Temperature and Precipitation Affect the Radial Growth of Berlin Poplar and Small-leaved Linden Trees in Saint Petersburg

The effect of temperature and precipitation on the change in the radial growth of wood of Berlin poplar (Populus × berolinensis Dipp.) and small-leaved linden (Tilia cordata Mill.) in Saint Petersburg was studied. Cores were taken from old trees in the Forestry Technical University park, in the Palevsky square, in the city of Pushkin (poplar trees) and in the Moscow Victory Park (linden trees). To eliminate the influence of the samples’ age factor on the change in its growth rings’ width, the generally accepted detrending methods were used; the calculations were carried out in the Arstan software. Precipitation and temperature fluctuations during the winter period do not significantly affect the growth of poplar and linden in Saint Petersburg. Summer precipitation has a positive, but overall not a decisive effect, in some cases, the radial growth increases with increasing rainfall. Temperature has no significant effect on standardised (age-adjusted) growth rates. Non-standardised average values of growth under the increasing temperature conditions in July–September significantly decrease. The effects of temperature and precipitation appear to be indirect, exacerbating or offsetting the effects of other factors, especially the air pollution. The impact of pollutants increases with the increase in temperatures at the end of the growing season, because they accumulate on the leaves’ surface. Precipitation washes away pollutants, reducing the intensity of their impact. Growth decline in poplar trees in the second half of the 1990s, in the absence of such an occurrence in linden, can be explained by the consequences of a prolonged outbreak of the poplar moth (Phyllonorycter populifoliella) mass reproduction in 1991–1999. The above assumptions require additional research; in particular, determining the level of leaf contamination during the growing season and taking into account the impact of other factors.