Aim In this study, we explored spatial patterns of phylogenetic diversity (PD) and endemism in the flora of Norway and tested hypothesized post‐glacial environmental drivers of PD, including temperature, precipitation, edaphic factors and time since glacial retreat. Location Norway. Taxon Vascular plants (Trachaeophyta). Methods We produced a multi‐locus maximum‐likelihood (ML) phylogeny using a combination of newly produced DNA sequences from herbarium specimens and sequences available from public repositories. We combined the phylogeny with species occurrence data to estimate PD and phylogenetic endemism across Norway, using a spatial randomization to judge statistical significance. We used multiple‐model inference to identify environmental variables that contributed the most to the patterns of PD. Finally, we estimated phylogenetic turnover and used this to identify Norwegian plant assemblages in terms of composition and evolutionary history. Results Our ML phylogeny contained 87% of all currently described native Norwegian vascular plants. Assemblages were phylogenetically overdispersed in warmer and wetter regions of Norway, as well as in regions with a longer post‐glacial history. In cold and dry regions, plant assemblages were phylogenetically clustered, and characterized by neo‐endemism, while the mild and wet regions were characterized by both paleo‐ and neo‐endemism. PD was positively correlated with summer temperature and habitat heterogeneity, and peaked in the southeast of Norway. Main conclusions Both contemporary ecological factors (climate and habitat heterogeneity), and post‐glacial history seem to have shaped the phylogenetic structure of the flora of Norway. The flora in the far north of Norway appear to be a result of recent diversification while the coastal regions are assemblages of deeper lineages. Our results suggest that there is an evolutionary signal in the distribution of the Norwegian vascular flora.

The alpine treeline ecotone is expected to move upwards in elevation with global warming. Thus, mapping treeline ecotones is crucial in monitoring potential changes. Previous remote sensing studies have focused on the usage of satellites and aircrafts for mapping the treeline ecotone. However, treeline ecotones can be highly heterogenous, and thus the use of imagery with higher spatial resolution should be investigated. We evaluate the potential of using unmanned aerial vehicles (UAVs) for the collection of ultra-high spatial resolution imagery for mapping treeline ecotone land covers. We acquired imagery and field reference data from 32 treeline ecotone sites along a 1100 km latitudinal gradient in Norway (60-69°N). Before classification, we performed a superpixel segmentation of the UAV-derived orthomosaics and assigned land cover classes to segments: rock, water, snow, shadow, wetland, tree-covered area and five classes within the ridge-snowbed gradient. We calculated features providing spectral, textural, three-dimensional vegetation structure, topographical and shape information for the classification. To evaluate the influence of acquisition time during the growing season and geographical variations, we performed four sets of classifications: global, seasonal-based, geographical regional-based and seasonalregional-based. We found no differences in overall accuracy (OA) between the different classifications, and the global model with observations irrespective of data acquisition timing and geographical region had an OA of 73%. When accounting for similarities between closely related classes along the ridgesnowbed gradient, the accuracy increased to 92.6%. We found spectral features related to visible, red-edge and near-infrared bands to be the most important to predict treeline ecotone land cover classes. Our results show that the use of UAVs is efficient in mapping treeline ecotones, and that data can be acquired irrespective of timing within a growing season and geographical region to get accurate land cover maps. This can overcome constraints of a short field-season or low-resolution remote sensing data.

Aim:The treeline is an obvious ecotone between forest and tundra ecosystems.Climatic warming is expected to lead to the treeline advancing, although in many cases this has not been observed. This is most likely because other factors can also influence treeline dynamics, notably land use and herbivory in European treelines.In this study, the roles of climate and herbivory as determinants for change in stem number, growth and mortality responses of treeline ecotone trees were investigated.Location: Thirty-six sites along a 1,000 km latitudinal gradient in the Scandes Mountains in Norway (60-69° N). Methods:We recorded changes in stem numbers and height, and mortality between 2008 and 2012. A partial least-squares regression analysis (PLS) was carried out to find the relative importance of groups of variables representing climate, herbivory, site and tree properties for explaining the variation in these three response variables.We also fitted general additive models for each response with selected variables from the PLS analysis. Results:We found an increase in number of stems and tree height for short and medium tall trees. The climatic variables explained the greatest proportion of the variation of the change in stem numbers, while tree height growth and mortality were best predicted by the growth stage of the tree and climate. Conclusions:Our study shows that climate explains more of the variance in treeline performance than herbivory, tree properties or latitude. Relatively weak explanatory power of all variables suggests high context dependency of treeline dynamics between sites. It seems that at large scales, variables known to be important in regulating treeline dynamics within sites are poor predictors of treeline change in the short term. K E Y W O R D S climate change, herbivory, latitudinal gradient, Norway, treeline | 393 Journal of Vegetation Science MIENNA Et Al.

Treelines are expected to expand into alpine ecosystems with global warming, but herbivory may delay this expansion. This study quantifies long-term effects of temporally varying sheep densities on birch recruitment and growth in the treeline ecotone. We examined treeline ecotone successional trajectories and legacy effects in a replicated experimental setup, where enclosures were present for 14 years with three different sheep densities (0, 25, 80 sheep km−2). Before and after the enclosures were present, the site had an ambient sheep density of 20–25 km−2. We sampled field data 4 years after enclosure removal and compared these to data sampled 8 and 9 years after enclosure erection. We sampled data on birch browsing pressure, birch distribution across life-stages (recruits, saplings, and mature trees), and birch annual radial growth. Fourteen years of increased or decreased sheep density had observable legacy effects depending on birch life-stage. Birch recruit prevalence decreased in areas, where sheep were reintroduced after being absent for 14 years. For the same areas, sapling and mature tree prevalence increased, indicating that these areas have entered alternative successional trajectories compared to areas, where sheep were present the whole time. Birch annual radial growth showed a lag effect of 2 years after enclosure removal, with growth decreasing in areas where sheep had been absent for 14 years and increasing where sheep densities were high. Thus, decadal-scale absences of herbivores can leave legacy effects due to increased numbers of trees that have high resistance to later-introduced herbivore browsing.