PRODUCTIVITY OF HARVESTERS IN COMMERCIAL THINNINGS IN THE FOREST STANDS OF DIFFERENT COMPOSITION OF SPECIES

Transcription

1 FORESTRY AND WOOD PROCESSING PRODUCTIVITY OF HARVESTERS IN COMMERCIAL THINNINGS IN THE FOREST STANDS OF DIFFERENT Latvia University of Agriculture Abstract The aim of the study is to ascertain how different compositions of stand species affect the work of the harvester in commercial thinning under Latvia s conditions. The data of the harvester time-tracking files (*.drf) have been used as a basis for the study, where productivity is expressed as the prepared amount of round timber in cubic meters in a unit of time an hour (m 3 h -1 ). The data were collected from 100 commercial thinning areas which were divided into three types depending on the composition of the species: pure pine stands, pure spruce stands and deciduous tree mixed stands (mixed with coniferous trees). All the data for the study were collected in the forests managed by JSC Latvia`s State Forests. By summarizing the data, it has been established that in pure pine stands the average volume of the stem to be removed is m 3, in mixed stands m 3 and in pure spruce stands m 3. The research demonstrates that the harvester showed its highest productivity while working in pure pine stands 3.96 m 3 h -1, the second best result was achieved in the mixed stands 3.67 m 3 h -1, but the lowest rate was demonstrated in pure spruce stands 3.09 m 3 h -1. Significant differences were observed in the productivity of the harvester between pure pine and pure spruce stands. Comparing the calculations of standard deviations in the harvester productivity, it can be seen that they are the biggest in mixed stands, while the lowest rate is demonstrated in pure spruce stands. Key words: thinning, harvester productivity, different composition of species. Introduction Forestry plays as important a role in Latvia s economy as other business sectors do, thus, one of its objectives is to produce high quality wood at the lowest possible costs in compliance with Latvian rules and regulations. In parallel with the introduction of machine operated processes in logging, this research into the productivity of logging machines is being carried out. If in final fellings the machine operated technologies are an effective and quick solution to deal with trees that are planned to be cut and moved in difficult driving conditions, in commercial thinnings a significant aspect emerges after felling the residual stand should be healthy and perspective, excluding the damages of remaining tree roots and surface parts, thus reaching the optimum of the target stand (Розинь, 1978; Савельев, 1989). Regardless of the afore mentioned, one of the most important economic characteristics also in machine operated logging is harvester work productivity. According to the definition, the work productivity is a parameter showing the amount of products produced in a given amount of time. The productivity of a harvester is generally measured as the amount of the product roundwood processed in an hour (m 3 h -1 ). The work productivity of a harvester in commercial thinnings is influenced by various factors. Summarizing the findings of several forestry scientists, these factors can be divided into 3 big groups: 1) forestry factors; 2) technical factors; 3) operator s factors. It can be concluded from the afore mentioned that the productivity of a harvester in commercial thinnings is a complicated multifactor parameter. Most of the research pertaining to the use of machinery in timber harvesting shows that the forestry factors which are influential are mainly derived from the parameters of forest stand evaluation: average volume of the stem of the tree to be cut; composition of tree species in the stand; stand density; type of forest growth conditions (gound stability, mutual location of trees); shape of the tree stem to be cut. Most thoroughly the relationship between the average stem volume of the trees to be cut and logging productivity has been analysed. The parameters of work productivity for practically all the machinery used in logging correlate closely with the average volume of the tree stem (m³). This relationship was also studied by a group of scientists from the Latvian State Forest Research Institute Silava, stating that with an increase in the average volume of the tree stem, the productivity of the harvester increases. This relationship has also been proved by a lot of research in Nordic countries (Brunberg, 1997; Brunberg et al., 2007; Eliasson, 1998; Lageson, 1997; Siren and Aaltio, 2003), and in North America (Kellog and Bettinger, 1994; Landford and Stokes, 1995, 1996; Pulkki, 2003). Modern harvesters are so efficient that processing of a big tree takes a little longer time than processing of a small sized tree. That inevitably leads to the increase in work productivity, although the relationship is not linear. At a definite stem volume the work productivity of the respective harvester starts decreasing again (Lageson, 1997). At this moment 76 RESEARCH FOR RURAL DEVELOPMENT 2014, VOLUME 2

