Whole-tree harvesting with stump removal versus stem-only harvesting in peatlands when water quality,biodiversity conservation and climate change mitigation matter

This article examines alternative forest harvesting regimes when ecosystem services in terms of water quality, biodiversity conservation and climate change mitigation are included in the analysis. The harvesting regimes are whole-tree harvesting with stump removal and conventional stem-only harvesting. The harvesting regimes are evaluated under two alternative climate policy contexts. The first alternative is a carbon neutral bioenergy policy, which assumes the carbon dioxide (CO₂) neutrality of bioenergy and produces substitution benefits, as bioenergy replaces fossil fuels. The second alternative climate policy, a carbon non-neutral bioenergy policy, takes into account the fact that bioenergy causes carbon dioxide emissions, producing substitution costs, and that harvested woody biomass affects the ability of a forest to act as a carbon sink. We extend the traditional Faustmann (1849) rotation model to include nutrient load damage, biodiversity benefits, and climate impacts. The empirical analysis is based on Finnish data from a catchment experiment carried out on drained peatland forests. The empirical results show that under a carbon neutral bioenergy policy, whole-tree harvesting with stump removal produces the highest net social benefits. However, if a carbon non-neutral bioenergy policy is assumed, the net social benefits are greater under stem-only harvesting.     

Soil-CO2 flux after patch scarification,harrowing and stump harvest in a hemi-boreal forest

Abstract

Stump harvesting is one way of increasing the amount of bioenergy, but little is known about the consequences of tree-stump harvesting on the carbon balance in the forest. Therefore, soil-surface CO₂ flux (soil respiration, R _s) was determined two years after clear-cutting for common soil disturbances occurring after patch scarification, harrowing and stump harvest in southern Sweden. R _s from intact soil was found to be of the same magnitude as emissions from areas of mixed humus, indicating only small effects of disturbance. Elevated mounds produced lower emissions than in the intact soil during the second year despite larger amounts of organic matter, probably due to low soil moisture. The lowest R _s was found in soil surfaces with exposed mineral soil. The treatment effects on R _s were estimated considering the actual area of different disturbances. During the first year, there was no difference in R _s among the treatments, whereas in the second year the flux was 10% higher after harrowing and stump harvesting than after patch scarification, implying that the effects on CO₂ flux after stump harvest were comparable to conventional harrowing. However, it is unclear whether this finding basically applies to regions where decomposition is limited by soil moisture during the summer.     

Effects of bioenergy extraction on visual preferences in boreal forests: a review of surveys from Finland,Sweden and Norway

Increased forest biomass production for bioenergy will have various consequences for landscape scenery, depending on both the landscape features present and the character and intensity of the silvicultural and harvesting methods used. We review forest preference research carried out in Finland, Sweden and Norway, and discuss these findings in relation to bioenergy production in boreal forest ecosystems. Some production methods and related operations incur negative reactions among the public, e.g. stump harvesting, dense plantation, soil preparation, road construction, the use of non-native species, and partly also harvest of current non-productive forests. Positive visual effects of bioenergy production tend to be linked to harvesting methods such as tending, thinning, selective logging and residue harvesting that enhance both stand and landscape openness, and visual and physical accessibility. Relatively large differences in findings between studies underline the importance of local contextual knowledge about landscape values and how people use the particular landscape where different forms of bioenergy production will occur. This scientific knowledge may be used to formulate guiding principles for visual management of boreal forest bioenergy landscapes.     

