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Ecology and Management of West Coast Plant Communities
Alistair Hamilton
2000
PhD Thesis, The University of Edinburgh
Supervisors: Colin Legg (School of GeoSciences)
Helen Armstrong (Forest Research, Northern Research Station)
Angus MacDonald (Scottish Natural Heritage)
ABSTRACT
The wet and mild climate in north-west Scotland has resulted in a landscape dominated by wet heath and blanket-bog vegetation. Blanket bog is of high conservation value, but of poor agricultural quality. Along with wet heath, it is used as extensive grazing for sheep and deer and, over these large unfenced areas, fire is one of the few viable management options available to estate managers and crofters. Fire in these areas is used to promote the rapid spring regrowth of grass and sedge species (the ‘early bite’), in contrast to the better-known grouse moor (dry heathland) fires where regeneration of Calluna vulgaris is the aim. The characteristics and effects of management fires in blanket-bog vegetation are virtually unknown, and this lack of knowledge is reflected in the almost universal recommendation of conservationists that blanket-bog vegetation should not be burnt at all, or that burning should be minimised. Information about the management fires themselves, and their effect on the blanket-bog habitat, is therefore required in order to refine burning guidelines in accordance with the management objectives.
This thesis describes the background to the use of fire in north-west Scotland, putting fire in the context of a changing landscape and culture. Using fires from the spring of 1996, 1997 and 1998, the fuel complex is described, and equations to predict fuel load from pre-fire survey variables are presented. The results emphasise the very high spatial variability in fuel load, and this is in turn reflected in the variability in fire temperature regimes and in estimates of fire intensity. The usefulness of different fire characteristics is discussed with respect to possible objectives for fire studies, and the importance of appreciating the different spatial and temporal scales at which various processes and fire effects operate, and at which fire characteristics should be measured, is stressed. |
Moisture content (percentage of the ovendry weight) of Molinia leaf litter recorded at three positions in the vegetation before burning. The ‘aerial’ fuel is held in the Calluna canopy, ‘raised’ is on the ground but not in contact with the Sphagnum moss, and ‘base’ is actually lying on Sphagnum. Mean and SE bars shown.
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Maximum temperatures recorded at the four thermocouple positions (n = 39 for each). Positions of thermocouples: ‘above’ = 20 cm above the vegetation canopy; ‘top’ = at the top of the vegetation canopy; ‘middle’ = the middle of the vegetation (measured as half the vertical height of the vegetation at that point); ‘surface’ = on the surface of peat or moss. Mean and SE bars shown. |
This thesis describes the background to the use of fire in north-west Scotland, putting fire in the context of a changing landscape and culture. Using fires from the spring of 1996, 1997 and 1998, the fuel complex is described, and equations to predict fuel load from pre-fire survey variables are presented. The results emphasise the very high spatial variability in fuel load, and this is in turn reflected in the variability in fire temperature regimes and in estimates of fire intensity. The usefulness of different fire characteristics is discussed with respect to possible objectives for fire studies, and the importance of appreciating the different spatial and temporal scales at which various processes and fire effects operate, and at which fire characteristics should be measured, is stressed. |
The effects of fire on the Sphagnum layer are described with respect to fuel availability, grazing, and position, and the recovery of the Sphagnum followed for up to three years after burning. The regrowth rates of the two most important vascular species, Calluna vulgaris and Molinia caerulea, are compared under grazing and no-grazing treatments. The considerations for and against burning blanket bog are reviewed, and recommendations for management of prescribed burning given. The urgent need for further research into fire characteristics and effects in the UK is stressed, with recommendations made for the areas most in need of further study.
Recovery of Sphagnum 18 months after an experimental fire.
Sphagnum condition recovery curves for spring 1996 and 1997 fires. A score of 0 indicates all Sphagnum damaged by fire, and 8 indicates completely healthy Sphagnum. Mean and SE bars shown.
For more information contact Alistair Hamilton.