6 Wood Discoloration

8.2 Tree Wounds and Tree Care 179
8.2.4
Detection of Tree and Wood Damages
Fig.8.10. Discoloration of beech at the
control wound protected with wound
dressing (a) and at the cavity filled with
polyurethane (b) (from Dujesiefken and
Kowol 1991)
To investigate trees with regard to microbial damage, particularly to detect decay,
discolorations, cavities, shakes and generally pathological changes, as well
as to determine wood quality in felled timber, construction wood and woodbased
composites, numerous methods are available. Inspection methods were
described by McCarthy (1988, 1989), Zabel and Morrell (1992), Niemz et al.
(1998), Londsdale (1999), Harris et al. (1999), Unger et al. (2001). Methods
can be classified as destructive, nondestructive, or near-nondestructive. They
reach from technically simple procedures like using increment bore tools to
expensive equipment like computer tomography (Habermehl and Ridder 1993;
Habermehl 1994) as well from subjective visual inspection to objective molecular
techniques. In view of tree care, noninvasive or less destructive methods are
preferable (Niemz et al. 1999; Kaestner and Niemz 2004). Modern techniques
for nondestructive characterization and imaging of wood were reviewed by
Bucur (2003) and comprise ionizing radiation computed tomography, thermal
imaging, microwave imaging, ultrasonic imaging, nuclear magnetic resonance
and neutron imaging. Some methods are preferentially used for trees, others
for lumber, some may be used on the spot, others are pure laboratory tech-
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