Dirk Jaeger

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• University Professor University of Göttingen, Dean of Studies, Head of Department of Forest Work Science and Engineering, Forest Engineer (P.Eng. APEGNB Canada) and Adjunct Professor University of New Brunswick
• Professor at University of Göttingen

Our research explored the impact of forest machinery on soil when trafficking off-road through forest stands. In particular, we assessed soil compaction caused by harvesting operations. This study had two objectives: (i) Quantify the increase of soil bulk density (absolute and relative density) by forest machinery; and (ii) Analyze the persistence...

Steel flexible tracks (SFT) are regularly installed on bogie axles of forwarders to improve traction and extend trafficability by increasing the contact area between machines and operating surface. The study quantified dynamic peak loads exerted by a forwarder driving either on wheels or using additional SFT on its rear bogie axle. To examine load...

The term Industry 4.0 (I 4.0) has been shaping the discussion about increasing digitization in industrial and service value chains for several years. The concepts and technologies driving the fourth industrial revolution are increasingly moving to focus on forestry’s practice and research. They both are attempting to develop new solutions for the f...

Conservation and management of forest ecosystems are currently largely conflicting goals in the Brazilian Atlantic Forest biome. At present, all parts of the Atlantic Forest are protected and commercial logging is highly restricted. However, sustainable forest management systems can offer significant income opportunities for landholders, and thereb...

Cable-based timber extraction offers some advantages with regard to impacts to forest stands and soils, and can be used under a wide range of conditions. It is important not only in steep terrain, but also increasingly in flat terrain when soils have low bearing capacity. In this study, utilization data from two commonly used tower yarding systems...

Forests roads follow standardized design protocols which utilize unpaved gravel to ensure rapid water drainage but also leaves them prone to erosion. However, in many places, precipitation patterns are significantly affected by global climate change. The design of forest roads should be adapted to these changing conditions, which requires a fundame...

Traction assistance of forest machines via traction aid winches has gained widespread application in steep-terrain forest operations as it can mitigate soil disturbance by reducing wheel or track slip of the assisted machine. Since slip affects machine operations in flat terrain as well, especially on fine-grained and moist soils, the effectiveness...

Spatiotemporal modeling is an innovative way of predicting soil moisture and has promising applications that support sustainable forest operations. One such application is the prediction of rutting, since rutting can cause severe damage to forest soils and ecological functions. In this work, we used ERA5-Land soil moisture retrievals and several to...

Large clear-cut areas as a consequence of drought and bark beetle infestations necessitate extensive replanting efforts in German forests, leading to an increased interest in efficient planting systems. In addition to manual planting, mechanized and semi-mechanized systems utilizing surplus forest machine capacities available after completion of sa...

Climate change and associated heat waves and droughts are causing enormous amounts of damaged wood in Central Europe. To face these challenges, mechanized timber harvesting systems consisting of single-grip-harvesters and forwarders are commonly employed due to their high productivity and work safety. Despite the advantages of these work systems, t...

European pellet production will be a future challenge due to two effects: (1) the share of hardwood species in Europe will increase and (2) the pellet market will face raw material shortages. Therefore, we investigated the blending of conifer sawdust with black locust sawdust. Twenty-one physical and chemical pellet quality parameters were recorded...

The increasing worldwide energy demand in parallel to the increasing climate change effects require the utilization of sustainable energy sources. Biomass residues are a feasible energy source, but their chemical composition often compromises their utilization due to slag formation or high emissions. It is investigated in this study whether hydroth...

Spatiotemporal modelling is an innovative way of predicting soil moisture and has promising applications in supporting sustainable forest operations. One such application is the prediction of rutting, since rutting can cause severe damage to forest soils and ecological functions. In this work, we used ERA5-Land soil moisture retrievals and several...

Purpose of Review Biodiversity is one of the most important features of forest ecosystems. One of the goals of Sustainable Forest Management is to reduce biodiversity disturbance, which can occur as a consequence of timber harvesting. The aim of this review was to define which silvicultural systems and forest operations can have an influence on for...

