Late frost reactions of different populations of Quercus robur L. and Tilia cordata Mill. in Germany

摘要

The German government amended the Federa Nature Conservation Act (BNatschG) in 2010 and six defined areas of origin were assigned (BMU, 2012) for the use of plants in free nature. The transfer of propagation material between them is forbidden from March 1st, 2020. This should protect locally adapted tree populations from losing their adapted traits by hybridization with non-local populations. However, the question of local adaptation in woody species in Germany is not clearly demonstrated. To get nearer to the answer of this question the current study was carried out to investigate differences in late frost reactions among German populations of Quercus robur and Tilla cordata by artificial freezing shoots at -6 degrees C and -12 degrees C in April/May 2012. Bud burst was rated prior to the freezing experiments after transferring populations from different origins to Hannover, and frost damage, sugar, starch and proiirie concentration were measured afterwards. To estimate long term survival, whole plants were frozen simultaneously and then cultivated to investigate their regeneration ability. We did not find differences in bud burst and late frost hardiness of shoots between German populations of the target species. Differences in these traits only occurred in the Hungarian population of Quercus tabor which;exhibited a higher grade of bud burst but lower frost damage. With few exceptions, no biochemical differences occurred among populations of the target species and late frost hardiness was not affected. Regarding late frost reactions, local adaptation of German tree populations seems not to be as distinctive as the defined areas of origin assume.