Intraspecific variation in climate response of Norway spruce in the eastern Alpine range: Selecting appropriate provenances for future climate

Abstract Enhancing adaptation of forest ecosystems to prospective climate change is a major challenge in current forest management. Beyond potential negative effects of climate change such as decreasing productivity due to an increasing number of drought periods and damages from intensified disturbance regimes, there is also a potential for increasing productivity due to prolonged vegetation periods and higher photosynthetic rates. Quantitative genetic variation is crucial for adaptability of species towards environmental changes. The use of suitable reproductive material for forest regeneration will be a key factor essential for both, mitigating negative effects and making the most of potential positive effects. Therefore, insights into intraspecific variation within and among tree populations in climate response are of paramount importance. In our study we investigated intraspecific variation in climate response among Norway spruce (Picea abies) populations in the eastern Alpine range. Results from a comprehensive Austrian provenance test, comprising tree heights at age 15 from 379 populations planted at 29 test sites across Austria, were used to calibrate climate response functions for groups of Norway spruce populations. Potential future changes in productivity for climate change conditions as represented by a regionalized A1B scenario were estimated using height at age 15 as a productivity proxy. Climate response functions were calculated for single populations and aggregated clusters of populations from climatically similar origins. Our results hardly revealed any declines in employed proxies for productivity of Norway spruce throughout its current distribution range in Austria. For most parts of Austria an increase of tree heights up to 45 percent can be expected until 2080. However, the impact of a warming climate is different for individual population groups. Generally, variation in climate response increases with higher temperatures and less precipitation. Thus, an optimized choice of seed material according to prospective future climate conditions has the potential for an additional increase of productivity up to 11 percent. In general, populations from currently warm and drought prone areas seem to be well adapted to respective climate conditions and may be appropriate candidates for extended utilization in future. Furthermore, populations showing the best productivity indices originate from regions, which are phylogenetically distinct from the core distribution area of Norway spruce, suggesting that population history might explain part of the variation in climate response among populations.