Rising policy conflicts in Europe over bioenergy and forestry

Growing concerns over emissions of green-house gases causing climate change as well as energy security concerns have spurred the interest in bioenergy production pushed by EU targets to fulfil the goal of 20 per cent renewable energy in 2020, as well as the goal of 10 per cent renewable fuels in transport by 2020. Increased bioenergy production is also seen to have political and economic benefits for rural areas and farming regions in Europe and in the developing world. There are, however, conflicting views on the potential benefits of large scale bioenergy production, and recent debates have also drawn attention to a range of environmental and socio-economic issues that may arise in this respect. One of these challenges will be that of accommodating forest uses – including wood for energy, and resulting intensification of forest management – with biodiversity protection in order to meet EU policy goals. We note that the use of biomass and biofuels spans over several economic sector policy areas, which calls for assessing and integrating environmental concerns across forest, agriculture, energy and transport sectors.In this paper, we employ frame analysis to identify the arguments for promoting bioenergy and assess the potential policy conflicts in the relevant sectors, through the analytical lens of environmental policy integration. We conclude that while there is considerable leverage of environmental arguments in favour of bioenergy in the studied economic sectors, and potential synergies with other policy goals, environmental interest groups remain sceptical to just how bioenergy is currently being promoted. There is a highly polarised debate particularly relating to biofuel production. Based on our analysis, we discuss the potential for how those issues could be reconciled drawing on the frame conflict theory, distinguishing between policy disagreements and policy controversies.     

Comparison of ground disturbance of frozen peatland during stump harvesting using a stump drill and rake

ABSTRACT

Tree stumps could be a source of renewable energy, contributing to a reduced dependence on fossil fuels. In Finland, stumps are currently harvested when the ground is not frozen to avoid co-removal of large amounts of soil and stones. Hence, the machinery used for stump extraction is not operated year-round. On peatlands, stumps could potentially be harvested when the ground is frozen. However, peatlands are highly sensitive to ground disturbance. There is, therefore, a need to identify equipment that causes low ground disturbance. In this study, peatland ground disturbance at stump level caused by stump harvesting using either a stump drill or a conventional stump rake was evaluated and compared in winter conditions. Results show that the stump drill caused up to 90% less ground disturbance per harvested stump than the conventional stump rake, but harvested 32–53% of the stump wood. Additionally, the size and shape of the disturbed areas changed between the harvesting year and following year, indicating that frost heaving plays a role in filling holes caused by stump extraction. The stump drill also consumed similar time to the conventional stump rake when harvesting Scots pine stumps on mineral soils, but far more when harvesting Norway spruce stumps.     

Immediate Effects of Logging,Mounding, and Removal of Logging Residues on Epixylic Species in Managed Boreal Norway Spruce Stands in Southern Finland

The immediate effects of bioenergy harvesting methods on epixylic species were studied in mature managed Norway spruce dominated forests in southern Finland. The treatments included logging, residue harvesting, and soil preparation as either mounding or mounding combined with stump harvesting. Altogether, 110 logs and 440 species sample plots on logs were inventoried before and after logging, and after soil preparation treatments. Logging decreased the cover and species richness in all epixylic species groups. The soil preparation decreased the cover of macrolichens, while stump harvesting was significantly most devastating both for cover and richness in bryophytes. We suggest that bioenergy harvesting critically affects the epixylic species, and therefore the use of less devastating methods and compensation for the loss of coarse woody debris is recommended on a landscape level.     

Long-term effects of stump harvesting on soil properties and tree growth in Scots pine and Norway spruce stands

Abstract

Effects of stump harvesting on the properties of surface soil and on the density, structure and growth of Scots pine (Pinus sylvestris L.) and Norway spruce (Picea abies (L.) Karst.) stands were estimated in a field trial in western Finland. The experiment was established in 1977 and measured in 2010. Stems and logging residues were harvested after clear-cutting, and stumps were lifted and removed from half of the experimental area. Sixteen plots were planted with pine seedlings and 16 with spruce. The main effects of stump harvesting were improved survival of planted trees and an increase in natural regeneration. No clearly negative effects were noted in the stand development. Stump harvesting had no or minimal effects on the properties of the organic layer and those of the 0- to 10-cm mineral-soil layer. Soil properties did not differ between tree species. Pine production was higher on plots with stump removal compared to plots without soil treatment.     

