Understanding Climate Sensitivity of Central European Conifers: Insights from Multivariate and Multi-Parameter Tree-Ring Analysis

Abstract

Environmental changes have recently increased the frequency and intensity of climatic extremes, particularly hotter droughts. The effects of shifting climatic conditions on tree growth vary across species’ distribution ranges, with large spatial heterogeneity and inter-population variability, but with significant consequences for contemporary forest dynamics and future ecosystem functioning. Despite numerous studies on the impacts of regional droughts, large uncertainties remain regarding the mechanistic basis of drought legacy effects on wood formation and the ability of individual species to cope with increasingly drier growing conditions and rising climatic variability.To unravel the complexity of climate-growth interactions and species-specific responses to severe droughts, we combined forward modelling of tree growth (VS-lite model) with correlation analysis including climate (temperature, precipitation, and the SPEI-3) and growth responses to extreme drought events from multiple tree-ring parameters (including tree-width and Blue Intensity parameters). We used an extensive dataset with over 1000 tree-ring samples of Norway spruce and Scots pine from 23 nature forest reserves across an elevational range in Czechia and Slovakia.Our results revealed systematic spatiotemporal variability in growth responses to summer temperature and moisture availability across species and tree-ring parameters. A general trend of increasing spring moisture-growth sensitivity in recent decades was observed in the Scots pine mountain forests and lowland forests of both species. The VS-lite model effectively captured nonstationary climate-growth relationships and accurately estimated high-frequency growth variability, indicating a significant incidence of regional drought events and growth reductions. Notably, growth reductions during extreme drought years and discrete legacy effects were most pronounced in the lowland forests. Together with the observed growth declines in recent decades, these findings suggest an increasing vulnerability of Norway spruce and Scots pine in dry lowlands under intensifying climatic constraints.

Keywords: dendroclimatology, Vaganov-Shashkin Lite, superposed epoch analysis, drought legacy effects, basal area increment, blue intensity