Data are documented in the following article: Oberhuber W., G Wieser, F. Bernich, A. Gruber (2022) Radial stem growth of the clonal shrub Alnus alnobetula at treeline is constrained by summer temperature and winter desiccation and differs in carbon allocation strategy compared to co-occurring Pinus cembra. Forests 2022, 13, 440. doi: 10.3390/f13030440. Summary: Global change is affecting species areal distribution in many regions. A better understanding of how land-use change and climate warming affects shrub growth is essential for improved predictions of forest dynamics at the alpine treeline. Evaluation of radial stem growth of the clonal shrub Alnus alnobetula (= Alnus viridis) and the co-occurring tree species Swiss stone pine (Pinus cembra) within an alpine treeline ecotone revealed that mean ring width of nitrogen fixing A. alnobetula was about four times lower compared to P. cembra. Our findings are based on ring width data from A. alnobetula and P. cembra stems sampled at the alpine treeline ecotone on Mt. Patscherkofel (47°12’N, 11°27’E, Central European Alps, Austria, elevation range 2050 to 2190 m asl). Ring width time series include 86 radii from 51 stems of A. alnobetula (stems had mean age of 18±7 yrs) and 24 radii from 16 stems of P. cembra (18±4 yrs). We explain our findings by different carbon allocation strategies, i.e., preference of “vertical” stem growth in late successional P. cembra vs. favoring “horizontal” spread in the pioneer shrub A. alnobetula. By favouring clonal propagation over individual stem growth A. alnobetula is able to quickly spread at the alpine treeline ecotone.

Data files contain metadata and ring width data of measured stem radii after cross-dating. This study was funded by the Austrian Science Fund (FWF), P34706-B.