The Niepołomice Forest, though relatively natural, is affected by air pollutants transported from nearby urban areas. To assess the impact of air pollution, we analyzed the bioaccumulation of elements (Ca, Cd, Cu, Fe, Hg, Pb, S, Zn) in thalli of Hypogymnia physodes (L.) Nyl., together with oxidative stress biomarkers (SOD, TBARS) and thallus condition, at 15 sites during heating and non-heating seasons. Seasonal variability was observed: Cd and TBARS were higher in non-heating season (0.97 µg·g⁻¹ and 0.95 mmol·g⁻¹ FM respectively), while S increased during heating season (1331 µg·g⁻¹), suggesting emissions from fuel combustion. Spatial differences were most pronounced for Cd and Zn. In the western part of the forest, H. physodes was absent at some sites, and lichens showed elevated Pb and Cu concentrations with increased SOD activity, indicating strong traffic-related pollution. In the east, thalli contained a high proportion of degenerated algae, associated with elevated Cd, Hg, and S, as well as other stressors. Overall, element concentrations were comparable to values reported from other regions of Poland. The study highlights that even seemingly natural forests are subject to significant pollution pressure. Combining chemical data with biomarkers offers deeper insight into the effects of toxic elements on lichen bioindicators.