Activities carried out.

WP4 carried out the analyses quantifying species range shifts and changes in community composition and searched for dependences between the observed vegetation changes and climatic factors or other drivers (e.g. land-usechange: grazing, tourism). WP4 relied on data obtained by teams working in WP1-3 with the aim to analyse the data statistically and to develop publications, posters, conference presentations, therefore, all results described under those WPs are related in some degree to WP4. WP4 also supported all writing teams during the process of manuscript production. To make manuscript development easier, all Norwegian researchers responsible for data analyses paid approximately one week visits to Polish study sites during 2014 (montane site), 2015 (forest site) and 2017 (forest site) during which they took part in field work and learned about study design. The same effect was achieved due to participation of the Polish PhD student in resampling of Scandes in northern Norway (2014) and post-doc in resampling of forest plots in Geitaknottane (2016).

Results achieved.

Aside to the results described under WP1, WP2 and WP3, some extra data processing took place in WP4. Most of it concentrated on preparation of wider syntheses, where KlimaVeg dataset is just one of several datasets used.

In the mountain ecosystems the analyses have shown asignificant acceleration in the rate of plant species establishment in alpine ecosystems from 1880 onward. This acceleration is a direct and immediate response to the acceleration in the rate of temperature change observed on mountain ranges taken into account. The other global change determinants, such as precipitation changes and nitrogen deposition changes do not explain the species richness increase and some of them even show opposing trends. Therefore, the increase in plant species richness on mountain summits is suggested to be a direct, immediate response to climatic changes expected to lead to losses of high-altitude specialists, jeopardizing alpine species diversity (Steinbauer et al., in prep.). We also analyzed how mean values and diversity of six functional traits of plants related to productivity, resource acquisition and competitive ability, and functional group composition of the summit plant communities changed over the past century. We found that functional diversity increased for all traits and community mean values shifted towards taller plants and larger leaves, suggesting colonization of summits by more competitive species. The increase in plant height was directly related to increasing summer temperatures. Trait changes related to resource acquisition were less pronounced in the short- than in the long-term dataset, which suggests that equilibrium in the functional structure of plant communities may be prone to considerable time lags. Together, the increase in functional diversity and plant height indicate an increase in biomass production, with likely impacts on microclimate and soil characteristics, which can steer the further development of alpine ecosystems (Kulonen et al. in preparation).

High Arctic, Norway. Results from vegetation resurveys in the High Arctic (data were collected prior to the project but submitted by NIBIO to KlimaVeg as dataset) showed that plant communities have changed significantly over the past 80 years. The total number of species was stable, but species composition and species’ distribution (frequency of occurrence in plots) was found to have changed significantly. The results indicate that vegetation of moist habitats has changed most and in favour of species of drier habitats. The observed changes may be explained mostly by the facts that (i) climate has changed drastically over the past decades with temperature increases exceeding the worldwide average, (ii) propagule pressure of species new to the area has increased, and (iii) the time scale of c. 85 years of change is relatively long for vegetation to respond. Changes in grazing regimes by Svalbard reindeer may explain further changes, in particular increases in occurrence frequencies of several grass species. Our analysis suggests that the plant community changes are due to internal factors occurring at the local scale. This internal community restructuring,in addition to the relative stability in species richness in the vegetation studied, might on the one hand be due to time-delayed responses of well-established communities to a changing environment, but on the other hand, might be explained by the limited size of the species pool in the area. However, all observed changes suggest that processes influencing community structure and diversity can be described as direct (e.g. drier soil conditions) or indirect (e.g. winter climate controlling grazing reindeer population size) responses to long-term climate change. With continuing directional change in environment, more drastic responses might be expected even in well-established and long-lived plant communities in the High Arctic (Kapfer & Grytnes 2017).

In forest ecosystems of the Białowieża Forest there has been significant warming since the 1950s. The greatest increase in mean temperature was observed for winter and spring (0.6°C per decade in March). This change was not well expressed in the species composition of forest ecosystems but strongly affected phenology of most of the spring-flowering plant species, which show a strong tendency to flower earlier in years with warm winters and springs and early snow-melt. Summer-flowering plants have a weaker, but still clear response to global warming. However, it must be stressed that there is a high variation in plant sensitivity and high individuality in species response to climate warming. Precipitation changes do not seem to drive phenological shifts in the understorey (Telford et al. in preparation).