Variation in knot size of Pinus sylvestris in two initial spacing trials

Abstract

The objective of this study was to investigate the variation in internal knot size of Scots pine (Pinus sylvestris L.) stems sampled from mature permanent plots, and for which the silvicultural history was known. It was based on a sample of mature trees removed from two different spacing trials representing a moderate and high site index. Knot size was measured with non-destructive methods using a CT-scanner and digital image analysis. Initial spacing varied between 0.75 and 3 m on the high site-index trial and between 1.5 and 2.5 m on the moderate site-index trial. Wider initial spacing on the high site index resulted in larger knots near the base of the stem. However, due to successive thinnings which gradually equalised stand density among plots, the difference between most plots was less further up in the stems. The effect of silvicultural regime was much more limited on the lower site index. Within-stand differentiation resulted in a variation of tree diameter (DBH); larger trees had significantly larger knots. Furthermore, knots were larger towards south than towards north in both trials. These results illustrated that, by using non-destructive measurements on trees sampled from permanent research plots, it was possible to simultaneously study the variation of internal knot size at stand (such as site and silviculture effects), within-stand (such as relative tree size) and withintree levels (such as height and azimuth). However, lack of replication prevented valid statistical inference as to stand-level effects.

Effect of Planting Density on Knot Attributes and Branch Occlusion of Betula alnoides under Natural Pruning in Southern China

“…In the present study, the mean occluded branch diameter decreased significantly with increasing planting density. Similar findings had already been recognized in previous studies not only for OBD in Pinus sylvestris [24] and Picea abies [25] but also for the diameter of dead or live branches in Douglas-fir [35,36], Endospermum medullosum [37] and Eucalyptus pilularis and E. grandis [38]. In addition, high density planting could significantly lower the percentage of large branches as shown in the present study (Table 5).…”

“…Nonetheless, the effects of planting density on branch occlusion and knot attributes have been rarely assessed. Most studies have mainly focused on predicting or comparing the branch occlusion and knot attributes under natural or artificial pruning [18][19][20][21][22], and the relationship between planting density and knot size was only studied for some species, such as Pseudotsuga menziesii, Picea abies and Pinus sylvestris in temperate zones [23][24][25]. There have been no published reports on the effect of planting density on branch occlusion and knot attributes for valuable tropical and subtropical tree species.…”

Predicting maximum branch diameter from crown dimensions, stand characteristics and tree species

“…Previous studies have shown that the largest branches are found above the crown base (Mäkinen et al 2003, Garber and Maguire 2005, Hein et al 2007), suggesting that estimates of current maximum branch diameter provide an approximate upper limit to past maximum branch diameters. Observations of knot diameters along the stem of Scots pine (Moberg 1999) are broadly consistent with this supposition; knot sizes remained more or less constant between the base of the crown and the butt region. To better incorporate product quality into remote sensing-based resource inventory, the next step will be to establish relationships between living branch diameters and branch characteristics below the crown base, and more importantly between crown characteristics and knottiness in the wood products.…”

Predicting knottiness of Pinus sylvestris for use in tree bucking procedures

“…As a result of this distinguished work, it is known that stem branchiness decreases within limits with increasing stand density and that high growth rate, affected greatly by site fertility, increases stem branchiness. Recent Swedish studies have focused on finding appropriate stem characteristics 522 J. Uusitalo & J. Isotalo combined with some stand characteristics in predicting knottiness at a general level (Bjö rklund & Petersson, 1999;Moberg, 1999). There have also been attempts to construct models to predict the shape and characteristics of the dead/sound knot border (Kärkkäinen, 1986;Moberg, 2000) and to link tree growth models to simulated sawing (Samson, 1993;Mäkinen & Song, 2002;Ikonen et al, 2003;Mäkelä & Mäkinen, 2003).…”