The impact of red deer management on liverworts associated with the mixed hepatic mat community and other terrestrial cryptogams

Abstract

Background: Exclosure is often regarded as the most effective means of encouraging woodland regeneration in the presence of high deer densities. This has potential implications for terrestrial cryptogam diversity at a time when the Scottish Government is encouraging an increase in woodland cover. The hepatic mat assemblage at Coire Dhorrcail, Knoydart, is unique to the Scottish mainland in that it occurs from sea-shore to mountain summit throughout the full range of vegetation. No previous study has examined the response of this rare liverwort community to the absence of red deer.

Aims: To compare the species richness, diversity, dominance and abundance of bryophytes and lichens either side of the twenty-year-old deer exclosure at Knoydart.

Methods: Percentage cover of cryptogam species has been estimated from quadrats within paired sample plots at different altitudes on either side of the exclosure. Sampling was randomised at each stage. Simple linear models were used to analyse the data.

Results: Succession within the exclosure has created conditions suitable for bulkier species of moss to attain local dominance, causing significant reduction of Herbertus hutchinsiae cover, cryptogam species richness and diversity.

Conclusions: What is good for tree regeneration may be bad for terrestrial cryptogams. Careful consideration of existing biodiversity is necessary before exclosing large areas for woodland regeneration.

Keywords:

• bryophytes
• Cervus elaphus
• deer exclosure
• grazing
• Herbertus hutchinsiae
• species diversity
• species richness
• succession
• trampling
• woodland regeneration

Acknowledgements

The authors are grateful to the John Muir Trust and the Letterewe Estate for financial support of this research. The logistic support provided by the Letterewe staff is also gratefully appreciated. Thanks are also due to the anonymous reviewers for their comments and advice during an earlier draft of the manuscript.

Additional information

Notes on contributors

Oliver Moore

Oliver Moore is a field ecologist with a special interest in the flora and fauna of the Scottish Highlands. He is currently attached to Imperial College London, researching the impact of red deer management on bryophyte and lichen communities in north-west Scotland.

Lester Standen

Lester Standen is Deer Officer and Knoydart Property Manager for the John Muir Trust. He is responsible for ensuring that the deer cull on all properties is carried out in line with the Trust’s deer management policy, and he represents the Trust in deer-related forums. Lester supports, encourages and promotes the conservation of wild land in the Knoydart area and works with neighbouring land owners and managers in achieving this.

Michael J. Crawley

Mick Crawley FRS is Professor of Ecology and Dean at Silwood Park Campus. He has published widely on plant ecology and plant–herbivore dynamics. He is author of the Flora of Berkshire and a number of books on statistics and computing.