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TECHNOLOGY 45
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larger dimensions in the highest quality classes. It has been grading.
calculated that larger logs generally entail lower processing In addition to the presence and size of knots in the sawn
costs, potentially resulting in greater earnings per cubic meter. wood, the characteristics of the branches on the standing tree
However, larger dimensions do not always guarantee better can also be linked to the development of anomalous internal

material quality. colouring in the wood.
The height from the crown or the first branch provides More specifically, Wernsdörfer et al. linked the characteristics
an indication of the length of the sawlog free from knots, at of dead branches and branch scars visible on log surfaces to
least externally. the presence of red heartwood in beech, an internal defect
Additionally, slenderness, defined as the ratio of height that decreases the material value, especially aesthetically,
to diameter, has been found to be positively correlated with because it presents itself as an alteration of the wood colour.
the mechanical properties of sawn timber obtained from Damage to trees from abiotic degradation or injuries alters
measured trees. woody tissue, reducing its mechanical properties and aesthetic
Quality classes based on stem sinuosity and straightness appeal. Such alterations significantly impact product value

have been shown to differentiate the value of timber or potential and are typically excluded from merchantable timber, thereby
sawlog recovery; the straighter the stem, the higher the value. reducing yields and revenues.
Stem leaning, on the other end, may be associated with
the presence of reaction wood and cross-sectional eccentricity. Techniques and Tools
Indeed, local tree slope was positively correlated with tension Among the visual characteristics, dimensions (stem diameter,
wood distribution in 10 poplar trees. height, and volume) are the basis of forest inventory surveys
Finally, ovality affects both transformation yields (as generally and will not be addressed in this work. For a comprehensive

do the diametric irregularities of the cross-section) and may review of new technologies like LiDAR applications in evaluating
relate to the presence of eccentric pith and reaction wood. above-ground biomass at the tree scale, see Krok et al. and
The presence and size of knots in the sawn timber result Xu et al. Similar technologies have been utilised to determine
from the number and size of branches in trees. Knots are the height of the crown or first branch.
major defects in solid wood products, affecting aesthetics Furthermore, the usage of smartphone applications for forest
and mechanical properties. inventory has been described and compared by Sandim et al.
Therefore, evaluating branchiness in standing trees is Then, turning to the other visual attributes like stem form,
crucial for defining their quality. However, few studies have branch characteristics, and the presence of damage, those
analysed the correlation between branch attributes in standing can be assessed quantitatively or qualitatively.

trees and the characteristics of sawn timber after processing. Quantitative surveys involve measuring each characteristic
Höwler et al. investigated the relationship between tree
characteristics and the properties of the boards produced Forestry.ie
(performing visual strength grading and mechanical performance
after destructive tests). They mainly focused on wood density,
which showed no correlation with branch number, but they
also noticed only a weak correlation between the number of

branches bigger than 4 cm measured in the standing trees
and the knot size used as a parameter in the visual strength