The primary factor affecting vegetation dynamics on Sudbury’s barren soils is their acidic, aluminum-, copper- and nickel-toxic properties, although certain plant species avoid the problem through genetically-based metal-tolerance. The soil can be detoxified sufficiently to initiate colonization by the surface-application of ground limestone, the dolomitic variety being more effective at certain sites. The drought-vulnerability of seedlings, resulting from toxicity engendered root growth limitation, is exacerbated by enhanced frost action resulting from the lack of leaf litter. Phosphorus deficiency can be a problem on sandy valley-bottom soils, but most barren soils contain a substantial reservoir of phosphorus and nitrogen in the form of residual organic matter. Both rhizobial and actinorhizal species play an important role in dynamics, and it is likely that the role of mycorrhizae is critical, although more research is required on the latter topic. 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 liming. The process of “succession” can follow one of three different routes, depending on whether the barrens are left untreated, treated with limestone only, or treated with limestone and a grass-legume seed mixture.