Environmental degradation and rehabilitation of the landscape around Sudbury, a major mining and smelting area

A century of sulphur dioxide fumigation, copper and nickel particulate deposition, fire, soil erosion, and enhanced frost action has created 10 000 ha of barren land and 36 000 ha of stunted, open birch-maple woodland in the Sudbury area. The primary factor limiting plant colonization is the acidic and aluminum-, copper-, and nickel-toxic properties of the soils, although certain plant species survive the challenges through genetically based metal tolerance. In revegetation programs, the soil can be detoxified sufficiently to initiate colonization by the surface application of ground limestone. The drought vulnerability of seedlings, resulting from soil toxicity limiting root growth, is exacerbated by enhanced frost action resulting from the lack of leaf litter. Manual surface application of ground limestone, with or without an accompanying fertilizer and (or) grass-legume seed application, leads to immediate colonization by woody species including birch, aspen, and willows, and more than 3000 ha have been treated in this way by the Regional Municipality of Sudbury since 1978. Native coniferous species have also been planted in groups to form a seed source for future colonization. Most barren soils contain a substantial reservoir of phosphorus and nitrogen in the form of residual organic matter, but both rhizobial and actinorhizal species play an important role in dynamics, and the role of mycorrhizae is probably critical. The seed availability factor is rarely limiting; while the seed bank is small, in most sites the seed rain of light, wind-dispersed seeds is adequate to colonize soil detoxified by limin