2 PRODUCTIVITY OF HARVESTERS IN COMMERCIAL the tree dimensions are too big for a definite logging machine. The tree species as a factor influencing the productivity of a harvester in commercial thinnings has been studied only partly. Some specialists acknowledge that the work in coniferous stands presents fewer problems than that in deciduous and mixed composition stands. Thus, it has been acknowledged that the harvester productivity in coniferous stands is higher than under similar conditions in deciduous stands. For commercial thinnings it is important to establish a target stand model which would depend on the composition of species in the stand. The more complicated the composition of tree species in the stand before thinning, the faster the decline in the productivity of the machinery used, when compared to pure stands (Uusitalo, 2004). Taking into consideration the above mentioned, the aim of the research was set: to compare the harvester s work productivity in commercial thinnings in the stands of different composition of tree species. Materials and Methods Harvester productivity depending on the characteristics of the stand was analysed using harvester s operation time recording files (*.drf). They were automatically created and accummulated in each harvester s computer individually for each fellig site, and they store information on the active operation time and idle time, and also the information about the average volume of roundwood in m³ has been processed in a certain unit of time in an hour (m 3 h -1 ) in each felling site, distributed per operator, etc. For this research the harvester s operation time recording files were obtained from the data archive servers of JSC Latvijas valsts meži. At first, the machine thinned stands were selected and assessed from the data base. To exclude the regional, operator s harvesting companies and harvester s characteristics, the harvested stands were selected uniformely located over the entire territory of Latvia. It was assumed that in this research it was necessary to analyse the productivity of work by using the data from about 100 commercial thinning sites. These thinned stands were selected so that their area would not be smaller than 2.0 ha. Afterwards, these machine operated thinned stands were divided according to their composition of species. The commercial thinning areas in which, according to the distribution by compartments, the dominant species and forest types differed, were excluded (wet and swamp forest types). In the researched sites the three most popular commercial thinning harvester make and models used in Latvia were: JohnDeere 1070, Ponsse Beaver and Valmet The information about the researched felling sites is summarised in Table 1. Characteristics of thinning sites Table 1 Forest district Forest block Compartment (s) Area, ha Species composition Harvester brand, model Aknīstes 37 12; E1B John Deere 1070 Žīguru E1B John Deere 1070 Krīvukalna E John Deere 1070 Misas E1B Ponsse Beaver Aknīstes E1B Valmet Zilokalnu ; E1B John Deere 1070 Pededzes 522 6;9; E1B John Deere 1070 Madonas 4 4;5;7; E1B Valmet Limbažu 45 4; E1B John Deere 1070 Aknīstes E Valmet Lubānas E1B John Deere 1070 Piebalgas ; E1B John Deere 1070 Vecumnieku E John Deere 1070 Ludzas 196 2;13;18; E John Deere 1070 Lejasciema E1B John Deere 1070 Apriķu E1B John Deere 1070 Madonas E1B Valmet Limbažu 134 2; E1B John Deere 1070 Silvas E1B John Deere 1070 RESEARCH FOR RURAL DEVELOPMENT 2014, VOLUME 2 77

