Using cattle for conservation objectives in a Scots pine Pinus sylvestris forest: results of two trials

It has been argued that large ungulates play a key role in natural forest dynamics, but in Britain, the largest native ungulates (aurochs and elk) are extinct. Cattle could have some similar effects, and are widely used, but rarely tested, for nature conservation management. Here, we test conservation management with cattle at a native Scots pine Pinus sylvestris forest in Scotland. Our hypotheses were that cattle impacts would (a) increase the abundance of an understorey shrub of conservation importance, bilberry Vaccinium myrtillus; and (b) increase Scots pine seedling establishment. Two cattle trials were established, one for each objective, based on a 14-ha plot within the forest, and a 6.1-ha plot at the forest edge. Cattle were introduced for 2 months to both plots, giving an approximately 100- to 150-fold increase in ungulate biomass per hectare when compared to background deer abundance. The ground layer vegetation in both treatment and matched control plots was monitored before and after treatment, and subsequently over a 4-year period. At the within-forest trial, bilberry percent-cover, 4 years after treatment, was 1.9 times higher in the cattle area than in the control (95% confidence limits 1.6-2.3). Bilberry percent-cover increases were directly related to the degree of trampling impact on heather Calluna vulgaris, as recorded immediately after the trial. At the forest-edge trial, there were vegetation changes in the cattle plot that were considered favourable to pine seedling establishment: reduced moss/litter depth and vegetation percent-cover, and increased ground-level light incidence. However, too few new pine seedlings were found for formal analysis, partly due to unexpectedly low seed-fall. Nevertheless, the potential for cattle to create conditions that would subsequently promote pine regeneration was illustrated by the observation of large numbers of new, young pine seedlings at the within-forest cattle plot. We recommend that managers and researchers collaborate to develop further trials like the ones reported here, to give an improved understanding of the conditions under which cattle can yield nature conservation benefits in woodlands.