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Land-use changes, pollution and climate warming during the 20th century have caused changes in biodiversity across the world. However, in many cases, the environmental drivers are poorly understood. To identify and rank the drivers currently causing broad-scale floristic changes in N Europe, we analysed data from two vascular plant surveys of 200 randomly selected 2.5 × 2.5 km grid-squares in Scania, southernmost Sweden, conducted 1989-2006 and 2008-2015, respectively, and related the change in frequency (performance) of the species to a wide range of species-specific plant traits. We chose traits representing all plausible drivers of recent floristic changes: climatic change (northern distribution limit, flowering time), land-use change (light requirement, response to grazing/mowing, response to soil disturbance), drainage (water requirement), acidification (pH optimum), nitrogen deposition and eutrophication (N requirement, N fixation ability, carnivory, parasitism, mycorrhizal associations), pollinator decline (mode of reproduction) and changes in CO levels (photosynthetic pathway). Our results suggest that climate warming and changes in land-use were the main drivers of changes in the flora during the last decades. Climate warming appeared as the most influential driver, with northern distribution limit explaining 30%-60% of the variance in the GLMM models. However, the relative importance of the drivers differed among habitat types, with grassland species being affected the most by cessation of grazing/mowing and species of ruderal habitats by on-going concentration of both agriculture and human population to the most productive soils. For wetland species, only pH optimum was significantly related to species performance, possibly an effect of the increasing humification of acidic water bodies. An observed relative decline of mycorrhizal species may possibly be explained by decreasing nitrogen deposition resulting in less competition for phosphorus. We found no effect of shortage or decline of pollinating lepidopterans and bees.

In a north European context, identifying invasive species is far from trivial because the vegetation has been influenced by human activities for thousands of years. New species have immigrated continuously since the end of the last glaciation, both spontaneously and through direct or indirect help by man. Still, newly immigrated species may be problematic in a nature conservation context and may harm biodiversity, and cause changes in ecosystem services. In this study, all 721 presently established vascular plant and bryophyte taxa known to have been introduced to, or to have immigrated to, Sweden since the year 1700 are assessed for their invasive potential. The assessment is based on six components considered relevant for their invasiveness: 1) ability to compete in natural vegetation, 2) ability to form dense populations, 3) realized dispersal ability, 4) gene flow to native relatives, 5) time since immigration and 6) distance to their native range. Although the relative importance of these components is context dependent, a compound general index of invasive concern is proposed and calculated for all taxa. The index of invasive concern is validated by comparing it to assessments by a Bayesian Belief Network in which the influences of the same six components are assigned by expert opinions. In addition, rough estimates of the present‐day abundance of each taxon in Sweden are presented. The origin, biology and possible impact of the 150 taxa with the highest index values are discussed. Based on the index of invasive concern, Campylopus introflexus, Epilobium adenocaulon, E. ciliatum, Rosa rugosa, Lamiastrum galeobdolon subsp. argentatum, Orthodontium lineare, Solidago canadensis, Calystegia sepium subsp. spectabilis, Rubus armeniacus and Prunus serotina are identified as the ten most problematic alien vascular plant and bryophyte taxa in Sweden.

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Question When evaluating forests in terms of their biodiversity, distinctiveness and naturalness, the affinity of the constituent species to forests is a crucial parameter. Here we ask to what extent are vascular plant species associated with forests, and does species’ affinity to forests vary between European regions? Location Temperate and boreal forest biome of Northwestern and Central Europe. Methods We compiled EuForPlant, a new extensive list of forest vascular plant species in 24 regions spread across 13 European countries using vegetation databases and expert knowledge. Species were region‐specifically classified into four categories reflecting the degree of their affinity to forest habitats: 1.1, species of forest interiors; 1.2, species of forest edges and forest openings; 2.1, species that can be found in forest as well as open vegetation; and 2.2, species that can be found partly in forest, but mainly in open vegetation. An additional “O” category was distinguished, covering species typical for non‐forest vegetation. Results EuForPlant comprises 1,726 species, including 1,437 herb‐layer species, 159 shrubs, 107 trees, 19 lianas and 4 epiphytic parasites. Across regions, generalist forest species (with 450 and 777 species classified as 2.1 and 2.2, respectively) significantly outnumbered specialist forest species (with 250 and 137 species classified as 1.1 and 1.2, respectively). Even though the degree of shifting between the categories of forest affinity among regions was relatively low (on average, 17.5%), about one‐third of the forest species (especially 1.2 and 2.2) swapped categories in at least one of the study regions. Conclusions The proposed list can be used widely in vegetation science and global change ecology related to forest biodiversity and community dynamics. Shifting of forest affinity among regions emphasizes the importance of a continental‐scale forest plant species list with regional specificity.

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