Data are documented in the following article: Oberhuber W., A-L. Dobler, T. Heinzle, F. Scandurra, A. Gruber, G. Wieser (2023) Climate overrides the influence of microsite conditions on radial growth of the tall multi-stemmed shrub Alnus alnobetula at treeline. Plants 12, 1708. doi: 10.3390/plants12081708. Summary: Green alder (Alnus alnobetula), a tall multi-stemmed deciduous shrub characterized by shoots showing arched ascending growth, is widespread at high elevations in the European Central Alps. Its growth form frequently leads to asymmetric radial growth and anomalous growth ring patterns making development of representative ring width series needed for analyzing climate-growth relationships or site-specific growth rates and long-term growth trends quite a challenge. In order to assess the variability among radii of one shoot, among shoots belonging to one individual (=stock) and among individuals, 60 stem discs were sampled at treeline on Mt. Patscherkofel (Tyrol, Austria). Annual increments were measured along 188 radii and analyzed in terms of its variability by applying dendrochronological techniques. Results revealed a high agreement in ring width variation among radii of one shoot, among shoots of one individual and largely among individuals from different sites, which confirms the pronounced limitation of radial stem growth by climate forcing at the alpine treeline. In contrast to this, a high variability in absolute growth rates and long-term growth trends was found among shoots belonging to one individual and among individuals, which we attribute to different microsite conditions and disturbances. These factors also override climate control of radial growth under growth limiting environmental conditions, i.e., the agreement in inter-annual variations of radial growth is directly related to the growth rate. Based on these findings we provide recommendations for the number of samples needed to carry out inter- and intra-annual studies of radial growth in this tall multi-stemmed shrub.

The research was funded by the Austrian Science Fund (FWF), P34706-B.