1

Fig. 1. Schematic of the study design indicating the location of machine operating trails and treatment plots. Grey shaded plots were subjected to quality bucking (OFF) whereas white plots were subjected to automatic bucking (ON).

2

Fig. 2. A. Ponsse Bear single grip-harvester, B. Ponsse H8 harvesting head.

Table 1. Harvesting machine specifications (Ponsse).
Dimensions Minimal and usual weight 23 800 kg; 24 500 kg
Engine Engine output 260 kW (350 hp)
Torque 1400 Nm (1300–1600 rpm)
Traction 230 kN
Boom C6 Slewing torque (gross) 67 kNm
Lifting moment (gross) 310 kNm
Reach 10 m
Harvesting head Ponsse H8 Weight (depending on the equipment) 1250 kg
Maximum felling diameter 800 mm
Feeding speed 5 m/s
Maximum opening of front and rear knives 740 mm / 780 mm

Fig. 3. Flowchart indicating the general steps of the bucking optimization proposal (Uusitalo 2010).

Table 2. Assortments, diameters, and lengths used in the study along with a percentage based price-matrix where the products of highest value were set at 100%.
Assortments Top diameter (without bark) [cm] Length [m] Diameter class (range in cm)
1b 2a 2b 3a 3b 4 5 6
(15–19) (20–24) (25–29) (30–34) (35–39) (40–49) (50–59) (60+)
Pulpwood ≥ 10 2 + 3 68% 68% 68% 68% 68% 68% 68% 68%
Low grade pulpwood ≥ 7 2 + 3 44% 44% 44% 44% 44% 44% 44% 44%
Pallet ≥ 25 3.6 62% 67% 74% 74% 74% 74% 41% 41%
Sawlog ≥ 14 4 + 5 77% 86% 95% 95% 95% 95% 95% 95%
Large diameter sawlog ≥ 40 5 - - - - - 100% 100% 100%
Table 3. Description of work cycle elements.
Work cycle element Start End
Boom-out Boom extending towards tree Harvesting head positioned at base of tree or start of processing motor-manually felled trees
Felling Head is in vertical position and saw is activated Tree crown touches the ground or feed rollers are activated
Processing Feed rollers are activated with stem in harvesting head Tree-top is released
Manipulation1 Other boom tasks
Moving Traction system is activated Traction system is deactivated or other elements, e.g. Boom-out, Manipulation2 dominates
Delay3 Tasks, which could not be allocated to another work cycle element
1 Movements of the boom, which cannot be allocated to the processing element: building a brush-mat, sorting/piling processed logs, etc.
2 Meaning: If the boom moves away from the vehicular-middle while the machine still continues moving, the task “Moving” ends in favor of the task “Boom-out”/”Manipulation”.
3 Interruptions which are not part of the pure working time: repairs, phone calls, influences due to the study, etc. Because of the chosen unit stating the productivity in PMH0, all delays were removed for analysis.
Table 4. Pre-harvest tree inventory data with sample size (number of trees harvested), dbh, height, standing volume per tree, and respective standard error by treatment.
Treatment Operating trail N dbh [cm] Height [m] Single-tree volume [m3 with bark]
Average SE Average SE Average SE
OFF A 10 48.4 a1 3.42 35.5 a 0.58 3.2 ab 0.47
C 50 48.9 a 1.47 33.5 ab 0.67 3.1 a 0.17
G 45 45.2 a 1.52 32.5 b 0.55 2.6 ab 0.19
I 41 43.9 a 1.58 33.3 ab 0.52 2.5 b 0.18
J 27 48.0 a 2.57 31.0 b 0.85 2.8 ab 0.27
ON B 29 48.6 a 1.41 33.9 a 0.46 3.0 a 0.19
D 16 51.9 a 3.04 34.4 a 0.80 3.5 a 0.41
E 34 47.4 a 1.98 33.5 a 0.79 3.0 a 0.24
F 11 43.6 a 2.39 32.7 a 0.66 2.4 a 0.26
H 23 43.0 a 2.27 32.0 a 0.81 2.4 a 0.25
Total
OFF All 173 46.6 a 0.83 32.9 a 0.31 2.8 a 0.01
ON All 113 47.0 a 0.99 33.3 a 0.34 2.9 a 0.12
1 Different lower case letters indicate a statistical difference at α = 5% in means from each attribute (dbh, height, and single-tree volume) between operating trails within a respective treatment based on Fisher’s LSD test.
4

Fig. 4. A. Volume [m3 without bark] by diameter class and treatment, B. Proportion of total volume by treatment and diameter class; all harvested trees with pre-inventory data.

