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Open access

Zuzana Sitková, Roman Sitko, Monika Vejpustková, Jozef Pajtík and Vít Šrámek

Abstract

We examined the effect of weather variables on radial growth of Norway spruce and European beech at the intra- and interannual level. We used database of regular growth measurements at 9 forest sites distributed along an altitudinal and spatial gradient within the Slovakia and Czech Republic. In the period of 2010–2017, we analysed data from 213 dendrometers with manual reading in monthly or biweekly interval. The mean daily and annual diameter increments were analysed in relation to air temperatures and precipitation observed during the respective growing seasons. The general intra-annual diameter increment was modelled using a log-normal function. Results of modelling suggest that precipitation was a better predicting factor of the increment in spruce, while air temperature enhanced predictions of increments in beech. The highest, eight-year-cumulative increment of spruce (31.1 mm) and beech (22.8 mm) was found in the mixed mountainous forest at Poľana site, where both species occur in their growth optimum. The interspecific comparison of radial growth at this site revealed earlier culmination of increment in spruce compared to beech. The growth-limiting weather conditions for spruce occurred especially during the dry season 2015, while in beech sites the slight decrease of annual increment was observed in 2016. In the lowest altitudes of studied forest sites (beech 350 m a.s.l., spruce 440 m a.s.l.) the radial growth was reduced due to high summer temperatures. In the context of further predicted increase of air temperatures, these altitudinal limits for tree growth should be considered in the future forest management in Central Europe.

Open access

Zuzana Sitková, Paulína Nalevanková, Katarína Střelcová, Peter Fleischer Jr., Marek Ježík, Roman Sitko, Pavel Pavlenda and Tomáš Hlásny

Abstract

We focus on the analysis of sap flow and stem circumference changes in European beech (Fagus sylvatica, L.) in relation to available soil water and weather conditions during the growing seasons 2012 and 2013. The objective was to examine how soil water potential affects growth and transpiration of a mature beech stand situated at the lower distributional limit of beech in Slovakia. To be able to evaluate beech response to soil water shortage, we irrigated a group of 6 trees during the period of pronounced drought, while the control group of other 6 trees remained exposed to actual weather conditions. Mean air temperatures of both seasons were considerably above the long-term average and the temporal pattern of precipitation differed between the years. During the whole growing season 2012, beech samples transpired an average volume of 6.9 m3 of water in the control and 7.7 m3 in the irrigated group. A slightly higher average volume was found in the growing season 2013 under both treatments (7.7 m3 in control and 10.5 m3 in irrigated trees). In the drought period 2012, when the irrigation experiment was commenced, the sap flow in the control group was reduced by 30% as compared with the irrigated group. In 2013, a 38.1% difference in sap flow was observed between the groups. Sap flow in the non-irrigated trees decreased with reducing soil moisture, and ceased at soil water potential -0.6 MPa. In both treatments and years, we found significant correlations between hourly sap flow and investigated weather variables. A reduction in stem circumferences of the control trees, which was observed during stem shrinkage phase, was up to 19% in 2012 and 10% in 2013. We conclude that stem circumference shrinkage during the peak of soil drought was induced by the cessation in the sap flow process.

Open access

Denisa Sedmáková, Róbert Sedmák, Michal Bosel’a, Marek Ježík, Roman Sitko, Tomáš Hlásny and Miroslav Blaženec

Abstract

The main objective of the study is to facilitate cross-dating of sensitive tree-ring series from living European beech (Fagus sylvatica L.) trees in the absence of a regional chronology. The main idea lies in the preliminary dating of marker rings or ring patterns visually identified on the wood (before the ring-width measurements), which is independently validated through a moving correlation between a tentative reference chronology and instrumental climate records (after the ring-width measurements). Following the detection of low moving correlations, potentially misdated segments or series are re-examined and a new tentative reference chronology is constructed. The process is repeated as long as a higher correlation with climate is obtainable. The applicability of this method was investigated on three difficult-to-date sets of tree-ring series of beech trees which were growing at temperature- or precipitation-sensitive locations in under-canopy or canopy positions. A good ability of the combined method for the cross-dating was practiced on datasets almost impossible to cross-date by commonly used approaches. Highlighting the actual correlation of ring widths with climate in tree-ring series makes the cross-dating process more independent from human decisions, so the com-bined cross-dating has the potential to improve the reliability of various dendrochronological studies.