3 PRODUCTIVITY OF HARVESTERS IN COMMERCIAL Forest district Forest block Compartment (s) Area, ha Species composition Harvester brand, model Žīguru 315 9;10; E1B John Deere 1070 Mālupes E John Deere 1070 Pededzes E1B John Deere 1070 Aknīstes E1B Valmet Skaistkalnes E1B John Deere 1070 Pededzes 150 6;7;8;9 9 10E John Deere 1070 Piejūras 344 9;14; E1B John Deere 1070 Salacgrīvas E1B John Deere 1070 Ogres ; E John Deere 1070 Krīvukalna E John Deere 1070 Aknīstes ; E Valmet Lejasciema ;16 3 9E1B John Deere 1070 Valmieras 38 5; E John Deere 1070 Pededzes 482 5; E1B John Deere 1070 Sikšņu E John Deere 1070 Rēzeknes 100 7;8;9; B2M2E1A Ponsse Beaver Melnupes 146 7; Os3E2B1Ba1A John Deere 1070 Engures ; B2E2L Ponsse Beaver Mālupes B3A2E John Deere 1070 Krīvukalna A4B1Ba John Deere 1070 Vēru 208 9;10;11; B2P1E1Ba John Deere 1070 Rendas 336 1;5;6;13; B2M1P1E Ponsse Beaver Balvu B4A1E John Deere 1070 Ābeļu 106 3; B3A1E John Deere 1070 Balvu 57 9;10; B4A2E John Deere 1070 Pededzes B2E1A John Deere 1070 Rūjienas 285 1;3;5; Ba3E3B1A John Deere 1070 Lubānas 582 2; A3Ba2B Valmet Venemas B2E1M1A John Deere 1070 Limbažu B3Ba2M1E John Deere 1070 Pededzes 181 1;2; B3L2M John Deere 1070 Rendas ; B3M1Ba Ponsse Beaver Lejasciema ;15;16;17; B2E1M1A John Deere 1070 Balvu 160 2;6;8;9; B2P2A1E1M John Deere 1070 Limbažu Ba3M2E1B1Os John Deere 1070 Sikšņu 29 1; A4B1W John Deere 1070 Ābeļu 161 5; B3A3E John Deere 1070 Mālupes ;23;24;29; B2A2M1E1P John Deere 1070 Engures ;15; A3B3P1E Ponsse Beaver Rendas B2A1E1P Ponsse Beaver Limbažu B2M2E2A John Deere 1070 Lejasciema ;28; B3A2P1E John Deere 1070 Ropažu 309 3; B2M1A1E John Deere 1070 Kokneses 232 1;3;7;8; B3E1M John Deere 1070 Mālupes B4A2L John Deere 1070 Sventenes 36 13; B2E2P1M John Deere 1070 Ogres L3A2Ba2B John Deere 1070 Kokneses ; B3E1M John Deere 1070 Lejasciema 116 4;5; A4B2E Ponsse Beaver Ventas 376 2;3;4;5;6;7;8;9; 8.4 9P1E Ponsse Beaver Ventas 374 1;2;3;4;5;6;10; P1E John Deere RESEARCH FOR RURAL DEVELOPMENT 2014, VOLUME 2

4 PRODUCTIVITY OF HARVESTERS IN COMMERCIAL Forest district Forest block Compartment (s) Area, ha Species composition Harvester brand, model Silvas 20 3; P1E John Deere 1070 Skaistkalnes 203 3; P1E Ponsse Beaver Engures P John Deere 1070 Jaunjelgavas 61 14; P1B Ponsse Beaver Ventas 31 17;18; P1B Ponsse Beaver Usmas 129 1; P1E John Deere 1070 Lejasciema ;30;31;32;34; P1E John Deere 1070 Rendas 415 5;6;7; P John Deere 1070 Grobiņas P1B John Deere 1070 Strenču 449 8;16;17;18; P1B Ponsse Beaver Ventas ; P John Deere 1070 Lejasciema P1E John Deere 1070 Lubānas P1B Ponsse Beaver Rendas ;14; P1E John Deere 1070 Alsungas P1E John Deere 1070 Sikšņu P1E John Deere 1070 Balvu 78 17;18; P John Deere 1070 Jaunjelgavas 41 10; P1B John Deere 1070 Pededzes 608 2;12;13;15; P1E Ponsse Beaver Rendas P1E John Deere 1070 Grīņu ; P1E John Deere 1070 Alsungas 382 7;9 2 9P1E Valmet Balvu P1B John Deere 1070 Ērģemes P1E John Deere 1070 Ugāles P1E Ponsse Beaver Jaunjelgavas 161 2;3; P1E John Deere 1070 Ventas P1E Ponsse Beaver Alsungas 132 4;5; P1E Ponsse Beaver Birzgales P1E John Deere 1070 Ventas P1E John Deere 1070 Bauskas P1E John Deere 1070 Krāslavas P1B John Deere 1070 Ventas ;14;15; P1E Ponsse Beaver Explanations: P pine, E spruce, B birch, A aspen, L - lime, M black alder, Ba grey alder. As the number of limiting criteria is big, the selected felling sites were divided in three types by the composition of species: 1) pure pine stands (dominant species pine making up at least 80%); 2) pure spruce stands (dominant species spruce making up at least 80%); 3) mixed deciduous stands (dominant species deciduous trees making up 51 70%). Afterwards, harvester operation time recording files were found for the selected felling sites. These files were opened using the software programme Silvia. The information obtained from these files was summarized, using the average harvester productivity of the felling sites (m 3 h -1 ) and the average volume of the tree stems (m 3 ) to be removed as the basis, not taking into consideration the idle time of the harvester, distribution by operators, etc. Then the data were entered into the software programme SPSS 17 where they were statistically processed. For statistical processing the one-way Anova analysis and the T-test were used. The Anova analysis was used to find whether the difference in harvester productivity with regard to the composition of species in the stand is or is not significant. The T-test was used to calculate the credibility interval and to show it in a graphical way. Results and Discussion The results of the Anova analysis are summarized in Table 2. RESEARCH FOR RURAL DEVELOPMENT 2014, VOLUME 2 79

