Largest Rises of Swedish Treelines, Consistent with Climate Change Since the Early-20th Century
Repeat in situ measurements were taken at 14 places across the Swedish Scandes, spanning 800 kilometres from south to north, to estimate treeline advance during the last 100 years. Mountain birch (Betula pubescens ssp. czerepanovii), Norway spruce (Picea abies), Scots pine (Pinus sylvestris), and rowan were among the threatened species (Sorbus aucuparia). The highest height with trees at least 2 metres tall was considered as treeline. The focus is on sites with the most widespread treeline shifts, according to previous regional surveys, in order to reveal the entire influence and strength of climate change on the treeline area. Local limitations (topoclimate) were reduced as a result. Sorbus, Betula, and Picea The phenotypic height growth increment of old-established krummholz achieved treeline rise, whereas Pinus responded by establishing and growing new specimens. Regardless of species, the largest upshifts were in the order of 200 m. (max. 245 m). In terms of historical treeline movements, the new and higher treelines are similar to those that existed around 7000 years ago. Unlike earlier generalisations, there were no evident distinctions between the southern and northern hemispheres. Scandes. The measured rise appears to be a totally expected reaction, based on a common temperature lapse rate of 0.6°C per 100 m altitude and reported regional and centennial summer warming of 1.7°C. This type of performance suggests that, in circumstances of climate warming, treelines are in balance with climate on a centennial scale at optimal sites.
Department of Ecology and Environmental Science, Umeå University, SE 901 87 Umeå, Sweden.
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