Table 1. Definitions of thinning treatments in the experiments. In all treatments, the width of the strip road was between 4.0–4.5 m, and the strip roads were pre-marked in the centre of the plot. In selective thinning (Sel) treatments, the areas between strip roads were thinned from below, removing the smallest, poorer and possibly damaged trees. In systematic boom corridor (BCTp, BCTf) treatments, 2.5 m-wide corridors, with 7 m between the machine position, were harvested. In all BCT treatments, the areas between the corridors were left untreated. | |
Treatment | Definition |
Sel1 | Selective thinning, no pre-clearing needed. |
Sel2 | Selective thinning, pre-cleared (i.e., undergrowth hindering harvester work was removed before test cutting). |
BCTp | Completely systematic perpendicular boom corridor thinning, no pre-clearing needed. Corridors 90° from each machine position were harvested. The trees to be removed from the corridors were marked. |
BCTf | Completely systematic fan-shaped boom corridor thinning, no pre-clearing needed. Corridors 30° from each machine position were harvested. The opposite corridors of the machine positions were staggered at 2 m. The trees to be removed from the corridors were marked. |
BCTsemi1 | Semi-selective boom corridor thinning, no pre-clearing needed. In the middle of the plot, the advisory corridor locations on opposite sides of the strip road were marked. The width and distance of the corridors were, on average, the same as in BCTp and BCTf. The operator chose the exact location of the corridors based on the standing trees. The trees to be removed from the corridors were not marked. |
BCTsemi2 | Semi-selective boom corridor thinning, pre-cleared. In the middle of the plot, the advisory corridor locations on opposite sides of the strip road were marked. The width and distance of the corridors were, on average, the same as in BCTp and BCTf. The operator chose the exact location of the corridors based on the standing trees. The trees to be removed from the corridors were not marked. |
BCTsemi3 | Semi-selective boom corridor thinning, no pre-clearing. In the middle of the plot, the advisory corridor locations on opposite sides of the strip road were marked. The width and distance of the corridors were, on average, the same as in BCTp and BCTf. The operator chose the exact location of the corridors based on the standing trees. The trees to be removed from the corridors were not marked. |
BCTsel | Selective boom corridor thinning, no pre-clearing needed. The width and distance of the corridors were, on average, the same as in BCTp and BCTf. The operator independently chose the location of the corridors based on the standing trees. |
Table 2. Tests of thinning treatment effects and estimated marginal means (adjusted by covariate effects) and standard errors (SE) in ANOVA for stand characteristics 4–5 growing seasons after selective thinning (Sel) and boom corridor thinning (BCT) treatments (Eq. 1). Thinning treatments are described in Table 1. Significant treatment effects are shown in bold. | |||||||||||
Experiment | No. of plots | Stand basal area (m2 ha−1) | Volume (m3 ha−1) | Mean diameter (cm) | Mean height (m) | Mean stem volume (dm3) | |||||
Mean | SE | Mean | SE | Mean | SE | Mean | SE | Mean | SE | ||
Seeded pine | |||||||||||
Treatment | F = 0.59 | p = 0.630 | F = 0.52 | p = 0.676 | F = 0.21 | p = 0.891 | F = 1.49 | p = 0.257 | F = 0.58 | p = 0.637 | |
Sel1 | 5 | 15.0a | 0.14 | 109.5a | 1.10 | 16.4a | 0.06 | 14.6a | 0.02 | 138.4a | 1.13 |
BCTp | 5 | 15.0a | 0.11 | 109.1a | 0.83 | 16.3a | 0.06 | 14.6a | 0.02 | 136.4a | 1.10 |
BCTf | 5 | 15.1a | 0.11 | 110.2a | 0.83 | 16.4a | 0.06 | 14.6a | 0.02 | 137.9a | 1.15 |
BCTsemi1 | 5 | 15.2a | 0.12 | 110.5a | 1.00 | 16.4a | 0.06 | 14.6a | 0.02 | 137.5a | 1.11 |
Planted pine | |||||||||||
Treatment | F = 0.65 | p = 0.542 | F = 0.66 | p = 0.537 | F = 0.72 | p = 0.506 | F = 0.81 | p = 0.470 | F = 0.80 | p = 0.474 | |
