Delineation of thinning tracts at Holmen Skog : an evaluation of problems and possibilities

A common goal in practical forest management is to maximize the yield, measured in economical terms. When a forest stand is thinned a so called inoptimality loss can arise due to non-optimal decisions. This means that the selected management schedule results in a lower net present value than the optimal one which lowers the profitability for the forest owner. Holmen Skog uses the term tract which means an aggregation of stands made before a management action. A tract should be delineated in different tract parts in connection with pre-thinning planning if there is different bearing capacity within the tract, different thinning grades should be used or if the tract contains a weaker part that should not be thinned. If this delineation is neglected and a standardized forest management is practiced over a bigger thinning area, there is a risk of non-optimal decisions. Inaccurate estimation of forest variables in the pre-thinning planning, e.g. basal area, has also been a problem at Holmen Skog´s region Örnsköldsvik. There is also a fear that the volume production capacity is not fully used. The aim of this study was to examine the planning of tracts done at Holmen Skog as today and analyze the possible consequences of insufficient tract delineation. 53 tracts where inventoried with an objective plot survey and the differences between the estimated basal area and dominant height and the planners’ judgments of these values were calculated. An examination was also done of how often tracts were delineated by the planners through a search in Holmen Skog´s tract bank. This was followed by two analyzes in Heureka PlanWise to determine how much of the inoptimality loss that can be assigned to erroneous forest data respective insufficient tract delineation. Interviews were done with employees at Holmen Skog to look into the possibilities and difficulties with tract delineation. The results show that planners overestimated the basal area with 3,4 m2/ha on average while dominant height on average was underestimated with 1,8 m. The planners judgments were aggregated around the average basal area in a typical thinning stand and the overestimation can partly be explained by the fact that the planners did not exclude weaker parts from thinning in a sufficient way. The extent of tract delineation varied also a great deal between different districts at region Örnsköldsvik. The analyzes in PlanWise showed an inoptimality loss of just over 2 % because of erroneous forest data and about 1 % due to insufficient delineation of the tract. The interview respondents had in general a positive attitude to tract delineation since the work becomes easier for the machine drivers, especially if areas without need for thinning are excluded. They also thought that tract delineation for different thinning grade and thinning form is good as long as the map over the tract is intelligible. The possibility to in practice delineate a tract in parts is mostly dependent on how much time the planners have vacant for this. They work under time pressure since every district has to reach a minimum limit according to the estimated harvest level made at the head office.Holmen Skog använder begreppet traktindelning när en gallringstrakt delas efter skillnader i bärighet, gallringsuttag eller ifall svagare delar undantas från gallring. Om inte det bästa åtgärdsalternativet väljs inför gallring uppstår en förlust i nuvärde, en s.k. inoptimalförlust, Inoptimalförluster kan uppstå om föreslagna åtgärder baseras på en felaktigt skattade beståndsdata men även om samma skötsel tillämpas på ett större och heterogent område, d.v.s. vid bristande traktindelning. Syftet med detta arbete var att se hur traktplaneringar görs vid Holmen Skog och vilka konsekvenserna kan bli vid en bristande traktindelning. En objektiv fältinventering gjordes för 53 trakter följt av differensberäkningar mellan uppmätt grundyta och övre höjd respektive traktplanerarnas motsvarande värden. Omfattningen av traktindelning undersöktes genom att analysera traktbanken och analyser gjordes i Heureka för att beräkna inoptimalförluster p.g.a. felaktiga indata respektive bristande traktindelning. Intervjuer genomfördes för att undersöka anställdas syn på traktplanering men även möjligheter och svårigheter med traktindelning. Resultaten visar att traktplanerarna i snitt överskattade grundytan innan gallring med 3,4 m2/ha. En dragning mot mitten bland angivna värden i traktdirektiven var tydlig och överskattningen förklaras delvis av att traktplanerarna missat att exkludera sämre delar från trakten. Omfattningen av traktindelning varierade också mycket mellan olika distrikt på region Örnsköldsvik. Heureka-analyserna visade en inoptimalförlust på ca 2 % p.g.a. felaktiga indata och ca 1 % p.g.a. bristande traktindelning. Intervjurespondenterna var överlag positivt inställda till traktindelning då skogsskötseln kan varieras mer på en trakt samtidigt som maskinförarnas arbete underlättas. Möjligheten till traktindelning beror dock till stor del på traktplanerarnas arbetssituation eftersom de jobbar under tidspress

Logging costs in thinning with multi-tree handling harvester head, from stand to industry

