Table 1. Three thinning treatments tested at each site, 1) heavy thinning, 2) ordinary thinning and 3) light thinning. Means for tree height (H), stem number (N), basal area (BA) and tree diameter (Dg, tree of mean basal area) refer to the situation prior to thinning.
Site 1 – Järpås
Year Stand age
(yrs) 		Heavy thinning Ordinary thinning Light thinning
H
(m) 		N
(stems ha–1) 		BA
(m2 ha–1) 		Dg
(cm) 		H
(m) 		N
(stems ha–1) 		BA
(m2 ha–1) 		Dg
(cm) 		H
(m) 		N
(stems ha–1) 		BA
(m2 ha–1) 		Dg
(cm)
2002 9 8.9 2433 12.2 8.0 9.0 2429 12.5 8.1 8.7 2407 12.2 8.0
2007 14 15.2 726 10.5 13.6 14.9 1154 14.3 12.6 14.7 1566 17.1 11.8
2012 19 18.7 711 15.3 16.6 18.4 804 15.8 15.8 17.8 990 16.7 14.7
Site 2 – Bökö
2003 10 2053 2103 2138
2008 15 13.5 804 9.9 12.5 12.8 1260 12.2 11.1 12.7 1577 14.5 10.8
2010 17 14.7 804 11.7 13.6 13.9 1260 14.0 11.9 14.4 1106 14.0 12.7
2014 21 16.6 804 15.9 15.7 16.7 809 15.1 15.4 16.4 1106 18.9 14.7

Fig. 1. Illustration of how the knot samples were produced. A vertical cut with a chain saw was directed through the centre of the knot towards the pith (1). A second vertical cut directed towards the pith was made a few cm from the first (2). A third cut released the sample, shaped like a slice of cake. Picture taken from Rytter and Jansson (2009).

Table 2. Description of traits. Illustrations are presented in Fig. 2.
Trait Unit Description
CardP N, E, S, W Cardinal point of the twig. Every twig was designated to one of the four points.
KnAng Degrees (90°) Knot angle from a horizontal line (Fig. 2, no 2)
Radius mm Horizontal distance from pith to trunk surface, excluding the protuberance, (Fig. 2, no 5 in the lower illustration)
Dia mm Tree diameter at 13 dm above ground in autumn 2012 (age 19) at site 1 and 2014 (age 21) at site 2
TwHght cm Height from ground to the twig
KnDia mm Diameter of the knot at the outer end or trunk edge (Fig. 2, no 1)
Dist1 mm Length of new wood with wood defects (Fig. 2, no 3)
Dist2 mm Length of defect-free new wood (Fig. 2, no 4)
Dist3 mm Total length of new wood (Dist1 + Dist2)
BrkUp mm Length of ingrown bark above the knot (cf. BrkLow)
BrkLow mm Length of ingrown bark below the knot (Fig. 2, no 6)
ColIn % Proportion of wood discolouration within the knot (Fig. 2, no A)
ColOut % Proportion of wood discolouration outside the knot (Fig. 2, no B)
RotIn % Proportion of wood rot within the knot (Fig. 2, no A)
RotOut % Proportion of wood rot outside the knot (Fig. 2, no B)

Fig. 2. Example of measurements of traits in pruned (top picture) and unpruned (bottom picture) trees: 1 = vertical knot thickness; 2 = knot angle; 3 = discoloured wood and wood with rot in the horizontal direction; 4 = defect-free wood outside the knot; 5 = distance from pith to knot end; 6 = length of ingrown bark; A = area within the knot from which areas affected by discolouration and rot were estimated as a percentage; B = area between knot end and vertical trunk edge (excluding the protuberance commonly found outside a twig) from which areas affected by discolouration and rot were estimated as a percentage.

Table 3. Number of observations (N), arithmetic means (Mean), standard deviations (Std), minimum (Min) and maximum (Max) values for different traits at each site, based on individual knot/twig data. Description of traits are given in Table 2.
Trait Unit Site = 1 (Järpås) Site = 2 (Bökö)
N Mean Std Min Max N Mean Std Min Max
Dia mm 335 141 20.0 102 179 348 138 18.7 91 273
Radius mm 335 59 8.8 38 84 348 54 7.9 33 73
TwHght cm 335 238 37.0 150 300 348 240 37.8 140 300
KnDia mm 335 12.1 5.8 2 40 348 10.8 6.7 2 55
KnAng ° 335 42 9.1 7 64 348 41 10.2 11 65
Dist1 mm 335 0.9 1.9 0 12 348 0.7 1.7 0 10
Dist2 mm 335 9.1 8.1 0 32 348 6.0 6.8 0 30
Dist3 mm 335 10.1 8.1 0 32 348 6.6 7.2 0 30
BrkUp mm 335 11.1 11.4 0 66 348 18.9 23.6 0 105
BrkLow mm 335 5.3 5.7 0 32 348 6.1 6.9 0 35
ColIn % 335 30 14.7 0 90 348 29 18.2 0 100
ColOut % 335 4.9 12.0 0 90 348 4.0 13.0 0 100
RotIn % 335 7.9 9.5 0 40 348 11.5 11.9 0 100
RotOut % 335 0.0 0.0 0 0 348 0.7 6.4 0 100
Table 4. Statistical results for difference in pruning treatments and least-square means of pruned and unpruned trees for different traits for each site (Eq. 1) and for both sites (Site 1 + 2, Eq. 2). A “x” in the column “Covar” indicates the result when the covariate KnDia was included in Eq. 1 and 2. Bold figures are significant at the 5%-level. Description of traits are given in Table 2. View in new window/tab.
Table 5. Correlations between different traits at site 1. Bold figures are significant at the 5% level. Description of traits are given in Table 2.
Trait KnAng Dist1 Dist2 Dist3 BrkUp BrkLow ColIn ColOut RotIn
KnDia 0.52 0.15 –0.22 –0.18 0.14 0.01 0.24 0.14 0.07
KnAng 0.06 –0.04 –0.03 0.34 –0.11 0.06 0.05 –0.01
Dist1 –0.11 0.13 0.07 0.06 0.13 0.75 0.06
Dist2 0.97 0.03 –0.07 0.22 –0.18 –0.13
Dist3 0.05 –0.05 0.25 0.00 –0.11
BrkUp 0.27 0.11 0.05 0.33
BrkLow 0.04 0.09 0.48
ColIn 0.15 –0.23
ColOut 0.09
Table 6. Correlations between different traits at site 2. Bold figures are significant at the 5% level. Description of traits are given in Table 2.
Trait KnAng Dist1 Dist2 Dist3 BrkUp BrkLow ColIn ColOut RotIn
KnDia 0.40 0.07 –0.09 –0.07 0.13 –0.25 0.05 –0.02 0.09
KnAng –0.02 –0.13 –0.13 0.41 –0.20 –0.12 –0.02 –0.15
Dist1 0.12 0.36 –0.10 0.04 0.08 0.69 0.11
Dist2 0.97 –0.16 –0.09 0.18 0.00 0.02
Dist3 –0.17 –0.07 0.19 0.17 0.04
BrkUp 0.20 0.22 –0.10 0.11
BrkLow 0.42 0.10 0.53
ColIn 0.07 0.64
ColOut 0.09