The study on the potential use of potassium octadecanoate (C₁₇H₃₅COOK) in the protection of silver fir, Scots pine and sessile oak against browsing and bark stripping by cervids on ten 0.1 ha study plots in the Jeleśnia and the Radomsko Forest Districts during the autumn and winter season 2021 and 2022 was carried out. Naturally regenerated trees Abies alba, Pinus sylvestris, and Quercus petraea were treated with potassium soap and Cervacol Extra PA repellent. For each tree species four study plots were established where 200 trees (100 treated by repellent and 100 untreated) selected randomly were tested. Moreover, at one plot, as a pilot study where early thinning was performed prior, an additional 60 Scots pines were left as browsing trees to evaluate the protective effect of potassium stearate. Damage inspections on research plots were carried out twice per month by checking the extent and degree of damages. Potassium octadecanoate protected best on the older Scots pine plantation, since it had a significant impact on the trees protection in relation to pines free from repellent. In the case of natural regenerated fir trees, a significantly higher percentage of damaged trees protected with Cervacol Extra PA was found compared to silver fir trees protected with the use of potassium octadecanoate. At the sessile oak plots protected with both tested repellents, no significant differences were found in the extent and degree of damage to trees. It was shown that potassium octadecanoate persists on protected plants maintaining an intense odour and durability during storage over the winter period. Considering the satisfactory results and the original research profile (besides ecological character of the substance), it is recommended to continue field experiments with the use of potassium octadecanoate in protecting forest plantations and natural regenerated stands against damage caused by cervids. Further research could consider enrichment of the substance composition with a quartz sand as well as increase the number of experimental plots and their distribution in various regions of the country.

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