Highly mechanized forestry operations are essential for efficient timber harvesting. Therefore, the skills of harvester operators appear to be key to productive and sustainable use of the machines. Recent research has revealed a knowledge deficit regarding the work practices of forest machine operators. This urges systematic research into forestry...

Variance in productivity of fully mechanized timber harvesting under comparable stand and terrain conditions requires the investigation of the influence of work practices of machine operators. Work practices can vary among operators and may result in a wide range of productivity. Therefore, it is of great interest to identify positive and negative...

Subject to overexploitation in the past centuries, the Atlantic Forest is subject to very rigorous protection rules. However, the law is a controversial issue since landowners are not compensated for the limited choice of land use possibilities. We believe that, alternatively to a general timber harvest ban, sustainable forest management of the Atl...

Water leaching and hydrothermal carbonization are tools to upgrade biomass residues for combustion. Water leaching reduces the ash content, which increases the heating value, while hydrothermal carbonization (HTC) increases heating value and ash content and decreases the organic fraction of the fuel. The objective of this study is to investigate, w...

Purpose of Review Mechanized logging operations with ground-based equipment commonly represent European production forestry but are well-known to potentially cause soil impacts through various forms of soil disturbances, especially on wet soils with low bearing capacity. In times of changing climate, with shorter periods of frozen soils, heavy rain...

Fully mechanized timber harvesting systems are well established in forest operations worldwide. In cut-to-length (CTL) systems, forwarders are used for extracting logs from the stand. The productivity of a forwarder is related to site- and stand-specific characteristics, technical parameters, organizational aspects, and the individual skills of the...

Milder winters and extended wetter periods in spring and autumn limit the amount of time available for carrying out ground-based forest operations on soils with satisfactory bearing capacity. Thus, damage to soil in form of compaction and displacement is reported to be becoming more widespread. The prediction of trafficability has become one of the...

The utilization of detailed digital terrain models entails an enhanced basis for supporting sustainable forest management, including the reduction of soil impacts through predictions of site trafficability during mechanized harvesting operations. Since wet soils are prone to traffic-induced damages, soil moisture is incorporated into several system...

The worldwide transformation from fossil fuels to sustainable energy sources will increase the demand for biomass. However, the ash content of many available biomass sources exceeds the limits of national standards. In this study, short-rotation coppice willow biomass was hydrothermally treated at 150, 170 and 185 °C. The higher heating value incre...

The work presented looks at methods to model field measured spatio-temporal variations of soil moisture content (SMC, [%vol])-a crucial factor for soil strength and thus trafficability. We incorporated large-scaled maps of soil characteristics, high-resolution topographic information-depth-to-water (DTW) and topographic wetness index-and openly ava...

Milder winters and extended wetter periods in spring and fall limit the amount of time available for carrying out forest operations on soils with satisfactory bearing capacities. Thus, damage in the form of rutting and compaction is reported to be becoming more widespread. The prediction of soil strength, and therewith stand trafficability, in conn...

Through wider spacing of machine operating trails, less stand area is impacted by off-road traffic of timber harvesting and extraction machinery and more productive forest area is maintained. In Germany, the national standard of FSC (Forest Stewardship Council) as well as some state forest enterprises support a spacing of 40-m of machine operating...

Milde Winter und vermehrter Niederschlag im Frühling und Herbst können die Zeitspanne für effiziente Holzernte auf trockenem oder gefrorenem Boden verkürzen. Daher kommt es im Zuge von maschinellen Nutzungen vermehrt zu Bodenschäden, wie Spurrillenbildung oder Bodenverdichtung. Eine genaue Vorhersage von Bodenfeuchte und Bodentragfähigkeit ist von...

Early bark beetle detection is still a challenge, as the symptoms of early infestation stages are hard to identify. Conventional foot-based detection is time consuming, and the associated costs mostly depend on stand characteristics. Detection by gas sensor equipped drones has the potential to be more economical, as it does not rely on the limitati...

In order to compare the vibration and noise exposure of STIHL’s battery-powered MSA 220 C and the combustion driven MS 201 C, a professional operator was monitored during a pre-commercial thinning operation in a twenty-year-old hardwood stand. The vibration levels were measured with a tri-axial accelerometer on the front and rear handle of both the...

