Damage to trees and regeneration as a result of motor-manual timber harvesting using equipment aggregated with farm tractors

The research was conducted in thinned pine stands, age class II, where cutting was carried out with chainsaws. Subsequent operations were performed using a NIAB 5−15 and HYPRO 450 delimber−bucker processor and a FRANSG RD 6000 cable winch aggregated with farm tractors. The timber harvesting technology was applied with a cut−to−length system using processors, and with a tree−length system using a cable winch. In the selected stands, nine study plots were established, in which the inventory of stand layers: trees and undercanopy regeneration was carried out twice (before and after felling). Based on the obtained data, the level of damage to trees and regeneration after thinning operations was calculated. In the case of the technology using processors, the level of damage to trees in individual manipulation plots was within the range of 4.3%−8.6% (total 7%), while for the winch technology it was from 3.1% to 5.8% (total 4.5%). As regards regeneration, damage resulting from the harvesting and skidding of timber using processors in individual manipulation plots was at a level of 4.1%−13.5% (total 8.5%) and damage resulting from the harvesting and skidding using a winch cable from 5.8% to 17.0% (total 9%)

Use of heart rate monitor in assessing the net energy expenditure during motor-manual cutting

Energy expenditure during labour constitutes one of the criteria used for assessing the laboriousness of timber harvesting. The major objective of this study was to point out the possibilities of defining work net energy expenditure (NEE) as related to the frequency of heart rate in the field exercise tests by changing posture and varied external work load. The scope of the study was restricted to the work of chainsaw operators performing hard physical labour during late thinning of fir and spruce on the middle mountain (Beskid Makowski, Beskid Śląski). The research involved dynamic work with elements of static load for which the NEE was investigated by means of heart rate as well as respiratory – indirect estimation of oxygen consumption as results of airflow measurement. The advantage of both methods is simplicity of application, the lack of necessity to perform additional analyses as time study and expected medium error. The conducted calculations pointed out to a strong linear correlation, where correlative coefficient was equal to 0.67. The conducted model analysis (including, among others: the normality, autocorrelation of residuals and identification of influential values) has confirmed its validity at the 10% statistical error. The obtained regression coefficient indicates a larger increase in value as compared to the available formulas with acceptable in practice standard error of prediction on 6.05 kJ/min level

Time consumption of log extraction from the stand to the skid trail using the skidder

Skidders are used at two stages of log extraction: when pulling logs to a skid trail and for further semi−suspended log skidding along the trail to a landing. The aim of the study is to characterise the working time structure of a skidder operator performing timber extraction from the stand to the trail, and to develop time−consumption models depending on terrain slope and skidding distance. The research was done in stands situated in central and southern Poland, where late thinning and cutting in areas between tree groups (group clear cut) were performed. The timber was transported to skid trails by means of LKT 82 cable skidders. The timber was pulled to the trail on slopes with inclinations ranging from –30° (up the slope) via 0° (on a flat surface) to 38° (down the slope) at a maximum distance of 70 m. Time study of work cycles was performed and the volume of timber harvested in each package was calculated. Analyses of working time and its time consumption were performed for the operational working time. The measurements covered a total of 269 log extraction cycles with a total duration of over 20 hours. Altogether 752 logs with a total volume of over 520 m3 were extracted. The large share of time was devoted to load attaching and detaching (40%). Quite a large share of log extraction (24%) was associated with the long skidding distances. The time of stretching the collecting rope in the case of skidding up the slope (an average of 60 s) was significantly shorter than in the flat terrain or skidding down the slope (70 s). The average duration of a skidding cycle was also affected by the direction of the slope. Rectilinear relationships were determined between the duration of a skidding cycle and the terrain slope, as well as the skidding distance. The combined effect of these features on the duration of skidding was described. The duration of a skidding cycle was influenced by distance (61% of the general variability) more than the slope (16%). The time consumption of the skidding amounted to ca 12 min/m3. Two homogeneous groups were determined: uphill skidding as well as skidding in flat terrain and downhill. The relationship between the time consumption and the number of logs extracted along with their volume took the form of an exponential regression. The time consumption standard of log extraction performed with the use of a skidder along a skid trail should be supplemented with the time of forming timber packages in the stand and pulling them to the trail, with an additional distinction between the direction of skidding and terrain slope

