| 1. |
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| 2. |
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| 3. |
- Berg, Simon, et al.
(författare)
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Distance driven and driving speed when forwarding during final felling in Central Sweden
- 2019
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Ingår i: Journal of Forest Science. - 1212-4834 .- 1805-935X. ; 65, s. 183-194
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Tidskriftsartikel (refereegranskat)abstract
- Factors affecting forwarding work are interesting because they can be used to better optimize forwarding routes and to predict costs. The main objective of this study was to investigate the association between driving speed and driving distance when forwarding. Data was automatically collected during 2.5 years from two large forwarders operating during final felling in central Sweden. Driving speeds for the work tasks Driving unloaded, Loading drive and Driving loaded were analysed using correlation, least-squares regression, and quantile regression. The results showed that speed and distance were strongly correlated for the work element Driving unloaded, while the correlation was weaker for Loading drive and Driving loaded. Possible factors leading to these results are as follows: longer travelling distances stimulate better planning and the establishment of better extraction roads; operators may feel stressed and drive faster as travelling distance increases; and finally, the relative influence of accelerations and decelerations decreases with increasing driving distance. Also, the use of quantile regression was successful and provided information that normal least-squares regression does not provide.
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| 4. |
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| 5. |
- Bergsten, Urban, et al.
(författare)
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Functional Products in Forestry: Challenges and Opportunities
- 2012
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Konferensbidrag (refereegranskat)abstract
- Worldwide, sustainable forestry requires a holistic view over the use of forests as a resource. However, there are no holistic business models to support sustainable forestry. Hence, there exist a potential to use new business models such as Functional Products. Based on a literature study, this paper highlights important challenges and opportunities regarding the use of the Functional Product concept in forestry, and assesses how to best fuse the two fields. The results indicate that there are opportunities to achieve win-win situations by introducing Functional Products in forestry.
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| 6. |
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| 7. |
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| 8. |
- Ersson, Back Tomas
(författare)
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Advances in the Mechanization of Regenerating Plantation Forests: a Review
- 2020
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Ingår i: Current Forestry Reports. - : Springer Science and Business Media LLC. - 2198-6436. ; 6, s. 143-158
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Forskningsöversikt (refereegranskat)abstract
- Purpose of Review The mechanization of silvicultural work on forest plantations is usually driven by a decreasing supply of motivated labour which increases its relative cost. Mechanization can also result in other advantages like increased effectiveness, higher efficiency, and improved working conditions. The purpose of our review is to examine the last few decades' endeavours to mechanize the regeneration activities of plantation forestry in the southern and northern hemisphere. In this case, regeneration activities include (1) site preparation; (2) tree planting; and (3) stand tending until the crop trees are free from vegetative competition. Recent Findings Originally, the mechanization of silvicultural work commenced in the northern hemisphere, but over the past decades, the most notable progress has been made in the southern hemisphere plantation forests. Although soil preparation is largely mechanized across the globe, tree planting and stand tending activities lag behind because of factors such as global variations in the manner in which they are performed, higher level of complexity, and low-cost competitiveness compared with existing labour-intensive methods. For mechanization of regeneration/silvicultural activities to progress, productive and adaptable machines will be required where economies of scale permit cost-efficient operations. These machines will probably have to be modified to the specific forestry context of different countries. Knowledge of the existing and state-of-the-art regeneration technologies available in both the northern and southern hemispheres is important for foresters to make informed decisions about the selection and application of mechanized regeneration systems.
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| 9. |
- Ersson, Back Tomas, et al.
(författare)
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Aerial seeding of forests in Russia: A selected literature analysis
- 2019
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Ingår i: IOP Conference Series: Earth and Environmental Science. - : IOP Publishing. - 1755-1307 .- 1755-1315. ; 226
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Konferensbidrag (refereegranskat)abstract
- The study is intended for international readers or those unable to read Russian. Information search was carried out in Russian-language databases (Russian libraries and ELibrary.ru) and English-language databases. . Currently, there are a large number of sites in the Russian forests that need to be restored. For many of them, reforestation by ground-based seeding or planting is inefficient or not available. Sowing forest from the air in Russia has more than half a century of history. The results of retrospective analysis show that the choice of the reforestation method depends on the site characteristics and the level of negative environmental impact. Generally, the cost of aerial seeding on such sites with unmanned aerial vehicles (UAV) is lower compared to the use of manned aerial vehicles (MAV). This study will aid in the planning of new forestry experiments to study reforestation with the assistance of natural reforestation in Russia. The study will enable correct plant propagation protocols for sustainable forest management. However, many questions remained unresolved: what types of UAV and sowing apparatus to use; how to position the UAV under a forest canopy?
