Effect of provenance and climate on intra-annual density fluctuations of Norway spruce Picea abies (L.) Karst. in Poland.

Highlights • The climatic conditions of Central Europe favor primarily IADFs in earlywood and transition zone. • Frequency of IADFs in Norway spruce is mainly caused by site-related climatic conditions. • Temperature and precipitation sensitivity determines the variability between Norway spruce provenances in the IADFs frequency. • Frequency of IADF E and E + depends on climatic distance between provenance trials and provenance origin. Abstract Understanding the growth pattern of trees of various provenances in response to climatic conditions provides information on the adaptive potential of trees. Intra-annual density fluctuations (IADFs) are anatomical markers of variations in wood density within the annual wood increment. Latewood-like cells within earlywood, resulting from severe drought during spring and early summer, express the structural adaptation of the wood tissue to unfavorable climatic conditions. In this study, we used two 40-year old IUFRO provenance trials of Norway spruce located in the western and north-eastern Poland to i) determine the effect of provenance on the IADF frequency and ii) to define the climatic factors determining the formation of IADF. Three highly polymorphic nuclear microsatellites are used to determine the differentiation among provenances in particular between the northern and southern Polish distribution area. Our results demonstrate that the frequency of all types of IADFs is determined by the growing conditions, and only the IADFs in the transition zone are determined by provenance origin. The highest variability between provenances in response to climatic differences was observed for IADF in transition zone, where temperatures and rainfall of spring and early summer differentiated northern and southern provenances. Moreover, the IADF frequency was influenced by drought, thereby differentiating provenances in terms of their sensitivity to severe conditions. Furthermore, environmental differentiation of climate-growth reaction was expressed by a stronger impact of climatic conditions observed in the western than in the northeastern trial site. The results of this study confirm the dependency of climate related changes in wood characteristics on provenance origin. Therefore, density fluctuations seem to be an appropriate adaptive trait for selecting Norway spruce provenances with varying degree of drought sensitivity. [ABSTRACT FROM AUTHOR]