Early development of vegetation on urban demolition sites in Sheffield, England

Vegetation on extensive areas of land cleared of housing 5 years previously was surveyed. Parts had been disturbed again and there was a clear distinction by association analysis and in measured parameters between these and those carrying the more mature vegetation. The most recently disturbed sites, indicated by the presence of Atriplex hastata and/ or Polygonum aviculare were characterised by a higher number of species, a higher proportion of annuals, smaller ground cover and reduced canopy height. Undisturbed areas were dominated by a limited number of perennial herbs and grasses, although where Lolium perenne was present, species numbers and numbers of annuals were significantly greater, and canopy height smaller. Woody plants were scarce on extensive demolition sites remote from a seed source, but smaller sites adjacent to mature vegetation were readily invaded by trees and shrubs. The practical applications of this work are discussed.