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| 10. |
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| 11. |
- Ersson, Back Tomas
(författare)
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Concepts for mechanized tree planting in southern Sweden
- 2014
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The underlying reason for mechanizing tree planting in southern Sweden is the biologically good planting results produced by today's tree planting machines. Nevertheless, the productivity of these tracked excavators with crane-mounted tree planting devices is too low for them to compete economically with manual planting. The objective of this thesis was to investigate concepts for 1) seedling packaging, 2) base machines, 3) planting devices, and 4) seedling carousels that could cost-efficiently increase the productivity of today's planting machines in southern Sweden. Article I analyzed the cost-efficiency of two seedling packaging concepts that decrease the time needed to reload planting devices with seedlings. The analysis showed, however, that machine-specific seedling packaging was costlier than delivering the seedlings in their cultivation trays, although band-mounted seedlings will probably be the most flexible and cost-efficient packaging system as mechanized planting becomes more common. Article II and III used a discrete-event simulation tool and detailed terrain, machine, and planting device models to simulate the productivity of conceptual two-armed excavators and multi-headed crane-mounted planting devices. Two arms per excavator proved to be an inefficient concept for increasing the productivity of today's planting machines when compared to multi-headed planting devices. Although four planting heads per device was the most productive configuration on easy to moderate terrain, three-headed devices were best at combining high productivity with acceptable silvicultural results on all terrain types. Article IV used a test-rig to study the feasibility of tray-wise seedling reloading on today's most common planting device. Seedling reloading was twice as fast when done tray-wise rather than seedling-wise, and deplugging proved to be a reliable method of extracting seedlings from suitable cultivation trays even when performed at the excavator’s boom-tip during mounding work. Overall, this thesis confirms that there is high potential for technical improvements that increase the productivity and lower the planting costs of today's tree planting machines. Such improvements will likely include faster seedling reloading via tray-wise-loaded carousels or band-mounted seedlings, multi-headed planting devices that produce high quality planting spots using adapted soil preparation methods, and sensors that aid the operator in choosing microsites.
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| 12. |
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| 13. |
- Ersson, Back Tomas
(författare)
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Cost analysis of seedling supply systems adapted for mechanized tree planting: a case study from southern Sweden
- 2022
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Ingår i: Silva Fennica. - : Finnish Society of Forest Science. - 0037-5330 .- 2242-4075. ; 56
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Tidskriftsartikel (refereegranskat)abstract
- Because today's tree planting machines do a good job silviculturally, the Nordic forest sector is interested in finding ways to increase the planting machines' productivity. Faster seedling reloading increases machine productivity, but that solution might require investments in specially designed seedling packaging. The objective of our study was to compare the cost-efficiency of cardboard box concepts that increase the productivity of tree planting machines with that of today's two most common seedling packaging systems in southern Sweden. We modelled the total cost of these five different seedling packaging systems using data from numerous sources including manufacturers, nurseries, contractors, and forest companies. Under these southern Swedish con-ditions, the total cost of cardboard box concepts that increase the productivity of intermittently advancing tree planting machines was higher than the cost of the cultivation tray system (5-49% in the basic scenario). However, the conceptual packaging system named ManBox_fast did show promise, especially with increasing primary transport distances and increased planting machine productivities and hourly costs. Thus, our results show that high seedling packing density is of fundamental importance for cost-efficiency of cardboard box systems designed for mechanized tree planting. Our results also illustrate how different factors in the seedling supply chain affect the cost-efficiency of tree planting machines. Consequently, our results underscore that the key development factor for mechanized tree planting in the Nordic countries is the development of cost-efficient seedling handling systems between nurseries and planting machines.
