Browsing by Subject "birch"

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  • Christita, Margaretta; Overmyer, Kirk (2021)
    Witches' broom of birch (Betula spp.) caused by Taphrina betulina is an understudied disease that causes the formation of woody tumours, from which ectopic axillary buds and branches grow to form a broom-like structure. We have addressed two aspects of this disease using naturally infected mature trees in the field. Broom symptoms offer a convenient means of scoring susceptibility in the field. Variation in broom symptom presentation suggests possible variation in resistance against witches' broom disease. We tracked the local distribution of susceptible individuals among 721 trees at 159 independent sites. The analysis supports the hypothesis that there was genetic resistance segregating in these birch populations. Anatomical changes in broom symptom bearing branches of European silver birch (Betula pendula) were also addressed by comparing sections of tissues from three locations in the same branch, which were normal, swollen in infected tissue adjacent to a tumour, and inside a tumour. Examination of tumours revealed disorganized and swollen xylem, expanded secondary phloem and expanded periderm. Swollen tissues newly infected from spreading disease adjacent to tumours exhibited enhanced growth only in secondary phloem and the periderm, which also exhibited distortions. This finding suggests that tumour formation and possibly pathogen colonization may initiate in these tissues.
  • Rautiainen, Mari (Helsingin yliopisto, 2014)
    Carbonization is thermochemical conversion, where biomass is thermally degraded in the absence of oxygen. Solid char, pyrolysis oil and non-condensable gases are produced from the biomass. Torrefaction is early phase of the carbonization in temperatures of 220–300 °C. Torrefied wood is promising as a renewable fuel for industrial use in coal co-combustion and gasification-combustion. Torrefaction and carbonization increase the higher heating value and fuel properties of wood compared to untreated wood. There’s a lack of knowledge in torrefaction and carbonization effects to higher heating value, carbon content and turn from endothermic to exothermic reaction of conifer zone wood species. Raw material was stemwood of birch (Betula pubescens) and pine (Pinus sylvestris) including bark. Trees were harvested from the Helsinki district and chipped, particle size 16 ? 8 mm. Samples were torrefied and carbonized at 250, 300, 350, 400 and 450 ?C without nitrogen flow. Carbon content (%), higher heating value (MJ/kg), mass yield (%) and turn of endothermic to exothermic reaction were inspected. Carbon content of untreated birch and pine increased from 47 % to 82 % (at 450 ?C). Higher heating value exceeded 26 MJ/kg at 300 ?C and 28 MJ/kg at 400 ?C, reaching bituminous coal’s values. Mass yield declined to 45–54 % of the initial mass at 300 °C. In low temperature, gradual exothermic peak was observable. In higher temperatures peak was evident. Carbonization and torrefaction improved the higher heating value and carbon content of wood but decreased the solid char yield.