The effects of management intensification on the size, activity and structure of soil microbial communities in botanically diverse haymeadows were examined. Paired traditionally managed and intensively managed haymeadows, at three submontane regions in northern England and north Wales, were sampled over four seasons. Management intensification had no significant effect on soil nutrient status, soil microbial biomass and soil microbial activity. Management intensification did influence soil microbial community structure, resulting in a significant reduction in soil fungal biomass, measured as soil ergosterol content, and a decline in the proportion of fungi relative to bacteria in the soil microbial community. Fungi of the genera Fusarium, Mucor, Absidia, Cladosporium, Trichoderma, Acremonium, Zygorhynchus, Phoma and Paecilomyces were commonly isolated from litter and soil of both the traditionally and intensively managed haymeadows of the site tested. Management had a significant effect on the relative isolation frequency of these fungi at this site. All commonly isolated species had proteolytic and urease activity and approximately half had cellulolytic and lignolytic activities. These findings were taken to suggest that although management improvements to submontane haymeadows will induce changes in the size and composition of the fungal community, they do not necessarily influence the functioning of the soil microbial community with respect to soil ecosystem-level processes of organic matter decomposition and nutrient cycling. We suggest that changes in soil microbial communities are related primarily to changes in plant productivity and composition or the form and quantity of fertiliser applied to the site. (C) 2000 Elsevier Science Ltd.