Future quantities and spatial distribution of harvesting residue and dead wood from natural disturbances in Canada

Interest in the use of bioenergy is increasing because of the need to mitigate climate change, the increasing costs and finite supply of fossil fuels, and the declining price of lumber and paper. Sound bioenergy policies must be informed by accurate estimates of potential feedstock production, rights to the production, social values and economics. Two of the main sources of bioenergy feedstock from forests are (i) harvesting residue and (ii) dead wood resulting from natural disturbances (i.e. standing dead timber). We modeled the production of bioenergy feedstock from these two sources from 2005 to 2020 for Canada's managed forest south of 60° N so that this information can be used in provincial and national strategic planning. Published estimates of harvesting residue vary widely, and our objective was to provide more precise estimates based on new forest inventory data and regional modeling. Natural disturbances result in very large quantities of dead wood on the landscape, but estimates of future stocks and annual production have not previously been made. Our estimates included a 50% discount factor to net-down theoretically available quantities to a more realistic estimate of potential ecologically sustainable bioenergy feedstock. The total future annual production averaged 51 ± 17 Tg year⁻¹ from natural disturbances and 20 ± 0.6 Tg year⁻¹ from clearcut harvesting residues. Harvesting residue for the area logged varied spatially from a low of 1.0 ± 0.77 kg m⁻² year⁻¹ to a high of 6.7 ± 0.1 kg m⁻² year⁻¹. Dead wood production due to insects was forecast to peak in the Montane Cordillera of British Columbia (BC) at 16.7 Tg year⁻¹ due to the current mountain pine beetle outbreak. Total dead wood production due to fire was highest in the western portion of the boreal forest (3.6 Tg year⁻¹ in the Boreal Shield of Saskatchewan), in part due to the high frequency of fires in these ecosystems and the large area of western boreal forest, but the highest density production was in BC: >9 kg m⁻² year⁻¹ in the burned area. Our results showed that the dead wood stocks of 331 Tg oven-dry matter potentially available for bioenergy in 2020 are much smaller than the 3100 ± 84 Tg of dead wood stocks estimated based on ecosystem dynamics. While bioenergy use will accelerate the release of greenhouse gases compared to on-site decay, the energy is renewable and can be used as a substitute for fossil fuels. The net benefit to the atmosphere of forest bioenergy use is affected by many factors, and future research should further assess which sustainable wood-based bioenergy strategies yield the greatest net greenhouse gas benefits over the different time scales needed for post-disturbance forest recovery.     

Potential forest biomass resource as feedstock for bioenergy and its economic value in Indonesia

Indonesia has abundant forest biomass resource, which should not be considered as a low economic value resource. This forest biomass resource can be converted into bioenergy through various technologies and it becomes one of sources in Indonesia's energy mix. This paper focuses on forest residues generated primarily from the harvesting of natural production forests and industrial forest plantations; and wood processing mill residues. The estimated total potential forest biomass in Indonesia for bioenergy in the year 2013 was 132 PJ. About 50.4% resulted from harvesting residues and 49.6% from wood processing residues. Riau province has the largest potential bioenergy followed by Central Kalimantan, East Kalimantan, East Java, South Sumatera, Central Java and Jambi, which all together accounted for 87% of total potential bioenergy. Moreover, three major islands accounted for 95% of total potential bioenergy. Using a conversion return approach, the economic value of forest biomass when it was pelletized was estimated to be about US$ 5.6 per ton wood residues. The economic value of forest biomass is more sensitive to changes in the price of wood pellet than to changes in the collection and hauling cost of wood residues.     

Energy Audit of Wood Harvesting Systems

A computer-based model for the evaluation of energy use in mechanized wood harvesting systems (EnergyCalc) was developed with aid of life cycle analysis methodologies. The system boundaries were determined "from stump to roadside" with wood volume over bark (m³) as the functional unit. The computer model (based on a database system) used a Visual Basic program, and the energy audit was based on fuel and oil consumption, and the energy consumed in the manufacture of the machines and replacement parts. The general scenario from the literature, results from Sweden and a preliminary study from Ireland are presented. In the overall energy audit of mechanized wood harvesting systems in Ireland, fuel consumption was the most significant item (82%), followed by oils (7%) and machine repairs and replacement (11%). The mean energy use from the data for Ireland was found to be 16% higher than the equivalent in Sweden (120 vs 103 MJ m^?3). An energy reduction strategy that has the potential to reduce overall energy consumption for Irish systems by up to 13% was suggested.     

