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  • 1
    Electronic Resource
    Electronic Resource
    Water relations of Yezo spruce and Todo fir in declined stands of boreal Forest in Hokkaido, Japan (1997)
    Springer
    Journal of forest research 2 (1997), S. 79-84 
    Details
    ISSN: 1610-7403
    Keywords: Abies sachalinensis ; forest decline ; Picea jezoensis ; typhoon damage ; water stress
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Recently, symptoms of decline have been widely observed in Yezo spruce (Picea jezoensis) and Todo fir (Abies sachalinensis) in Hokkaido. In order to clarify the mechanism of decline, the water status of Yezo spruce and Todo fir trees in the Tokyo University Forest in Hokkaido were investigated. The decline is observed mainly in stands damaged by Typhoon XV of 1981 (D-stands), but is not observed in undamaged stands (C-stands). Sampled trees in both types of stands were selected, the severity of their decline estimated, diurnal water potentials measured and water relation parameters such as water potential at turgor-loss point ( $$\Psi _{w(tlp)} $$ ) and osmotic potential at full saturation ( $$\Psi _{s(sat)} $$ ) were estimated by pressure-volume analysis. The diurnal trends of leaf water potential and midday water potential ( $$\Psi _{w(min)} $$ ) of the sample trees were clearly different between the D-stands and the C-stand. Water stress in trees was much more severe in the D-stands than in the C-stand. $$\Psi _{w(tlp)} $$ and $$\Psi _{s(sat)} $$ of the declining trees were lower in the D-stands than in the C-stand. However, $$\Psi _{w(tlp)} $$ and $$\Psi _{s(sat)} $$ were not significantly different between declining trees and healthy-looking trees in D-stands. It was concluded that stand-level water stress, induced by the destruction of the canopy by the typhoon, was associated with the decline symptoms. The measurement of water relation parameters proved to be useful for diagnosis and prediction of decline at a stand level in this area.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02348473
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Physiological process of the symptom development and resistance mechanism in pine wilt disease (1997)
    Springer
    Journal of forest research 2 (1997), S. 171-181 
    Details
    ISSN: 1610-7403
    Keywords: Bursaphelenchus mucronatus ; Bursaphelenchus xylophilus ; cambial resistance ; Pinus densiflora ; Pinus thunbergii
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Pathophysiological changes during the symptom development of pine wilt disease are reconsidered from recent investigations. The symptom development is divided into two stages: the early and the advanced stages. In the early stage, small number of nematodes migrate in cortex, then in xylem of the stem, and induce denaturation and necrosis of parenchyma cells. These changes in parenchyma are regarded as defense reactions of pines which result in terpene synthesis in xylem cells and embolism in tracheids. Such changes in the early stage can be induced in both susceptible and resistant pine species by either virulent or avirulent isolates of pinewood nematode (Bursaphelenchus xylophilus), or byB. mucronatus. No change occur in physiological status of leaves, and nematode reproduction is suppressed during this stage. Pine trees can survive if symptom does not progress from this stage. The symptoms of the advanced stage usually occur only in susceptible pines infected by virulent nematode isolates. At the beginning of the advanced stage, enhanced ethylene production by stem which coincides with cambial destruction occurs, and results in embolism of the outermost xylem in the portion. The embolism causes decrease in leaf water potential and cessation of photosynthesis. After cessation of photosynthesis, symptoms develop drastically with a burst of nematode population. There seems to be some unknown mechanism which suppress nematode reproduction and invasion to the cambial zone. This mechanism is thought to be photosynthesis-dependent, so that in photosynthesis-decrased conditions, even avirulent nematodes can multiply and invade cambium to induce tree death. Water stress in hot and dry summer should accelerates symptom development from the early to the advanced stage through such decrease of photosynthesis-dependent “cambial resistance”.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02348216
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    Paper (German National Licenses)
    Fulltext
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