Response of conifers to UV-B and climate in mountain areas

The current study was focused to examine the combined effects of climate and ultraviolet-B radiation on conifer tree-ring density. Statistical methods were employed to extract tree responses in annual ring density and to identify functional relationship in trees when the level of ultraviolet-B radiation changes regardless of climate variations. In this study, the consideration was given to the series of total ozone content (instead of ultraviolet-B), tree-ring density, and De Martonne aridity index. After the correlation analysis, all trees were divided into two groups: 1) Trees whose correlation between tree ring density and UV-B values in April is significantly positive; 2) Trees whose correlation between tree-ring density and aridity index values in March-September is significantly negative. Then, tree-ring series for the Swiss Alps in each group were generalized and decomposed into separate components: long period trends, ultraviolet-B and climatic signals. For the ultraviolet-B-responsive tree group in the period 1932-1974, the correlation coefficient between the tree-ring density and ultraviolet-B was 0.55 at p <0.05. For the climate-responsive tree groupthe correlation coefficient between tree-ring density and aridity index was -0.51 at p < 0.05. Data mining diagrams showing the impact of atmospheric factors that affect the anatomic changes in the wood growing in mountain regions reveal that hormone сan link the interaction of stem and crown. Generalized tree-ring density series may also be used to reconstruct past changes in ultraviolet-B and climate and to predict the conifer state in other mountain regions in the world.

Keywords:

Climate change , Conifers , Growth hormones , Principal components , Singular Spectrum Analysis , tree-ring density , Ultraviolet-B radiation