Non-Destructive Evaluation of Downy and Silver Birch Wood Quality and Stem Features from a Progeny Trial in Southern Sweden

Abstract

This study investigated whether improved downy birch could perform as well as improved silver birch, and whether there was sufficient genetic variation and control for non-destructive testing (NDT) values to include them as selection traits in breeding programs. NDT tools were applied to a 15-year-old downy birch family trial intermixed with improved silver birch. Average diameters, fissured bark height, and grain angle were higher for silver than downy birch. The genetic analysis for downy birch provided estimates of narrow-sense heritability (h2) for acoustic velocity and Pilodyn penetration depth that were above 0.3 but had low genetic variation. Grain angle had relatively high genetic variability (18%) and an h2 of 0.20. A subsample of 49 trees had 4 mm cores x-rayed for wood density estimates, and 34 stems had 12 mm cores macerated for cell measurements. t-tests revealed that average wood density and cell measurements were not significantly different between species. For silver and downy birch, fiber length and vessel length increased between inner and outer measurement positions, and fiber length was reasonably correlated with acoustic velocity. Silver birch tended to have denser and stiffer wood, while downy birch had less rough bark and straighter grain, and these results are in agreement with existing knowledge. The h2 values were similar to those observed in other birch species and indicate there is potential to breed for improved wood density and grain angle in downy birch.

Evaluation of Mechanical Wood Properties of Silver Birch (Betula pendula L. Roth.) of Half-Sib Genetic Families

“…This study showed a negative correlation between MOEdyn calculated by acoustic velocity and wood-density values, with a log of (r = −0.20) and a sample hardness of (r = −0.25). Correlation in both Sweden studies showed a moderate relationship between wood hardness and wood density [10,11]. Similar trends were found in this study of Lithuanian genetic trials.…”

“…These differences may be due to different tree ages and specific growing conditions. Another study in Sweden showed similar mean woodhardness parameters to this study (17.4 mm) for standing trees obtained with a Pilodyn instrument for silver birch [11].…”

“…The genetic progeny test plots showed a wide range of wood-density parameters, as shown in the Swedish studies, where the average wood-density values ranged from 408 to 444 kg/m 3 [10,11]. The wood density determined during the genetic studies in Sweden was 21%-28% lower than the data from the genetic research in Lithuania.…”

“…The Jones et al [10] study found a positive, relatively weak relationship, with r values of 0.09 and 0.16. Later studies by Jones et al [11] showed a negative correlation between acoustic velocity and wood hardness (r = −0.18). This study showed a negative correlation between MOEdyn calculated by acoustic velocity and wood-density values, with a log of (r = −0.20) and a sample hardness of (r = −0.25).…”

“…The studies in Sweden analysed wood quality for the genetic trials of silver birch [10,11]. Other studies focused on wood quality distribution by site conditions [12,13].…”