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| 14. |
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| 15. |
- Ersson, Back Tomas, et al.
(författare)
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Forest management in northern Fennoscandia: the need for solutions that mitigate conflicts during forest regeneration and increase the use of continuous cover forestry
- 2023
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Ingår i: Silva Fennica. - 0037-5330 .- 2242-4075. ; 57
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Tidskriftsartikel (refereegranskat)abstract
- Today, conflicts often occur in northern Fennoscandia (also known as Sápmi) between forestry and reindeer husbandry. Continuous cover forestry (CCF) is requested by both reindeer herding communities and the general public and is becoming more common, but the forest industry criticizes CCF for lower wood production. Mechanical site preparation (MSP) increases regeneration success and, thus, increases wood production in CCF. To reduce the conflict between forestry and reindeer husbandry, MSP in Sápmi should destroy as little ground lichen as possible. Today, there are no solutions for gentle and lichen-adapted MSP in CCF. Thus, there is a strong need to develop and test new technical solutions that increase regeneration success in a lichen-adapted way during CCF in Sápmi. We suggest that MSP solutions be developed which are gentle, work selectively and function in shelterwoods, gap cuts, and selection cutting stands. We envision that these solutions could fill the gap between the desired adaptivity on the part of the reindeer herding communities and the desired efficiency on the part of the forest industry. Such MSP technology would contribute to increased acceptance of CCF in the forest industry, higher biodiversity, and considerably reduce the conflict between forestry and reindeer herding communities.
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| 16. |
- Ersson, Back Tomas
(författare)
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Forwarding during final felling: work element-specific distributions of driving distances at the stand level
- 2020
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Ingår i: International Journal of Forest Engineering. - : Informa UK Limited. - 1494-2119 .- 1913-2220. ; 31, s. 51-69
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Tidskriftsartikel (refereegranskat)abstract
- Automatic data collection is becoming increasingly common in cut-to-length forest operations. However, only few studies have analyzed automatically collected follow-up data from forwarders. In this study, we analyzed the driving distances of the four work elements Driving empty, Loading drive, Driving loaded, and Unloading drive (the sum of which being Total driven distance) of two forwarders operating in central Sweden. The analysis included finding the most appropriate probability density functions for each distance at the stand level (46 final felling stands in total, with one load as the unit of observation). The results showed that the mean intra-stand Total driven distance ranged 364-2393 m, and that most distances in the majority of the stands were positively skewed. Versatile probability distributions like Generalized Extreme Value and Log-logistic were the most common probability distributions. Our results provide researchers and managers a numeric understanding of the intra- and inter-stand variation of forwarding work. Hence, our study can help spread awareness of this variation to managers and foresters. With this awareness, managers, foresters, and researchers can better understand the pros and cons of follow-up data from forwarders, and how to best use and collect it. Our results can also be used by researchers as high-resolution indata during simulations of forwarding work Additionally, the results can be used as a reference or control when determining the most suitable data distributions in future studies.
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| 17. |
- Ersson, Back Tomas
(författare)
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Hyggesfritt skogsbruk
- 2020
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Omfattande vetenskaplig forskning i Norden de senaste tio åren har visat att hyggesfritt skogsbruk kan vara bättre än trakthyggesbruket på att optimera skogens ekonomiska, ekologiska, och sociala värden. Speciellt intressant för svenska privatskogsägare är den forskning som visar att hyggesfritt skogsbruk kan vara mer lönsamt (generera högre nuvärden) än trakthyggesbruk på marker med låga ståndortsindex, vid höga skogsvårdskostnader, när risken för skogsskador är hög, vid låga rotnetton, och när räntan är hög. Därmed är det viktigt att det svenska skogsbruket fortsätter att utveckla kunnandet och forskningen om hyggesfritt skogsbruk, så att hyggesfri skogsskötsel kan vara en beprövad och flitigt använd metod i Skogssveriges verktygslåda.
