Tree establishment under high browsing pressure in Eriksberg Wildlife Park, Sweden
Abstract: The aim of the study was to investigate under which conditions (in terms of topography, amount of rocks, presence of thorny bushes, visibility, etc.) temperate trees can establish under very high browsing pressure. The study was conducted in Eriksberg Wildlife Park (EWP), Blekinge, Sweden. EWP is a 915 ha fenced area with c 1600 game animals being managed mainly for hunting reasons. The following species are present: European bison (55), red deer (350), mouflon (200) and fallow deer (750). Strong browsing and grazing by wild animals has been going on since the fence was erected in the 1940s in a smaller part and since 1976 in the whole fence. Seedlings of trees (4-300 cm) and two bush species (Sambucus and Rosa) were searched for in 37 transects of 250 m length and 10 m width, a total area of 11.5 ha was covered. Tree establishment was evaluated in ten habitat types: previous agriculture field, big solitary rock, cliff, fallen tree, flat area, juniper stands, road, rocky area, thorny bush and wet area. In total, 253 seedlings were found over the surveyed 11.5 ha. Seedling density was the highest on big rocks and cliffs with 222.37 and 109.17 seedlings'ha-1, respectively. In flat area seedling density was 2.9 seedlings'ha-1. As a control, tree density was surveyed in one exclosure, where it was found 2320 seedlings'ha-1. No seedlings were found on agriculture fields. 62% of the seedlings were lower than 50 cm. Mean height (+/- SE) of all seedlings was 63.5 cm (+/- 4.7) cm The highest seedlings were found in thorny bushes: 112.0 cm (+/- 18.9), on cliffs: 97.9 cm (+/- 9.9) and on the top of big rocks: 88.2 cm (+/- 16.2) cm. On the flat area the average height was the lowest: 10.7 (+/- 1.5) cm. Seedlings appear almost only in habitat types with some kind of protection features as fallen tree, big rock, thorny bushes, junipers stand or cliff, but in comparison with exclosures tree establishment is sparse.
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