Effects of snowmelt timing on leaf traits, leaf production, and shoot growth of alpine plants: Comparisons along a snowmelt gradient in northern Sweden

Effects of snow-melt timing on leaf traits (for five deciduous and five eve rgreen species), shoot growth, and leaf production (for five evergreen spec ies) of tundra plants were studied along a snow-melt gradient in an alpine snowbed in northern Sweden. In deciduous plants, leaf life-span and leaf ma ss per area (LMA) decreased, and nitrogen concentration (leaf N) increased with decreasing growing season, whereas in evergreen plants, both leaf life -span and leaf N increased with decreasing growing season. By extending lea f life-span, evergreen plants are able to have a large leaf mass, which may contribute to maintain net annual carbon gain in short snow-free seasons. In two predominantly boreal evergreen species, Empetrum hermaphroditum and Vaccinium vitis-idaea, leaf lifespan was negatively correlated with both an nual leaf production and shoot growth, but there were no similar significan t correlations for the other three, strictly arctic-alpine evergreen specie s (Cassiope tetragona, Loiseleuria procumbens, and Dispensia lapponica). Ba sed on these results, we predict that extension of season length will decre ase leaf N of both deciduous and evergreen species, and will accelerate lea f turnover of evergreen plants. Although annual leaf production and shoot g rowth of boreal species may increase with an extension of season length, th ey will remain unchanged in strictly arctic-alpine species.