| dc.description.abstract | As a consequence of climate change, colder regions such as the Arctic and alpine areas are experiencing a higher rate of warming compared to the global average. The effect of warming varies across the tundra biome, and the differences in vegetation composition and soil moisture further contribute to this variation. To monitor and better understand the effect of climate change on the tundra vegetation, the International Tundra Experiment (ITEX) uses open-top chambers (OTCs) located at different sites across the Arctic, which simulate anthropogenic climate change by increasing air and soil temperature. The dwarf shrub Dryas octopetala is one of few species with circumpolar distribution and can be found in both High Arctic and alpine regions, making it ideal for studying the effect of warming across sites. This thesis examined the effect of warming on D. octopetala at two different sites, one located in Endalen on the High Arctic Archipelago of Svalbard, and the other in the alpine site Finse, on the Norwegian mainland. The study aimed to assess how experimental warming affected the dwarf shrub in terms of abundance, plant height, and NDVI, and whether there was a correlation between these variables and soil moisture. Lastly, the study investigated the difference in species composition and richness after over 20 years of experimental warming.
The two sites displayed both different and similar responses to warming. Species richness and composition did not differ between control and OTC warming plots in either site. In the alpine site, the cover of bryophytes and lichens increased with higher soil moisture and with taller D. octopetala. There was a negative relationship between soil moisture and NDVI with warming in the alpine site, whereas in the High Arctic site, this relationship was positive. In both sites, higher cover of D. octopetala was positively correlated with NDVI. The results from this study suggest that D. octopetala experiences unfavourable conditions with increased warming in the alpine site, whereas in the colder High Arctic site, this “tipping point” has not yet been reached. The findings from this study highlight the importance of context dependency when investigating warming effects on the tundra vegetation. | |
