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The anatomy and functioning of stem secondary xylem in relation to the decline of European ash (Fraxinus excelsior L.) was examined and the hypothesis that declining trees show changes in the structure of wood, resulting in impaired water transport was tested. Anatomical analyses were carried out on samples comprising annual rings formed between 1970 and 2009 and collected at the breast height of the main stem of fifteen trees 40−90 years old. Trees were based upon health condition and classified as healthy, weakened or dead. Tree−ring widths as well as diameter and density of earlywood vessels were measured and the theoretical hydraulic conductivity index through the secondary xylem calculated by application of Hagen−Poisseuille formula. Over the whole investigated period the smallest early vessels were attribute to ashes dead at the time of sampling. In the period when dieback symptoms where manifested in the stand, the diminishment of vessels diameter occurred in weakened and eventually dead trees, whereas healthy trees produced even slightly larger vessels than before. Having large vessels implies that healthy trees were able to keep high hydraulic conductivity index, whereas trees in decline at this time produce smaller vessels and hence had reduced conductivity in respect to previous.
The paper contains analyses of pine wood features, carried out on 27 areas, representing forest stands on Carpathians and Sudetes area. On studied area it was possible to separate origin groups differing according annual growth widths, late wood contribution and its density. The highest values these features entertain in wood of pines on areas of Bieszczads, whether the lowest ones in origins recognized as montanes. In Beskidian forest stands, values of wood features were intermediate.
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