EN
The aim of the study was to investigate how industrial pollutants and change of thermal conditions of winter season in the second half of the 20th century affected the basal area increment (BAI) and the climatic signal in the BAI chronologies of Pinus sylvestris and Pinus banksiana. Samples were collected from 21 trees of both species growing in the Chrzanów Forest District (50°20‵ N, 19°47‵ E) which is located between the Upper Silesian and Krakow Industrial Regions. Two cores were taken from each tree. Tree−ring widths were measured at the cores and the BAI for each year in the period 1930−2016 was calculated. The growth reductions of both pine species in the years 1951−1970, increasing of diversity of growth reactions from year to year and also reduction of strength of climatic signal in the period 1963−1994 may have been caused by industry pollution. The reduction of wood growth, the increase of the diversity of short−term incremental reactions and also the reduction of strength of the climatic signal were greater in Jack pine. This indicates that Scots pine was more resistant to pollution. As an industrial production declined and environmentally friendly technologies were introduced in the 1990s homogeneity of growth reactions and strength of dependence between BAI and climate parameters in both species increased. A significant increase in the strength of the relationship between January temperature and BAI of Scots pine and Jack pine was observed in the early 2000s. This may suggest that the vegetation season starts already in January in the study area.