| Summary: | The Arctic embraces one of the simplest terrestrial ecosystems in the world and yet it covers roughly 11% of the world’s surface. Summer temperatures rarely exceed 10°C and most of the limited precipitation falls as snow. The landmasses are predominantly polar tundra, while the Arctic Ocean is frozen solid for the main part of the year. However, in recent decades, arctic temperatures have in-creased between two and three times that of the global averages, which have had a substantial impact on the physical environment of the arctic ecosystem, such as deglaciation of the Greenland inland ice sheet, loss of multiannual sea-ice and significant advances in snowmelt days. The biotic components of the arctic ecosystem have also been affected by the rapid changes in climate, for instance resulting in the collapse of the collared lemming cycle, advances in spring flowering and changes in the intra-trophic interaction patterns. However, while studies have documented the climatic effects on the arctic biotic ecosys-tem, detailed studies have been constrained by short time series or the lack of comprehensive multivariate tools, which enables the disentanglement of direct effects and effects mediated through biotic interactions. Hence, through the use of up-to-date multivariate statistical tools, this Ph.D. study has been concerned with analyzing how the observed rapid climate changes are affecting the arctic ecosystems. The primary tool has been the implementation of structural equation modeling (SEM) which allows for the disentanglement of effects, together with the possibility to construct latent variables as placeholders for underlying unobserved variables. Results from the study have demonstrated significant temporal trends in the high arctic ecosystem, located in the Zackenberg Valley, Greenland. Additionally, the study demonstrated that climate effects had distinct direct and indirect effects on different trophic levels, indicating cascading effects of climate through the trophic system. Results suggest that the Arctic is being significantly affected by the observed climate changes and depending on the resilience of the ecosystems, ecosystem changes can accelerate along with the predicted acceleration of climate changes. Therefore I propose that the ecosystem approach used in this study is applied to resilience studies in order potentially assess ecosystem resilience, which would enable forecasts’ of ecosystem re-sponses to the future global climate change.
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