Investigation of Trees' Sensitivity to Drought: A Case Study in the Opole Region, Poland

Pinus sylvestris L. is the most common tree species growing in Poland. Trees of this species are considered to be resistant to difficult meteorological conditions; however, in the past decades, many of them have died and been cut down by foresters. The measurements of the annual tree ring width can provide information on how trees respond to drought events. This study aimed to investigate the potential differences between healthy and declining trees (identified as trees to be cut down by foresters). For this purpose, we collected samples of five trees from each group and analysed them using dendrochronological and quantitative wood anatomy approaches. We measured ring width index (RWI) chronologies for healthy and declining trees and compared them with climate data. Additionally, we compared some anatomical features of trees from both groups as cell wall thickness (CWT) and lumen area (LA). The conducted analyses showed significant differences between healthy and declining trees. In particular, declining trees were characterised by lower RWI, LA and CWT values, especially in the past 20 years, and showed greater sensitivity to changes in temperature and humidity than healthy trees.