Acta Scientiarum Polonorum
Silvarum Colendarum Ratio et Industria Lignaria

Abstract Tree ring chronologies of Scots pine (Pinus sylvestris L.) and black pine (P. nigra Arnold) from the dry coniferous forest and the fresh mixed coniferous forest, as well as black alder (Alnus glutinosa (L.) Gaertn.) from the alder swamp forest, in the Słowiński National Park and neighbouring forests (Damnica Forest District) are presented. For both pine species 1940, 1956, 1976, and 1996 were the negative signature years, while 1946, 1957, and 1989 were the positive ones. In black alder the diameter increment depressions occurred in 1997 and 1998. The tree ring width in both pine species was positively correlated with the mean monthly air temperatures in February and March, while there was no univocal precipitation-tree growth relationship found. In some cases, in black pine from the fresh mixed coniferous forest and black alder from the alder swamp forest, the statistically significant coefficients describing the precipitation-increment relationship had negative values. The increment depressions, which occurred in both pine species during 1981-1983, were the result of the nun moth (Lymantria monacha L.) outbreak. Black alder was not attacked by this phyllophagous insect. The positive July precipitation-tree growth relationship was found in both pine species during the nun moth outbreak.