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Master’s thesis 2019 60 credits Faculty of Environmental Sciences and Natural Resource Management Changes in species richness and altitudinal distribution of vascular plants in Jotunheimen, Norway Erlend Tandberg Grindrud Ecology Changes in species richness and altitudinal distribution of vascular plants in Jotunheimen, Norway Photo: Visdalen with Kyrkjetjønne in the upper valley. The photo was taken on Spiterhøi. Master’s thesis Erlend Tandberg Grindrud Preface First of all, I want to thank my supervisor Kari Klanderud for the opportunity to resample the sites in Jotunheimen. I feel lucky to have been trusted with such an important task, and think my master's thesis could not have been more interesting. Because of personal issues I was not able to finish when planned, and at one time started to doubt if I would ever finish. However, thanks to Kari's continued support and patience I finally present this work. For this I am truly grateful. I also want to thank my second supervisor John-Arvid Grytnes for being patient, and giving me the opportunity to finish my thesis. When I needed input on analysis and statistics he found time to help me in spite of busy days at work. I want to thank fellow master student Jon Peder Lindemann for accompanying me on some of the mountains. I am also grateful for valuable information provided by Hanne Heiberg and Inger Hanssen-Bauer at The Norwegian Meteorological Institute and Wenche Aas at the Norwegian Institute for Air Research. Finally, thanks to Rigmor Solem, Pål Grev, Hans Nørstnes Graffer, Torkjel Solbakken and Rolv Rustem for providing information on reindeer and sheep in Jotunheimen. Ås, 12 May 2019 ___________________________ Erlend Tandberg Grindrud 1 Abstract Species richness was sampled on 254 sites distributed along the altitudinal gradient of 23 mountains in Jotunheimen, Norway. The sampling was conducted during the summer of 2014, on sites that previously had been sampled in 1930-31 and 1998. The purpose of the study was to investigate possible changes in species richness and altitudinal distribution of vascular plants, and try to explain any observed change. The results show that species richness in Jotunheimen increased between 1998 and 2014, and that the relative increase was highest at higher elevation sites. Species richness also increased more in eastern parts of Jotunheimen than in western parts, both in 1930/31- 1998 and 1998-2014. Species richness on the most species-rich sites has declined in 1998- 2014, and high-altitude species have possibly declined at lower elevations. The high-altitude species Beckwithia glacialis, Ranunculus pygmeus, Poa flexuosa, Saxifraga Cernua and Erigeron uniflorus experienced a reduced number of occurrences at lower elevations in 1930/31-1998, and has continued this tendency in 1998-2014. High-altitude species that did not decline at lower elevations in 1930/31-1998 (e.g. Cardamine bellidifolia, Luzula confusa and Juncus biglumis) have started to decline in 1998-2014. A process called thermophilization, which can be described as the decline of cold-adapted species and/or the increase of higher temperature-adapted species, was detected for both 1930/31-1998 and 1998-2014 in Jotunheimen. Plant communities have hence become “warmer”. A strong warming tendency is observed after the 1998 sampling, and climate warming is the most likely driver of the observed changes in Jotunheimen. Nitrogen deposition and grazing pressure have been discussed, but further investigation is needed to determine their role. Hiking tourism, pseudoturnover and natural succession, are found to not explain the general changes observed in this study. 2 Table of Contents Preface .................................................................................................................................. 1 Abstract ................................................................................................................................ 2 Introduction .......................................................................................................................... 5 Materials and methods ......................................................................................................... 8 Geography, vegetation and topography ............................................................................ 8 Temperature and precipitation .......................................................................................... 9 Nitrogen (N) deposition ................................................................................................... 11 Other anthropogenic impacts .......................................................................................... 12 Sampling .......................................................................................................................... 13 Recording problems......................................................................................................... 14 Misidentifications and nomenclature of species .............................................................. 14 Data analysis ................................................................................................................... 15 Results ................................................................................................................................ 18 Change in species richness between 1930, 1998 and 2014. ............................................. 18 Change in species richness along the west-east gradient ................................................. 19 Change in number of species according to initial species richness ................................... 20 Change in number of species according to temperature indicator values ........................ 20 Thermophilization ........................................................................................................... 21 Changes in species groups with different climate optimum, along the altitudinal gradient .. 22 Species changes in the “MAlp, MAlp-HAlp” group, between 1998 and 2014.................... 23 New altitudinal limits, altitudinal shifts and change in Poaceae family ............................. 25 Signs of grazing ................................................................................................................ 26 Discussion ........................................................................................................................... 28 Change in species richness, new altitudinal limits and upward shifts ............................... 28 Change in species richness along the west-east gradient ................................................. 28 Changes in species groups with different climate optimum, along the altitudinal gradient .. 30 Change in number of species according to initial species richness ................................... 31 Change in number of species according to temperature indicator values ........................ 33 Thermophilization ........................................................................................................... 33 Possible drivers for the observed changes ....................................................................... 34 3 Climate change ............................................................................................................ 34 Grazing......................................................................................................................... 35 Natural succession ....................................................................................................... 36 Pseudoturnover ........................................................................................................... 37 Tourism ........................................................................................................................ 38 Conclusions ......................................................................................................................... 39 References .......................................................................................................................... 40 Appendix 1 .......................................................................................................................... 47 Appendix 2 .......................................................................................................................... 95 Appendix 3 .......................................................................................................................... 99 Appendix 4 ........................................................................................................................ 101 Appendix 5 ........................................................................................................................ 105 4 Introduction Life in alpine environments is harsh, with low temperatures, strong winds, lack of nutrients and prolonged snow cover during the year. In this environment facilitation is believed to be the dominant form of interaction among plants (Callaway et al., 2002). Abiotic stress is so limiting that amelioration of stress from neighbour plants, helps survival and reproduction. Under recent climate change however, abiotic stress is reduced as temperatures rise (Britton et al., 2009), and plant interactions in the alpine environment may switch from facilitation to competition (Callaway et al., 2002). Alpine plants can therefore be faced with another challenge: the competition from neighbour plants and new colonizers, which are climbing the mountains

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