Funding: This research was undertaken as part of the REPLICATE project (20-22351Y) funded by the Czech Science Foundation (GAČR), as well as by the Czech University of Life Sciences Prague institutional project (IGA Grant funding 2022/2023, project No A_21_22). JT was supported by Charles University [PRIMUS/24/SCI/004] and Programme JAC [CZ.02.01.01/00/22_008/0004605]. JB received funding from the SNF Sinergia project CALDERA (no.183571). JB and GvA received funding from the SNF project XELLCLIM (no. 200021_182398).Central European forests experienced high rates of air pollution in the second half of the 20th century, especially along the borders of Czechia, Germany and Poland. Consequently, tree-growth declines were detected in heavily polluted forests. However, information about how pollution has influenced growth-climate responses beyond tree-ring width (RW) in pollution-affected forests remains sparse. In this study, we investigated the impact of high-level pollution during 1960s-1980s in Central Europe on the climatic signals of various tree-ring parameters of Norway spruce, including RW, latewood Blue Intensity (LWBI), and maximum cell wall thickness (CWT), to understand how tree growth and climatic sensitivity were affected. Tree-ring cores were collected from six temperature-limited high-elevation sites within four pollution-affected regions in Czechia and northern Slovakia. RW and LWBI were measured for all samples and CWT was produced from two sites with contrasting pollution impacts. Distinct pollution-related RW growth suppression was detected in 1970s to 1980s at several sites. LWBI and CWT chronologies were highly correlated (rLWBI = 0.52–0.75; rCWT = 0.63–0.68) with growing season (April-September) temperature and did not exhibit clear signs of distortion by pollution compared to RW (rRW = 0.28–0.58). Pollution stress seemed to reduce tree growth by decreasing cell numbers and made RW less sensitive to climate. This study reveals that impacts of pollution on different tree-ring parameters varied which can further influence their climatic sensitivities. It provides valuable insight in improving the utility of pollution-affected tree-ring chronologies by choosing appropriate parameters, which can ultimately contribute to substantially improving the calibration of climate reconstructions from heavily polluted regions.Peer reviewe