5 PRODUCTIVITY OF HARVESTERS IN COMMERCIAL The comparison of the productivity of a harvester (m 3 h -1 ) in stands of different composition (Anova analysis) Table 2 Groups Count Sum Average Variance Std. Deviations Pure pine stands Pure spruce stands Mixed deciduous stands Source of Variations SS df MS F P-value F crit Between Groups Within Groups Total Harvester productivity (m 3 h -1 ) comparison in stands of different composition (T-test) Table 3 Type of Stand t df Average 95% confidence interval highest lowest Pure pine stands Pure spruce stands Mixed deciduous stands By comparing the standard deviations in Table 2, it is evident that they are the highest in deciduous mixed forest stands. It means that when thinning different deciduous mixed stands, the parameters of the harvester productivity can be within a wide range, whereas in pure spruce stands the standard deviations are the smallest. It could be difficult for the loggers to predict how productive the work will be in each felling site of a mixed stand, whereas in pure spruce stands there should be no great surprises in this respect. Viewing the second part of Table 2, it can be seen that the actual Fischer s value is greater than the critical Fischer s value (F = > Fcrit = 3.088). That means that the zero hypothesis can be rejected with a 95% possibility that the harvester s productivity is identical in all groups of forest stands. The same can be concluded when observing the P-value < 0.05, thus we reject the zero hypothesis with the probability of 95%. Comparing the grading classes, it was stated that there were significant differences in harvester s productivity between pure pine and pure spruce stands (Table 2). In Figure 1, the credibility intervals calculated by the T- test can also be seen. The credibility interval of mixed deciduous stands coincides with that of pure spruce and pine stands, which means that when the harvester operates in mixed deciduous stands, its productivity does not differ significantly from the productivity in pure coniferous stands. Figure 1 shows that the highest harvester productivity is in pure pine stands, the second highest is for the harvester operating in mixed deciduous stands, but the lowest in pure spruce stands. A peculiar situation in Latvian state forests can be observed with regard to deciduous tree stands. In Latvia, there are comparatively few deciduous trees in pure stands of average age. They are mostly mixed stands of different combinations. These mixed stands are often located in wet areas, in fertile soils with a great diversity of species. The situation with pure coniferous stands in Latvia s forests is as interesting as with deciduous stands. They have a specific historical origin, development and age structure. Today the pure spruce stands of Latvia which are to be commercially thinned are the artificially regenerated stands of the 70s and 80s of the last century. The ensured planting intensity there was 8 10 thousand plants per hectare. Commercial thinning of young stands was also not carried out intensively enough, since the goal at that time was to grow dense spruce stands (Epalts, 2005). 80 RESEARCH FOR RURAL DEVELOPMENT 2014, VOLUME 2

6 PRODUCTIVITY OF HARVESTERS IN COMMERCIAL Figure 1. Harvester productivity depending on the composition of the stand s species. Thus, when the stands reach the age when commercial thinning is to be carried out, they in most cases are very dense. It influences the harvester productivity in Latvia s conditions comparing spruce stands with pine and deciduous tree stands. The forest type as a factor influencing the productivity of logging machines is most often associated with the bearing capacity of the soil. Some authors (Epalts, 2002) consider that this factor can significantly influence the productivity of the machinery; however, it largerly depends on the season and climatic conditions; thus, this factor will not always be significant. The shape of the tree stem also significantly influences the productivity of the machinery, but there is no uniformed conclusion on that. Several researches acknowledge that the shape of the stem influences debranching and the end result of the assortments of the commercial timber (Uusitalo, 2004). In this research when selecting data from 100 felling sites, which are uniformly scattered throughout the entire territory of Latvia, the peculiarities of the shapes of tree stem should not influence the results of the research. Some researchers record the density of the stand (the number of trees per ha) before and after carrying out the commercial thinning