Growth of Norway spruce ( Picea abies (L.) Karsten) from artificial and natural regeneration in the Krkonoše Mts. and air temperature variability

Our research was concerned with a description of the influence of variability in average temperatures on the height growth of selected young populations of spruce in the Krkonose Mts. Several populations of spruce were evaluated while the majority of them originated by natural regeneration on plots under disturbance of the original tree layer. In addition, several planted spruce populations in similar environmental conditions were also evaluated. The main questions of this study are as follows: is there a difference in height growth between populations of natural and artificial origin? Is it possible to find a relationship between height growth and climate feature during the last several years? The growth of young spruce populations that originated by natural regeneration was different from the growth of the planted populations. The average air temperature in the growing period, estimated as average temperature during the months of May to August, was proved to have a significant influence on year-on-year variability in spruce growth. Based on this finding, it was possible to estimate an increase in the height increment of young spruce caused by warming up since the mid-70s of the 20 th century to equal approximately 16% per decade in the spruce altitudinal zone in the Krkonose Mts.