The influence of wind on spiral grain formation in conifer trees

Abstract

The correlation between spiral grain formation and crown asymmetry was investigated in 18 Scots pine (Pinus sylvestris L.) and 17 Norway spruce [Picea abies (L.) Karst.] trees selected from clones of each species growing in the south of Sweden. The angle between the longitudinal direction of the tracheids in the outermost year ring compared to the longitudinal direction of the stem was measured by scribing lines which followed the direction of the tracheids. The crown asymmetry was measured by taking photographs of the trees followed by a simple picture analysis of the tree. Wind data for the growing seasons of 1997 and 1998 were obtained from the Swedish Meteorological and Hydrological Institute. The results showed a significant correlation between the angle of the tracheids compared to the stem longitudinal direction going from a left-handed angle if the trees had a crown projected to the north towards a right-handed angle the more the crown projects to the south.

Spiral and interlocking grain in Eucalyptus dunnii

“…Conversely, trees with a north-easterly eccentricity tend to have spiral grain that is less negative. Kucera (1997, 1998) and Eklund and Säll (2000) argued that the direction of spiral grain can be attributed to the torsion effect of the prevailing wind, but this view was not supported in the present study. At Boambee, light winds (7-30 km/ha, 32% of the time year-round) tend to come from the southwest quarter, but strong winds tend to come from the north-east (>30km/hr, 15% of afternoons during September-February).…”

“…As crown asymmetry may be correlated with spiral grain Kucera 1997, 1998;Eklund and Säll 2000), we used existing measurements of crown width in each of the cardinal directions (N, E, S, W) to derive two estimates of crown asymmetry, the horizontal displacement and orientation of the crown centroid relative to the stump.…”

“…Pape (1999) reported a similar pattern for Norway spruce, but noted that the formation of spiral grain appeared to be under genetic control, while the expression of spiral grain could be influenced by silviculture and growth rate. These widely-held views were challenged recently by Kucera (1997, 1998) and Eklund and Säll (2000) who argued that spiral grain formed in response to wind torque, and that the direction of the spirals depended on crown asymmetry and prevailing winds. Cown et al (1991) found that measurements of spiral grain taken from individual rings did not provide a reliable indication of whole-tree values.…”

Evaluation of heat balance and heat dissipation methods for sapflow measurements in pine and spruce

“…Ideally, the systems should have been installed close to each other in the same segment of the xylem, to ensure that they were measuring exactly the same sapflow. However, this is not possible, because the systems would affect each other in an unpredictable fashion, and if the vertical distance is increased, the presence of spiral grain must also be considered [15,48]. It was therefore decided to install the systems using standard set-ups at different heights.…”

Modelling spiral grain angle variation in New Zealand-grown radiata pine

“…approximately 7.3 % of the total variation), it is still considered worthwhile to investigate this further as previous studies have shown that SGA may be affected by exposure to wind (Eklund and Säll 2000;Fonweban et al 2013). Other site factors, such as soil type, temperature and rainfall distribution may also contribute and these vary widely across New Zealand, are strong determinants of stand productivity (Watt et al 2010) and have also been shown to affect other wood properties, most notably density (Palmer et al 2013).…”