Scots pine is an adaptable and prevalent European tree species that grows naturally throughout Europe and has been planted in a wide range of environments. Previous studies have indicated that climatic variables affect tree-ring growth patterns in this species, but it is also possible that certain aspects of the growth environment moderate this response. In order to understand the potential impact a shifting climate has on this important species, this study compared the growth response of two populations of Scots pine. Trees from similar bioclimatic regions in Hungary and Poland were compared using the hypothesis that differences in the association between climate and growth would be reflected by the degree of tree-ring width variation. We also wanted to know how changing climatic conditions influenced the temporal stability of the climate–growth signal in the most important periods for tree growth. Clear similarities in the effect of temperature and precipitation on tree-ring width variation were found between the two sites, but there were also some interesting differences. In the late winter to early spring period both populations reacted to warming with a decreasing association with temperature. Summer precipitation was shown to be the dominant factor in controlling ring-width. A decreasing trend in summer precipitation values at both Hungarian and Polish sites resulted in a weakening in correspondence for the Hungarian trees, while the Polish trees showed a significant increase in correlation with summer precipitation. The results indicated that changes in climate influenced the studied trees in different ways which has implications for the future balance of Scots pine growth in Europe.

Negative climatic extremes occur more frequently in the last decades. Since the Carpathian Basin is highly concerned in their impacts it is important to investigate prior events and estimate the response of the environment to them to get useful information for the future. In our work we selected a stand which is seriously affected by unfavorable summer conditions to examine what kind of fingerprint the negative extreme events have left. We investigated narrow rings and intra-annual density fluctuation to describe years with extreme events. Their stabilized frequency was tested against climatic and groundwater data, as well as against aridity index to determine climate-growth relationships using Pearson and Spearman's correlations. Our results show positive significant correspondence between summer precipitation and treering growth together with negative connection with summer temperature. The Spearman's correlation between stabilized frequency of intra-annual density fluctuations, narrow rings and climate data ended with significant relationship in summer. According to the comparison of intra-annual density fluctuation and narrow ring data with drought periods it can be said that narrow rings are better tool for the examination of negative extreme events in summer.

Key Message Climate change has a significant influence on the climate-growth relationship of Scots pine in Western Hungary, and this typically expressed as a decrease in the strength of the connection between treering width variation and climate data. Abstract This paper aims to expand our understanding of the climate-growth relationship of Scots pines in Transdanubia. Changes in the influence of climate on tree growth over various time-scales have been the subject of numerous investigations with pine trees, but these relationships have never been explored for Scots pines in Hungary. In this research, Pearson correlation values in 25-year moving windows were used to evaluate the temporal relationships of temperature, precipitation and tree-ring width variation, and additionally to investigate how these might be connected to climate change between 1915 and 2014. In the cases of summer precipitation and late winter-early spring temperature, our results detected a significant positive influence on the tree-ring width development of those Scots pines at our study sites. Furthermore, intensive warming over the last 100 years has resulted in a changing relationship between tree-ring width variation and climate data. In this study, the temporal instability of the climategrowth relationship was observed in every important month of tree-ring growth, and the response of growth to climate declined sharply in most of the studied periods. This indicates that ongoing climate change has already altered the Communicated by S. Leavitt.

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