The flora of a cultural landscape: Environmental determinants of change revealed using archival sources

In a novel approach to the use of archive biological information, qualitative vascular plant abundance categories from the 1930 Flora of Northamptonshire were matched with quantitative distribution data from the 1995 Flora in order to reveal the species that have changed in commonness relative to their pre-1930 populations. Factors thought to be responsible for these changes were analysed by investigating differences in habitat preference, dispersal ability and climate change indicators, using information from published sources. Changes in status were most dramatic for plant species associated with arable, wetland and woodland habitats. A highly significant factor was the trophic status of preferred habitats: burgeoning species were associated with higher soil nitrogen levels. In addition, evidence for the effects of habitat fragmentation were detected both in terms of changes in abundance being correlated with dispersal-related ecological characteristics and to the number of habitats with which particular species were associated. The discussion concerns the changing land use and farming practices in the county of Northamptonshire, which are widely held to be linked with a deterioration in plant biodiversity since 1930.