Selective bark-stripping of beech, Fagus sylvatica, by free-ranging horses

Incidence and intensity of bark-stripping by horses was surveyed in stands and tree lanes of European beech (Fagus sylvatica L.) in Veluwezoom National Park, by using transects. Damage was apparent on 38% of beech trees, and 11% were seriously damaged (score 3 or more). Susceptibility to bark-stripping was found to be strongly size dependent, with highest damage rates occurring at the smaller DBH classes (≤40 cm). Another significant factor affecting damage rate was bark structure, albeit this factor was confounded with tree size. Beech trees with a smooth bark were significantly more damaged compared to individuals with a rough bark structure. Occurrence pattern was another significant factor. Stand trees had higher damage rates compared to trees occurring in lanes along roads and paths. Mean rate of fungal infection of bark-stripped beeches was much higher in stands (46%) than in tree lanes (11%), and strongly increased with increasing damage class. We also analysed beech bark for several macronutrients and compared these with those of several other commonly occurring tree species. Macronutrients in bark tissue could not explain horses’ preference for beech.