Aim: There is an intense debate about whether habitat fragmentation has a negative or positive effect on biodiversity. We examined whether species richness and incidence of forest plants were negatively or positively associated with fragmented forest configuration. We also analysed whether the results support the fragmentation threshold hypothesis with fragmentation effects only in landscapes with small habitat amount.

Location: Sodermanland province, south-eastern Sweden (8,388 km(2)).

Methods: Data consisted of plant distribution maps and landscape data on forest amount and configuration in 2.5 km x 2.5 km quadrats. We carried out models including forest area together with clumpiness index (CL models) or edge density (ED models) as the measure of habitat configuration. We focused on plant taxa with positive association between incidence and forest area (163 taxa in CL models; 119 taxa in ED models).

Results: Responses to fragmented configuration were negative more often than by random (33 and 22 taxa in CL and ED models, respectively; includes only models without significant forest area x configuration interaction), whereas positive responses were rare (four taxa in both models). When forest area x configuration interaction was significant, the most common response had a negative effect of fragmented configuration when forest area was low and no effect of configuration when forest area was high, which agrees with the fragmentation threshold hypothesis. Species richness also had this type of response. In another common interactive response, the effect of fragmented configuration was negative at low forest area and positive at high forest area.

Main conclusions: Responses to fragmented forest configuration, when significant, were usually negative. When responses to fragmented configuration were modulated by forest area, they were negative when forest area was low. The findings of complex interaction between forest area and configuration have implications for selection of appropriate patch sizes in sustainable forest management.

To assess the effects of landscape configuration on local plant species richness, we tested whether local species richness of forest understory plants is affected by the total forest area and forest edge length in the adjacent landscape. We also tested whether the landscape effect on species richness is different for forest and edge species. We estimated species richness from 113 forest sites in four regions in Northern Europe. At each site, we studied two plots, one at the edge and one in the core of the forest. Total forested area and forest edge length in circles with a 1-km radius, together with plot-specific variables of environmental conditions and temporal continuity of forests, were recorded at each plot. The amount of forest and the length of the forest edge in the adjacent landscape had a significant positive effect on local species richness of all understory plant species. As expected, edge species were positively affected by increasing length of the forest edge in the landscape, but surprisingly there was no effect of forest area on species richness of forest species. Temporal forest continuity had a negative effect on species richness of edge species but no effect on species richness of forest species. Our results suggest that forest edge length had a stronger landscape effect on understory plant species richness than forest area. Implications of these findings for the management of forest landscapes depend on priorities given to different species groups in biodiversity conservation, i.e. if emphasis is in total species richness or species richness of forest or edge species.

The forest interior and the forest edge are different due to the characteristics of the adjacent land cover surrounding the edge. When large forest areas are divided into smaller fragments the interface between the forest interior and surrounding environments increases and various processes start affecting remaining forest ecosystems and forest species. Urban or rural landscapes, cultivated monocultures or grasslands can influence the edge regions differently.

This review is focusing on edge effects in forested environments. Edge effects on plant species diversity and species composition are expected to vary according to forest patch size, patch configuration and placement in the landscape. In general, edge effects are expected to have higher impact on species diversity and composition when the remaining forest patches are small, have an irregular shape or when the surrounding land use is significantly different from the forest patch. Edge effects depend on both biotic and abiotic factors, applied management regimes and on land use history. Further studies on landscape level can shed more light on the underlying mechanisms generating the observed patterns.

De inre partierna av en skog skiljer sig från kanten då skogskanter i stor utsträckning återspeglar landskapet utanför skogen. När stora skogsområden delas i mindre fragment ökas kontaktytan med omgivningen och olika processer börjar påverkar de återstående skogsekosystemen och de skogsarter som finns i de delade skogspartierna. Skogskanter kan se väldigt olika ut beroende på om de vetter mot stadsmiljö, lantbruk, fält med monokulturer eller betesäng.

Denna sammanfattning fokuserar på kanteffekter i skogslandskapet. Mångfald och artsammansättning av kärlväxter i skogen påverkas av kanteffekter genom skogens storlek, form och placering i landskapet. Generellt förväntas kanteffekter påverka växternas mångfald och artsammansättning mer när skogarna är små, har oregelbunden form eller när det omgivande landskapet skiljer sig mycket från skogsmiljön. Effekten är beroende av både biotiska och abiotiska faktorer, rådande skogsbruk och skogens historia. Ytterligare studier på landskapsnivå kan hjälpa till att belysa de underliggande mekanismerna som skapar de mönster vi ser idag.

In studies concerning nature conservation issues common lichen species have usually been neglected although collecting of these results gives comparatively small disturbance of the populations and is easily done. Instead rare or threatened species or species usually have been used as indicators of sites with high biodiversity. Here, the macrolichen diversity is compared with the diversity of woody plants and other characteristics of different sites in Estonia, Finland and Sweden as a part of a larger project including comparative studies on habitats with presumably high species diversity The site selection was based on the occurrence of Daphne mezereum which usually occurs in semi-open habitats in transitions zones containing species from the surrounding biotopes. One of the main objectives with the study was to develop a fairly rapid method of evaluation of biodiversity using easily identified species. As total inventories are time consuming and reflects snapshots of a certain occasion it is beneficial to use other methods which may give a little less but sufficient information for many purposes, e.g., estimations on biodiversity. The ecological and evolutionary processes that shape diversity and distributions are general and results are assumed to be translatable from the target species to other species. The combination of data from a small number of species may constitute a useful monitoring protocol for lichens and higher plants. In total about 50 lichen species and 25 substrates are included and analyzed in the study. Most of the most common lichens are sorediate or isidiate and asexually reproducing and occur on several substrates. The relation between the diversity of lichen and woody plants is presented.