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  • 1
    ISSN: 0931-1890
    Keywords: Key words Dendroecology ; Wood anatomy ; Picea abies ; Radial cracks ; Frost drought
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract  Intra-annual radial cracks were studied on 294 cross-sections of Norway spruce sampled at two forest sites in the eastern Alps (Italy) and from seven isolated trees in the Jura region (Switzerland). Cracks were occasionally accompanied by traumatic resin canals in the wood that was formed after the cracking. Most of the cracks, however, were without such canals. Traumatic resin canals are not significantly more abundant in tree rings formed after cracking, and their occurrence is not related to the cracking. Cracks developed when the cambium was inactive. Water imbalances during the early spring, due to transpiration losses and inadequate moisture supply from very cold roots, are the likely cause of these cracks.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 0931-1890
    Keywords: Key words Dendroecology ; White fir ; Norway spruce ; Climate ; Drought
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract  The influence of biotic (tree species) and abiotic factors (regional climate, altitude and stand aspect) on extreme tree-ring widths is dendroecologically investigated. Negative pointer years are observed when abrupt radial growth reductions (exceeding 40%) occurred synchronously in a given tree population. Pointer year intensity is expected to follow several theoretical models when trees are sampled along ecological gradients in various site conditions. Hypotheses are made about expected patterns of pointer year spatial distribution. They are compared with observed results obtained with Norway spruce [Picea abies (L.) Karst.] and silver fir (Abies alba Mill.) sampled in two French Alpine valleys (Tarentaise and Maurienne) with different regional climates, on two aspects and three altitude levels. Results reveal that extreme years follow expected patterns well. Thus, clear site modulations are observed in 1956 and 1986 (only trees located in Maurienne reacted). Moreover, species differences are observed, with typical cases of single species sensitivity (for spruce, occurring in 1962 and 1992). Abiotic factors such as altitude and aspect also involve clear pointer year patterns, such as narrow rings in 1976 due to summer drought that occurred especially at lower altitudes. However, some observed extreme years sometimes appear to be a combination of two (or three) of these one-factor theoretical models (e.g. 1921 with both lower altitude level and only observed in Tarentaise; 1948 involving both higher altitude and northern slopes). These results demonstrate the consistency of various tree-ring and climate relationships along ecological gradients.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1432-2285
    Keywords: Dendrochronology ; Abrupt growth changes ; Periodicities
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Growth ring sequences in conifers and broadleaved trees show abrupt growth reductions persisting for several years. The frequency and duration of such reductions in almost 10000 trees in forest stands of Central Europe, in particular Switzerland, and in the Front Range, Colorado, USA, is related to species, climate and weather, and geographical unit. The growth reductions in the populations investigated are concentrated in certain periods and, in all species examined, essentially related to periods of drought in the spring and summer months. During the years covered by the study (1850–1985), periods of growth reduction occur in Central Europe, the Front Range, Colorado, and also in the Hudson Valley, New York, at irregular intervals of 6–34 years, and on average every 13–14 years. The growth reduction periods normally do not show synchronism between the three areas investigated. Regionally valid growth periodicities can only be definitely determined through the examination of a very large amount of material comprising a number of species growing in different forest stands and on different sites within a major phytosociological unit. Findings from studies on trees in different climatic areas or on few samples scarcely allow reliable comparisons.
    Type of Medium: Electronic Resource
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