Regional Features of the Radial Growth of Scots Pine under Climatic Conditions of the Forest-Steppe and Steppe Zones of Eastern Transbaikalia According to Multiparameter Tree-Ring Chronologies

A dendroecological study of the annual ring parameters of Scots pine (Pinus sylvestris L.) trees growing in the forest-steppe and steppe zones of Eastern Transbaikalia has been carried out. Using the methods of digital anatomy of annual rings, two (Nov and Tz) tree-ring chronologies based on four parameters (annual ring width, earlywood width, latewood width, and latewood optical density) have been constructed for the studied territory for the first time. A comparative analysis of the chronologies has made it possible to evaluate tree growth parameters under conditions of the forest-steppe (Nov) and steppe (Tz) zones and reveal the presence of reliable relations between them. The calculation of moving correlation coefficients reveals period*s when correlation coefficients fell below reliable values, indicating the impossibility of constructing a generalized regional chronology for the forest-steppe and steppe zones of Eastern Transbaikalia. A comparison of the chronologies with the weather parameters (ground air temperature and precipitations), as well as with the calculated drought and moisture indices (Selyaninov’s hydrothermal coefficient, Ped’s drought index, and Palmer drought severity index (PDSI)) reveal the most sensitive characteristics of annual rings in the studied area. In the forest-steppe zone, the highest correlation coefficients are obtained between the average annual precipitation and the annual ring width (r = 0.59) or the earlywood width (r = 0.59), as well as between the average air temperature for a hydrological year and the latewood width (r = 0.51). For the trees from the steppe zone, the most significant correlation is revealed between the annual precipitation and the annual ring width (r = 0.43) or earlywood width (r = 0.43), as well as between the PDSI for June–September and the earlywood width (r = 0.52).