Сlimate-induced treeline dynamics in the Ural Mountains: drivers, constraints, and the role of genetic adaptation

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Challenge: Elevational treelines in the Urals respond positively to industrial warming. If ongoing forest expansion keeps pace with future global change it will squeeze vast areas of pristine alpine tundra habitats, possibly to extinction. However, the rate of climate change may outrun a treeline advance. Furthermore, maladaptation and poor genetic connectivity in the landscape may constrain the adaptation of local populations. Hence, only a genetic survey in combination with dendroecological data fed into a spatially explicit model that can simulate trait adaptations will be able to unravel the important factors for treeline migration and provide realistic predictions of the future treeline position.Hypotheses: (1) Given the fast warming over recent decades, we expect the rate of structural changes in tree stands at the treeline in the Urals to increase significantly, but will depend on the interplay amongst regional climate and local site conditions. (2) Although seed dispersal in the Urals is sufficiently mobile to enable the treeline to migrate over long-term climate changes, genetic isolation is caused by dominant short-distance reproduction strategies. Consequently, (3) the primarily climate-driven treeline dynamics are constrained by the adaptation potential of populations with the traits necessary for rapid global warming.Approach: Our project will combine molecular and dendroecological analyses as inputs for an individual-based simulation model. We selected six permanent elevational treeline transects dominated by deciduous larch forests in the Urals. Rerunning previous assessments of tree position and population data in new surveys will allow time-series analyses to characterize the ongoing treeline migration. From the dendroecological analyses, we will infer climatic drivers and map spatial patterns of responses in the Urals (WP1). We will sample and genotype individuals growing along the transects and beyond to estimate effective seed dispersal via parentage analyses, landscape connectivity, and population genetics (WP2). We will further develop the individual-based spatially explicit model LAVESI and simulate transects covering past millennia to improve our understanding and the importance of the involved processes, especially trait adaptation, for migration responses. The model will be applied to forecast and evaluate population dynamics and migration rates (WP3). Finally, we will synthesise our findings of the more realistic treeline response and likely consequences to inform the debate on climate adaptation strategies (WP4).Research team: The German-Russian research team combines exceptional field knowledge and long-term treeline monitoring data with expertise in molecular methods and individual-based modelling of trees in Arctic regions.Expected impact: Based on a profound understanding of climate impacts and adaptation processes at elevational treelines in the Urals, we will deliver roadmaps for future forest feedbacks.