The colonisation by plants of calcareous wastes from the salt and alkali industry in Cheshire, England

Abstract Calcareous wastes from the salt industry occupy approximately 150ha of land in Cheshire, a county devoid of natural calcareous substrata. The wastes are pumped into lagoons and on drying put become colonised by plants. The resulting lime beds vary in the extent to which they are invaded by plants but a number of areas support rich and varied grassland communities. The Witton lime beds, Northwich, support large populations of a number of species of base-rich habitats, which are uncommon in Cheshire and are of restricted distribution in northwest England as a whole. These include a number of orchid species, of which Dactylorhiza praetermissa and Gymnadenia conopsea are the most abundant. Information analysis was used to analyse the vegetation of Witton lime beds and the vegetation groupings recognised were used to examine possible successional sequences. The edaphic factors limiting growth in lime wastes were examined and the effects of fertilizer additions on the growth of indigenous species at Witton are described. Phosphorus was the major element limiting growth but on older wastes, with a higher unreacted lime content, phosphorus only partially removed the infertility. The findings are discussed in terms of the conservation and management of Witton lime beds to ensure continued floristic diversity and the possible reclamation of other lime waste areas.