Niko Torelli

The formation of a ligno-suberised layer and necrophylactic periderm in beech bark (Fagus sylvatica L.)

Beech (Fagus sylvatica L.) bark was wounded in early April of 1993 and tissue changes followed on days 7, 14, 21, 28, 35, 42, 49, 56, 84, 112, and 140. In 7 days, tissue at the wound surface became necrotic and discoloured. In 14 days the walls of the parenchyma cells immediately underneath the necrotic tissue became thickened and after 21 days became lignified. In 28 days these lignified cells showed intracellular-suberisation. In 42 days the ligno-suberised layer was continuous with the phellem of the superficial periderm. In 35 days we first noted differentiation of the necrophylactic phellogen under the ligno-suberised layer. In 49 days suberised phellem of the necrophylactic periderm differentiated. At 112 days the phellem of the necrophylactic periderm had coalesced with that of the surface periderm. In I40 days abscission of the wound rhytidome began.

Mexican tropical hardwoods. Comparative study of ash and silica content

Data on ash and Silica content of 43 Mexican tropical hardwoods are presented. The highest silica portions were found inPoulsenia armata (1.0–4.7%),Dialium guianense (0.37–1.40%) andDipholis Stevensonii (0.49–0.68%)ZusammenfassungAngaben über das Asche- und Siliciumgehalt von 43 mexikanischen tropischen Laubhölzer. Hölzer mit dem höchsten Siliciumgehalt:Poulsenia armata (1.0–4.7%),Dialium guianense (0.37–1.40%) undDipholis Stevensonii (0.49–0.68%)

Some Wood Anatomical, Physiological, and Silvicultural Aspects of Silver Fir Dieback in Slovenia (NW Yugoslavia)

Silver fir dieback in Slovenia (NW Yugoslavia) was evaluated, and growth suppression and some physiological and anatomical aspects of growth ring formation were studied. The drastic growth suppression after 1950 was reflected in poor basal area increment, and by discontinuous as weil as missing rings. Only in the most diseased trees the height increment was affected. Generally latewood percentage and tracheid dimensions remained unchanged. The physiological mechanism of wetwood formation in sapwood of fir is discussed and compared with red heart formation in beech. On the basis of preliminary experiments, osmotic transport is suggcsted from sapwood to heartwood through the intermediate dry zone.

Electric Current Density Imaging of Pedunculate Oak (Quercus Robur L.) Twigs by Magnetic Resonance Imaging

The use of Electric Current Density Imaging (CDI) technique to map spatial distribution of induced electric currents through two years old twigs of pedunculate oak (Quercus robur L.) is presented. Specifically, this magnetic resonance technique was implemented to image conductivity contrast in different tree tissues. Imaged electric conductivity distributions of pith, wood, and phloem together with cambial zone and undifferentiated xylem were compared with flame atomic absorption spectrometry measurements of potassium. Good correlation was observed. The undifferentiated xylem + cambial zone + complete phloem showed higher electrical conductivity and normalized potassium values than both differentiated xylem and pith. By a novel magnetic resonance imaging technique it is demonstrated that the path of least resistance to an electric current was along tissues of maximum free potassium concentration.

Comparative decay resistance of 43 mexican tropical hardwoods

Decay resistance (natural durability) of 43 Mexican tropical hardwoods were tested according to ANSI/ASTM D 2071-71.ZusammenfassungEs wurde die Abbauresistenz bzw. die natürliche Dauerhaftigkeit des Holzes von 43 mexikanischen tropischen Laubhölzer nach ANSI/ASTM D 2071-71 geprüft.

Mexican tropical hardwoods: pH-value

This study reports the pH-value in sapwood and heartwood (if present) of 43 Mexican tropical hardwoods.ZusammenfassungDieser Bericht enthält Angaben über den pH-Wert des Splint-und Kernholzes (wenn vorhanden) von 43 mexikanischen tropischen Laubhölzern.

