Investigating changes in plant diversity and species composition in a selection of Irish semi-natural grasslands over the past decade
Lynch Milner, Oliver
Lynch Milner, Oliver
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Publication Date
2025-01-10
Type
master thesis
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Abstract
Semi-natural grasslands are managed through low-intensity management practices, such as extensive grazing and/or annual mowing. As a result, they are species-rich ecosystems. Europe has lost between 50–90% of the area of semi-natural grasslands, accompanied by losses in diversity and changed species composition in the extant semi-natural grasslands. This is largely due to agricultural intensification and abandonment. In Ireland, 1,192 semi-natural grassland sites were surveyed through the 2007–2012 Irish Semi-natural Grassland Survey (ISGS). Using the ISGS as a baseline, the current study aimed to determine if the species diversity and composition has changed since the ISGS. This study is part of the larger Department of Agriculture, Fisheries and the Marine funded project called ‘StableGrass’. The overall aim of this large project is to assess the impact of plant diversity on carbon storage and yield stability in semi-natural grasslands. This study forms one component of this StableGrass project. This study re-surveyed 12 sites from three habitats (4 sites each); GS1 (Dry calcareous and neutral grassland), GS3 (Dry-humid acid grassland) and GS4 (Wet grassland). Fifty-four relevés were collected that included data on the species composition and cover. Vegetation diversity indices (Species Richness, Simpson’s Diversity, and Simpson’s Evenness) were calculated for these relevés.
GS1 had the highest Species Richness and Simpson’s Diversity followed by the GS4 habitat, while GS3 had the lowest values. There was no significant difference in the diversity measures between the ISGS and StableGrass surveys. Ordination analysis suggested evidence for homogenisation in the StableGrass relevés in comparison to the ISGS relevés. This was also observed at the species level with the loss of specialist and rare species and decreased frequencies of herbaceous species across the grasslands. Subtle changes in management, namely an increase in intensity since the ISGS survey was the likely cause for the observed homogenisation. However, management may also be maintaining the diversity at these sites considering the lack of a significant difference since the ISGS. This suggests that these trends could be reversed, provided improved management practices and future monitoring are in place to ensure this.
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University of Galway
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Attribution-NonCommercial-NoDerivatives 4.0 International