Observations on bark-stripping by red deer in a Picea sitchensis forest in Western Scotland over a 35-year period

ABSTRACT

The impact of bark-stripping by red deer on an 1825 ha plantation of Picea sitchensis is reported. Monitoring began in 1978 with initially 6500 trees at 37 sites; by 2014, only 10 sites remained due to felling. Sites became vulnerable to bark-stripping once the trees reached 7 years’ age, and from then until felling at age c. 45 years, incidence rates averaged 1% of the trees damaged yearly. Intense damage at a site in a year (>2% trees damaged) was often followed by intense damage next year, but, on average, 53% of sites were undamaged in a year. Many trees suffered repeat wounding, which reduced final impact by c. 30% compared to the theoretical impact calculated from annual damage and damage duration. The trees bark-stripped were on average smaller than plot mean girths once these means exceeded 20 cm; this had only a minor effect on the final impact since bark-stripped small trees had similar mortality to undamaged small trees. Most wounds (>90%) were small (<180 cm²) and healed quickly, so were unlikely to develop decay. Larger wounds never healed in less than 8 years, but the proportion healed increased progressively from 10 to 20 years after wounding.

KEYWORDS:

• Bark-stripping
• Picea sitchensis
• red deer
• Scotland
• wound healing

Acknowledgements

We are grateful to many people who have assisted in the Glenbranter study since 1978, both staff of the Forestry Commission, owners of the forest, and staff of the Centre for Ecology & Hydrology (formerly Institute of Terrestrial Ecology). For the first ten years, the study included research on the activity and behaviour of the red and roe deer in the plantations, and the main field work was carried out jointly by deer researchers, David Catt and Dr (later Professor) Brian Staines, and the present authors. We are also indebted to Dorian Moss, Don French, and David Elston for at various times guiding our planning, data handling and statistics, and to Manuel Hinge and Phil Ratcliffe (deer) and Sandy Cram and Fred Last (forestry) for expert advice.

Disclosure statement

No potential conflict of interest was reported by the authors.