Table 5. Sample size by harvesting system, tree shape, diameter class, and treatment; in brackets volume in m3 without bark.
Diameter class Harvesting system
Fully-mechanized Semi-mechanized
Undamaged Damaged Undamaged Damaged
OFF ON OFF ON OFF ON OFF ON
1b 1 (0.2) 1 (0.2) - - 1 (0.2) 1 (0.1) - -
2a 2 (0.8) - - 1 (0.4) 2 (0.7) - - -
2b 6 (3.5) - - - 1 (0.5) - 1 (0.8) -
3a 3 (2.7) 5 (4.5) - 2 (1.8) 4 (3.3) 5 (4.7) 1 (0.7) 1 (0.8)
3b 12 (16.8) 3 (3.7) 2 (2.7) - 5 (6.6) 7 (7.4) 1 (1.1) 1 (1.3)
4 26 (43.5) 12 (20.6) 11 (16.6) 6 (10.2) 14 (24.2) 11 (18.6) 8 (13.9) 8 (13.3)
5 23 (56.2) 13 (28.9) 7 (16.2) 3 (8.0) 10 (24.4) 15 (35.4) 12 (29.4) 5 (13.7)
6 8 (26.8) 4 (12.2) 4 (12.4) 1 (3.2) 6 (21.5) 5 (14.9) 1 (2.9) 1 (3.0)
7 - 1 (3.5) - - 1 (4.0) 1 (3.7) - -
Total 81 (150.4) 39 (73.5) 24 (47.9) 13 (23.6) 44 (85.3) 45 (84.7) 24 (48.8) 16 (32.1)
Average single-tree volume 1.9 a1 1.9 a 2.0 a 1.8 a 1.9 a 1.9 a 2.0 a 2.0 a
Relative product recovery 72% a 68% a 65% b 70% a 68% ab 66% a 70% ab 69% a
1 Different lower case letters indicate a statistical difference at α = 5% in means between treatments (OFF and ON) within a respective attribute based on Fisher’s LSD test.
Table 6. Relative product recovery by harvesting system, tree shape, and treatment.
Harvesting
system 		Treatment
OFF ON
Fully-mechanized 71% a1 69% a
Semi-mechanized 69% a 67% a
Undamaged 71% a 67% b
Damaged 68% a 69% a
Total 70% a 68% a
1 Different lower case letters indicate a statistical difference at α = 5% in means between treatments (OFF and ON) within a respective attribute based on Fisher’s LSD test.
Table 7. Volume in m3 without bark by harvesting system, tree shape, assortment, and treatment; in brackets is the relative frequency expressed in percentage.
Assortment Harvesting system
Fully-mechanized Semi-mechanized
Undamaged Damaged Undamaged Damaged
OFF ON OFF ON OFF ON OFF ON
Large diameter sawlog 5.5 (4) 2.0 (3) 0.9 (2) 0.7 (3) 7.2 (8) 1.1 (1) 1.8 (4) 0.9 (3)
Sawlog-5.0 m 115.3 (77) 27.7 (38) 37.2 (78) 8.9 (38) 63.4 (74) 32.9 (39) 37.5 (77) 12.0 (37)
Sawlog-4.0 m 1.6 (1) 39.4 (54) 1.0 (2) 12.5 (53) 3.5 (4) 45.7 (54) 2.6 (5) 16.3 (51)
Pallet 20.1 (13) 1.6 (2) 6.6 (14) 0.6 (3) 7.7 (9) 2.7 (3) 4.1 (8) 2.2 (7)
Low-grade pulpwood
2–3 m 		6.2 (4) 1.4 (2) 2.0 (4) 0.3 (1) 2.2 (3) 1.1 (1) 1.7 (3) 0.5 (1)
Pulpwood 2–3 m 1.7 (1) 1.4 (2) 0.2 (0) 0.6 (2) 1.4 (2) 1.0 (1) 1.2 (2) 0.3 (1)
Total 150.4 (100) 73.5 (100) 47.9 (100) 23.6 (100) 85.3 (100) 84.7 (100) 48.8 (100) 32.1 (100)
Table 8. Harvesting productivity [m3 PMH0–1] by harvesting system and treatment; harvested trees with pre-inventory data.
Harvesting system Treatment N Average single-tree volume
[m3 without bark] 		Harvesting productivity [m3 PMH0–1] SE
Fully-mechanized-undamaged OFF 106 1.8 a1 43.3 a 1.4
ON 54 1.8 a 50.3 b 2.1
Fully-mechanized-damaged OFF 29 1.9 a 45.9 a 1.8
ON 14 1.8 a 48.6 a 3.9
Semi-mechanized-undamaged OFF 92 1.8 a 53.9 a 2.1
ON 76 1.7 a 60.6 a 3.0
Semi-mechanized-damaged OFF 39 2.1 a 58.3 a 2.7
ON 25 1.9 a 54.9 a 2.9
Fully-mechanized OFF 135 1.8 a 43.9 a 1.2
ON 68 1.8 a 50.0 b 1.9
Semi-mechanized OFF 131 1.9 a 55.2 a 1.7
ON 101 1.7 a 59.1 a 2.4
Undamaged OFF 198 1.8 a 48.0 a 1.2
ON 130 1.7 a 56.0 b 1.9
Damaged OFF 68 2.0 a 52.9 a 1.9
ON 39 1.8 a 52.6 a 2.3
Total OFF 266 1.9 a 49.2 a 1.0
ON 169 1.7 a 55.3 b 1.6
1 Different lower case letters indicate a statistical difference at α = 5% in means between treatments (OFF and ON) within a respective attribute based on Fisher’s LSD test.