Torque required to twist and cut loose Scots pine stumps

Abstract

Stump wood is a possible source of renewable energy, but before its potential as a fuel can be utilised to a high degree, new harvesting techniques should be developed to reduce the environmental impact (notably ground disturbance) of harvesting stumps. The forces required to lift and drag stumps out of the soil are known. In this study, two unknown and important parameters were addressed: the torque required to uproot stumps by twisting them and the torque required to cut lateral roots around stumps. A new, improved stump-twisting rig was designed and used in trials with 28 Scots pine (Pinus sylvestris) trees (breast-height diameter over bark, 153–427 mm). The measured torque requirements ranged from 10 to 50 kNm. Twisting stumps required more torque than cutting lateral roots around stumps and the required torque increased with increases in stump size. The results indicate that a wrist on a big feller-buncher, but not a conventional rotator used on forest machines, should be able to generate sufficient torque to cut the roots around stumps such as those used in this study.     

Fuel quality of Norway spruce stumps – influence of harvesting technique and storage method

Abstract

The interest in using stump biomass as a biofuel has recently increased in Sweden. The uneven consumption of wood fuel during the year creates a need for storage. This study examined the properties of stump biomass and how they vary at two sites in Sweden depending on harvesting technique, storage method and storage period. Norway spruce stumps, extracted using three different stump harvesting heads (Pallari, Rotary Cutter and Aalto), were stored in windrows or heaps. After 3 months, stumps stored in heaps were gathered into windrows. The fuel quality parameters moisture content (MC), ash content (AC) and calorific value (CV) were evaluated on five occasions in the period May 2008–September 2009. After 16 months of storage, the MC in all treatments had decreased to <25% (wet basis). Average AC decreased from 3.8% to around 1% (dry basis), whereas CV marginally increased. Stumps split during harvesting dried better than those harvested in one piece. The influence of storage method was minimal, although initial storage in heaps allowed better drying in the stumps harvested in one piece. In general, fuel quality improved in all treatments after storage.     

Pine and spruce stump harvesting productivity and costs using a Pallari KH 160 stump-lifting tool

Abstract

Even though stumpwood may become a significant part of the future fuel mix for combined heat and power plants in Sweden, the harvesting of stumps after regeneration felling is still only performed on a trial basis. Results from time studies on two, 23 tonne, excavators fitted for stump lifting, together with follow-up data on stump lifting and forwarding, are presented. Lifting, splitting, and piling the stumps accounted for 17, 32, and 32%, respectively, of the total productive work time. A predictive model was developed to estimate operational times and productivities when lifting pine and spruce stumps. Stump diameter, species, and terrain conditions contributed significantly to the fit of the model. The model predicts that productivity of stump lifting in spruce sites with easy terrain conditions and average stump diameters of 20 and 40 cm will be 1.23 and 4.19 oven-dry tonnes (ODT) per productive work hour, respectively. This is 43% higher than in pine sites with difficult terrain conditions and the same diameters. In the follow-up data, the productivity in stump lifting varied from 1.5 to 2.9 ODT per productive work hour while the cost for lifting and extraction to roadside varied from 37.8 to 59.4 €/ODT.     

