Abstract:
Shrub advance into tundra areas alters albedo and carbon storage and is an important feedback mechanism to global climate change. However, the existence of such vegetative expansion in North-Sweden, its rates, and the precise nature of climate-growth relationships is unknown. Our study in the sub-alpine belt of the Swedish Scandinavian Mountains investigates the three most abundant shrub species
... (Juniperus nana, Betula nana, Salix glauca) above tree-line on two slopes with different exposure (NE/S). Here we present the preliminary results of the dendrochronological analysis of 35 individuals of Juniperus nana concerning the climatic influence on ring widths. Summer temperatures showed highest correlations with ring width, while there is evidence for an influence of winter snow depth. Shrub radial growth has mainly increased since the 1850s, with a small decrease in growth 1940-60. The recent strong increase starting 1956 coincides with rising average and winter temperatures in the area. Our preliminary findings point to a possible shrub expansion for Juniperus nana, warranting further investigation (including other species). 
