Spatial distribution of introduced Norway spruce growth in lowland Poland: The influence of changing climate and extreme weather events

Norway spruce trees grown outside their natural range were intensively studied in terms of their adaptability to increased late winter temperature. A total of 708 cores of Norway spruce were taken from 35 sites throughout northwestern and western Poland at sites outside or at the margin of its natural range. Clustering reveals that research sites are grouped geographically. The mean ring widths, however, are similar among the three regions. The relationships between tree growth and temperature together with precipitation are comparable to those in lower elevations in Central and Eastern Europe and southern latitudes in Scandinavia. In total, 18% of the single correlations for all months were significant at p < 0.05. The generally positive precipitation effect was found for all months except January. Temperature had mixed effects on ring width. Higher temperatures in late winter and early spring increased ring width (13% of all significant correlations). High summer temperatures in both the previous and the current year, on the other hand, generally had a negative impact on tree-ring width during the growing season. On most of the sites, the observed long-term trend for increasing temperatures in February and March had no significant negative influence on tree growth. Also the effect of extreme weather events was taken into account. In 1994 and 1995 the wider rings were mostly observed in humid sites from southwestern Poland. In selected time spans, growth recovery following extreme weather events is particularly strong. (C) 2012 Elsevier Ltd and INQUA. All rights reserved.