Growth response of Betula pendula Roth to changing climatic conditions in urban areas of central Europe: different strategies within a single species
Description
Betula pendula is a wide-spread tree species, important as a part of natural forests, a source of timber, and an ornamental tree in urban regions. It is generally considered a pioneer tree with fast growth and a short lifespan, but great genetic variability and phenotypic plasticity. To better understand how the ongoing climatic change would influence the trees in urban environment, we conducted dendrochronological sampling of 42 specimens in Bratislava, varying in trunk diameter and vitality. The data provide the location and characteristics of the sampled specimens and the measured widths of their tree rings.
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A preliminary analysis of the state of B. pendula in Bratislava has been carried out prior to picking the trees for sampling. We measured the biometrical parameters and determined the vitality of 428 trees growing among the built-up areas of the city. Trunk circumference has been measured by tape measure 130 cm above ground. The vitality of the trees has been assessed on a 5-point scale, with 5 representing the healthiest specimens. Based on this analysis, individuals for dendrochronological sampling were picked to create a representative sample of the different circumference classes (very loosely used as a proxy for age, which could only be estimated after the sampling) and different levels of vitality. Dendrochronological samples of 42 trees (Fig. 1) were taken using a 2-thread Haglöf increment borer with 5.15 mm core diameter. Samples were taken at 130 cm from the surface at an angle of 90º. The cores were marked and dried in a wooden base with a 5.5 mm wide grooves to fit the samples. The cores were glued to the wooden base and polished by sandpaper of increasing grit up to 1200. Chalk dust was used to increase the visibility of the tree rings before the analysis. The width of the tree-rings was measured using the Lintab 6 Tree Ring Analysis Station (Rinntech), with the TSAP-WinTM software for tree-ring measurement and analysis. The cores were measured in the direction from bark (most recent tree ring) towards the centre.