Abstract
The response of vegetation to a large reduction in red deer numbers was assessed over a 20 year period in two contrasting glens in the Eastern Cairngorms. Monitoring was done in spring when the annual maximum herbivore impact accumulates on the heather. We estimated deer presence from pellet-group counts, and for heather we measured cover, height and shoot browsing. Deer numbers declined earlier in Glen Derry, and correspondingly heather height increased sooner. Trends in Glen Lui were related to plot wetness and distance from places where the deer were fed in winter; dry plots received much heavier usage from deer and rabbits initially, keeping the heather short and cover stable, whereas on wet plots usage was much lower and heather increased both in cover and height. Subsequently, as deer densities fell, the Lui heather thrived, and by 2013 heather height on dry plots had surpassed height on wet plots. Colonisation by pine saplings was very patchy, being virtually confined to plots within 50 m of mature trees and having heather swards less than 25 cm tall. Despite deer numbers falling, saplings still suffered browsing by black grouse, lagomorphs and voles. Annual increments were greatest on dry plots in Glen Lui. However, we estimate that another eight years of negligible deer numbers are needed for the present sapling crop to become safe from deer damage. A limited regime of burning near mature pines may assist regeneration.
Highlights
Which landscapes and vegetation types are wanted in the British uplands is currently receiving much debate, with widely divergent options advocated by different organisations, landowners, and the general public
The present paper reports the heather trends and tree colonisation up to 2015 in the two glens on 186 plots monitored since 1991
A very sharp decline between 2001 and 2002 in Glen Lui reflected increased culling and the cessation of winter feeding on the central grasslands; hay, carrots or potatoes spread every day or two days in winters till 2000 had attracted many stags which, after their feeding bout, moved onto the surrounding heather moorland
Summary
Which landscapes and vegetation types are wanted in the British uplands is currently receiving much debate, with widely divergent options advocated by different organisations, landowners, and the general public. Much is known about the Scottish uplands, as shown by the wide variety of papers included in a book edited by Thompson et al (1995), but these studies deal largely with cultural moorlands managed by burning. In such moorlands the natural successions to woodland are prevented in order that dwarf shrubs heather (Calluna vulgaris) can flourish and provide good food and habitat for livestock and game birds, these being agricultural or sporting managements
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