Diversification of increment reactions of Douglas fir (Pseudotsuga menziesii Franco) from mountainous regions of southern Poland

Dendroclimatological research presented in this paper concerns Douglas fir (P. menziesii) at 17 sites located in the area of the Sudetes Mountains, the Polish part of the Carpathians and Roztocze. The methods of principal components analysis, response function and coefficients of convergence allowed the researchers to determine that the factor which integrated chronologies and determined the annual rhythm of changes in radial increment of the trees under research was the thermal conditions of winter preceding the vegetation season. Thermal conditions and summer rainfall had a slightly smaller impact on the tree increment. The influence of thermal and pluvial conditions on the process of xylem cell formation changed as longitude changes occurred. The pressure of winter temperatures and summer rainfall increased with an increase in the degree of climate continentality. On the other hand, the role of summer temperatures decreased. Despite these differences, the rhythm of annual changes in tree-ring width of Douglas fir from the Sudetes, Carpathians and Roztocze is highly similar. Southern Poland can be considered as dendrochronologically homogeneous for this species. We can distinguish two areas that are dendroclimatologically homogeneous.