Vegetation analysis of upland burren grasslands of conservation interest

Abstract

This study addresses the classification of grassland and heath communities found within the Burren uplands of Co. Clare and identifies threats to their integrity. Quadrats were taken on a range of sites, focusing on semi-natural, upland grassland and heath of conservation interest. Before analysis, the data set was divided into a heath group and a grassland group based on cover of dwarf shrubs. The data were analysed using TWINSPAN and canonical correspondence analysis. Within the grassland group, two main associations were found: the Sesleria caerulea-Breutelia chrysocoma association of low- nutrient, calcareous, species-rich grasslands, and the Dactylis glomerata-Holcus lanatus association of more-mesotrophic grasslands. Within each group three sub-associations were identified. The heaths also fell into two main groups: one dominated by Dryas octopetala, and the other by Calluna vulgaris. The Dryas heath association formed three sub-associations, while the Calluna heaths formed three distinct associations, including associations of rare alpine heaths with Empetrum nigrum and Arctostaphylos uva-ursi. From direct ordination, significant environmental and management factors, such as altitude, soil depth and grazing pressure, were identified. Trends within the data set suggest a gradual increase in agriculturally favoured species with increased summer grazing. Abandoned and less-grazed areas are threatened by scrub and bracken encroachment.