Efficiency of timber skidding on the slopes

The aim of the study is to characterise the working time structure of an operator of the LKT 82 skidder performing timber skidding on the sloping area, and to develop models of efficiency and time−consumption of the work depending on selected factors characteristic of the described transport process. The research was performed in the Sucha Forest District (S Poland). We considered two treatments: late thinning and felling performed in stands with the dominating share of beech. Logs obtained with chainsaws were initially extracted with horses and laid at the slope road. Later on the additional skidding with skidder tractor was done. Continuous timing of individual operations was performed with the use of a microcomputer equipped with time measurement software (accuracy of 1 second). We also determined skidding distance using a GPS device, the number of extracted logs in the load, and the volume of the logs. The total timing measurements lasted for a total of 70 h 24 min 27 s. During that time, the tractor made 72 cycles, transporting 998 logs with a total volume of 493.3 m3. In the mature stand, the average skidding distance amounted to approximately 1,160 m, a single load consisted of 3−4 logs with a volume of 7.7 m3. The operational efficiency of the skidding was 9.1 m3/h. In the thinning stand, the skidding distance was 1,230 m, the average load consisted of 22 logs with a volume of 5.8 m3. The operational efficiency amounted to 7.8 m3/h, on average. The working time structure was dominated by auxiliary (over 60%) and effective (nearly 30%) times. The obtained regression models of the duration of activities from the group of operational times were characterised by high correlation coefficient (about 0.75 for skidding time and driving without a load). Relatively strong relationships (r > 0.5) were also found between the times of collecting cable pulling and load attachment, and the volume of the extracted loads, and in the case of the times of collecting cable pulling also the type of treatment performed. The regression models for the times of log stacking, pulling the loads up with the winch and detaching them, despite the fact that they were statistically significant, characterised by relatively low correlation coefficients. The relationship between skidding efficiency and skidding distance was also determined (fig.). The duration of skidding cycles was described using the multiple regression with the volume of single loads and the skidding distance as the determinants. The regression models of skidding efficiency and time−consumption of skidding cycles may find practical application in estimating the efficiency of the tasks performed in stands and under conditions similar to those analysed in the present research

The size and nature of damage to the topsoil caused by timber extraction and skidding during early thinning operations in spruce stands

The study concerns the impact of two harvesting technologies – one based on a traditional horse skidding and one using a small MultiFKS winch powered by chainsaw motor on the size and nature of damage to the surface soil layer. The study was conducted in a spruce stand where early thinning was carried out. The total share of soil disturbed during harvesting operations was not large accounting for 2.99% of the cutting area for horse skidding and 1.73% for skidding using a MultiFKS winch. The volume of damage to the topsoil was 8.38 m3/ha and 2.64 m3/ha, respectively. The likelihood of disturbances of the soil layer was 47% for horse skidding and 31% for skidding by means of a winch. Both technologies were character−ized by a similar, ca 5% likelihood of cutting of topsoil to a depth larger than 5 cm. For both technologies the likelihood of soil compaction was significantly lower than soil cutting

Factors affecting the changes in penetration resistance of forest soils during timber harvesting

The objective of the studies was to determine the penetration resistance (cohesion) of soil compacted at timber harvesting in Scots pine stands subjected to late thinning. The scope of the investigations was limited to two technologies – the mechanized one, using a harvester−forwarder machine set, as well as the motor−manual one, employing petrol chainsaws and a farm tractor for forwarding and dragging of felled trees. The analyses were performed in central Poland, in the Staszów Forest District, for two habitats – fresh mixed coniferous forest and fresh mixed deciduous forest. The measurements of soil cohesion were taken with the use of Eijkelkamp 06.15.SA Penetrologger penetrometer along the five measurement lines situated perpendicularly to the main skidding track. The soil penetration resistance was measured in eight spots for every measurement line: in the middle of the left and right wheel−rut, between the wheel−ruts, on the left and right roadside within a distance of 0.5 and 1 m from the wheel−rut edge, and 10 m from the right wheel−rut; the latter location was treated as the reference. The mechanized timber harvesting caused stronger compaction of soil, particularly in wheel−ruts, where the recorded values of soil cohesion exceeded 3 MPa (fig. 1). For the technology with farm tractor for skidding, the greatest soil compaction was also encountered in wheel−ruts, reaching up to 2.5 MPa. With regard to both logging technologies, the analysis of variability in penetration resistance of the top 10−cm soil horizon revealed a statistically significant increase in soil compaction in wheel−ruts when compared with other measuring points along and nearby the skid track (fig. 2). The employed technology of timber harvesting and the degree of soil cohesion in wheel−ruts were proved to be correlated. In respect of the mechanized variant, the mean value of soil penetration resistance in the top 10−cm layer counted up to 2 MPa and was significantly greater than the one in motor−manual technology, where it did not exceed 1.3 MPa. No significant differences in soil compaction in reference to the investigated forest habitats were revealed, though it was stronger in fresh mixed coniferous forest, with regard to both technological variants. The motor−manual technology caused the increase in soil penetration resistance by 2% on the roadside, nearly 20% in the middle of the skid track and over 70% in wheel−ruts. While the mechanized logging operations resulted in 30% increase in soil cohesion on the roadside, 55% between the wheel−ruts and over 250% inside the wheel−ruts (fig. 3)