Factors relating to soil fertility and species diversity in both semi-natural and created meadows in the West Midlands of England

The post-war decline in the area and diversity of neutral meadows in Britain, resulting from agricultural intensification, has prompted schemes to restore and create new habitats. Their success relies on understanding the relations between soil fertility and species diversity. We have investigated these relations, using multivariate analysis, in 28 semi-natural meadows and eight artificially created urban meadows. Mineralizable nitrogen was the most important soil characteristic in the semi-natural sites; the more N the soil contained the fewer were the species characteristic of traditional meadows. Both potassium and total magnesium favoured diversity, perhaps because their deficiency in many traditionally managed meadows jeopardizes the survival of broad-leaved species in competition with grasses. Available lead, at sub-lethal concentrations and measured as a Pb:Ca ratio, appeared to favour diversity in the semi-natural sites, possibly by inhibiting the uptake of P by competitive grasses and allowing the less competitive species associated with diversity to flourish. The main differences between the soils of the artificial and the semi-natural meadows were that the former contained more extractable P and less mineralizable N and organic matter. It seems that large soil phosphorus concentrations may be the main reason why relatively few species colonize or survive in grassland on many urban soils.