Characteristics and prospects for rational use (harvesting) of Mexican tropical forest

Some typical areas of Mexico were selected to demonstrate the influence of historic (Maya) and recent use of tropical forest regarding botanical composition and status. Instead of the deveasting selective felling a varied and sustained usage of the forests is proposed comprising much more wood species and following an end use oriented marketing.ZusammenfassungIn einigen typischen Gebieten werden die Auswirkungen des historischen antropogenen Einflusses (Maya), sowie der rezenten selektiven Nutzung auf die botanische Zusammensetzung und den Zustand der mexikanischen Tropenwälder dargelegt. Anstelle des zerstörischen selektiven Fällens wird eine gleichmäßigere nachhaltige Nutzung der holzproduzierenden Wälder mit wesentlich mehr Holzarten nach den Prizipien des “end use oriented marketing” vorgeschlagen.

Mexican tropical hardwoods : machinability, nailing and screwing

Machinability, nailing and screwing behaviour of 43 previously described Mexican hardwoods were determined according to standard procedures.ZusammenfassungIm Weiterführung früherer Untersuchungen wurden vergleichende Untersuchungen von Hobel-, Fräs- und Dreheigenschaften nach ANSI/ASTM D 1666-64, sowie die Rißbildung beim Nageln und Schrauben nach Davis (1962) für 43 mexikanische tropische Laubhölzer bestimmt.

Mexican tropical hardwoods — Dimensional stability

In previous articles origin and basic mechanical and physical properties of 43 Mexican hardwoods were described. Here the swelling behaviour of these wood species is pesented: (1) differential swelling (qT, qR), (2) swelling coefficients (hT, hR), (3) sorption coefficient (s) and (4) the time to equilibrate between EMC at 80% RH and 65% RH.ZusammenfassungIn vorangehenden Veröffentlichungen waren Herkunft und grundlegende mechanische und chemische Eigenschaften von 43 mexikanischen Hölzern vorgestellt worden. Hier werden deren Quellungseigenschaften beschrieben. Bestimmt wurden (1) die differentielle Quellung (qT, qR), (2) der Quellungskoeffizient (hT, hR), (3) der Sorptionskoeffizient (s) und (4) die Angleichszeit zwischen den Glichgewichtsfeuchten bei ϕ=80% und ϕ=65%.

Influence of phenolic compounds in heartwood of Silver fir (Abies alba Mill.) on the equilibrium moisture content

Experiments were undertaken to differentiate between sapwood and uncolored (light) heartwood of Silver fir (Abies alba Mill.). Paired samples of sapwood and heartwood were removed from five randomly selected healthy trees without wetwood, aged over 170 years, and (a) the percent of extractives, (b) the amount of total soluble phenols and (c) the equilibrium moisture content (EMC) at three relative humidities (RH) were determined. The percentage of extractives and the amount of total soluble phenols in the heartwood were significantly higher and EMC lower than in the sapwood. The effect of extractives on the EMC was most marked in the upper range of the RH. ZusammenfassungEs wurden Versuche zur Unterscheidung zwischen Splintholz und nicht verfärbtem Kernholz der Weisstanne (Abies alba Mill.) durchgeführt. Aus fünf zufällig ausgewählten, über 170 Jahre alten, gesunden Bäumen ohne Nasskern wurden aus dem Splint- und Kernholz Probenpaare entnommen. Anschliessend wurden (a) der prozentuale Anteil der Extraktstoffe, (b) die Gesamtmenge der löslichen Phenole und (c) die Gleichgewichtsfeuchte (EMC) bei drei verschiedenen relativen Luftfeuchten (RH) bestimmt. Der prozentuale Anteil der Extraktstoffe und die Gesamtmenge der löslichen Phenole waren im Kernholz deutlich höher als im Splintholz, wohingegen die Gleichgewichtsfeuchte niedriger war. Der Einfluss der Extraktstoffe auf die Gleichgewichtsfeuchte war bei höheren relativen Luftfeuchten besonders ausgeprägt.