Despite an intensive mechanization trend in German forest operations since the early 1990s, many sites restrict the efficient implementation of fully mechanized harvesting systems. Trafficability and singletree selection harvest-based silviculture, focusing on high stem volume broadleaves, such as European beech, are the main limitations. Thus, mot...

In Germany, management restrictions for Norway spruce (Picea abies (L.) H. Karst.) due to climate change lead to increasing interest in Douglas fir (Pseudotsuga menziesii (Mirb.) Franco) as a potential substituting species. However, Douglas fir requires cost-intensive silvicultural treatments, such as periodic thinnings and, in particular, pruning....

Digitalization and its associated technology are shaping the world economy and society. Data collection, data exchange, and connection throughout the wood supply chain have become increasingly important. There exist many technologies for the implementation of Industry 4.0 applications in forestry. For example, the integration of harvester productio...

The success of the pellet industry depends on internal and external factors, comprising pellet quality, pellet production parameters and market variables. This study investigated the pellet production process from the raw material properties to the economic production parameters in order to quantify the feasibility of a new production concept. The...

The impact of machines on forest soils is regularly assessed and quantified using absolute bulk density, which is most frequently obtained by soil cores. However, to allow for repeated measurements at the exact same locations, non-destructive devices are increasingly being used to determine soil bulk density and moisture content in field studies. A...

The project PROTECTFOREST deals with improvements in early bark beetle (e.g., Ips typographus and Pityogenes chalcographus) detection to allow for fast and effective response to initial infestation. The removal of trees in the early infestation stage can prohibit bark beetle population gradation and successive timber price decrease. A semiconductor...

Timber harvesting operations using heavy forest machinery frequently results in severe soil compaction and displacement, threatening sustainable forest management. An accurate prediction of trafficability, considering actual operating conditions, minimizes these impacts and can be facilitated by various predictive tools. Within this study, we valid...

Subject to overexploitation in past centuries, the Atlantic Forest is now strictly protected, including a ban on timber harvesting. However, this strict protection is a very controversial issue. It resulted in a lack of willingness of landholders to conserve and possibly even expand native forest areas. The lack of knowledge on impacts of potential...

Recently, forest operations are facing unfavorable climatic conditions more frequently. In Central Europe, machine trafficability and induced soil disturbances are negatively affected by periods of high precipitation and less intensive frost during ground-based harvesting operations. Winch-assist technology is assumed to reduce soil disturbance by...

The project PROTECTFOREST deals with the improvement of early bark beetle detection to allow a fast and effective response to initial infestation. The removal of trees in the early infestation stage can prohibit bark beetle population gradation and successive timber price decrease. A semi-conductor gas sensor array was tested in the lab and attache...

Die Holzernte und -rückung mit Seilkrananlagen bietet im Hinblick auf die Bodenpfleglichkeit von Holzerntesystemen einige Vorteile. So ist die seilgestützte Holzrückung nicht nur in Hanglagen, sondern auch zum Schutz ebener Lagen von Bedeutung. Auch kann sie hinsichtlich des Verfahrens variieren, beispielsweise je nach Stärkeklasse des ausscheidend...

Bioenergy in Mexico offers a great potential as a transition strategy for introducing new energy supply chains. However, studies which focus on wood supply chains for bioenergy generation at a national level are scarce. Hence, this paper presents a model for predicting short-term availability of woody biomass for energetic use according to two scen...

Winching is a common practice for extracting logs in forest operations; however, it requires significant physical effort by humans to pull-out the cable to the felling site. The aim of this study was to quantify the intensity of this activity by measuring human effort parameters during different winching operations under experimental conditions wit...

Through a portable spiroergometric device linked to a beat-to-beat heart measurment, METs and %HRR of test persons were quantified during winching operations with a mini forestry crawler

Year-round accessibility of forest road networks is crucial for an efficient wood supply chain, particularly for timber harvesting operations and transport activities. In this respect, detailed knowledge about the seasonal accessibility including the maintenance status of forest roads is highly recommended. The prerequisite for any approach to gain...

