Northern red oak - suitable candidate for forest conversion

Northern red oak was introduced to Europe in the late 17th century and has since developed into the most important deciduous non-native tree species in Germany. It has a broad site amplitude as well as a high resistance and adaptability, that means the resilience of native forests can be increased through the targeted introduction as secondary tree species in mixed stands. These characteristics, which are in demand in the face of climate change, were a key reason for its selection as Tree of the Year 2025 by the 'Baum des Jahres – Dr. Silvius Wodarz Stiftung'. Nevertheless, northern red oak is subject of controversial discussions concerning its possible potential for invasion. However, due to the comparatively long time of cultivation throughout Germany and the promising results from scientifically monitored provenance trials, red oak is considered worthy for cultivation.

The results of our research show the superiority of German provenances over those from North America. German provenances not only displayed an above-average growth performance, but also a high tolerance to late frost. Their drought tolerance was lower compared to the slower-growing provenances from North America. Considering the superiority in adaptive traits, the German provenances are identified as suitable generalists for forest conversion. In contrast, provenances from Canada proved to be specialists on a dry site with an overall high tolerance to drought. Regarding rising temperatures, these represent a promising opportunity to refresh the genetic diversity of introduced stands. Provenances from the southern part of the natural distribution area are not suitable for cultivation Germany due to their overall poor growth and low tolerance to climatic extremes.

The question remains, whether German provenances have already adapted to local conditions. From an evolutionary perspective, the time period for this process is very short. Nevertheless, differences in bud break suggest that selection processes (natural and/or anthropogenic) have already taken place.

The ‘RubraSelect’ project was successfully completed by the end of 2024. Detailed results can be found in the following publications:

Kormann JM, van der Maaten E, Liesebach M, Liepe KJ, van der Maaten-Theunissen M (2024) High risk, high gain? Trade-offs between growth and resistance to extreme events differ in northern red oak (Quercus rubra L.). Front Plant Sci 15:1374498, DOI:10.3389/fpls.2024.1374498

Kormann JM, van der Maaten-Theunissen M, Unterholzner L, Liesebach M, Liepe KJ, van der Maaten E (2024) Variation in vessel traits of northern red oak (Quercus rubra L.) provenances revealed high phenotypic plasticity to prevailing environmental conditions. Trees 38(5):1283-1295, DOI:10.1007/s00468-024-02557-y

Kormann JM, Liesebach M, Liepe KJ (2023) Provenances from introduced stands of Northern Red Oak (Quercus rubra L.) outperform those from the natural distribution. Forest Ecol Manag 531:120803, DOI:10.1016/j.foreco.2023.120803

Kormann JM, Liesebach M, Liepe KJ (2023) Wachstum der Roteiche (Quercus rubra L.) in zwei Herkunftsversuchsserien in Deutschland. Thünen Rep 105:257-266 https://literatur.thuenen.de/digbib_extern/dn066295.pdf