Impact of a variety of forestry machine types on soil compaction is evaluated in this study according to the measurement of soil penetration resistance at 0 to 80 cm depth. It is concluded in the study that soils with poor bearing capacity (PBC), comparably small penetration resistance and organic layer thicker than 5 cm are less vulnerable to soil compaction. The use of small-size forwarder Vimek 610 allows to reduce soil compaction to an insignificant level in comparison to the control sites, and most or ruts disappear within a few days in PBC conditions. Whereas John Deere 810E, which belongs to the middle-size class of forwarders, significantly compacts soil through the whole measured depth in similar conditions. Rottne F10B and John Deere 810E forwarders represent the same weight category, and soil compaction due to the use of these machines on soils with moderate bearing capacity (MBC) is similar too; however, on soils with weak (WBC) and good (GBC) conditions results are different, mostly due to a different amount of extracted roundwood in both trials. Tracked forwarder was used only in GBC conditions and the results demonstrated significant compaction only down to 22 cm depth. The trials confirm that the depth of the intensity of impact depends on the weight of the machine and amount of material extracted; however, additional measurement data are necessary to characterize the impact quantitatively in different conditions.

In Latvia, the management of grey alder stands is an important issue in non-state forests, where this species accounts for 14 % of the total non-state forest area. The motor-manual felling and processing of timber with a chainsaw is still a commonly used method in non-state forests, while timber harvesting in final felling is fully mechanized in state forests. This study examined the productivity and costs of the mechanized and motor-manual harvesting of grey alder following the cut-to-length CTL system and analysed factors influencing the productivity of harvesting of grey alder stands under Latvian conditions. Productivity rates achieved for mechanized and motor-manual harvesting were 7.04 and 2.99 m(3) per productive work hour, respectively. Despite lower productivity, motor-manual harvesting was more cost-effective than mechanized harvesting. Improved working methods that could ensure higher production levels and increase the labour costs in the future have potential to increase the cost competiveness of the mechanized harvesting of alder stands in Latvia.

Thinning of young forest stands is a contribution to the future of the stand development. Our study focuses on damage of the remaining trees and soil. Now it is common to see thinning of young stands with heavy forest machines, but most of these operations take place in commercial thinning. This study is focused on precommercial thinning to evaluate different mechanized thinning methods in relation to the damage done to the remaining trees and soil in deciduous tree stands. Data were collected in four stands where the average diameter of trees at breast height was 6.2 cm, the height of average trees - 9.5 m, but number of trees per hectare was more than 2900. The stands regenerate naturally. Damage was evaluated separately after harvester and forwarder operations. The study proves that forwarding makes much less damage to the remaining trees than harvesting. According to the study data, the traditional method results in the largest number of damaged trees, because operators need to cut all trees closer than 1.5 m from the target tree. Both schematic thinning methods result in significantly less damage. A statistically significant difference (p<0.001) was found in a proportion of damaged remaining trees between all of the applied working methods. The smallest amount of damage is associated with complex symmetrical thinning method. The most damage appears during harvesting. The aim of this study was to compare three working methods of biofuel production in pre-commercial thinning using harvester John Deere 1070D with accumulating felling head Bracke C16.b in grey alder (Alnus incana) pure stand.

In the nemoral forest zone where Latvia is situated, silver birch (Betula pendula) is among the pioneer species that most commonly invade clear-cut forest sites and abandoned lands. Still, it would pay to apply silvicultural tending to naturally appearing young stands of birch the more so because top quality birch timber has recently become a desired raw material for plywood industry with its small dimension stems suitable for pulpwood. To maintain high productivity and fast growth of silver birch in naturally established stands a proper timing of early thinning (cleaning) of young stands is crucial. In Latvia, motor manual felling of undesired trees by brush cutter or chainsaw and leaving the felled stems on-site for decomposing is a typical method used in pre-commercial thinnings. However, recovery and utilization of woody biomass in pre-commercial thinnings can provide a potential for compensating a part of expenses, thus increasing the cost-efficiency of cultivating forest crops. The aim of the given study on extraction woody biomass in pre-commercial thinnings of young natural origin silver birch stands was to evaluate the costs and possible gains of motor-manual operations, using chainsaw equipped with a felling handle for small dimensions trees. In the given study the prime costs of wood chips produced from the material recovered in pre-commercial thinnings of natural origin silver birch stands were EUR 9.02 per m. According to the base scenario the harvesting of woody biomass resulted in a positive financial balance of EUR 133.4 per ha.