Tree ring characteristics depend on various factors. Typically, when analyzing the influence of external factors, the contribution of age to radial increment is removed. Along with individually fitted curves for each tree, regional growth curves are used for this step. Regional growth curves are empirically determined curves describing the relationship between age and tree ring characteristics in a given area. The aim of this study is to identify differences in radial increment of Siberian spruce at the upper limit of its distribution in the Southern Urals by analyzing regional growth curves. In total, growth measurements from 989 trees were used in the analysis. The expected tree ring width of Siberian spruce in the Southern Urals is described using the Hugershoff curve. Spruce populations were studied on three ridges: Nary, Zigalga, and Taganay. Since the Siberian spruce is currently spreading across the alpine tundra, it was not possible to estimate the parameters of the regional curves at all altitude levels. The highest value of the expected maximum increase (from 2.1 to 2.7 millimeters) was noted at the lower altitude levels of the south-eastern slope in the pass between Mount Poperechnaya and Mount Kruglaya (Zigalga ridge), which can be explained by favorable insolation conditions and low wind speed, compared to the Taganay ridge.
Lozhkin et al. (Fri,) studied this question.