We conducted a survey of wood formation in European beech (Fagus sylvatica L.) from the Moncayo mountain in Spain in the growing season of 2011. The research was conducted at 2 sites (ML, MH) at different altitudes (41.81 N, 1.82 W and 1171 m a.s.l.; 41.80 N, 1.82 W and 1560 m a.s.l.). The sampling was conducted in 1 or 2 week intervals, from March 24 until November 23, 2011. 20 samplings were performed, and micro cores containing bark, cambium and outer wood were taken from 6 trees on each of the sites. Permanent slides of cross-sections were prepared for each micro core. Using light microscope and image analysis system the width and the number of cells of the cambium from the forming growth ring of 2011 were measured in the phase of post-cambial growth (PC), the phase of development of secondary cell wall (SW), and the phase of fully matured cells (MT). Cambial production with first PC was first recorded on ML site (May 1-14), slightly earlier than at MH. Cell production ended at ML slightly later (August 26) than at ML. Consequently, the average 2011 xylem growth ring width was 438.3±198.1 μm at MH, slightly less than that at ML, where it was 477.3±344.5 μm. Phloem at the MH generally had clearly visible growth ring boundaries, whereas they could not be
clearly identified at the ML. Wood formation in beech at Moncayo, representing an isolated population at extreme south-west edge of its distribution area, is seasonally limited and without summer interruptions, so typical for trees from Mediterranean ecosystems.
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