The effective implementation of sustainable forest management depends largely on carrying out forest operations in a sustainable manner. Climate change, as well as the increasing demand for forest products, requires a re-thinking of forest operations in terms of sustainability. In this context, it is important to understand the major driving factors for the future development of forest operations that promote economic, environmental and social well-being. The main objective of this paper is to identify important issues concerning forest operations and to propose a new paradigm towards sustainability in a changing climate, work and environmental conditions. Previously developed concepts of forest operations are reviewed, and a newly developed concept - Sustainable Forest Operations (SFO), is presented. Five key performance areas to ensure the sustainability of forest operations include: (i) environment; (ii) ergonomics; (iii) economics; (iv) quality optimization of products and production; and (v) people and society. Practical field examples are presented to demonstrate how these five interconnected principles are relevant to achieving sustainability, namely profit and wood quality maximization, ecological benefits, climate change mitigation, carbon sequestration, and forest workers' health and safety. The new concept of SFO provides integrated perspectives and approaches to effectively address ongoing and foreseeable challenges the global forest communities face, while balancing forest operations performance across economic, environmental and social sustainability. In this new concept, we emphasize the role of wood as a renewable and environmentally friendly material, and forest workers' safety and utilization efficiency and waste management as additional key elements of sustainability.

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Purpose of Review Lowering the impact of forest utilisation on the forest environment is a part of the improvement in sustainable forest management. As part of forest utilisation, timber harvesting can also cause environmental implications. The main impact of forest operations is on the soil, on regeneration and on the residual stand. The aim of the present review was to identify the state of the art in forest utilisation, identifying how and how much forest operations affect forest soil, regeneration and the remaining stand. Particular attention was paid to the level of impact and potential to limit this. Recent Findings There are a large number of publications tackling forest harvesting, but most of them do not give a comprehensive framework and they mainly focus on one or very few aspects of forest damage. In order to improve general knowledge of the impact of forest operations, it was proposed that the scope of recent findings should be examined and a compilation of the available results from different regions should be presented in one paper. Summary It was found that the least impactful machine-based forest operations were harvester-forwarder technologies, while a larger scale of damage could be expected from ground-based extraction systems (skidders) and cable yarders. Animal power, if applicable, tended to be very neutral to the forest environment. A decrease in damage is possible by optimising skid trail and strip road planning, careful completion of forest operations and training for operators. The existence of legal documents controlling post-harvesting stand damage are rare and have been implemented in only two countries; there is no post-harvesting control on soil damage and natural regeneration.

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The application of a harvester for thinning operations in young stands can pose several dilemmas. Firstly, the value of the timber obtained should be higher than the cost of the thinning operation-this is especially difficult with young stands, where the timber is of a small size and productivity is low. In addition, small harvesters used for thinning usually have short cranes, less than 10 m in length, which is rather impractical in stands where the distance between strip roads is a standard 20 m. The aim of this research was to select the best mechanised thinning operation, taking into account economic suitability and some environmental aspects (damage to the remaining stand and density of strip roads). The research was carried out in a 31-year-old pine stand (11.27 ha) in which three different harvester thinning (T) operations were designed: TM1) with midfield and one harvester pass, TM2) with midfield and two harvester passes and TWM) without midfield and one harvester pass. In all the proposed operations, a Vimek 404 T5 harvester (with a 4.6 m-long crane) and a Vimek 606 TT forwarder were used. The most economic operation was TWM, with a total cost of €13.73 m −3 , while TM1 was 13% more expensive at €15.51 m −3. The lowest level of damage, 1.5%, was recorded in TWM, while in TM1 the level was 2.1%. The TWM operation required a net of strip roads twice as dense as in TM1. Taking into account all the analysed aspects, a thinning operation with midfield and one harvester pass is recommended when using the Vimek 404 T5 harvester and the Vimek 606 TT forwarder in the first thinning of a pine stand.

