Influence of climatic conditions and air pollution on radial growth of Scots pine (Pinus sylvestris L.) in Szczecin’s city forests

Abstract The aim of the present work was to characterize the growth – climate relationship of pines growing in the Szczecin city forests in intensively used recreational areas and to identify the effect of air pollutants emitted by a nearby chemical factory on tree-ring width. Our research area was located in the Głębokie forest complex, which is one of the most frequently visited. The chemical factory Police that produces fertilizers is located at a distance 11 km away from the study plot. The largest emissions of pollutants from the factory in terms of volume occurred in the 1980s and early 1990s. Wood samples were collected from Scots pine (Pinus sylvestris L.) with the Pressler borer from 30 trees and examined using standard dendrochronological methodology. The result was a local chronology of 169 years from 1848–2016. Dendroclimatological analyses indicated that the weather conditions at the turn from winter to spring are the dominant factors influencing radial growth. For example, higher than average temperatures in February, March and April result in a wide tree-ring in the upcoming growth season. Following Nowacki and Abram’s method, we also determined the relative growth change in order to delimit the timeframe when air pollution potentially alters tree-ring width. Due to the lack of data for the period 1848–1945, the increasing and decreasing relative growth could not be linked to specific events. For the period 1944–1972 however, we observed and increase in the tree-ring width, which in this case can be attributed to favorable weather conditions. The final period, 1973–1991, on the other hand showed the strongest decline in annual growth throughout our chronology and this was largely due to the nearby chemical factories, which released huge amounts of pollution into the atmosphere during this period. At present, despite new technologies and a decrease in overall production by the nearby chemical factory, we found a negative trend in ring width dynamics indicating a need for pollutant monitoring and further research.