Characteristics of Bark Stripping Damage by Deer and Nutrient Content in Black Cherry (Prunus serotina Ehrh.)

Large ungulates significantly influence forest ecosystems through shoot biting and bark stripping, but their impact on the dynamics of invasive plant species still remains insufficiently investigated. The North American black cherry (Prunus serotina Ehrh.) is a widespread invasive species in European forests, known for its strong defensive capabilities against herbivores. Despite this, recent observations indicate that deer occasionally utilize its bark and phloem as a food source. This study aimed to determine the extent of deer bark stripping on P. serotina across different age/size classes and evaluate the associated nutrient content in plant tissues. Conducted in two Polish forest districts varying in P. serotina stand and deer pressure structure, we inventoried bark wounds on mature and mid-aged trees. Furthermore, we analyzed nitrogen, glucose, total non-structural carbohydrates (TNC), and the C:N ratio in both healthy and damaged trees. Our findings reveal that mature trees were damaged more often than mid-aged individuals, with wounds positioned higher on the trunks. Interestingly, the dimensions of individual wounds did not significantly differ between age classes. Chemical analysis showed that undamaged mid-aged trees naturally possess higher TNC and glucose contents than mature trees. Given the occurrence of bark stripping, one would expect higher browsing pressure; however, this is not the case. Following bark stripping, only mature trees exhibited a significant chemical response: damaged trees showed increased relative nitrogen content (decreased C:N ratio) and a marked reduction in glucose and TNC. These results suggest the rapid reaction in mature individuals, leading to reduction in local palatability, which likely explains the observed lack of repeated feeding on previously stripped trees. Ultimately, while deer herbivory alone may not directly limit the expansion of P. serotina, the resulting physical wounds provide critical entry points for pathogenic microorganisms, highlighting a novel trophic interaction with significant implications for the biological control of this invasive species.