Tree-ring widths and the stable isotope composition of pine tree-rings as climate indicators in the most industrialised part of Poland during CO₂ elevation

Scots pine (Pinus sylvestris L.) growing in 16 sites in three industrial regions in Poland was analysed to delineate dendroclimatologically uniform areas. A dendrochronological and mass spectrometric analysis revealed the following: a dry and sunny previous September, low winter temperature, and moisture supply in July limit the radial growth of the pines in all the regions. The weather conditions of the current growing season have been the most strongly reflected in the isotopic ratio. Positive relationships were noted between δ¹³C and temperature and δ¹³C and sunshine. A negative relationship was observed between δ¹³C and precipitation and δ¹³C and humidity. At the same time, a positive relationship was noted between δ¹⁸O and sunshine and δ¹⁸O and temperature, but negative between δ¹⁸O and humidity. The climate signal recorded in the stable isotope composition was temporally unstable and only for a few of the climatic parameters did we find temporally stable climate signals. However, variability in the strength and direction of the relationships between variables has been observed. In general, the weather in July and August is important for determining the δ¹³C and δ¹⁸O signals. Instability can reflect the physiological adaptation of the plants to changes in the ecosystem.