Shifts in Climatic Influences on Radial Growth of Scots Pine in the Central Scandinavian Mountains with an Evident Transition in the 1970s

Radial growth of trees, as reflected by tree ring width, serves as a vital proxy for past climate conditions, offering insights into climate dynamics over centennial and millennial time scales. Traditionally, in the high altitudes and latitudes of the central Scandinavian Mountains, summer temperatures, particularly in July, have significantly influenced the radial growth of Scots pine. This research aims to reassess the climatic determinants of Scots pine radial growth in Jämtland, central Scandinavian Mountains, by incorporating a refined analysis that considers temperature, precipitation, and snow depth, and their correlations with tree growth over time. Using a dynamic moving window heatmap correlation analysis, this study revisits a Scots pine chronology to explore the evolving climatic influences on radial growth. This approach allows for the identification of temporal shifts in growth-limiting factors. We observe a notable transition in the 1970s, marking a shift where water availability, rather than temperature, emerges as a critical limiting factor for radial growth at both the beginning and the end of the growing season. This shift is reflective of the broader global trend of decreasing tree growth response to increasing temperatures in the latter half of the 20th century, underscoring the significant impact of ongoing climate change on forest ecosystems. The results highlight the necessity for adaptive forest management strategies that consider the changing dynamics of climatic influences on tree growth. Furthermore, our study contributes to the broader understanding of forest growth patterns in the face of climate change, with substantial implications for ecological research and forest management.