The aim of the study was to investigate natural values and the occurrence of pendulous lichens species in two areas located in subalpine coniferous woodland in Tärnaby, Västerbotten county in northern Sweden. The two areas have similar geology, hydrology and vegetation. Area A is affected by forestry, whilst area B isn’t. Forestry is one of the biggest threats to woodland species because it causes habitat fragmentation a loss of habitat. Pendulous lichens are most occurring in old growth forests where natural processes have been left undisturbed. Therefore, red-listed pendulous lichens are often used as a nature value indicator for identifying old-growth forests. In each study area, five sample areas was studied. In each sample area, a nature value assessment and an inventory of pendulous lichen species and red-listed pendulous lichen species was performed. In area A, three species of pendulous lichen where found, and five species were found in area B. In area B, two of the species found were Alectoria sarmentosa and Bryoria nadvornikiana, both listed as NT in the IUCN red list. In area A, no red listed species were found. Results also showed a higher natural value in the area not affected by forestry, area B, than in area A. The natural values and occurrence of pendulous lichen and red-listed pendulous lichen was higher in area B than in area A. The cause of the differences can’t be identified by this study, but the effect of forestry is probably one of the causes.

The boreal forest in Fennoscandia has been subjected to major loss and fragmentation of natural forests due to intensive forestry. This has resulted in that forest edges are now abundant and important landscape features. Edges have documented effects on the structure, function and biodiversity in forests. Edge influence on biodiversity is complex and depends on interactions between many local and regional factors. This thesis focuses on sharp forest edges and their potential to influence biodiversity at the landscape-level. I have developed a method for quantification and characterization of sharp forest edges by interpretation of colour infrared (CIR) aerial photographs in combination with line intersect sampling (LIS) and sample plots. The method was used to estimate density of forest edge in 28 landscapes (each 1600 ha) in northern Sweden, differing in management intensity, landscape composition and geographical location. Forest edges were described in detail using edge, canopy and neighbourhood attributes. By combining these attributes it was possible to classify edges with respect to levels of exposure. A field experiment was conducted to examine the effect of edge contrast on growth of the old forest lichen Usnea longissima. The edge quantification method is accurate and efficient for estimating the length of sharp forest edges on an area basis (edge density, m ha-1) and for collecting detailed attributes of edges and their surroundings. In northern Sweden, the forest edge density is high (54 m ha-1) but varies extensively (12-102 m ha-1) between landscapes. Edge density is strongly correlated with the level of human disturbance and increases towards the southern part of the study area, at lower altitudes were management intensity is highest. Edge orientation, contrast and neighbourhood size shows an immense variation between edges and also varies between edge types. Regenerating edges are generally of higher contrast and face larger neighbourhoods than natural edges. Maintained edges had high contrast but small neighbourhoods. A larger proportion of edges in mature forests are highly exposed to microclimatic edge influence than edges in general. The field experiment revealed that growth of U. longissima was highest near edges where the vegetation on the adjacent area was sheltering, but not shading, the lichen. In the present thesis, I have provided a valuable tool for estimating density of forest edges with potential to yield information on important factors determining edge influence at landscape-level. The large variability in edge density, edge and neighbourhood attributes imply large differences in microclimate anf thus in the potential for ede influence. Management and conservation strategies must incorporate these factors to realistically address edge influence on biota at the landscape-level.