Short rotation coppice (SRC) plantations are predominantly established as monocultures. Reasons include simplicity and thus efficiency in planting, homogeneous growth, and a desire to maximize yields by selecting top-performing species. However, pests and disease outbreaks generally cause much greater damage to monocultures than to mixed plantation...

Forest soils often exhibit low bearing capacities and as a result are often incapable of withstanding high axle loads. In New Brunswick, Canada, five different brush amounts (0, 5, 10, 15, and 20 kg·m–2) were applied as brush mats on machine operating trails during a cut-to-length harvesting operation in a softwood stand to analyze soil disturbance...

This study presents a semi-conductor metal oxide gas sensor system for the online flue gas monitoring during oak wood drying. Oak wood flakes and solid oak wood were heated on laboratory scale. The emissions were analyzed by gas chromatography–mass spectrometry and monitored by a semi-conductor metal oxide gas sensor setup. The calibrated sensor sy...

The term Industry 4.0 (I 4.0) has been shaping the discussion about increasing digitization in industrial and service value chains for several years. The concepts and technologies driving the fourth industrial revolution are increasingly moving to focus on forestry’s practice and research. They both are attempting to develop new solutions for the f...

Mechanized cut-to-length forest operations often rely on the use of brush mats created from harvesting debris (tree limbs, tops, and foliage) to reduce soil disturbances as a result of in-stand machine traffic. These brush mats, placed directly on the forest floor within machine operating trails, distribute loads of timber harvesting and extraction...

Forest fire risk estimation constitutes an essential process to prevent high-intensity fires which are associated with severe implications to the natural and cultural environment. The primary aim of this research was to determine fire risk levels based on the local features of an island, namely, the impact of fuel structures, slope, aspects, as wel...

Productive forests, as a major source of biomass, represent an important pre-requisite for the development of a bio-economy. In this respect, assessments of biomass availability, efficiency of forest management, forest operations, and economic feasibility are essential. This is certainly the case for Mexico, a country with an increasing energy dema...

Over recent decades, China’s forestry sector went through a transition phase characterized by a management and institutional reform process, with a constant rethinking of the ecological and societal role of forests within a unique political system. Nevertheless, despite impressive achievements in forest restoration and conservation efforts, the enh...

The goal of this research was to examine the mitigating effect of brush mats on soil disturbance caused by off-road traffic of forest machinery, specifically how brush quantity affects rutting and soil displacement in a cut-to-length (CTL) harvesting operation. A field test was performed to analyze the effects of brush mats of varying quantities on...

The impacts of soil compaction along skid trails (haul roads) on the growth of seedlings were monitored during the first growing season in a mature deciduous stand in the Hyrcanian forests, northern Iran. Two native pioneer tree species, alder (Alnus subcordata C.A.M.) and maple (Acer velutinum Boiss.), were seeded within and beside the upslope and...

The Atlantic Forest in southern Brazil has been subject to overexploitation in the past prompting the formulation of a rigorous conservation orientated policy by the government including a strict ban of timber harvesting. In the region, the forestland is mostly owned by farmers. The economic value of the forest is rather limited for those farmers,...

User-behavior of small wood heating appliances - European survey

The globally emerging concepts and strategies for a “bioeconomy” rely on the vision of a sustainable bio-based substitution process. Fossil fuels are scarce and their use contributes to global warming. To replace them in the value chains, it is essential to gain knowledge about quantities and spatial distributions of renewable resources. Decision m...

Skid trails in the Hyrcanian forest of northern Iran are important for moving wood to log landings; however, they can cause soil compaction and alter water infiltration. This research therefore presents an analysis of the impact of ground-based skidding on soil hydrophysical properties in Kuhmiyan forest located in the Hyrcanian forest. Soil infilt...

A time study was done to evaluate two different methods in early thinnings: a schematic reducing of stem number by spacer and chainsaw and a future crop tree orientated clearing by chainsaw. In both cases 2 m logs have been produced if the trees were not more than 5 m away from skid trails. The study showed that it is economically not efficient to...

In order to accommodate foreseen climate change in European forests, the following are recommended: (i) to increase the number of tree species and the structural diversity; (ii) to replace unsuitable species by native broadleaved tree species, and (iii) to apply close-to-nature silviculture. The state forest department of Baden-Württemberg (BW) cur...

