Provenance Variation in Phenotypic Traits in Quercus robur and Quercus petraea in Danish Provenance Trials
A study of 33 provenances in Danish field trials with Quercus robur and Q. petraea was made between 1993 and 1998. The trials include Danish, Dutch, German, Norwegian and Swedish provenances, and were established between 1900 and 1988. Growth, flushing, stem form and epicormic shoot formation were studied. There were strong geographical clines for growth; however, the variation within regions was considerable. Time of flushing followed a more complex clinal pattern and was related to both latitude and distance from the ocean. Stem form was highly variable within different geographical regions and it is suggested that this could be caused by different management regimes in the past. Oaks from some locations in Sweden and Norway seemed especially straight. Stem form is one of the most important parameters for commercial oak management and could be seriously improved through breeding, as it was under considerable genetic control. Epicormic shoot production was in part under genetic control, but no geographical patterns were found. Danish provenances of Q. petraea were growing more rapidly than similar Q. robur on sandy locations. Quercus petraea produced fewer epicormic branches and stem form was equal to or better than Q. robur. Quercus petraea should be recommended for landscape use on windy locations in Denmark.