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| 18. |
- Ersson, Back Tomas
(författare)
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Innovative productivity improvements in forest operations: a comparative study of the Assortment Grapple using a machine simulator
- 2020
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Ingår i: Journal of Forest Science. - 1212-4834 .- 1805-935X. ; 66, s. 443–451-
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Tidskriftsartikel (refereegranskat)abstract
- Because of generally small log piles, loading forwarders during thinning is time consuming. The Assortment Grapple, an innovative grapple with an extra pair of claws which facilitates the handling of two assortments during one loading crane cycle, has been designed to decrease forwarders’ loading time consumption. A standardized experiment was performed in a virtual thinning stand using a machine simulator with the objectives to form guidelines for working with the Assortment Grapple and to analyse its development potential. Four experienced operators participated in the study. According to the results, the Assortment Grapple’s accumulating function is beneficial only when there are no remaining trees between piles loaded during the same crane cycle. In such cases, none of participating operators lost time, and 3 of 4 operators saved time notably. The problem with the remaining trees is the extra time required to steer the crane tip around them. Therefore, a harvester should place those log piles that are later to be forwarded together in the same space with no remaining trees between the piles. Furthermore, we recommend that the Assortment Grapple’s usability will be improved by adding an own rocker switch on the forwarder’s controls to command the extra claws.
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| 19. |
- Ersson, Back Tomas
(författare)
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Maskinell plantering – analys av planteringsmaskinen PlantmaX potential inom privatskogsbruket
- 2022
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Privatskogsbruket äger mer än hälften av Sveriges produktiva skogsmark, och intresset för självverksamhet inklusive skogsplantering minskar generellt bland de privata skogsägarna. Sedan hösten 2019 finns planteringsmaskinen PlantmaX, och den utvecklades huvudsakligen för storskogsbruket. Mekanisering av skogsodlingen förväntas på sikt leda till en kostnadsbesparing för skogsbruket, och då är det viktigt att privatskogsbruket också följer med i den mekaniseringstrenden. Syftet med denna analys är att utvärdera PlantmaX:s lämplighet för det svenska privatskogsbruket. Analysen gjordes med hjälp av indata från en mängd källor, både muntliga och skriftliga, från höstarna 2020-2021. En fältstudie av PlantmaX planteringskvalitet visade att planteringsmaskinen i dagsläget ger sämre planteringskvalitet än vid manuell plantering, men bedömningen är att skillnaden troligen inte är avgörande för privata skogsägares acceptans av PlantmaX-konceptet. Dock verkar PlantmaX i dagsläget vara lämpligast på tallmarker pga maskinens svårighet att på ett högkvalitativt sätt plantera i omvänd torva. Uppskattningsvis verkar 4 ha vara den minsta traktstorleken för att PlantmaXkonceptet ska vara konkurrenskraftigt. I och med att medeltrakten på privatägd skogsmark är lägre än 4 ha i både Svealand och Götaland bör dock samordning av trakter vara en möjlighet för att motverka de högre planteringskostnaderna som små trakter medför. Slutbedömningen är att utvecklingspotentialen för PlantmaX plantreringskvalitet är stor, speciellt vid inkorporering av fler sensorer och automatisk identifikation av planteringspunkter. Därför kommer sannolikt PlantmaX framtida planteringskvalitet att öka, något som i sin tur ytterligare kommer att stärka PlantmaX-konceptets lämplighet för det svenska privatskogsbruket.
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| 20. |
- Ersson, Back Tomas
(författare)
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Mechanization of coniferous seeds grading in Russia: a selected literature analysis
- 2020
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Ingår i: IOP Conference Series: Earth and Environmental Science. - : IOP Publishing. - 1755-1307 .- 1755-1315. ; 595
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Konferensbidrag (refereegranskat)abstract
- The review is intended for international readers or those unable to read Russian. The review is based on long-term research of the affiliated University and search in Russian-language databases. Currently, there is a large number of sites in the Russian forests that need to be restored. Mechanization of grading seeds in Russia has more than half a century of history. The results of retrospective analysis show that the choice of the sorting method depends on the seed characteristics and the level of achieved technologies in equipment design. The prospects for the use of optoelectronic and mechatronic devices for such purposes are due to low costs and negative impact compared to the use of grid and trier. The research materials will allow planning new experiments to find a reliable protocol for testing and preparing coniferous seeds, depending on the method of further seeding or storage. The study will allow to correct plant propagation protocols for sustainable forest management. However, many questions remained unresolved: what types of grader and pelleting apparatus to use, what wavelength range is best used to identify viable seeds?
