, such as vegetation and ameliorated soil were expected to speed recovery of ecosystem functioning processes. Erosion control blankets and combinations of fertilizer, sulfur and organic amendments at different application rates were evaluated in three limestone substrates in the greenhouse and field. Amendments were hay, straw, wood shavings, pulp mill biosolids, beef manure compost, beef manure mix (6:1:1 manure, waste feed, wood chips), topsoil and clean fill. Revegetation with seeded native grasses (Poa alpina, Agropyron trachycaulum, Elymus innovatus, Festuca saximontana, Trisetum spicatum), transplanted and seeded woody species (Picea glauca, Pseudotsuga menziesii, Populus tremuloides, Betula papyrifera, Juniperus horizontalis, Alnus crispa, Arctostaphylos uva-ursi) and forest floor litter were assessed. Evidence of soil microbial community development, including arbuscular mycorrhizal fungi, was evaluated. All amended substrates supported plant growth in two greenhouse experiments. Fertilizer with pulp mill biosolids and soil caps significantly increased above and below ground biomass of grasses. Agropyron, Festuca and Poa performed best. Best treatments from the greenhouse were evaluated for three years in the field. Fall planting and seeding increased plant survival. Erosion control blankets increased seeded plant establishment while reducing unseeded non native species. Manure mix biosolids increased plant establishment, soil nutrients, microbial biomass and viable fungi and bacteria. Picea, Pseudotsuga and Populus showed revegetation promise. Nursery stock survived better than local transplants. Woody plants did not establish from seed. Arbuscular mycorrhizae infection was found in all 15 species sampled, more in grasses. Site characteristics such as slope, aspect, initial soil nutrient concentrations, surrounding vegetation and browsing by bighorn sheep influenced early plant community development and overall effects of soil treatments. Reclamation is postulated to be best with erosion control blankets, organic soil amendments such as manure mix, seeded grasses and transplanted woody species. Results from this work can be extrapolated to other limestone quarries or similar disturbances.