Abstract. The aim of the study is to evaluate the impact of the accumulating grapple on forwarding productivity in thinning in comparison to the standard grapple and to evaluate potential areas of application of accumulating grapples. Trials were conducted in 3 coniferous stands on nutrient-poor mineral soil with the total area of 15.2 ha. Two work methods are compared in the study -forwarding with a John Deere 1110D ECO III forwarder, equipped either with an accumulating grapple (first method) or a standard grapple (second method). According to the study results the use of the standard grapple results in slight increase of productivity (2.3 % per load and 1.4 % per m 3 of logs). The difference is not significant, however additional trials are recommended to compare both grapples in more fertile forest stands with a larger number of assortments and extracted volumes, also in regenerative felling. According to the study results the prime forwarding cost is 9.4 EUR m -³, if the standard grapple is used and 9.5 EUR m -³, if the accumulating grapple is used. The difference is not significant. No significant difference is found between the methods also in terms of damages to the remaining trees.Keywords: forwarding, accumulating grapple, productivity, thinning. IntroductionProductivity and cost of forwarding, as well as damages to remaining trees are affected by several factors. Productivity of forwarding is influenced by the types and number of assortments, dimensions of extracted trees, extracted volume, forwarding distance and the machine utilized in the operation. The size and shape of grapple is one of the factors affecting the productivity [1]. Theoretically productivity can be improved by use of grapples, which can load different types of assortments per crane cycle, just like accumulating felling heads can handle several stems simultaneously. According to the results of a study carried out in Canada, productivity of a forwarder ranges from 7.9 to 17.0 m 3 per productive work hour [2]. In trials conducted in Sweden in 2014, focusing on productivity and fuel consumption, the standard grapple was equipped with an additional grip. It was found that additional grips do not affect fuel consumption during forwarding. Productivity in this trial increased by 5-8 %, when the accumulating grapple was used. The productivity was mainly influenced by the operator skills and their ability to use the advantages of the accumulating grapple [3].One of the most important factors influencing productivity of forwarding is the size of the assortment bundle gripped per working cycle. In the study conducted in Sweden the gripped assortment bundle is larger by 15 %, when the standard grapple is used. Assuming that the grip can load 0.2 m³ of logs per crane cycle, it is estimated that the accumulating grapple theoretically can load 0.38 m 3 of logs per crane cycle. Studies so far approve that use of the accumulating grapple increases productivity of forwarding by 1 %, which is considerably less than theoretical improvement of the forw...

The aim of this study is to investigate potential uses of Kranman Bison 10000 6WD forwarder in stands, where roundwood is extracted with a chainsaw and Vimek 404 T5 harvester in normal and difficult forwarding conditions. Productivity of Kranman forwarder was compared with medium-sized John Deere 810 forwarder under normal conditions. In total 230 loads were forwarded during the study, including 63 loads from areas, harvested with a chainsaw, and 167 loads from areas, harvested with Vimek 404 harvester. The average forwarded load is 2.0 m³ (the maximum load is 2.5 m³ therefore the average load capacity is 80%). In average 33 minutes of productive work time were spent by forwarding one load (the proportion of productive working time is 94% from total engine hours of the machine). The average length of forwarding road in trials is 286 m. In normal conditions forwarding of 1 m³ of roundwood extracted with a chainsaw takes 15 minutes of productive working time, but in difficult forwarding conditions the time consumption increases by 13%. The average forwarder fuel consumption is 1.8 L per hour. Accordingly, 0.8 L of fuel are consumed to forward 1 m³ roundwood. In comparison, John Deere 810 under similar conditions consumed 1.6 L fuel to forward 1 m³ roundwood. Study results prove that the best application of Kranman Bison 10000 is forwarding small stands or individual trees logged with a chainsaw. Forwarder can work on soils with low bearing capacity, however productivity can be significantly reduced by stumps and uneven terrain.

The ability to accurately assess the impact of organic soil drainage on greenhouse gas emissions (GHG) is still limited. Methane (CH4) emissions are characterized by significant variations, and GHG emissions from nutrient-rich organic soil in the region have not been extensively studied. The aim of this study was to assess CH4 and nitrous oxide (N2O) emissions from nutrient-rich organic soil in hemiboreal forests to provide insights into their role in regional GHG balance. Over the course of one year, CH4 and N2O emissions, as well as their affecting factors, were monitored in 31 forest compartments in Latvia in both drained and undrained nutrient-rich organic soils. The sites were selected to include forests of different ages, dominated by silver birch (Betula pendula Roth), Norway spruce (Picea abies (L.) Karsten), and black alder (Alnus glutinosai (L.) Gärtner), as well as clearcuts. Soil GHG emissions were estimated by collecting gas samples using the closed manual chamber method and analyzing these samples with a gas chromatograph. In addition, soil temperature and groundwater level (GW) measurements were conducted during gas sample collection. The mean annual CH4 emissions from drained and undrained soil were −4.6 ± 1.3 and 134.1 ± 134.7 kg CH4 ha−1 year−1, respectively. N2O emissions from undrained soil (4.1 ± 1.4 kg N2O ha−1 year−1) were significantly higher compared to those from drained soil (1.7 ± 0.6 kg N2O ha−1 year−1). In most of the study sites, undrained soil acted as a CH4 sink, with the soil estimated as a mean source of CH4, which was determined by one site where an emission hotspot was evident. The undrained soil acted as a CH4 sink due to the characteristics of GW level fluctuations, during which the vegetation season GW level was below 20 cm.

The aim of the research is to find out changes in productivity depending on the diameter of the tree to be cut as well as the most important factor influencing the reduction of productivity using small size forest machines in thinning in Latvia. The equipment used in the study-both the harvester and the forwarder is Vimek. The results of the research confirm the appropriateness of the exact technique in thinning if diameter of the harvested trees is 3 to 30 cm. The average productivity of the harvester achieved with a harvester head Keto Forest Eco (option 2) in Norway spruce stands with 8 cm weighted average tree reached 9.59 m 3 h-1 , in deciduous tree stands with 9 cm weighted average was 10.17 m 3 h-1 , but in Scots pine stands with 12 cm average weighted tree diameter reached 10.19 m 3 h-1. By using the Keto Forest Eco Harvester head according to the thinning productivity figures, no significant difference among the tree species was detected. For the forest owner to predict the theoretical productivity of the harvester, it is possible to apply the equation R = K + KD * D, that is statistically significant, R 2 =0.85. This equation is applicable to thinnings when the diameter of thinned trees is between 4 and 25 cm. Forwarder's average productivity in thinned stands is 8.63 m 3 h-1 .