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| 21. |
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| 22. |
- Ersson, Back Tomas
(författare)
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Mechanized Tree Planting in Sweden and Finland: Current State and Key Factors for Future Growth
- 2018
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Ingår i: Forests. - : MDPI AG. - 1999-4907. ; 9
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Tidskriftsartikel (refereegranskat)abstract
- In Fennoscandia, mechanized tree planting is time-efficient and produces high-quality regeneration. However, because of low cost-efficiency, the mechanization of Fennoscandian tree planting has been struggling. To determine key factors for its future growth, we compared the operational, planning, logistical, and organizational characteristics of mechanized planting in Sweden and Finland. Through interviews with planting machine contractors and client company foresters, we establish that mechanized tree planting in Sweden and Finland presently shares more similarities than differences. Some notable differences include typically longer planting seasons in Sweden, and a tendency towards two-shift operation and less frequent worksite pre-inspection by contractors in Finland. Because of similar challenges, mechanized planting in both countries can improve cost-efficiency through education of involved foresters, flexible information systems, efficient seedling logistics, and continued technical development of planting machines. By striving to have multiple client companies, contractors can reduce their operating radii and increase their machine utilization rates. Above all, our results provide international readers with unprecedented detailed and comprehensive figures and characteristics of Swedish and Finnish mechanized tree-planting activities. We conclude that cooperation between Sweden's and Finland's forest industries and research institutes could enhance the mechanization level of Fennoscandian tree planting.
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| 23. |
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| 24. |
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| 25. |
- Ersson, Back Tomas, et al.
(författare)
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Reloading mechanized tree planting devices faster using a seedling tray carousel
- 2014
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Ingår i: Silva Fennica. - : Finnish Society of Forest Science. - 0037-5330 .- 2242-4075. ; 48
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Tidskriftsartikel (refereegranskat)abstract
- On Nordic clearcuts, today’s tree planting machines produce high-quality but costly regenerations. Much of this high cost is attributable to the planting machines’ low productivity. One promising way of raising productivity is to lessen the time spent manually reloading seedlings onto the carousels of crane-mounted planting devices. Using MagMat, a carousel test-rig designed by engineering students, we studied how much faster tray-wise seedling reloading is on the Bracke Planter compared to reloading with today’s seedling-wise-loaded carousel. The MagMat test-rig held eight Hiko cultivation trays from which seedlings were deplugged individually and dropped into the planting tube. The time study confirmed that seedling reloading was on average twice as fast with MagMat compared to today’s seedling carousel, thereby increasing assumed planting machine productivity by 8–9% depending on the planting device used. MagMat’s cost-efficiency was analysed to be particularly reliant on its added investment cost, mechanical availability and how quickly trays can be switched automatically. Nevertheless, MagMat’s field performance illustrated the overall potential of tray-wise loading compared to piecewise seedling loading for increasing the productivity of crane-mounted planting devices. Also, deplugging proved to be a reliable method of extracting seedlings from the rigid, copper-painted Hiko cultivation trays even when performed at the excavator’s boom-tip during mounding work. We conclude that, rather than piecewise seedling loading, tray-wise loading combined with deplugging seedlings from suitable cultivation trays is a reliable and much more time-efficient method to feed seedlings on probably any type of tree planting machine.
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| 26. |
- Ersson, Back Tomas, et al.
