Dendrochronologia 29 (2011) 227–235 Contents lists available at ScienceDirect Dendrochronologia journal homepage: www.elsevier.de/dendro Original Article The impact of the 2003–2008 weather variability on intra-annual stem diameter changes of beech trees at a submontane site in central Slovakia Marek Jeˇ zík a,∗ , Miroslav Blaˇ zenec a , Katarína Stˇ relcová b ,L ’ ubica Ditmarová a a Institute of Forest Ecology, Slovak Academy of Sciences, ˇ Stúrova 2, 960 53 Zvolen, Slovak Republic b Faculty of Forestry, Technical University Zvolen, T.G. Masaryka 24, 960 53 Zvolen, Slovak Republic article info Article history: Received 30 June 2009 Accepted 20 January 2011 Keywords: Fagus sylvatica Diameter changes Seasonal increment chronologies Weather response Drought 2003 abstract The link between the dynamics of beech (Fagus sylvatica L.) diameter changes, recorded by mechanical dendrometers, and the weather activity was studied at a submontane site in central Slovakia between 2003 and 2008. A new approach was presented by constructing seasonal increment chronologies, dividing them into shorter periods and joining them across several seasons to analyse the main influencing factors. For this purpose, response functions and correlation functions and their intra-seasonal moving variants were calculated. The photoperiod appeared to be synchronising the culmination of the seasonal dynamics of diameter changes; however, the main factors influencing the seasonal dynamics were weather vari- ables. At the beginning of the season, the diameter increase was significantly correlated with temperature and its accumulation over a longer period. In summer, the diameter increase was hampered by long-term heat waves and the positive influence of precipitation became more pronounced. Precipitation towards the end of summer and in autumn significantly positively impacted the variability of the dendrometer signals. In 2003, the unusual seasonal dynamics were caused by a hot May and a hot and dry summer. In view of the expected climate change, including warmer springs and a higher frequency of summer droughts and heat waves, we expect a shift in the culmination of beech seasonal diameter increase towards May. Intensive drought and heat periods during summer will probably stress the beech populations growing close to their lower altitudinal limit. © 2011 Istituto Italiano di Dendrocronologia. Published by Elsevier GmbH. All rights reserved. Introduction Beech (Fagus sylvatica L.) is one of the most important and adaptive indigenous tree species in Europe (Pichler et al., 2009). It has a wide natural distribution and high abundance in central Europe (Ellenberg, 1996). In Slovakia, it grows in most forest asso- ciations, from the lowlands (200–330 m a.s.l.) up to the mountains (1260–1480 m a.s.l.) (Pagan and Randuˇ ska, 1987) and represents 31% of the entire wood stock (Collective, 2008). Its share in Europe is expected to increase, especially at sites where man-made spruce forests are declining (e.g. Tarp et al., 2000). It is important to know how and when trees produce their annual wood structure during the growing season and how they react to environmental stress (Downes et al., 2002). The main role in the seasonal diameter changes of trees is played by the vascular cambium. The time of its activity is the open window for the tree to receive and archive environmental signals directly (Frankenstein et al., 2005). We know that annual tree rings record ∗ Corresponding author. Tel.: +421 455320313; fax: +421 455479485. E-mail addresses: zvmayo@gmail.com, jezik@sav.savzv.sk (M. Jeˇ zík). the effects of dominant environmental factors during wood forma- tion ( ˇ Cufar et al., 2008a) as they are the final result of the complete metabolic balance (Beck, 2009). Therefore, the amount of newly- formed wood can be understood as a suitable indicator for tree vigour or tree physiology ( ˇ Cufar et al., 2008b), such as photosyn- thesis, the amount, redistribution and use of assimilates, and turgor pressures. Monitoring the dynamics of cambial activity and the develop- ment of woody cells (García-González and Eckstein, 2003), or of stem diameter variations throughout the season (Deslauriers et al., 2007) is crucial for the understanding of tree response to sea- sonal environmental changes. When shorter measuring intervals are used (Deslauriers et al., 2007), reversible shrinking and swelling of stems contribute to a significant part of the variability of diame- ter changes. These processes are attributed to sap flow and related variations of water content and water potential of xylem conduits (e.g. Irvine and Grace, 1997; Offenthaller et al., 2001) and phloem elastic tissues (Herzog et al., 1995; Zweifel et al., 2001; Zweifel and Häsler, 2001; ˇ Cermák et al., 2007). Gall et al. (2002) attached them to hygroscopic changes in bark related to humidity. There exist several works dealing with the intra-annual dynam- ics of diameter changes (e.g. Kramer, 1982; Lebaube et al., 2000; 1125-7865/$ – see front matter © 2011 Istituto Italiano di Dendrocronologia. Published by Elsevier GmbH. All rights reserved. doi:10.1016/j.dendro.2011.01.009