Can the structure of dormant cambium and the widths of phloem and xylem increments be used as indicators for tree vitality?
We investigated the structure and width of the dormant cambium and of the increments of phloem and xylem of Quercus robur to estimate their potential as indicators for tree vitality. The samples were taken from three woodlands, two in Slovenia [Krakovo forest (KRA) and Murska Suma (MUS)] and one in Croatia [Kobiljak (KOB)], with reported tree decline. The number of dormant cells seems to reflect the initial capacity of the cambium to accomplish cell division. With the exception of two trees at KRA, cell production was always higher on the xylem side than on the phloem side. The annual phloem increments were narrower, less variable among trees and with clear lower and upper limits. With increased cambial cell productivity, the share of the xylem in the total annual radial increment increased following a curvilinear function. In trees with an annual radial increment >3.5 mm, the xylem size represented more than 90 % of the total radial growth. The anatomical variables analyzed show that the most limiting environmental conditions seem to prevail at KRA, whereas the conditions at MUS seem to be most favorable in terms of radial growth. Analysis of the width and structure of xylem and phloem increments, the number of dormant cambial cells and their inter-relationships can provide additional information on the vitality of oaks.
KeywordsEuropean oak Lowland forests Tree decline Radial growth Light microscopy
The authors would like to thank the anonymous reviewers for their valuable comments and suggestions to improve the quality of the paper. The work was supported by the Slovenian Research Agency, program P4-0107 and project Z4-9662 and by EUFORINNO (RegPot No. 315982) of the FP7 Infrastructures program. The cooperation among the international partners was supported by the COST Action FP1106, STREeSS.
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