Climate at play: Norway spruce responses to weather and climate conditions across latitudinal and elevational gradients of Eastern Europe

Abstract

During the last decades, Norway spruce has been severely affected by climate change and disturbances, hence substantial alterations in species abundance are anticipated. Although substitution of Norway spruce is considered in Central and Western Europe, in vast parts of Northern and Eastern Europe, the species is still of high economic and ecological importance. To better understand population responses in terms of adaptability in relation to climatic sensitivity, this study aimed to identify and compare sensitivity to the main climatic drivers of Norway spruce from different populations in Europe across comparable climatic gradients. The responses of radial increment of Norway spruce to weather (locally) and climate (regionally) across the extended latitudinal and elevational gradients represented by 61 sites from three distinct populations, i.e., the eastern Baltic region, the Carpathians, as well as Central Europe, were assessed using a dendroclimatological approach and multiple regression techniques (generalized additive mixed models). Nonlinear, multi-month meteorological effects cumulatively explained 18% of interannual variability in radial increment. The responses, however, revealed some population specifics, with distinct sensitivities to water availability and winter and summer temperature. A clear drought signal was evident, particularly through June-July climatic water balance, with increment being highly sensitive to water deficits exceeding 100 mm (two-month scale) and variable responses to moisture excess among the populations. Temperatures in spring and summer had positive effects, yet optimal temperature ranges and response shapes (bell-shaped or sigmoid) varied among the populations. Accordingly, climate change will have disproportional, yet population-specific effects on Norway spruce across Europe, thus suggesting potential for the between-population assisted gene transfer for improvement of local breeding populations.