| Summary: | Numbers of red deer (Cervus elaphus) in the Highlands have more than doubled in the last few decades and conservation organisations have expressed concern over their potential impacts on the natural heritage. Bryophytes and lichens represent a substantial component of Scottish biodiversity and northwest Scotland has cryptogam assemblages that are rare elsewhere in the world. Few studies have separated the impacts of red deer from those of sheep and none has focused on the response of important bryophyte and lichen assemblages to red deer management. This thesis has started to address this shortfall in scientific knowledge. Research was centred at Letterewe and neighbouring estates near Loch Maree, Wester Ross where there has been no sheep grazing for decades. Existing exclosures were used to compare blocks of cryptogam communities associated with specific habitats either side of the deer fence. In this way bryophyte and lichen species cover, diversity, dominance and richness associated with low-lying siliceous rocks, globally rare wet heath/bog and the internationally important epiphytic Lobarion lichen community were investigated. Other approaches involved comparing cryptogam communities found on boulder tops inaccessible to red deer with those that were accessible, attempting to correlate red deer dung densities with localised impact to liverwort-rich oceanic heath and by contrasting summit moss-heath vegetation between two estates that have different mean deer densities. Liverworts associated with the mixed hepatic mat were also compared either side of a long-standing deer fence at Knoydart. These studies have shown that red deer and their management (using exclosures) have both positive and negative effects on important bryophyte and lichen assemblages in northwest Scotland. This body of research is presented as a series of self-contained scientific papers.
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