Intraspecific Variability of Radial Increment of Scots Pine (Pinus sylvestris L.) in Forest Sites in the East European Forest-Steppe

Abstract

This article presents results from a study of differentiated responses of the annual radial increment of individual Scots pine (Pinus sylvestris L.) trees (dendrophenotypes) to changes in climatic factors at two forest sites: mixed-grass pine forest and purple moor-grass pine forest. For the first time in Scots pine in the East European forest-steppe, intraspecific (intrapopulation) differentiation of trees based on their adaptive potential to changing climatic conditions was established, and principles for identifying dendrogroups based on responses to limiting climatic factors were developed. The identified dendrogroups differ significantly from one another. The relationship between pine radial increment dynamics and climatic factors decreases from the 1st to the 3rd dendrogroup at both studied sites. Correlation analysis between climatic factors and pine radial increment under the two forest-growing conditions showed that the climatic signal is stronger under moderately moist conditions (mixed-grass pine forest). For example, for dendrogroup 1, the correlation coefficient between radial increment and total atmospheric precipitation during May–September was 0.58 in the mixed-grass pine forest and 0.47 in the purple moor-grass pine forest during 1961–1990; during 1991–2020, the corresponding values were 0.27 and 0.22. The study also revealed a strong influence of May–September precipitation on pine radial increment, making it possible to construct regression equations that reflect radial-increment dynamics under changing climatic factors. The dendrogroups identified in this study showed differentiated responses to climatic factors limiting tree growth within populations. These data should support effective forest management in pine forests of the East European forest-steppe.

Keywords: influence strength, intraspecific variability, precipitation amounts, radial increment, Scots pine