Sel1 | 5 | 17.8a | 0.30 | 126.3a | 2.38 | 16.9a | 0.22 | 14.4a | 0.07 | 139.7a | 2.71 |
BCTsemi1 | 4 | 17.7a | 0.33 | 125.3a | 2.63 | 16.8a | 0.24 | 14.3a | 0.08 | 136.8a | 2.90 |
BCTsel | 6 | 18.1a | 0.26 | 128.8a | 2.10 | 17.2a | 0.19 | 14.4a | 0.06 | 141.4a | 2.33 |
Planted birch | |||||||||||
Treatment | F = 9.20 | p = 0.021 | F = 3.80 | p = 0.099 | F = 0.26 | p = 0.778 | F = 0.62 | p = 0.575 | F = 0.22 | p = 0.808 | |
Sel2 | 3 | 10.7a | 0.11 | 82.1a | 0.74 | 14.7a | 0.12 | 15.8a | 0.16 | 115.7a | 1.65 |
BCTsemi2 | 3 | 11.1ab | 0.11 | 84.7a | 0.73 | 14.7a | 0.09 | 15.9a | 0.11 | 115.6a | 1.14 |
BCTsemi3 | 3 | 11.4b | 0.11 | 84.6a | 0.74 | 14.9a | 0.11 | 15.7a | 0.15 | 114.5a | 1.40 |
Data for the same experiment marked with different letters are significantly different (p < 0.05) based on the estimated marginal means and post hoc LSD tests after Levene’s test for equal variances. |
Table 3. Tests of thinning treatment and tree location effects and estimated marginal means (adjusted by covariate effects) and standard errors (SE) in mixed model ANOVA for annual increment of diameter (dbh), height and stem volume of trees during 4–5 growing seasons after selective thinning (Sel) and boom corridor thinning (BCT) treatments (Eq. 2). Thinning treatments are described in Table 1. Significant treatment and tree location effects are shown in bold. | |||||||
Experiment | No. of trees | Dbh increment (mm year–1) | Height increment (m year–1) | Volume increment (dm3 year–1) | |||
Mean | SE | Mean | SE | Mean | SE | ||
Seeded pine | |||||||
Treatment | F = 3.29 | p = 0.035 | F = 5.60 | p = 0.003 | F = 3.35 | p = 0.032 | |
Sel1 | 340 | 3.0a | 0.12 | 0.30a | 0.003 | 7.1a | 0.21 |
BCTp | 416 | 2.7a | 0.13 | 0.28bc | 0.004 | 6.7a | 0.23 |
BCTf | 443 | 2.9a | 0.12 | 0.29ac | 0.004 | 7.0a | 0.22 |
BCTsemi1 | 436 | 2.7a | 0.13 | 0.28b | 0.004 | 6.6a | 0.24 |
Tree location | F = 45.54 | p < 0.001 | F = 26.19 | p < 0.001 | F = 41.10 | p < 0.001 | |
0 | 450 | 2.3a | 0.08 | 0.27a | 0.003 | 5.9a | 0.15 |
1 | 173 | 3.0b | 0.13 | 0.29bc | 0.005 | 7.1b | 0.25 |
2 | 729 | 2.7b | 0.07 | 0.28b | 0.002 | 6.6b | 0.13 |
3 | 283 | 3.4c | 0.09 | 0.30c | 0.003 | 7.9c | 0.17 |
Treatment × Location | F = 1.40 | p = 0.201 | F = 1.68 | p = 0.111 | F = 0.99 | p = 0.435 | |
Planted pine | |||||||
Treatment | F = 1.40 | p = 0.278 | F = 3.36 | p = 0.061 | F = 1.02 | p = 0.385 | |
Sel1 | 405 | 4.2a | 0.23 | 0.57a | 0.011 | 11.2a | 0.60 |
BCTsemi1 | 391 | 3.7a | 0.26 | 0.54a | 0.013 | 10.3a | 0.68 |
BCTsel | 555 | 4.2a | 0.21 | 0.57a | 0.010 | 11.4a | 0.55 |
Tree location | F = 20.73 | p < 0.001 | F = 11.85 | p < 0.001 | F = 5.66 | p < 0.001 | |
0 | 451 | 3.7a | 0.15 | 0.54a | 0.008 | 10.3a | 0.43 |
1 | 223 | 4.3b | 0.17 | 0.56b | 0.010 | 11.2ab | 0.52 |
2 | 518 | 3.6a | 0.17 | 0.55ab | 0.008 | 10.4a | 0.45 |
3 | 159 | 4.5b | 0.19 | 0.59c | 0.011 | 12.1b | 0.57 |
Treatment × Location | F = 3.76 | p = 0.005 | F = 0.95 | p = 0.433 | F = 1.02 | p = 0.397 | |
Planted birch | |||||||
Treatment | F = 1.02 | p = 0.394 | F = 0.76 | p = 0.489 | F = 0.25 | p = 0.784 | |
Sel2 | 177 | 4.9a | 0.23 | 0.56a | 0.021 | 10.6a | 0.33 |
BCTsemi2 | 238 | 4.8a | 0.25 | 0.60a | 0.022 | 10.6a | 0.37 |
BCTsemi3 | 259 | 5.3a | 0.24 | 0.56a | 0.022 | 10.6a | 0.35 |
Tree location | F = 9.10 | p < 0.001 | F = 3.28 | p = 0.020 | F = 11.03 | p < 0.001 | |
0 | 153 | 4.4a | 0.20 | 0.54a | 0.019 | 9.4a | 0.33 |
1 | 101 | 5.4bc | 0.25 | 0.59bc | 0.023 | 11.2bc | 0.42 |
2 | 308 | 5.0b | 0.17 | 0.57ab | 0.015 | 10.4b | 0.23 |
3 | 112 | 5.5c | 0.21 | 0.61c | 0.019 | 11.6c | 0.32 |
Treatment × Location | F = 1.88 | p = 0.113 | F = 0.57 | p = 0.682 | F = 0.82 | p = 0.515 | |
Data for the same experiment marked with different letters are significantly different (p < 0.05) based on the estimated marginal means and post hoc LSD tests after Levene’s test for equal variances. Tree location: 0 – not at the edge of the strip road or corridor, 1 – at the edge of the strip road, 2 – at the edge of the corridor, and 3 – at the edge of both the strip road and corridor. |