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

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.