Viltets inverkan på vegetationsutvecklingen i en sydsvensk skogsföryngring

Abstract: Herbivore impact on the Swedish forest has under a long time been a common subject of debate. There are many different opinions depending on what direction the forest owner has with his/her forest. Populations of moose and roe deer have increased significantly in Sweden during the last decades. The purpose of this study is to get a full picture of the herbivore impact on the regeneration areas. The field work was done once a year for seven years (1999–2005). The experimental area is situated in the V. Torsås parish, County of Kronoberg. The vegetation was measured in the tree, bush and field layer inside and outside an exclosure. The results in this report are in many ways supporting similar studies. All species in the tree and bush layer, except for Norway spruce (Picea abies, (L. Karst.)) and birch (Betula sp. L.), were exposed to browsing. Over 90 % of the trees were damaged and the difference in height between five and eight times for species as mountain ash (Sorbus aucuparia), alder buckthorn (Frangula alnus Mill.) and willow species (Salix sp.). For Scots pine (Pinus sylvestris L.) around 70 % of the trees were damaged outside the exclosure and the average height was 100% higher inside it. The average height of the birch was a bit lower outside the exclosure but the large number enabled enough birches to grow well. Spruce had only a small difference in average height but they were more abundant outside the exclosure. The distinctions in the field layer between the two areas have been relatively small, but there was a few more species inside the exclosure than on the outside. For some species that are very common in the forest in the south of Sweden, like wavy hair-grass (Dechampsia flexuosa (L. Trin.)), raspberry (Rubus idaeus L.) and some dwarf-shrubs, larger differences could be established. The coverage of wavy hair-grass was distinct from similar studies by a larger coverage inside the exclosure than the outside. Raspberry did not show any large difference in coverage but the average height was higher inside the exclosure. The coverage of bilberry (Vaccinium myrtillus L.), cowberry (V. vitis-idaea L.) and heather (Calluna vulgaris (L. Hull)) was reduced the first few years and was then constant during a few years but increased again the last year. Browsing did not have a very large influence on the forest production in this study, but the vegetation succession was accelerated with a few years. This can also reduce the biodiversity. The distribution of tree species will be drawn towards a more spruce-dominated forest. The browsing will vary with the populations of moose and roe deer but are also dependent on environmental factors, e.g. food supply, protective vegetation for the herbivores and predator populations.