Activities carried out.

The activities in WP3 concentrated on resampling of mountain peaks in northern Norway and in the Tatry Mountains (Poland) to study compositional and distributional changes in alpine vegetation. Aside of the summits, major valleys in the Tatry Mts. (Rybi Potok Valley with Morskie Oko Lake Region and Chochołowska Valley) were resurveyed and data from the arctic zone (Svalbard, Jan Mayen) was incorporated into the project for statistical processing. During the three vegetative seasons of 2014-2016 peaks in Norway (20 summits) and Poland (14 summits) were resampled by a Polish-Norwegian team of botanists. Vegetation of the two major valleys in the Tatry Mts. was also resampled to obtain data on changes in the composition, diversity and distribution of vascular plants.The field studies were preceded by intensive literature surveys in 2014, which allowed identification of data sets eligible for resampling. Two Master’s students (at UiB) and one PhD student (at UW) were involved in the KlimaVeg project working on their theses on topics linked with WP3 (MSc theses have beendefended in 2016 (see Table D7), PhD thesis defence is planned for 2018). The preliminary results were presented as posters or oral presentations at 33 international conferences.

Results achieved.

Tatry Mountains, Poland.The vegetation in the mountain valleys was surveyed for the first time by Prof. Szafer in Chochołowska Valley in 1922 (Szafer et al. 1923) and by Prof. Pawłowski in Rybi Potok Valley and Morskie Oko Lake Region in 1927 (Pawłowski et al. 1928). The summits in the Tatry Mts. (Western, High and Belianske Tatry Mts.) were originally surveyed by several researchers: Kotula in 1889-90, Sagorski and Schneider in 1891 and Pawłowski in 1956. In 2016 in Polish part of Tatry Mts, the distribution of the snowbed-specialist Carex lachenalii was resampled. The species was known in Poland just from a few spots and most of them have not been re-confirmed for a long time and date back to the period1872-1969.

In the Tatry Mts, plant species composition has changed significantly on those summits that had the highest accessibility for sheep, which suggests that grazing is an important driver of this change. Some effect of climate change on plant species composition was noticed for the higher-elevation and for the least accessible summits. There, the main driving factors were: decrease in the number of days with snow and increase in the number of days with rain. On the lower peaks, where sheep were grazing historically, the climate change signal was probably overwhelmed by the effect of ceasing of grazing after establishment of the Tatry National Park in the 1950s (Czortek et al. in review). In the Morskie Oko Lake Region (including Rybi Potok Valley) vegetation changed significantly over the past 90 years. The plant species composition change of snowbed communities was driven by climate related factor – decrease in duration of snow cover, which made them exposed to colonization by more dry-tolerant species. The concurrent significant increase of mean annual temperature might explain the observed thermophilization in snowbeds and small-sized patches of wet microhabitats on acidophilous grasslands. Along with increasing temperature and rain precipitation vegetation of snowbeds, hygrophilous tall herbs and mylonite grasslands became more dominated by nitrogen-demanding species. During the last century acidophilous grasslands at lower altitudes underwent colonization by forest and shrub communities. As disentangling of climate change and historical sheep grazing effect was difficult, an observed treeline progression should be considered as a combined effect of both factors. In Chochołowska Valley, the climate signal was found not significant. The most important factors influencing change in vegetation patterns were cessation of grazing, historical forest exploitation and wind disturbances of forest stands (Czortek et al. in prep.). The geographic distribution of Carex lachenalii shifted depending on plant community. Habitat filtering in the colonization of vegetation patches by C. lachenalii was strongly expressed on snowbeds and acidophilous grasslands at the highest elevations. This suggests that climate change was the focal factor driving an upward shift of this plant species, mainly in terms of decrease in the duration of snow cover. In contrast, moderate trampling by tourists enhanced the horizontal spread of C. lachenalii on grasslands located relatively close to the tourist paths. There is also a risk that C. lachenalii may go extinct on the acidophilous grasslands in the lower elevations, where sheep grazing allowed its persistence in past. Summarizing the above results: the climate change signal is well visible but only at the highest elevations, where historical land use did not disturb the natural character of vegetation. At lower elevations, the effect of historical land use predominates as local vegetation is slowly regenerating to its natural state. This regeneration process swamps the effect of climate change, which becomes not traceable (Czortek et al. in prep.).

Northern Scandes, Norway.The results obtained in the Scandes are in line with findings reported from the Tatry Mts., however the climate change signal is more clearly visible in the Norwegian mountains where alpine plants are on the move upward. The observed rangeshifts in alpine vegetation in Norwegian mountains was found to belowerat mountains with more snow-free days inspring. However, these changes in snow-free days cannot explain why so many plants show a higher upper range limit than observed historically. Less snow in spring means that plants are moreexposed to the elements, and may not survive. It is reasonable to assume that changes insnow-free days in spring influences much of the observed range shift in alpine plant species (Fossheim, 2016). A buffering effect on the upward range shift from grazing by semi-domestic reindeer and sheep was observed. All mountains have had a turnover in the species composition in the upper elevation range, but there was no detectable difference between mountains exposed to grazing and/or hiking and not. Hiking was not found to affect the upward range shift. The land use, especially grazing, is affecting the observed range shift. Grazers have effects on range shifts through a variety of mechanisms which are undistinguishable in this form of resurvey and should be focused by the experimental work in the future (Haugum, 2016).To understand the observed range shift in alpine vegetation more knowledge is needed.