Rings, growth/annual

For more than 80 years, tree-ring data have been used to make inferences about past climatic variation. In general, the characteristic most often used has been the variations in widths of the annual growth rings. However, during the past decade other properties, such as cell density (measured by x-ray densiometric techniques), relative widths of early and late wood, and isotopic composition of the cellulose have been used to infer past environmental conditions. It is the isotopic composition that is of interest here. 

There is little structure to be seen in jet thou in rare spedmens of rou material it is possible to see the annual growth rings of the original tree, which have been compressed to flat lines. 

Viewed under magnification, it is sometimes possible to see signs of flattened annual growth rings in the wood. 

Experimental load deflection curves (Fig. 3.) illustrate the large difference in crack propagation observed in each case. A difference in stiffness between both bonded specimens is observed and results from either a difference in the bond line quality or from interfacial conditions. For both specimens, adherends were made from the same sample of wood. Both wood substrates contained no apparent defects and had the same longitudinal Young s modulus (14500 MPa). Both also had the same growth characteristics (oven dry specific density, annual growth rings), and as a consequence very close values of transverse and shear modulus adjacent to the bond line. Thus, any difference in stiffness is likely to be due to... 

B. Martin, E.K. Sutherland (1990) Air pollution in the past recorded in width and stable carbon isotope composition of annual growth rings of Douglas-fir. Plant Cell Environ. 13, 839-844... 

Some species have notable differences in penetration between earlywood and latewood bands of the annual growth ring. Latewood cells with thicker walls mean the pit membranes are less likely to aspirate and permeability can remain high. This differential treatability sometimes results in a zebra treatment with alternating bands of treated latewood and untreated earlywood. 

Dendrochronology A dating technique used in archaeology to date old pieces of wood, based on the principle of annual growth rings in trees. 

EARLYWOOD. The portion of the annual growth ring that is formed... 

LATEWOOD. The portion of the annual growth ring that is formed after the earlywood formation has ceased. It is usually denser and stronger mechanically than earlywood. 

Fig. 13.11. Simplified cross-section diagram showing the structure of heartwood (duramen). Definition of grain (G = Lc (mm)) and texture (T = Bf/Lc) Lc, width of an annual growth ring Bi, early or spring wood Bf, late or summer wood (Vivas, 1997)...

In softwoods, the tracheids have considerable pitting in their radial walls. These bordered pits are specialized valves to seal and isolate tracheids if they become damaged or emboli-zed, but remain open for sap flow. At the pit location, the double cell wall takes the shape of the external part of a torus. The external diameter of this torus is in the range 10-20 jm, depending on the position in the annual growth ring (the diameter is smaller in latewood). The torus is suspended by... 

Bonded assemblies are prepared from straight-grained beech (Fagus Sylvat-ica L.) with a density of (700 50) kg/m at (12 1)% moisture content and annual growth rings oriented at 30° to 90° to the surface to be bonded. 

Annual growth ring Growth layer of a tree put on in a single growth year. This includes springwood and summerwood. 

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