Botanical processes in urban derelict spaces
This thesis set out to investigate the processes that determine the richness and composition of plant communities on derelict land in the West Midlands. Experimental work included vegetation surveys, soil seed bank investigation, field mapping and seed rain trapping methods. Interpretation of the data involved a range of approaches including vegetation classification and ordination, comparative analysis of plant functional attributes and the development of regression models incorporating landscape and habitat variables. Derelict habitats were identified as holding a diverse array of communities at the early stages of succession which are poorly represented by current vegetation classifications, functional diversity is however much lower in pioneer communities. The majority of these species employing the expected strategies of early succession notably high reproductive capacity and seeds which are small, highly dispersive and form persistent seed banks. Dense seed banks were typically formed on sites and were dominated by a small set of consistently occurring species. Changes in seed bank density and composition were consistent with time represented both by the chronosequence of sites and increasing soil depth. Little evidence was found to suggest that diversity or species composition is linked to site connectivity related to either patch density or the presence of linear features. These findings have considerable implications for application of principles of metapopulation and island biogeography principles to urban conservation. In particular the trend for planners to designate urban wildlife corridors is questioned as being probably of no benefit to native diversity and indeed these features are identified as being instead potentially significant pathways for invasive alien species. The most important factors influencing the composition of sites were seen to be those linked closely with past and present human activity. Particularly significant are the nature of dereliction substrates and haphazard disturbances such as fire and tipping which influence vegetation succession temporally and spatially.