%0 Research article
%T Variation in knot size of Pinus sylvestris in two initial spacing trials
%A Moberg, Lennart
%D 1999
%J Silva Fennica
%V 33
%N 2
%R doi:10.14214/sf.663
%U https://silvafennica.fi/article/663
%X 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 within-tree levels (such as height and azimuth). However, lack  of replication prevented valid statistical inference as to stand-level  effects.