Simulated bark stripping reduces stem growth in young Norway spruce: Evidence from continuous dendrometer monitoring

Norway spruce [Picea abies (L.) Karst.] is Europe's most important commercial tree species, whose stability, vitality, and production potential can be significantly compromised by cervids. Their populations in Europe have been growing over time. This study aimed to analyse the effect of simulated circumferential trunk damage – mimicking bark stripping by ungulates – on the diameter growth of young spruce trees through continuous measurements with point dendrometers at 15-minute intervals. Dendrometers were installed at two permanent research plots (PRPs) in the Luick hory (Lusatian Mountains) and at another two PRPs in the Krun hory (Ore Mountains) on spruce stands aged 16–21 years. At each PRP, 15 co-dominant trees were monitored; five served as undamaged control trees, while ten were experimentally damaged by removing bark over an area ranging from 5–90% of the trunk circumference. The most intense diameter growth occurred during an approximately 14-day period at the turn of May and June. The growth activity ceased on all PRPs during the second to third week of September. Even during the first growing season after the experimental damage, significantly lower diameter growth was observed in the evaluated trees when compared with undamaged control trees (P < 0.05). On PRP 2, undamaged trees achieved up to 87.8% higher growth than the damaged ones. Overall, the diameter growth of damaged trees was 37.9–43.2% lower than that of undamaged control ones, depending on the damage category, although no significant differences were found among the damage categories of 5–30%, 40–60%, and 70–90%, respectively. The results show that simulated bark damage can considerably reduce the diameter growth of young spruce trees as early as the first growing season, underscoring the importance of effective stand protection from harm caused by ungulates.