Effects of Strip Roads in a Pine Tree Stand (Pinus sylvestris L.) on the Diameter Growth and Pith Eccentricity of Trees Growing along Them

Although skid roads are more and more commonly used in Poland, they are still quite often criticised due to a certain loss of wood volume and the impact on edge trees. In this context, the results of the research described in this article can be used as a substantive contribution to discussions about strip roads. Research was carried out in a 42-year-old pine tree stand (Pinus sylvestris L.) in the Notecka Forest, where thinning had been performed and 2.5 and 3.5 m wide strip roads had been cut 10 years before. The analysis comprised two five-year periods recording diameter growth and pith eccentricity in trees growing at the distance zones of 0–1 m (adjacent trees), 2–4 m and 8–10 m (the control) away from the strip roads. The differences in growth and eccentricity between the different distance zones as well as the frequency of pith eccentricity in the N-W, S-W, N-E and S-E directions were assessed, related to the distance from the strip road and the measurement height. The measurements of the analysed traits were conducted on wood discs cut from the centres of two-metre-long sections on sample trees (12 trees in each distance zone). The trees growing directly beside the strip roads were statistically significantly thicker than those growing 8–10 m away, and in the case of the trees beside the narrower strip roads, in the second 5-year period, they were also thicker than the trees from the 2–4 m distance zone. The effect of the wider strip roads in the first growth period was also significant for the trees growing 3 m away from the strip road (their growth in this period was significantly greater than that of trees in the control zone). The research into tree-pith eccentricity showed no differences due to relative distance from the strip road. Furthermore, no statistically significant relationship between the distance of trees from the strip road, measurement height and frequency of tree-pith eccentricity to the N-W and S-W were found.

Investigating the out-of-roundness and pith-off-centre in stems of three broadleaved species in Hyrcanian forests

The out-of-roundness and pith-off-centre of Alnus subcordata, Acer velutinum and Quercus castaneifolia growing in Hyrcanian forests of Iran were investigated. Stem disks were cut from the breast height and stump height of felled trees in diameter classes of 20 cm to 90 cm. Results indicated that the pith eccentricity for Acer velutinum was significantly greater than that of Alnus subcordata and Quercus castaneifolia (P < 0.01). The pith-off-centre significantly increased with increasing stem diameter from 20 cm to 50 cm, while no significant difference were observed for pith-off-centre index from diameter class of 55 cm to 90 cm. The out-of-roundness in stems of Acer velutinum and Alnus subcordata was significantly greater than that of Quercus castaneifolia (P < 0.01). Moreover, out-of-roundness significantly decreased with increasing stem diameters from 20 cm to 45 cm except for 35 cm. There were no significant differences among diameter classes from 60 cm to 85 cm with respect to out-of-roundness. For all the species, the out-of-roundness and pith-off-centre at stump height were greater than those at breast height.

Stem eccentricity, crown dry mass distribution, and longitudinal growth strain of plantation-grown Eucalyptus nitens after thinning

Silvicultural treatments that aim to improve tree growth rates also have the potential to alter physical characteristics of the tree stem and thus affect the recovery of solid-wood products. We tested the hypothesis that manifest crown asymmetry in thinned Eucalyptus nitens (Deane & Maiden) Maiden plantations was affecting the development of stem shape. The crown and stem characteristics of 15 E. nitens trees from a 22-year-old thinning trial in northeastern Tasmania were examined. The trial had been thinned 16 years previously. Lowering the intensity of local intraspecific competition through thinning increased the crown dry mass in the north-facing aspect. No direct link was found between crown dry mass distribution and stem eccentricity. The direction of pith eccentricity at 3.0 m height was confined to the northwest and southeast sectors and averaged 11%; the degree of noncircularity in stems at 3.0 m height was strongly related to the ratio of stem diameter to total height squared. These results suggest that the dynamic loading from wind exposure plays a greater role in determining the extent and direction of pith eccentricity and stem cross-sectional circularity in E. nitens than does the static load from asymmetrical crown dry mass distribution.