Establishment of vegetation on serpentine asbestos mine wastes, southeastern Quebec, Canada

Published source details Moore T.R. & Zimmermann R.C. (1977) Establishment of vegetation on serpentine asbestos mine wastes, southeastern Quebec, Canada. Journal of Applied Ecology, 14, 589-599.
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Summary

In the mid-1970s, 5.5 km² of asbestos mine wastes were present in south-eastern Quebec. These areas were mainly devoid of vegetation (despite some being up to 60 years old) and were a potential health hazard. It was therefore desirable to develop techniques to produce a sustained plant cover. Laboratory and field experiments were performed to detect the factors inhibiting plant growth and to determine the levels of amendments necessary to sustain plant growth. The major findings of field experiments are summarised here.

Study site: The experiments were initiated in May 1973 on flat-topped asbestos mine tailings, and subsequently in 1974 on sloping tailings, at a site in southeastern Quebec.

Experimental design: Nine, 4 x 4 m experimental plots, were established. Treatments were:

i) agricultural fertilizer (ammonium nitrate, potassium sulphate and superphosphate (9-11-9)) added at 0, 0.1, 0.25, 0.5 and1 kg/m²;

ii) farmyard cow manure added at 1 and 4 kg/m²;

iii) 0.25 kg/m² fertilizer plus 1 kg/m² manure;

iv) 1 kg/m fertilizer plus 4 kg/m² manure.

The amendments were mixed into the top 5-10 cm of the tailings. Each plot was divided into two subplots (2 x 4 m), one receiving 1 kg/m² aluminium sulphate (which lowered topsoil pH to about 8.5). The plots were seeded with a mix of common agricultural grasses and legumes at a rate of 20 g/m². In 1974 as an alternative to manure, sawdust was added on tailings with slopes of 35-40º.

Deficiency symptoms and supplementary fertilization: Shoot tissue samples were collected from 'healthy' and 'unhealthy' grasses and lucerne Medicago sativa in September 1973. Plots treated with fertilizers and manure or sawdust at the highest rate were sampled.

Fertilizer addition: Only plots receiving 1 kg/m² fertilizer or 1 kg/m² fertilizer + 4 kg/m² manure had more than 90% vegetation cover at the end of the first growing season (September 1973). This was maintained up to 1975 but deficiency symptoms had developed in many plants, especially on fertilizer only plots. Fertilizer addition of below 1 kg/m² and manure alone produced low cover which rapidly deteriorated after the first growing season. Whilst germination was most rapid on the untreated tailings, plants did not survive more than 2 months. Manure increased early establishment, but strong deficiency symptoms developed in plant within the first year and growth was subsequently poor.

On the sloping tailings, establishment and growth was poorer than on the flat plots, probably due to drier substrate condition, poorer mixing in of amendments, and washing off of fertilizers and seeds. Less than 10% cover was achieved on slopes treated with 1 kg/m² fertilizer, more than 90% cover was obtained on those treated with both fertilizers and manure or sawdust; sawdust was less successful than manure.

Acidification: Aluminum sulphate addition did not improve plant growth, and germination was slow and patchy.

Species success: The most successful grasses were perennial rye-grass Lolium perenne (often dominant in the first year but largely replaced by other species later), smooth meadow-grass Poa pratensis, Russian wildrye Elymus junceus and smooth brome Bromus inermus. Fowl bluegrass Poa palustris and foxtail barley Hordeum jubatum were the most successful native species. Lucerne, Alsike clover Trifolium hybridum and white melilot Melilotus alba were the most successful legumes. Root growth of these species was largely confined to the layer of tailings mixed with the amendments. E. junceus was the only species producing roots penetrating more than 10 cm into untreated tailings.

Seedlings of several tree species were planted only in plots receiving 1 kg/m² fertilizer + 4 kg/m² manure. Mortality was high, but some balsam fir Abies balsamifera, quaking aspen Populus tremuloides, eastern cottonwood P.deltoides and red spruce Picea rubens seedlings survived for 3 years.

Costs: The estimated cost, at the time of the study, of treatments necessary to promote sustained vegetation growth on these mine tailings was CAN$ 2,960-3,460/ha.

Note: The compilation and addition of this summary was funded by the Journal of Applied Ecology (BES). If using or referring to this published study, please read and quote the original paper, this can be viewed at:

http://links.jstor.org/sici?sici=0021-8901%28197708%2914%3A2%3C589%3AEOVOSA%3E2.0.CO%3B2-N