Dendroecology of dwarf shrubs in the high mountains of Norway – A methodological approach

Dwarf shrubs cover large areas above the upper tree line in mountain areas. Their potential for dendroecological analyses has not yet been explored comprehensively. In order to study the growth reactions of dwarf shrubs on the impact of environmental factors the ring widths of Empetrum hermaphroditum were measured. We analysed dwarf shrubs along micro-topographic and altitudinal gradients in the continental Norwegian Scandes. Beside ring width, basal area increments were measured and serial sectioning was implemented to evaluate growth variability and cross-dating reliability. E. hermaphroditum shows highly individual growth histories. Thus, cross-dating of growth curves is restricted to several radii within an individual and to mean curves of individuals growing at the same micro-site. Wedging rings and missing rings as well as eccentricity and asymmetric geometry of the stem constrict the synchronisation of growth curves. However, varying micro-site conditions are clearly reflected by differences in the mean growth rates and the frequency of frost rings.