as a significant forestry factor influencing the productivity of machinery, but this factor is closely associated with technical specifications of the machinery used - the size of the machine, linear sizes of operational units, etc. (Савельев, 1989). The influence of these factors has not yet been fully researched and the influence should not be present on the results of this research, since similar thinning harvesters with almost identical parameters were used in this research. Conclusions 1. The highest harvester productivity implementing commercial thinning was recorded in pure pine stands 3.96 m 3 h -1 at the average removable tree stem volume of m 3. The second highest work productivity was recorded in mixed species stands 3.67 m 3 h -1 at the average removable stem volume of m 3 and the lowest in pure spruce stands 3.09 m 3 h -1 at the average removable stem volume of m Comparing the grading classes, significant diferences in harvester productivity were found between pure pine and pure spruce stands. 3. The credibility interval of mixed deciduous tree stands coincides with the credibility interval of pure spruce and pine stands, which means that when the harvester operates in mixed deciduous tree stands, its productivity does not significantly differ from that in pure coniferous stands. 4. Comparing the calculated standard deviations of harvester productivity, it is envident that they are the greatest in mixed stands, but the smallest ones in pure spruce stands. It means that the parameters of harvester productivity, when commercial thinning is carried out, can be in a wide range and it could be difficult for forest harvesting professionals to predict how productive the work will be in each felling site of the mixed stand, whereas the parameters of harvester productivity in pure spruce stands are in a narrower range. References 1. Brunberg T. (1997) Basic productivity norms for single-grip harvesters in thinning The Forestry Research Institute of Sweden, Uppsala, 118 p. RESEARCH FOR RURAL DEVELOPMENT 2014, VOLUME 2 81

7 PRODUCTIVITY OF HARVESTERS IN COMMERCIAL 2. Brunberg T., Thor M., Norin K. (2007) Logging productivity and price models in Sweden and Latvia. AS Latvijas valsts meži, Riga, 16 p. 3. Eliasson L. (1998) Analyses of single-grip harvester productivity Doctoral thesis, Swedish University of Agricultural Sciences, Department of Operational Efficiency, Umea. 24 p. 4. Epalts A. (2002) Mehanizētas sastāva kopšanas cirtes ietekme uz priežu audzes attīstību (Impact on the development of pine stands after mechanized thinning). LLU raksti, Nr. 5, lpp. (in Latvian). 5. Epalts A. (2005) Mehanizētās krājas kopšanas cirtes ietekme uz egļu audzes attīstību (Impact on the development of spruce stands after mechanized thinning). LLU raksti, Nr. 14 (309), lpp. (in Latvian). 6. Kellogg L.D., Bettinger P. (1994) Thinning productivity and cost for mechanized cut-to-length system in the Northwest pacific coast region of the USA. Journal of Forest Engineering, 5(2), pp Lageson H. (1997) Effects of thinning type on the harvester productivity and on the residual stand. Journal of Forest Engineering, 8(2), pp Landford B.J., Stokes B.J. (1995) Comparison of two thinning systems. Part I. Stand and site impacts. Forest Products Journal, 45 (5), pp Landford B.J., Stokes B.J. (1996) Comparison of two thinning systems. Part II. Productivity and costs. Forest Products Journal, 46 (11/12), pp Pulkki R. (2003) Minimizing negative environmental impacts of forest harvesting operations. Towards sustainable management of the boreal forest, NRC Research Press, Ottawa, Ontario, Canada, pp Siren M., Aaltio H. (2003) Productivity and costs of thinning harvesters and harwarders. Journal of Forest Engineering, 14 (1), pp Uusitalo J. (2004) Heartwood and extractive content of Scots pine in southern Finland: models to apply at harvest. Wood and Fibre Science, 36(1), pp Розинь Т. (1978) Исследование цикла машинного выноса деревьев при рубке леса выборным способом (Research of machine removal tree cycle in selective felling). Автореферат диссертации, Минск, 26 с. (in Russian). 14. Савельев А. (1989) Разработка технологии рубок ухода на основе исследования доступности деревьев при машинном способе заготовки (Development of technology for thinning on the basis of research in machine availability tree of harvesting method). Автореферат диссертации, Минск, 27 с. (in Russian). 82 RESEARCH FOR RURAL DEVELOPMENT 2014, VOLUME 2