A MODELING ANALYSIS OF THE EFFECTS OF CLIMATIC WARMING ON THE PROBABILITY OF SPRING FROST DAMAGE TO TREE SPECIES IN THE NETHERLANDS AND GERMANY

Two studies presented in the literature (Murray, Cannell & Smith 1989; Hanninen 1991) evaluate the effect of increasing winter temperature o n the probability of spring frost damage to trees, but yield contradic tory results. It is unclear whether the disparity can be ascribed to t he fact that different models were used, or is the result of different climatic warming scenarios being used, or is because the tree species at the different locations do indeed respond differently to warmer wi nters. To evaluate the effects of climatic warming to tree species in The Netherlands and in Germany, both models were fitted to long series of observations on the date of leaf unfolding of eleven tree species. The impact of the two scenarios (uniformly and non-uniformly changing winter temperature) on the date of leaf unfolding and on the probabil ity of freezing temperature around that date was evaluated. To test th e importance of adaptation to local climate, hypothetical provenance t ransfers were analysed. It was concluded that, for tree species in The Netherlands and Germany, the probability of spring frost damage will decrease. The contradictory results found in the literature could be a scribed to differences between provenances adapted to their local clim ate, and is not because different models and different climatic warmin g scenarios were used in these studies.