Carbon balance of a forest ecosystem after stump harvest

Abstract

Stump harvest in forests can cause both reductions of CO₂ emissions through a decrease of decomposable substrate (direct effect) and emission increases as a consequence of deep and extensive soil disturbance (indirect effect). Here, the effects of stump harvest on net ecosystem CO₂ exchange (NEE) in a former Norway spruce stand in mid Sweden are presented. CO₂ exchange was continuously followed by eddy-covariance measurements during the first years after harvest. Differences in NEE from stump harvested and mounded (reference) plots were determined by soil-surface respiration measurements. Respiration from decaying stumps was estimated by a decomposition model. Fluxes indicated a direct effect (decreased efflux) during the first year after harvest that corresponded to the absence of decomposing stumps. During the following years, this emission reduction was increasingly counteracted by an indirect effect (increased efflux) of similar magnitude. This means that the expected emissions caused by extra soil disturbance occur with a certain delay and seem to increase with time. By these emissions, the substitution efficiency of stumps as bioenergy resource is reduced. Furthermore, at a time scale of centuries, instant combustion of stumps leads to a larger contribution to global warming than slow decomposition, because the stump carbon is available earlier in form of greenhouse gas. This is estimated by the time integral of emissions. Thus, despite the surprisingly low initial emissions, the overall substitution efficiency and climate benefits of stump harvest are likely to be small. The long-term consequences of stump harvest for the carbon budget are, however, still uncertain.     

Precommercial thinning of beech (Fagus sylvatica L.): Early effects of stump height on growth and natural pruning of potential crop trees

Abstract

This paper reports the early effects of stump height on the growth and natural pruning of potential crop trees after precommercial thinning of a young stand of naturally regenerated beech (Fagus sylvatica L.) in Denmark. The experiment comprises five treatments based on combinations of three grades of precommercial thinning and three stump heights. Treatments include the unthinned control, thinning only of whips and wolf trees (using low stumps), and thinning for potential crop trees using low, medium or high stumps. All treatments were replicated three times. Stump heights averaged 10, 90 or 230 cm, respectively. Pretreatment stem number (live trees) varied from 17,500 to 41,000 ha^?1. In the potential crop tree treatment, post-treatment stem number ranged from 4750 to 9500 ha^?1. Following two growth seasons, the quantity of stump regrowth increased with increasing stump height, the rate of stump regrowth increased with increasing stump height, the diameter growth of potential crop trees increased with decreasing stump height, the increase in stand height did not depend on stump height or post-treatment stem number, and the natural pruning of potential crop trees increased with increasing stump height. It remains to be seen whether these trends hold in the long run, and whether additional economic return from the increase in wood quality with increasing stump height compensates for the reduction in diameter growth.     

Bioenergy from the forest sector: Economic potential and interactions with timber and forest products markets in Norway

Abstract

A partial equilibrium forest sector model which is augmented to include bioenergy was applied to project the use of bioenergy based on forest fuels and forest industry by-products in Norway for three different scenarios of the future prices of electricity and oil. The impacts on forestry and forest industries of the different energy price scenarios were also studied. The advantage of the suggested methodology is that it allows for assessments of the economic potential of bioenergy, taking into account the competition for raw materials, the specific heat demand of various regions, and interregional and international trade. Bioenergy will, according to this study, be fairly competitive in some market segments with the current price levels of electricity and oil, and only a minor increase (decrease) in energy (roundwood) prices would release substantially increased bioenergy production levels. Pulpwood prices of pine and non-coniferous species are projected to increase substantially when assuming increasing energy prices. Except for particleboard mills, production levels of forest industries appeared relatively insensitive to the energy price changes.     

Logistics of supplying biomass from a mountain pine beetle-infested forest to a power plant in British Columbia

Abstract

The search for alternative energy sources has increased the interest in forest biomass. During the past few years, the severe infestation of the mountain pine beetle (MPB) within the forests of interior British Columbia (BC) has led to huge volumes of dead wood that exceed the capacity of the lumber industry. One way to make the most value of the surplus wood is to use it as the feedstock for bioenergy. The high costs associated with harvest and transport, and uncertainty in supply logistics are issues related to forest biomass utilization. This paper presents the development of a forest biomass supply logistics simulation model and its application to a case of supplying MPB-killed biomass from Quesnel timber supply area (one of the most infested areas in the interior BC) to a potential 300 MW power plant adjacent to the city of Quesnel. It provides values of quantity, cost and moisture content of biomass which are important factors in feasibility study of bioenergy projects. In the case of a conventional harvesting system, the biomass recovered from roadside residues in 1 year will meet only about 30% of the annual demand of the power plant with an estimated delivered cost of Can $45 per oven-dry tonne of woodchips. Sensitivity analyses were also performed.     

