Interactions between climate and land use which drive dynamics in treeline ecotone scrub in Scotland
Treeline ecotone scrub, the suite of tall woody plant communities that bridge the boundary between tall forest and higher altitude open summit heaths, is a rare and little studied transition habitat in the UK. Individual species have recently attracted emergency measures to secure their future, but little is known about the current dynamics of the habitats. This thesis increases knowledge of treeline scrub dynamics, particularly in relation to young plants, and develops an understanding of the management required for future conservation. Climate and land use are the main drivers of treeline scrub dynamics, while land use policy will shape the future land use. This study focussed on three species: Betula nana, Salix myrsinites and Juniperus communis, as representatives of the main scrub communities. Firstly, the range of environmental conditions and the current land uses the species tolerate were surveyed for a large number of sites. This enabled the existing sites to be characterised to inform the selection of potential new sites for restoration. Secondly, experiments tested the response of young plants to the interaction between wind exposure and simulated browsing, and, separately, to over-wintering under snow. No evidence was found to suggest that declining snow cover will adversely affect the species, but while the response of the species to increasing exposure and browsing was complex heavy browsing is likely to limit expansion in the absence of specific management. Finally, a review of current land use policy identified that treeline ecotone scrub was included in existing implementation strategies. However, a survey of the understanding of and attitudes to these habitats by key individuals involved in creating, implementing and influencing policy demonstrated that restoration is unlikely to happen within the current structure, except through the interests of non-governmental organisations with a nature conservation focus.