Dendroclimatological regions of Douglas fir (Pseudotsuga menziesii Franco) in western Poland

Six Douglas fir (Pseudotsuga menziesii Franco) stands were selected in both the Sudety Mountains and the Great Poland Lowland. These two regions are distinctly different with regard to thermal and pluvial conditions. In each stand, two increment cores per tree were extracted from 20 approximately 100-year-old trees and the tree-ring widths measured. It is clear from the different growth reactions of the study trees to the climatic conditions that the Sudety Mountains and the Great Poland Lowland are two dendrochronologically separate regions. The tree-ring width chronologies form homogeneous groups for each region. The tree ring-climate models for Douglas fir in both regions indicate similarities and differences. The similarities among chronologies are attributed to winter temperature. The differences are attributed to rainfall (which changes with longitude and altitude of sites) during the vegetation season.