What have we learnt from the stand level estimates on stem bark browsing by large wild herbivores?

Abstract Damage on forests by large wild herbivores, especially by red deer (Cervus elaphus L.) has been increasing in Central Europe including Slovakia. Therefore, we attempted to estimate the forage potential, i.e. potentially available bark for consumption by large wild herbivores and actually consumed bark of common rowan (Sorbus aucuparia L.) and goat willow (Salix caprea L.). For these purposes, we measured basic tree characteristics and dimensions (length and width) of wounds due to bark browsing at 15 plots located in a young mixed forest stand (Javorníky Mts; Slovakia). Browsing was recorded separately for four stem sections: 0–50, 51–100, 101–150, and 151–200 cm measured from the ground level. Three stem bark browsing metrics were implemented: browsed bark area (cm2), browsed bark mass (g) and portion of browsed bark mass to total stem bark mass representing potential forage for game expressed in percent. We proved that while common rowan and goat willow were browsed in a great extent, nearly no damage occurred on stems of Norway spruce (Picea abies [L.] Karst.) and silver birch (Betula pendula Roth.). Our estimates showed that the total forage potential of stem bark at common rowan and goat willow was about 13.4 kg per 100 m2 of a forest stand. We learnt from our estimates for instance that the total available stem bark at 100 m2 of our young mixed forest might suffice (if theoretically entire potential was exploited) for red deer, fallow deer (Dama dama L.) and mouflon (Ovis aries musimon L.) for one, two and nearly four weeks, respectively. At the same, that during four years, large wild herbivores browsed nearly 2.6 kg of bark per 100 m2 area, i.e. about 1/5 of the available potential on rowans and willows. It seems like common rowan and goat willow might generate important resources of forage for large wild herbivores and would be treated as a part of biological protection of target tree species against bark browsing.