(författare)
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Simulated productivity of conceptual, multi-headed tree planting devices
- 2014
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Ingår i: International Journal of Forest Engineering. - : Informa UK Limited. - 1494-2119 .- 1913-2220. ; 25, s. 201-213
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Tidskriftsartikel (refereegranskat)abstract
- Mechanized tree planting is presently enjoying a revival in Fennoscandia with increased focus on further technical development. To explore the productivity effect of multiple heads on crane-mounted tree planting devices, we used a discrete-event simulation tool in which excavator-mounted one- to four-headed devices reforested clearcuts with variable frequencies of obstacles. During the simulations, the device models either mounded or inverted soil and then planted seedlings. A planting head could be hindered by stones and roots from performing these tasks, thus causing queuing delays for multi-headed devices. Surface boulders, stumps, and humus layers also slowed down the work. The results showed that productivity increased significantly with increasing numbers of planting heads on terrain with sparse or moderate obstacles, regardless of using faster or slower soil preparation methods or seedling reloading systems. However, on obstacle-rich terrain, three-headed planting devices were more productive than four-headed, while one-headed were as equally productive as twoheaded devices. Obstacle-rich terrain sometimes inhibited those large four-headed devices from planting even one seedling at a given machine stationary point. Therefore, we conclude that three planting heads per cranemounted device seems to be the most realistic configuration for combining high productivity with good silvicultural results on all the terrain types that a planting machine might work on in Fennoscandia. Future studies should investigate the silvicultural effects of different tree spacing geometries and the corresponding suitable geometrical design of three-headed crane-mounted planting devices.
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| 27. |
- Ersson, Back Tomas, et al.
(författare)
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Simulated productivity of conceptual, multi-headed tree planting devices
- 2014
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- The demand for mechanized tree planting has been growing steadily in southern Sweden over the last five years. This demand growth is mainly because seedlings on typical southern Swedish clearcuts survive better and grow faster when planted mechanically compared to operational manual planting after mechanical disc trenching. Today, planting machines in the Nordic countries consist of an ordinary tracked excavator with a crane-mounted planting device. Current boom-tip planting devices can be one- or two-headed, and scarify via mounding, plant deeply, and are especially suitable on mesic and moist sites. Practical experience has shown that two-headed devices are more productive than one-headed, especially on clearcuts with easy to moderate terrain. However, it is not known whether three- or four-headed planting devices could further increase planting machine productivity. Moreover, would such multi-headed planting devices remain more productive even on obstacle-rich terrain? To answer these questions, we used a discrete-event simulation tool to compare planting devices with one to four heads on clearcuts with varying frequencies of obstacles (ie. stones, stumps, roots) and different thicknesses of humus layer. Preliminary results show that planting machine productivity on easy to moderate terrain is highest with four-headed devices, while productivity on obstacle-rich terrain is highest for three-headed devices with obstacle-avoiding features. Also, tray-wise-loaded seedling carousels that were faster to reload increased the simulated productivity of one- and two-headed devices by 4-12% depending on terrain. These simulation results will guide us in choosing which configurations to test on actual planting device test-rigs.
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| 28. |
- Ersson, Back Tomas, et al.
(författare)
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Simulated productivity of one- and two-armed tree planting machines
- 2013
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Ingår i: Silva Fennica. - : Finnish Society of Forest Science. - 0037-5330 .- 2242-4075. ; 47:2
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Tidskriftsartikel (refereegranskat)abstract
- To increase mechanized planting, planting machine productivity must increase in order to improve cost-efficiency. To determine if excavators with two crane arms could potentially help to increase planting machine productivity under Nordic clearcut conditions, we modelled one- armed and semi-automated two-armed excavators with one- and two-headed planting devices. Using a recently developed tool for discrete-event simulation, these machine models then mounded and planted seedlings on terrain models with moraine soil having various frequencies of obstacles (stumps, roots and stones). Compared to if the two heads were mounted pairwise on only one arm, the results showed that productivity did not increase if two planting heads were attached individually to two separate crane arms. But productivity did increase if the planting machine had four planting heads mounted pairwise on two separate arms. However, despite assuming automated mounding and crane motion between planting spots, the two-armed, four- headed model never achieved high enough productivity levels to make it more cost-efficient than one-armed machines. The simulations illustrate that our terrain models generate realistic root architecture and boulder content distributions in moraine soil, while our machine models functionally describe mechanized planting work. Based on our assumptions, we conclude that further development work on two-armed excavator-based planting machines for Nordic clearcut conditions is not warranted. Our simulations reveal that increasing the number of planting heads per crane arm rather than number of crane arms per base machine offers the greatest potential to raise the productivity of intermittently advancing planting machines.
