Regional stability versus fine scale changes in community composition of mesotrophic grasslands over 25 years

Long-term studies of vegetation change in grasslands are important to our understanding of the ecology and management of grassland systems, especially for grasslands of high conservation value which have seen a drastic decline due to agricultural intensification and abandonment. This study investigated change over 25 years in 35 mesotrophic grassland sites which were described as species-rich at the start of the study period. Some sites had been consistently managed by mowing or grazing, while others had seen a change to more intensive management or to little or no regular management. Baseline data were available for both quadrat and species list surveys and repeat surveys were undertaken using the same methods on all 35 sites. Multivariate analysis using Non-metric Multidimensional Scaling revealed that the overall community composition was similar in the original and repeat surveys, but some differences were revealed when the sites were categorised by management type. The two survey methods provided different information about both the principal vegetation communities and about other aspects of the site including the presence of rare species. There were losses and gains of species of importance to conservation, with more losses than gains overall, and there was some evidence for species losses at sites which had been managed consistently for conservation. These changes may be linked to aspects of the management regime, isolation of sites or changes in soil fertility levels, but a greater understanding of the local and regional processes affecting diversity in mesotrophic grasslands is required to inform conservation management.