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Individual study: Vegetation and soil development on naturally-revegetated versus seeded reclaimed coal mine spoil in the Rocky Mountains near Sparwood, British Columbia, Canada

Published source details

Fyles J.W., Fyles I.H. & Bell M.A.M. (1985) Vegetation and soil development on coal mine spoil at high elevation in the Canadian Rockies. Journal of Applied Ecology, 22, 239-248

Summary

The vegetation and soil development of reclaimed coal mine waste near the treeline in southeastern British Columbia was examined by comparing six sites revegetated with a seeded grass-legume sward, ranging in age from 0 to 6 years, a naturally-revegetated disturbed area, and a native grassland.

Study area: The study was undertaken at a series of reclaimed coal mine waste dumps at around 2,000 m altitude on a ridge of the Rocky Mountains, on the property of Westar Mines Ltd. near the town of Sparwood in southeastern British Columbia, Canada.
The spoil was a result of past open pit mining. Prior to mining, the vegetation was mainly a sub-alpine coniferous forest with native grasslands on steep, south-facing slopes.

All sampling sites were located within 500 m distance of each other with an elevational range of 80 m. The six selected reclaimed areas ranged in age from 0 to6 years, were on fairly level terrain and the spoil comprised a mixture of sandstone, siltstone and mudstone rock fragments. Vegetation was derived from seeded species dominated by three grasses: cock's-foot Dactylis glomerata, red fescue Festuca rubra and timothy Phleum pratense, with sub-dominants including meadow foxtail Alopecurus pratensis, lucerne Medicago sativa and Alsike clover Trifolium hybridum.

Two unmanaged sites (the only grasslands which had developed under unmanaged conditions adjacent to the reclaimed sites) although not directly comparable, were also sampled: the one native grassland site was located on a steep slope on a south-east aspect with vegetation comprising native grasses, herbs and low shrubs; the naturally-revegetated site was an old exploration disturbance exposed approximately 15 years earlier, with colonizing vegetation of native species, including Trisetum spicatum, Hieracium gracile, Anaphalis margaritacea and Antennaria microphylla.

Sampling: Five 10 m x 4 m sampling plots were established on each site. Peak standing crop (PSC) by clipping all green, above-ground plant material inside five, 0.25 m² frames in mid-August prior to autumn die-back. All surface and standing dead plant material was separately collected. Samples were oven dried and weighed.

Root biomass was assessed by taking six random 10 cm diameter cores to a depth of 10 cm. from each plot (30 for each site). Cleaned roots were oven-dried and weighed.

Measurements of microbial respiration were made in the field in late August. To record cellulose decomposition sets of weighed, 5 cm square chips of alpha-cellulose paper were buried at 5-10 cm depth in each plot in late June, with one removed from each set monthly until late October. The chips were washed, oven-dried and weighed.

Soil samples were taken in late July and early August. Samples were air-dried and passed through a 2 mm mesh sieve. The fraction larger than 2 mm was weighed as an estimate of coarse fragments. Chemical analysis of the fraction less than 2 mm was carried out to determine: total nitrogen, available phosphorus, soil pH and organic carbon.

Plants established in the first growing season following seeding and grew well in the second year. The level of shoot growth on the 2-, 3- and 5-year sites was similar that which might be expected with a low fertilizer input. The 6 year site established in 1979, had a peak standing crop much greater than that of the other reclaimed sites, and approached that of the native grassland. It appears that this site maintained a sufficiently large nutrient pool to support substantial plant growth without fertilizer application.

On the reclaimed areas, root, shoot and detritus biomass, soil CO2 evolution (a measure of soil microbial activity), and cellulose decomposition increased. Soil pH decreased with site age. High levels of total soil nitrogen existed in all sites because of pre-existing nitrogen in the waste rock which undoubtedly assisted plant growth. Phosphorus availability was low in unvegetated and newly seeded spoil but was uniformly higher on older sites.

The oldest reclaimed site (6-years) was similar to the native grassland in many respects except that the stabilized pool of organic matter on the native site was apparently absent on the reclaimed area.


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