Exclusion of large herbivores: Long-term changes within the plant community

• Ground flora composition changes with time since large herbivore removal.
• Long-term removal of herbivores can simplify the woodland habitat.
• Implications for the management of woodlands for biodiversity conservation.

Semi-natural woodlands are a globally important relict ecosystem for biodiversity, which are threatened through a range of anthropogenically induced changes, including overgrazing by large herbivores. Fencing to conserve biodiversity is increasingly used as a management tool, so the long-term impacts of large herbivore removal requires investigation. The objective of this research is to investigate the effect of large herbivore exclusion on vegetation, through time, using empirical long-term vegetation data collected over ∼40 years. The responses of ground flora communities to this removal will be assessed, and it is predicted that a change in woodland vegetation will occur through time. Plant community composition was surveyed in a network of 7 large-herbivore exclosures, within protected temperate oak woodland in Ireland, at intervals up to 41 years. Ground flora species abundance was quantified and time since fencing was used to standardise the survey data, with three time groups being derived from this to assess beta diversity changes through time. With total removal of large herbivores from the oak woodland ecosystem, this study has identified significant changes in ground flora composition and abundance, and a general homogenisation of the vegetation community with increasing time since large herbivore removal. Large-scale long-term fencing of oak woodlands should be replaced by large herbivore management programmes, in order to ensure the conservation of diverse woodland ecosystems.