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| 29. |
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| 30. |
- Ersson, Back Tomas, et al.
(författare)
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Simulations of Mechanized Planting : Modelling Terrain and Crane-Mounted Planting Devices
- 2012
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Ingår i: OSCAR 2012. - : Latvian State Forest Research Institute "Silava". ; , s. 15-19
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- When reforesting clearcuts in southern Sweden, the Bracke Planter has shown to plant seedlings with better planting quality than operational manual tree planting (Ersson and Petersson 2011). Consequently, there is an increasing demand for intermittently advancing tree planting machines with crane-mounted planting devices in southern Sweden.Nevertheless, regardless of using one- (Bracke Planter) or two-headed planting devices (M-Planter), today’s average planting machine productivity is still too low (Rantala and Laine 2010, Ersson et al. 2011) for planting machines to cost-wise compete with manual tree planting in southern Sweden (Ersson 2010). There is, therefore, a need to develop new planting machines concepts that are significantly more productive on Nordic terrain, i.e. clearcuts on moraine soils with varying prevalences of stones and stumps where the slash has been harvested for bioenergy.For over 40 years, simulation studies have proven useful for testing prospective forest machine concepts (e.g. (Sjunnesson 1970)), including different types of planting heads (Andersson et al. 1977). In particular, simulations studies can nowadays help to cost-efficiently evaluate new ideas before real world implementation (Jundén 2011). However, previous forest machine simulations simplified terrain characteristics like stumps, roots and stones to the extent that these models are too simplistic for meaningful planting machine simulations. For this reason, we have built several terrain, base machine and planting device models for use during discrete-event simulations to test potential solutions that realistically might increase Nordic planting machine productivity. These simulations were performed using a simulator built with the SimPy discrete-event simulation language (Jundén 2011).TERRAIN MODELSPresently, our terrain models encompass stumps, roots and underground stones. To delineate the clearcuts, we used Herlitz’s (1975) type stands for clearcutting. These type stands also provided theinput data necessary for sizing and spatially allocating the stumps. To all stumps, we attached a root plate according to the deterministic data from Björkhem et al. (1975) and a stochastic root architecture inspired by Kalliokoski et al.’s (2010) root models.As concluded already during the 1960s (Bäckström 1978), the presence of non-visible, underground stones and boulders is what makes mechanized reforestation on moraine soils so difficult. To model this difficulty, we used parameter values from Andersson et al. (1977) to define incidences of stones and boulders (boulder quota or stoniness) and mean stone sizes. Then, we chose an exponential distribution to link stone frequency to stone diameter. In accordance with Eriksson and Holmgren (1996), our modelled stones are spherical in shape and are spatially allocated in a random manner.BASE MACHINE MODELSToday’s planting machines use excavators as base machines. If using standard components, it might be techno-economically feasible to add another arm to the excavator; thereby creating two- (Fig. 2) or four-headed planting machines where planting head interdependence is minimized. We hypothesized that the productivity of two-armed planting machines, compared to normal one-armed machines, might especially be higher on obstacle-rich terrain since one arm could be free to move while the other arm is busy working. Moreover, two-armed machines might particularly benefit from additional task automation. Preliminary results, however, show that this productivity increase might not be high enough to warrant further development of our two-armed planting machine concept.PLANTING DEVICE MODELSWe modelled today’s two most common planting devices, the one-headed Bracke Planter and the two-headed M-Planter. During simulation, the planting machine operator searches sequentially for microsites free from visible obstacles (stumps and main lateral roots). However, both devices can be impeded by underground roots or stones during mounding, and by stones during the planting phase. Striking obstacles with the M-Planter can result in delays for one or both heads.FURTHER DEVELOPMENTWe are currently expanding the terrain models to include humus layers and surface boulders, on which new multi-headed planting device concepts (with two to four planting heads) with obstacle-avoiding capabilities are being tested. Those simulation results will provide guidance as to how future crane-mounted planting devices should behave and be designed in order to increase planting machine productivity.
