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ŠUMARSKI LIST 9-10/2016 str. 61     <-- 61 -->        PDF

with altitude ranging between 250 m and 300 m above the sea level. The average monthly total rainfall for July, June and August in this region was 35.0, 31.6 and 40.7 kg/m², respectively. The study area covered 3000 hectares of a 25 years old plantation of the maritime pine (Pinus pinaster A.). The plantation is harvested in rotation usually for every 25-30 years. Soil types are clay in this region.
Skidding operation was performed by a farm tractor on skid road. During skidding, one end of the load is lifted clear from the ground and set on the back of the tractor while other end is skidded on the skid road. The slope of skid road was changed between 2 and 12 percent and the length of skid road is 280 m. The logging operation was performed by tree-length method where the stems were skidded to the roadside landings by farm tractor after the trees were felled, delimbed and topped at the stump area.
Technical Features of Tractor – Techničke znacajke traktora
Massey Ferguson 285 farm tractor was used in timber extraction. This tractor was used for skidding operation and it’s has back-lift system. During skidding operation, one end of the log was elevated on the back- lift system while other and of log was pulled on the ground (Fig. 2). Tractor was equipped with a cab to protect operator and to minimize noise level. The rear tires were larger than the front tires in width and in diameter. The dimension number of front and rear tires was 12.4-24PR12 and 18.4-30PR14, respectively. The width of the rear and front tires were 30 and 24 cm, respectively and their air pressure was 16 psi. The main technical features of the tractor were shown in Table 1.
Data Collection – Prikupljanje podataka
The total length of skid road was measured as 280 m. The slope of skid road was changed 2-12%. In this plantation area, the average length and diameter of the skidded stems were 16 m and 32 cm, respectively.
There were fourteen cross sections on skid road. On each cross section, soil compaction and rutting were examined and recorded for various numbers of tractor passes (4th, 8th, 12th, 16th and 20th passes) along the skid road (Fig. 3).
Deformation dimensions on skid road were measured with the steel tape and ruler. The distance between cross sections was measured by using measuring wheel. The each cross section shape was measured on the skid road. Then, the shapes of cross section were written in AutoCad program. The soil distribution area was calculated for each cross section. The compaction of soil was measured by a hand penetrometer. In this study, matest proving ring penetrometer was used. The measured depth of this penetrometer is 50 cm. The soil moisture content was measured a hygrometer. The depth of soil moisture content was changed between 0-15 cm. Besides, soil samples were collected on skid road and from forest site by using steel cylinders to investigate changes on soil properties (weight, texture, and pH) on the skid roads and the forest ground. Volume weight, Fine Soil Weight (< 2 mm) and Stone Weight (>2mm) (Gulcur, 1974), Soil text (Karaoz, 1992) and pH (Mc Lean, 1982.) were analyzed. For soil samples didn’t show normal distribution, average values were compared with Mann-Whitney U test in one of the nonparametric methods (Kalıpsız 1981; Ozdamar 2002; Senol 2004).