Winter supplementary feeding influences forest soil seed banks and vegetation

QUESTION: To what extent does winter supplementary feeding influence vegetation and soil seed banks in forest ecosystems? LOCATION: Białowieża Primaeval Forest, NE Poland. METHODS: Several dozen feeding stations, each composed of one to several haystacks, are used in Białowieża Forest for supplementary winter feeding of European bison (Bison bonasus). We checked the species composition and availability of seeds in hay in 15 haystacks of the eight oldest feeding stations, which could be a potential source of seeds. Vegetation and soil seed bank were sampled on the overlapping 10 m × 10 m plots distributed along 500‐m long transects running south and north of the studied feeding stations. Seed content in the soil samples was studied by the seedling emergence method in an unheated greenhouse. RESULTS: We revealed high dissimilarity of species composition of the hayseed, soil seed bank and standing vegetation. The dissimilarity between soil seed banks and standing vegetation increased with the distance from the haystack. The species richness of the standing vegetation was not affected by distance to the haystack, while seed bank species richness showed a significant negative correlation with distance. The mean weighted ecological indicator values of pH, light and soil fertility were negatively correlated with the distance from the haystack for the seed bank and the standing vegetation. The percentage of damaged bushes and juvenile trees was positively correlated with their density and decreased with the distance from the haystack. CONCLUSIONS: We revealed distinct but local (25–50 m off the haystack) effect of supplementary feeding on the vegetation and soil seed banks of forest ecosystems. Taking into account the ecosystem approach to nature conservation, the winter feeding in forest ecosystems should be concentrated in few places to avoid the expansion of non‐native plant species in forest ecosystems. To prevent potential plant invasions, the origin of the hay used as supplementary winter fodder should be carefully selected, with a preference for local origin and making of hay of native plant species in the forest's meadows or in its surroundings.