Profit in first commercial thinnings of today is hard to achieve. This is because of prevailing pulpwood prices and because of high costs of logging and transport. To reduce these costs higher productivity is advocated. One way to increase the productivity is the use of multi-tree handling harvester heads. The aim of this study was to calculate logging and transport costs in first thinnings, where multi-tree handling has been used. Some specific questions were addressed, e.g. how the harvester´s productivity is affected by harvested mean stem volume and proportion of multi-tree handled trees. We studied factors that affect productivity and road transport by means of machine cost calculations and productivity calculations. Costs for each machine were then calculated and the longest profitable transport distance was determined. Regression analyses were accomplished where the calculations were based on data from objects. The results show that harvester´s productivity is strongly affected by the harvested mean stem volume. Multi-tree handling can have a positive impact on productivity, but this is depending on the suitability of the technology used for specific tree sizes. The forwarder´s productivity is greatly affected by the hauling distance, and to some extent also by the mean stem volume. Transport costs from landing to industry are impacted by transport distance, which has a big effect on total cost in first thinnings. At a pulpwood price of 330 SEK/m3 (solid under bark), the longest profitable transport distance is 275 km for the study´s mean object. The pulpwood price has a large impact on the transport distance, where a price reduction of 20 % may reduce the transport distance by half. By dividing the costs in terminal and transport time, the different cost items can be compared. This shows that road transport cost may be significant with longer transport distance. Despite this, the most expensive cost item in first thinnings is generally the harvester. Its productivity can be increased through higher proportion of multi-tree handling and by so making the thinning more profitable.I dagens förstagallringar är det svårt att få lönsamhet p.g.a. rådande massavedspriser och höga kostnader vid drivning och vägtransport. För att minska kostnaderna förespråkas ökad produktivitet. Ett sätt att öka produktiviteten är användandet av flerträdshanterande skördaraggregat. Syftet med detta arbete har varit att beräkna drivnings- och vägtransportkostnader i förstagallringar där flerträdshantering använts. Frågeställningar som t.ex. hur skördarens produktivitet påverkas av skördad medelstam och andelen flerträdshanterade träd, avsågs att besvaras. Genom maskinkostnadskalkyler och produktivitetsberäkningar kunde vi undersöka påverkande faktorer på produktivitet och vägtransport. Kostnader beräknades därefter för respektive maskin samtidigt som längsta lönsamma vägtransportavstånd undersöktes. Regressionsanalyser utfördes för de beräkningar där grunden utgjordes av beståndsdata. Resultaten visar att skördarens produktivitet är starkt påverkad av uttagsmedelstammens volym. Flerträdshantering kan påverka produktiviteten positivt, men beror av teknikens lämplighet för skördad medelstamvolym. Skotarens produktivitet påverkas i stor grad av skotningsavstånd och i mindre omfattning av medelstamsvolym. Transportkostnaden från avlägg till industri påverkas främst av avståndet, och har en stor påverkan på totalkostnaden vid en förstagallring. Vid ett massavedspris på 330 kr/m3 (fast under bark) är längsta lönsamma vägtransportavstånd 27,5 mil för studiens medelobjekt. Massavedspriset har stor inverkan på avståndet där en 20 % sänkning av priset kan halvera lönsamt transportavstånd. Genom en uppdelning av kostnaderna i terminaltid och körtid kan de olika kostnadsposterna jämföras i kr/m3fub. Detta visar att vägtransportkostnaden kan bli betydande vid längre vägtransportavstånd, dock är skördaren generellt den tyngsta kostnadsposten vid förstagallring. Genom ökad flerträdshantering kan skördarens produktivitet öka och därmed möjliggöra ett bättre gallringsnetto

A comparison of ISO 2631-5:2004 and ISO 2631-5:2018 standards for whole-body vibrations exposure: A case study

Agricultural tractor drivers are exposed to high level of vibrations during different activities. Continued exposure to Whole Body Vibration (WBV) may cause musculoskeletal disorders and degenerative changes in lumbar spine. This study analyses the WBV transmitted to drivers associated to a typical operation with agricultural tractor. This measurement was based on the models defined in ISO 2631-5:2004 and ISO 2631-5:2018. The study had been carried out in order to make a comparison between the Standards. The R factor (defined in the ISO 2631-5:2004 to estimate the lumbar spine response acceleration), and Ra factor (defined in the ISO 2631-5:2018 to estimate internal spinal forces, ISO 2631-5:2018) were calculated to predict adverse effects in the lumbar spine. In this case study both standards provide similar assessment, low probability of an adverse health effect. © Springer Nature Switzerland AG 2019

Compromised root development constrains the establishment potential of native plants in unamended alkaline post-mining substrates

© 2018, Springer Nature Switzerland AG. Background and aims: Mined materials often require rehabilitation or ecological restoration through revegetation as part of mine closure and relinquishment practices, yet there is a widening gap between the expectations of recovery and what industry achieve. The edaphic conditions of post-mining substrates present a suite of potential limitations to plant growth and may constrain the establishment capability and development of native species. Methods: We assessed seedling emergence, relative growth rate and calculated standardised growth estimates using 10 measured root and shoot parameters for six locally-dominant native species from different families and nutrient-acquisition strategies in a range of representative mining restoration substrates (topsoil, tailings, capped tailings and waste rock), examining their suitability as pioneers for ecological restoration. Results: The establishment and growth of all six species in post-mining substrates were significantly compromised. Root development was significantly responsive to substrate, with measured root parameters on average 27% lower in capped tailings, 41% lower in waste rock and 67% lower for individuals grown in tailings compared with those grown in topsoil alone. Plant growth was compromised at different life cycle stages (seed germination, seedling establishment, early growth and development) and across a number of different traits, with primary edaphic constraints including high pH (>8.5) and insufficient available N. The highest-performing species on post-mining substrates was an N2-fixing legume, while lowest-performing species included those with ectomycorrhizal associations or no specific nutrient-acquisition strategy. Conclusions: Edaphic filters may be significant drivers of trajectory and success in rehabilitation and restoration projects at scales ranging from individuals (by limiting establishment or constraining growth and development) to communities (by causing species to assemble in a different manner than the desired reference community). If intractable edaphic parameters constraining plant establishment and early development such as extreme pH and a lack of available nutrients are not ameliorated, the restoration trajectory on post-mining landforms is likely unfavourable. Failure to adequately ameliorate post-mining substrates may represent a major liability for industry in meeting mine-closure requirements