While considering constraints in regard to sustainability, this paper reviews the development of a methodology to assess the introduction of bioenergy supply chains in Mexico based on forest woody biomass. Three research modules include analyses of forest biomass utilization residues that originated from: (1) harvesting activities, (2) non-extracte...

Firewood combustion is the main renewable heating source for households in Europe and responsible for a certain share of harmful emissions such as particle matters. Common wood combustion appliances in households are firewood stoves. Forced by stringent limits of European emission control legislation stove industry developed a wide variety of new p...

Wood pellet combustion for heating is increasing in importance in Europe. However, the most commonly used heating appliances such as wood pellet stoves are responsible for emissions which could negatively affect human health. The emissions quality of pellet stoves is influenced by pellet properties and combustion phase characteristics. The goal of...

Oak (Quercus petraea and Quercus robur), an emblematic species in French forests, has a strong patrimonial value and plays a leading role in the forestry and forest-based industry. However, the industry appears to be confronted with major problems (e.g. supply to markets). We tried to better understand and analyse those problems by studying the oak...

The crucial point in inorganic particle formation from biomass combustion is the temperature-dependent release of inorganic compounds, especially potassium (K). Currently common wood fuels comprise a comparatively low amount of K, but the increased usage of wood energy requires new feedstocks in the future. Potentially new feedstocks like short-rot...

The extension of plantations in the southern provinces of China was supposed to fill the demand-and-supply-gap within the country's forest products industry. But a factor strongly limiting the supply capacity is the low productivity of the conventional manual clearcut systems currently in use. In addition, a political shift in silvicultural objecti...

This case study analyzed the performance of a start-up cable yarding crew in southern China through operational monitoring by consecutive time studies, long-term log book recordings and efficiency evaluation by stochastic frontier analysis (SFA). The crew, which used a KOLLER K303 H mobile tower yarder, was monitored for two years. During this peri...

The temperature-dependent release of inorganic elements is the first step of the main formation pathway of particle emissions in automatically fired biomass burners. To investigate this step, a residential pellet boiler with an underfeed-burner was equipped with a direct firebed cooling. This test setup enabled decreased firebed temperatures withou...

Wood combustion is the main renewable heating source for European households and responsible for a large portion of the particle matter in the atmosphere. Firewood operated small-scale residential wood combustion units such as firewood stoves and tiled stoves are the most widespread wood combustion appliances in households. Next to purely technolog...

There was a fast increase in the planted area of forest plantations in Brazil in the period from 1966 until the beginning of the 1980s due to governmental fiscal incentives, when management practices were adopted from agriculture, which raised environmental concerns. Research investigation has been conducted in order to better adapt the management...

Forest fires consist one of the greatest hazards for the viability and sustainable development of forests with implications both on natural and cultural environment, affecting the economy and the quality of life of local population. The outbreaks of forest fires could stem from either natural (thunders) or anthropogenic causes 736 http://www.iises....

The sustainable management of forest resources can only be achieved through a well-organized road network designed with the optimal spatial planning and the minimum environmental impacts. This paper describes the spatial layout mapping for the optimal forest road network and the environmental impacts evaluation that are caused to the natural enviro...

This study investigates the general concept of reduced firebed temperatures in residential wood pellet boilers. Residential wood pellet boiler development is more and more concerned with inorganic aerosols characterized by a temperature-dependent release from the firebed. Hence, different concepts are applied aiming to reduce firebed temperatures....

In cut-to-length mechanized forest harvest operations, trees are cut, delimbed, and bucked to standard lengths directly in the harvest block. This in-stand processing, generates harvesting residue composed of tree limbs, tops, and foliage, which is frequently placed on machine operating trails to prolong trail trafficability and protect forest soil...

This case study examines the performance of the Igland Hauler employed in small diameter Eucalyptus clear-cut operations in Guangxi, China. A yarding crew of eight persons was monitored by a snap back elemental time study for 19.23 SMH (scheduled machine hours), with 159 yarding cycles and a yarded log volume at landing of 49.4 m³ solid over bark....