Restoration of blanket bog vegetation as a habitat for red grouse following clearance of immature Sitka spruce forest on the west coast of Scotland

Abstract

Blanket bog habitat is a globally scarce resource and as a result is amongst the most important of British vegetation types in an international context. The habitat supports four Annex 1 bird species including golden eagle (Aquila chrysaetos) as well as red grouse (Lagopus lagopus) which is only found on heather moorland habitats and provides an important food source for golden eagle. The habitat is a Biodiversity Action Plan habitat with a target to restore 845,000 hectares of degraded blanket bog by 2015. At least 190,000 hectares of blanket bog habitat have been planted with conifer plantation, mainly Sitka spruce (Picea sitchensis), which is unlikely to mature until 2020-2030. This thesis explores the potential for restoring blanket bog, to provide habitat for red grouse, through the removal of immature Sitka spruce plantation. Three different tree clearance techniques are considered in terms of impact on the developing vegetation plant community. . The most cost effective method of clearance, in situ chipping using an excavator mounted flail, is investigated in detail; in particular the effect of wood-chip depth on changes in wood chip decomposition, plant colonisation, plant community development and vegetation structure. Monitoring and experimental data were analysed using multivariate methods including Principal Response Curves, Detrended Correspondence Analysis and Redundancy Analysis, and univariate methods including linear mixed effects and spatio-temporal models. Restoration of blanket bog vegetation is clearly achievable within a relatively short timescale that is dependent on the size of the trees and hence depth of wood chip. Plant community recovery following in situ chipping of trees (yield class 10) that are 20, 25 and 30 years old is predicted to take 7,9 and 10.5 years respectively. Vegetation structure is linked to plant community, with the cover and age of Calluna vulgaris being particularly important. As a result it seems likely that suitable red grouse habitat will be achieved as the target blanket bog plant community is reached.