Dendroclimatological analysis of radial increments of invasive Acer negundo L. and Fraxinus pennsylvanica Marshall from the Warta river valley.
Invasive tree species are one of the most important threats to the riparian ecosystems. We aimed to check (1) whether invasive tree species have wider annual radial increments than native species and (2) which climatic factors (describing annual variability of air temperature and precipitations) influence radial growth of the investigated species. The study was conducted in the Warta river valley in Poznań (W Poland). Detrended chronologies were built using 28 cores bored from Acer negundo and 20 from Fraxinus pennsylvanica. Mean annual radial increment of A. negundo was of 3.91±0.19 mm and of F. pennsylvanica - 2.76±0.08 mm. Radial growth of A. negundo was significantly correlated to precipitation in June of the increment year and temperature in November of the year before the increment. In turn, radial growth of F. pennsylvanica was significantly correlated to precipitation in April and temperature in May and June of the increment year. These factors explained 44 and 55% of variance in radial increments widths of A. negundo and F. pennsylvanica, respectively. Annual radial growth of the alien species studied were higher than in case of native riparian species. Thus, studied invasive species constitute a serious threat for the analysed riparian ecosystems. Obtained results may be helpful for predicting their spread under projected climate change scenarios.