Fig. 5. Harvesting productivity [m3 PMH0–1] in function of single-tree volume: A. “total”, B. “fully-mechanized”, C. “semi-mechanized”; harvested trees with time and motion data.

6

Fig. 6. Harvesting productivity [m3 PMH0–1] in function of tree dbh for all harvested trees with pre-harvest inventory data.

Table 9. Mean revenue [€/m3] per harvesting system, shape, treatment, and diameter class; harvested trees with pre-inventory data.
Harvesting system
Fully-mechanized Semi-mechanized
Undamaged Damaged Undamaged Damaged
OFF ON OFF ON OFF ON OFF ON
Diameter class 1b 63.7 € 67.4 € - - 79.6 € 69.6 € -
2a 73.9 € - - 81.6 € 79.4 € - -
2b 78.5 € - - - 79.5 € - 91.3 € -
3a 91.3 € 97.0 € - 99.4 € 96.8 € 94.3 € 97.4 € 95.9 €
3b 96.1 € 99.1 € 102.8 € - 94.7 € 99.1 € 95.6 € 98.1 €
4 96.4 € 101.0 € 95.9 € 101.8 € 99.5 € 102.0 € 96.4 € 101.0 €
5 98.6 € 102.8 € 102.2 € 100.2 € 101.1 € 102.6 € 100.7 € 100.6 €
6 102.9 € 101.4 € 93.5 € 96.2 € 100.6 € 101.6 € 106.5 € 93.4 €
7 - 95.2 € - - 91.4 € 96.3 € -
Ø 95.1 € a1 100.0 € a 97.9 € a 99.1 € a 97.2 € a 100.0 € a 98.8 € a 99.9 € a
1 Different lower case letters indicate a statistical difference at α = 5% in means between treatments (OFF and ON) based on Fisher’s LSD test.
Table 10. Mean revenue [€/m3] per harvesting system, tree shape, and treatment; harvested trees with pre-inventory data.
Harvesting system Treatment Difference Proportional difference to revenue treatment OFF (%)
OFF ON
Fully-mechanized 95.8 €/m3 a1 99.7 €/m3 b +4.0 €/m3 4
Semi-mechanized 97.8 €/m3 a 100.0 €/m3 a +2.2 €/m3 2
Undamaged 95.9 €/m3 a 100.0 €/m3 b +4.1 €/m3 4
Damaged 98.3 €/m3 a 99.5 €/m3 a +1.2 €/m3 1
Total 96.6 €/m3 a 99.9 €/m3 b +3.3 €/m3 3
1 Different lower case letters indicate a statistical difference at α = 5% in means between treatments (OFF and ON) within a respective attribute based on Fisher’s LSD test.