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| 31. |
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| 32. |
- Ersson, Back Tomas, et al.
(författare)
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The cost-efficiency of seedling packaging specifically designed for tree planting machines
- 2011
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Ingår i: Silva Fennica. - : Finnish Society of Forest Science. - 0037-5330 .- 2242-4075. ; 45, s. 379–394-
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Tidskriftsartikel (refereegranskat)abstract
- Today’s crane-mounted planting heads plant seedlings with biologically similar or better results than operational manual planting. However, the total cost of mechanized tree planting in southern Sweden must decrease at least 25% to compete economically with manual planting. Although seedlings packed in machine-specific packaging increase the productivity of planting machines by reducing seedling reloading time, they also increase logistics and investment costs. In this study, we analyzed the total cost of outplanting seedlings with an excavator-mounted Bracke Planter and seedlings packed according to four different concepts: cultivation trays, cardboard boxes, band-mounted seedlings in cardboard boxes and linked pots in container modules. The total cost per planted seedling was calculated for each packaging system as the sum of all costs from nursery to the recovery of empty packaging. The results showed that today’s system of transporting seedlings in cultivation trays is the most cost-efficient of the four alternatives. Machine-specific seedling packaging was 16–23% costlier per planted seedling than cultivation trays when trucking distances were 100 km. Sensitivity analyses indicated that machine-specific seedling packaging increased in cost-efficiency relative to cultivation trays primarily when more planting machines were contracted, but also as planting machine fixed costs and productivity increased. Moreover, the relative cost-efficiency of band-mounted seedlings, but not seedlings in container modules, increased with increasing trucking distance. Thus, we show that investments in machine-specific seedling packaging for today’s planting machines are justified only when the fixed costs, productivity and number of contracted planting machines increase substantially
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- Lideskog, Håkan, et al.
(författare)
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Determining boreal clearcut object properties and characteristics for identification purposes
- 2014
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Ingår i: Silva Fennica. - : Finnish Society of Forest Science. - 0037-5330 .- 2242-4075. ; 48:3
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Tidskriftsartikel (refereegranskat)abstract
- After clearcutting, machines traffic the clearcut conducting different silvicultural activities. Many objects on a forest clearcut (slash residues, stones, stumps and roots) may disturb e.g. site preparation and planting. This paper describes properties and characteristics of these objects. A flowchart was developed that describes a possible computer-aided system that identifies the objects, and ultimately, makes a machine avoid or target them. A system for obstacle identification creates conditions for further technical development and (semi)automation of e.g., site preparation, mechanized planting, and stump removal.
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- Manner, Jussi, et al.
(författare)
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Mechanized tree planting in Nordic forestry: simulating a machine concept for continuously advancing site preparation and planting
- 2021
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Ingår i: Journal of Forest Science. - 1212-4834 .- 1805-935X. ; 67, s. 242-246
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Tidskriftsartikel (refereegranskat)abstract
- As labour for manual tree planting becomes scarcer, regeneration costs are steadily increasing in Nordic forestry. Today’s intermittently advancing tree planting machines provide excellent silvicultural results, but are expensive to operate because of poor productivity. In contrast, continuously advancing planting machines, thanks to high productivities, are increasingly being regarded as a solution to these runaway regeneration costs. The Silva Nova was a historical, continuously advancing tree planting machine with high productivity. However, Silva Nova’s weaknesses included high labour costs (it required two operators) and the random nature of how it chose planting spots. In contrast, SuperSilva, a purely conceptual modernisation of Silva Nova, involves both automation and microsite identification to make the machine more efficient. We used discrete-event simulation to analyse the stocking rate and spatial distribution of tree planting with SuperSilva. The simulation results showed that introducing sensors for identifying suitable microsites will allow continuously advancing planting machines (like SuperSilva) to plant seedlings in a numerically and spatially adequate manner on moraine soils. Hence, these sensors will increase the competitiveness and versatility of tree planting machines. Unfortunately, such reliable and robust sensor technology (unaffected by a wide variety of operating conditions) is not yet commercially available.
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