Materials and methods

Study area

The study was carried out along the Swedish-Norwegian border (60°45’-61°35’N, 11°55’ – 12°55’E) in the Norwegian municipalities of Trysil, Elverum, Våler and Åsnes and the Swedish counties of Värmland and Dalarna (Fig. 1). The topography of the study area exhibits a gradient from higher altitudes in the north to lower altitudes in the south, with approximate elevations ranging from 900 to 400 meters above sea level (masl) (Copernicus Land Monitoring, 2018). The northern part of the study area has a continental climate and is dominated by bare mountains, marsh complexes and deep valleys with dense old-growth forests and vast heathlands (Jansson and Antonson 2011). The forest is primarily composed of Scots pine (Pinus sylvestris ), Norway spruce (Picea abies ) and birch (Betula spp.) (Jansson and Antonson 2011). The mean daily temperature in January and July are –10° C and 15° C, respectively. The ground is typically covered with snow from late October to early May, and the vegetation period spans approximately 140-170 days (www.smhi.se;www.senorge.no). Annual precipitation in the area ranges from approximately 600 to 1000 mm. The southern part of the study area is mostly dominated by Scots pine, Norway spruce and birch forests, which are extensively managed for timber and pulp (Yrjölä 2002; Lundmark et al., 2013). The mean temperature in January and July is similar to the northern parts, but snow mostly covers the ground between December and March. Due to intensive silviculture practices, the study area features an extensive network of forest gravel roads. Additionally, the presence of national and regional roads contributes to a mean road density of 0.84 km/km2 within the study area.