Abstract ID: 3.11867 | Accepted as Poster | Talk/Oral | TBA | TBA

The range expansion and growth of tree seedlings on treeline ecotones are influenced by a combination of biotic and abiotic factors, including impacts of different land uses. Subarctic treeline ecotones are excellent manifestations of a stress gradient, where facilitation can be expected to increase and competition to decrease from favorable climatic conditions of closed forests to harsh climatic conditions of open tundra. We studied the growth and abundance of Scots pine (Pinus sylvestris) and mountain birch (Betula pubescens subsp. czerepanovii) seedlings on the treeline ecotone of the Finnish subarctic. We sampled 135 plots from an extensive reindeer pasture monitoring plot network, distributed in the main biomes of the ecotone: boreal coniferous forests, mountain birch forests and open tundra. In each plot, we measured seedling height, growth during the last three years (for Scots pine), described their microtopographic position, took soil samples and extracted climate data from the Finnish Meteorological Institute’s data. In this work, we will show the associations of seedling growth and density with climate and soil properties and intensity of reindeer pasture, aiming to shed light on the potential and requirements of these two species to maintain their dominance and to expand their ranges to open tundra, as the climate warms and environmental stress decreases in subarctic treelines.