THE INTRODUCTION OF NATIVE PLANT-SPECIES ON INDUSTRIAL-WASTE HEAPS - A TEST OF IMMIGRATION AND OTHER FACTORS AFFECTING PRIMARY SUCCESSION

1. Industrial waste heaps in north-west England have become colonized by interesting floras which include regionally uncommon species. Howev er, the range of species is restricted and the vegetation remains open even after 100 years. This appears to be due to (i) the chemical and physical characteristics of the sites, and (ii) difficulties of immigr ation for appropriate species. 2. To test these hypotheses and to expl ore the improvement of such areas for creative conservation and amenit y, introduction of further native species was undertaken. Several spec ies from calcareous grassland, were successfully established on alkali ne chemical waste and blast furnace slag, and species from acidic heat hland on colliery shale. Some species were established on pulverized f uel ash, but the successful ones had no obvious characteristics in com mon. 3. This demonstrates the limitations that can be set in isolated sites by problems of immigration. When suitably adapted species are in troduced, appropriate niches for their establishment appear to be avai lable. Failure of more nutrient demanding species showed that nutrient deficiency can also be a major factor controlling colonization. 4. Th e results reveal some of the factors affecting primary succession. The y indicate the limitations faced by species which might require to mig rate in the face of climatic or other environmental changes. They also show that it is practicable to diversify the species composition of s uch derelict sites for creative conservation or amenity purposes.