Relationships Between Wood-Anatomical Features and Resistance Drilling Density in Norway Spruce and European Beech

Abstract

Environmental conditions affect tree-ring width (TRW), wood structure, and, consequently, wood density, which is one of the main wood quality indicators. Although studies on inter- and intra-annual variability in tree-ring features or density exist, studies demonstrating a clear link between wood structure on a cellular level and its effect on wood density on a macroscopic level are rare. Norway spruce with its simple coniferous structure and European beech, a diffuse-porous angiosperm species were selected to analyze these relationships. Increment cores were collected from both species at four sites in Slovenia. In total, 24 European beech and 17 Norway spruce trees were sampled. In addition, resistance drilling measurements were performed just a few centimeters above the increment core sampling. TRW and quantitative wood anatomy measurements were performed on the collected cores. Resistance drilling density values, tree-ring (TRW, earlywood width–EWW, transition-TWW, and latewood width–LWW) and wood-anatomical features (vessel/tracheid area and diameter, cell density, relative conductive area, and cell wall thickness) were then averaged for the first 7 cm of measurements. We observed significant relationships between tree-ring and wood-anatomical features in both spruce and beech. In spruce, the highest correlation values were found between TRW and LWW. In beech, the highest correlations were observed between TRW and cell density. There were no significant relationships between wood-anatomical features and resistance drilling density in beech. However, in spruce, a significant negative correlation was found between resistance drilling density and tangential tracheid diameter, and a positive correlation between resistance drilling density and both TWW + LWW and LWW. Our findings suggest that resistance drilling measurements can be used to evaluate differences in density within and between species, but they should be improved in resolution to be able to detect changes in wood anatomy.

Predicting Wood Density Using Resistance Drilling: The Effect of Varying Feed Speed and RPM

“…However, it is essential to exercise caution when applying these findings, as variations may be species-specific, owing to differences between hardwood and softwood's internal structures. Additional testing is necessary to ensure broader applicability, taking into consideration factors such as wood anatomy [54] and variations in spiral grain [55], and also greater replication within each species. In particular, hardwoods may require further research to fully understand the relationships between basic density and the parameters "a" and "b", due to their more complex internal structures.…”

Non-destructive modeling using a drilling resistance tool to predict wood basic density of standing trees in a eucalypts plantation in North Sumatra, Indonesia

“…Further, Nikolas et al 2020 found that the drilling resistance technique can be useful for assessing silvicultural, genetics, and ecological studies of forest trees. Not only wood density, and other wood properties can also be explored through NDT drilling resistance techniques, such as the anatomical characteristics of grain direction and features of wood (Sharapov et al 2021;Arnič et al 2022). In addition, this technique has reportedly been used to estimate the age of pine, oak, and birch trees (Szewczyk et al 2018), but it was reported that drilling resistance density technique should not be used to replace dendrochronology in climate-tree growth studies (Orozco-Aguilar et al 2018).…”