Damage to the remaining stand on steep terrain can be quite severe and is usually difficult to control during winching. Timber skidding, especially by agricultural tractor, is a common solution in small-scale forestry. One of the factors influencing remaining stand damage is winching on steep terrain, although, to date, this has only been studied in general. Limiting stand damage is possible when the factors causing the damage are well-known. Therefore, the aim of this paper was to study in detail the impact of slope steepness on different types of damage in the stand after winching, focusing in particular on: (1) the share of trees with damage (including natural regeneration), (2) the size of the wound, (3) the number of wounds per tree, (4) wound intensity, and (5) the position of the wound on a tree. Field observations were carried out in three beech (two in Italy and one in Iran) and two pine stands (in Italy), in which four classes of slope steepness were selected for each stand. After timber harvesting, damage to the remaining stand as well as to any natural regeneration was recorded. It was found that the share of wounded trees was directly related to slope steepness, although this was less obvious in the natural regeneration. On steeper slopes, there were larger wounds and, on average, there were more wounds per tree. Wound intensity also depended on the gradient of the slope. The size, understood as diameter at breast height, of the remaining trees on the slopes also had an impact on the wound characteristics: on thicker trees, bigger wounds were detected and a higher number of them. However, thicker trees were less often wounded. Wound position on a tree did not depend on slope steepness but it may have been related to stand density and size of winched timber.

Reducing potential soil damage due to the passing of forest machinery is a key issue in sustainable forest management. Limiting soil compaction has a significant positive impact on forest soil. With this in mind, the aim of this work was the application of precision forestry tools, namely the Global Navigation Satellite System (GNSS) and Geographic Information System (GIS), to improve forwarding operations in hilly areas, thereby reducing the soil surface impacted. Three different forest study areas located on the slopes of Mount Amiata (Tuscany, Italy) were analyzed. Extraction operations were carried out using a John Deere 1410D forwarder. The study was conducted in chestnut (Castanea sativa Mill.) coppice, and two coniferous stands: black pine (Pinus nigra Arn.) and Monterey pine (Pinus radiata D. Don). The first stage of this work consisted of field surveys collecting data concerning new strip roads prepared by the forwarder operator to extract all the wood material from the forest areas. These new strip roads were detected using a GNSS system: specifically, a Trimble Juno Sb handheld data collector. The accumulated field data were recorded in GIS Software Quantum GIS 2.18, allowing the creation of strip road shapefiles followed by a calculation of the soil surface impacted during the extraction operation. In the second phase, various GIS tools were used to define a preliminary strip road network, developed to minimize impact on the surface, and, therefore, environmental disturbance. The results obtained showed the efficiency of precision forestry tools to improve forwarding operations. This electronic component, integrated with the on-board GNSS and GIS systems of the forwarder, could assure that the machine only followed the previously-planned strip roads, leading to a considerable reduction of the soil compaction and topsoil disturbances. The use of such tool can also minimize the risks of accidents in hilly areas operations, thus allowing more sustainable forest operations under all the three pillars of sustainability (economy, environment and society).

Small tree size represents the main challenge when designing a cost-effective harvesting system for European short-rotation plantations. This challenge is further complicated by the need to obtain 4-m logs for high-end products, which rules out the possibility of deploying whole-tree chipping. Both challenges can be met through mass or multi-tree handling (MTH), which must begin at the time of felling and continue uninterrupted along the whole supply chain. The objective was to: (1) gauge the productivity and the cost of CTL harvesting applied to these plantations; (2) assess log yield and capacity to match dimensional specifications; (3) determine if MTH applied to CTL technology offers a real benefit compared with conventional single-tree handling. The authors conducted a time study using a block design with a two-machine cut-to-length harvesting system (i.e. harvester and forwarder) in single- and multi-tree handling operations on the clear cutting of a hybrid poplar plantation in Poland, as well as we manually measured the produced volumes of the study. Higher productivity (+ 8%) was achieved under the multi-stem handling mode. The MTH system proved capable of containing harvesting costs below € 15 per green ton, while fulfilling set timber quality requirements in terms of value recovery and log quality specifications. A new, software-based, MTH system is recommended to be used in short-rotation poplar plantation for logs and biomass harvesting. When the coppicing season is over, the system can be deployed for the conventional thinning operations.