Collembola in low stumps at clear-cuts. Is stump harvesting a threat?

Abstract

Stump harvesting as a way to increase wood biomass production in order to meet the European Union targets for reduced CO₂ emissions is starting up in Sweden. The knowledge about if and how Collembola species can use low stumps as a substrate is very limited. Stumps of three different ages (4, 14 and 75 years) were sampled to see if Collembola used the dead wood during the whole rotation period of a forest. Stumps of spruce, pine and birch were compared. Both the bark and the splint wood of the stumps were sampled. To determine whether the stump also influenced the nearby soil, the soil close to the stump were sampled as well as the soil further away. In total, five Collembola species that are known to prefer dead wood as a substrate were found in the stumps. Wood specialists were more dominating in young stumps, but occurred also in the oldest stumps. No preference was found for any specific tree species. Wood-living Collembola seem to be able to survive in low stumps for a whole rotation period, at least in low numbers. There is, however, a risk for extinction debt due to their low capacity for active long-distance dispersal.     

Harvesting and extraction impacts on Eucalyptus grandis × E. urophylla coppicing potential and rotation-end volume in Zululand,South Africa

From the early 2000s there has been a general shift in South Africa in harvesting and extraction systems from the use of semi- to fully-mechanised systems. Any increase in mechanisation, as is occurring in Zululand, will need to take into consideration damage to stumps and the subsequent ability to regenerate by coppice. In 2002, four types of harvesting and extraction systems, arranged in a randomised complete block design, were used to clearfell a stand of E. grandis × E. urophylla. A motor-manual harvesting system was used to carry out the manual harvesting system (Man). The fully mechanised system (Mech) consisted of a single-grip harvesting head used with a tracked excavator to carry out all felling and processing operations. Two additional systems (Man_Mech_3W and Man_Mech_Flexi) had increased levels of mechanisation over that of the Man treatment. Both these harvesting systems made use of a Bell debarker, with loading carried out by a Bell three-wheeled loader in the Man_Mech_3W, and by a Flexiloader in the Man_Mech_Flexi treatments. Data collected from these four treatments were used to determine the effects of mechanised harvesting systems on type and severity of stump damage, coppicing potential and coppice growth over the rotation. Irrespective of harvesting system, more damage occurred to the top than bottom half of the stump, with a significant decrease in coppice regrowth with increasing stump damage. Most damage and least coppice regrowth occurred in the extraction rows where the damage recorded could be attributed to vehicle movement, tear-outs and/or log stripping. There was no significant difference between the harvesting systems in terms of stump mortality, final stem stocking and rotation-end volume. Thus, individual components within each harvesting system can have a larger impact than the overall harvesting system used. Future research should focus on these components, and where associated damage occurs for a specific component, this should be lessened through management intervention, training or technological improvements.     

Impacts of logging residue and stump removal on nitrogen export to a stream: A modelling approach

Abstract

The use of forest chips for energy can decrease net carbon emissions to the atmosphere, but harvesting logging residues and stumps may have adverse effects on the environment, including changes in nutrient export to water-bodies. The aim of this study was, with the aid of a computer model, to simulate the effects of logging residue and stump removal on nitrogen (N) export from a clear-cut area to a stream. A spatially semi-distributed FEMMA ecosystem model (tool for Forestry Environmental Management) was used to simulate N export from a catchment subject to clear-cutting and four different scenarios of logging residue and stump removal. These scenarios were compared with a conventional clear-cutting scenario, where the logging residues were left on site. Simulations suggested that the logging residue recovery does not decrease N export to the stream. In the model this was explained by a decrease in microbial immobilization, which in the case of conventional clear-cutting reduces net release of N in decomposition and mitigates the export of N. The decrease in immobilization is directly related to the removal of the woody debris from the site. Simulations suggested that harvesting of logging residues in low atmospheric N-deposition areas is not an effective strategy for reducing N loads in water-bodies.