Ivar Gjerde

Vascular plants as a surrogate species group in complementary site selection for bryophytes, macrolichens, spiders, carabids, staphylinids, snails, and wood living polypore fungi in a northern forest

Abstract Vascular plants were investigated as a potential surrogate group in complementary small scale site selection, such as woodland key habitats in Scandinavia. We compared the response of vascular plants to environmental gradients to that of seven other plant, fungal and animal groups within a forest reserve in western Norway using data from 59 plots of 0.25 ha. We also examined whether the spatial changes in species (beta-2 index) of vascular plants matched that of the other groups. All seven groups responded to the same gradients in nutrient richness and humidity as the vascular plants. Furthermore, changes in species composition of vascular plants were reflected in comparable degrees of change among the “target“ groups. The lower the degree of change in species composition between plots in the “target“ groups relative to that of vascular plants, the higher the percentage “target“ species encompassed in a complementary selection of sites based on vascular plants. We conclude that in practical site selection of small scale sites of conservation value, such as woodland key habitats, vascular plants may be used in combination with an inventory of important habitats for rare and/or redlisted forest species, such as dead wood, old trees, deciduous trees, and cliffs.

EPIPHYTIC LICHENS IN NORWEGIAN COASTAL SPRUCE FOREST: HISTORIC LOGGING AND PRESENT FOREST STRUCTURE

Current forestry policies worldwide aim at conserving and restoring biodiversity in managed forests. In this respect, epiphytic lichens have become a focal group in studies of how logging and silvicultural methods can be adjusted to mimic and restore old-growth conditions. We addressed this issue in a retrospective study in the coastal spruce (Picea abies) forest region of central Norway, surveying 31 old forest sites in order to relate a selected group of epiphytic macrolichens (Fuscopannaria ahlneri, Lobaria pulmonaria, L. scrobiculata, Nephroma spp., Platismatia norvegica, Pseudocyphellaria crocata, Ramalina thrausta, and Sphaerophorus globosus) to forest stand characteristics and previous logging history. The lichens were associated with brook ravines, F. ahlneri and P. crocata mostly so, being 10 times more abundant in ravine valley bottoms than on adjacent slopes and plateaus. All species used spruce trees as their main substrate, but L. pulmonaria, L. scrobiculata, and Nephroma spp. preferred scatt...

Effects on avian diversity of introducing spruce Picea spp. plantations in the native pine Pinus sylvestris forests of western Norway

Abstract We compared diversity of birds in 35 study plots of equal size (58 ha) and productivity in western Norway, ranging from pure native pine Pinus sylvestris forests ( n = 7), through different mosaics of native pine forests and spruce Picea spp. plantations ( n = 21), to pure spruce plantations ( n = 7). Diversity was evaluated by means of species richness, diversity indices, relative abundance curves and rarefaction. The diversity indices appeared to be less suitable for our purpose. Species richness was higher in pine forest than in spruce forest. However, a peak in species richness was found in mosaic forest. For pooled samples (408 ha), 11 bird species recorded in pine forest were not found in spruce forest, seven species were found in spruce forest but not in pine forest, and seven species were confined to the medium mosaics of pine and spruce forest (on average 56% pine and 44% spruce). We argue that, when mixing two habitat types A and B, the ratio of these habitats that maximize avian diversity depends on the ratio of species confined to habitat A and B, as well as the number of species favoured by the mixture of A and B. Existing spruce plantations (13% of the area) in native pine forests of western Norway have reduced the diversity of birds locally, but increased the diversity of birds on the landscape and regional scale.

Diversity of coleoptera of the bracket fungus Fomitopsis pinicola in a Norwegian spruce forest

The beetle fauna of 299 sporocarps of the bracket fungus Fomitopsis pinicola in a 200 ha spruce forest in southeastern Norway was investigated in relation to sporocarp, tree and forest variables. The sporocarps contained 36 species of beetles, of which six species are on the Norwegian Red List. Of 12,373 individual beetles collected, 91% were Cis glabratus. Plots of species accumulation curves suggested that there may be more than 60 beetle species present in F. pinicola in the area, but that probably all the specialist Ciidae were found. The major factor influencing beetle diversity turned out to be the level of dead wood at and in the vicinity of the sampling site, with a higher number of species per unit volume of sporocarps in areas with high levels of dead wood. There were also significantly more red-listed species in those areas. Analysing the species occurrence with stepwise logistic regression, we show preferential habitat selection of the six most abundant species of Ciidae. Conservation of beetles associated with bracket fungi using amount of dead wood as a surrogate measurement is discussed.

Abundance of two threatened woodpecker species in relation to the proportion of spruce plantations in native pine forests of western Norway

In a comparative study we investigated woodpecker abundance in forest landscapes with different proportion of native pine forest and spruce plantations in western Norway. In 100 circular study plots of 100u2009ha each we recorded 38 white-backed –Dendrocopos leucotos, 22 grey-headed –Picus canus, 13 great spotted –Dendrocopos major, 6 green –Picus viridis, and 2 lesser spotted –Dendrocopos minor woodpeckers in the breeding season. The mean number of recorded woodpecker species peaked at 20–40% spruce plantations. The two most common species in the study, the white-backed and the grey-headed woodpeckers are both Red-listed species in Norway and among the rarest woodpeckers in Europe. The white-backed woodpecker preferred plots with higher than average proportions of standing dead trees and deciduous trees, and low proportions of spruce plantations in the plots. The grey-headed woodpecker preferred plots in the western (coastal) parts of the study area with presence of large aspen Populus tremula trees. Logistic regression models did not reveal any clear threshold values with respect to proportion of spruce plantations in plots, although both woodpecker species were extremely rare in plots with >60% spruce plantations. We recommend spruce plantations to be kept at moderate levels to ensure viable populations of woodpeckers in western Norway.

Lost Hotspots and Passive Female Preference: The Dynamic Process of Lek Formation in Capercaillie Tetrao urogallus

The evolutionary processes behind the polygynous mating system known as leks are difficult to document. One approach is to study the behaviour that drives the formation of new leks today. Several hypotheses have been put forward to explain the formation of leks, and they can roughly be divided into two groups; one which advocates that the males are the driving force and one which argues that the females are the driving force. In this study we use data from a long-term study (1979–1998) of a capercaillie population at Varaldskogen in southeast Norway to develop a model describing how new leks are formed in this species. By using data on spacing pattern and behaviour of radio-marked young and adult birds of both sexes we demonstrate how the situation develops from winter towards mating in spring. Furthermore, we report on a few cases of new leks that have arisen in the area during the 20 years of study. We argue that both female mate choice, male territoriality and male attraction to locations with high densities of females are involved in a dynamic process of lek formation. We present results which indicate that new leks are mainly founded by young birds. Finally, we show that when new leks are formed the spacing patterns of the individuals involved change. This questions the method of using comparisons between the position of female home ranges and established leks to infer how leks are formed.