Greenhouse gas balance of harvesting stumps and logging residues for energy in Sweden

Abstract

In this case study, forest fuel procurement chains of stumps and logging residues were evaluated using a Life Cycle Assessment perspective. Direct emissions from combustion were not included, but soil organic carbon change was included as changes in carbon stocks in litter and soil. The results showed that primary forest biomass for energy has a climate impact which is time dependent. However, in long-time perspectives, there are large greenhouse gas (GHG) savings. In a short-term (20 years), there were no GHG savings when natural gas or coal was replaced. This is due to the fact that the harvest lead to decreased input of organic matter to the soil which is compared to a reference where biomass are left to decompose. The reduction in soil organic carbon may have been underestimated in the stump harvest systems studied, as the effect of soil disturbance per se was not included. Important factors when assessing GHG balance of forest fuels, besides the time horizon used, were site productivity, geographical position and forest fuel resource (stumps or logging residues). When assessing the greenhouse gas savings, efficiency of the end-use, allocation method between heat and power and type of fossil fuel replaced were also important.     

Greenhouse gas emissions from the use of primary energy in forest operations and long-distance transportation of timber in Finland

In Finland in 1993 the greenhouse gas emissions caused by machineryused in silvicultural and forest improvement work, wood harvesting,and timber transportation were 424.2 Gg carbon dioxide (CO₂(Gg = gigagram = 10⁹ g), 10.6 Mg nitrous oxide (Mg = megagram= 10⁶ g), 3.5 Gg carbon monoxide, 31.5 Mg methane, 5.6 Gg nitrogenoxide, and 0.7 Gg non-methane volatile organic compounds. Whenemissions were converted into equal units as global warmingpotential in terms of CO₂, the warming effects on a 20-yeartime frame equalled 1310 Gg as CO₂ and on a 100-year time frame669 Gg as CO₂. The proportion of silvicultural and forest improvementwork of the total emission was 8 per cent, cutting of timber13 per cent, haulage 18 per cent, long-distance transportation57 per cent, and transportation of machinery 4 per cent. Theemissions caused by the use of primary energy in forestry seemto be small compared with the amount of carbon in harvestedtimber, which was 30 300 Gg in terms of CO₂.     

木材含水率测定方法的比较研究

为修订国家标准“CB1931—80木材含水率测定方法”提供依据,本文对含树脂和挥发性物质较多的马尾松等5种木材,采用烘干法、真空干燥法和蒸馏法进行含水率测定的比较。结果表明,烘干法简便实用,但所测得的含水率结果比真空干燥法和蒸馏法为高,如果试样含有较多的挥发性物质,应用烘干法测定含水率误差偏大时,可采用真空干燥法。     

Impact of selective logging on genetic diversity of two tropical tree species with contrasting breeding systems using direct comparison and simulation methods

The impact of selective logging on genetic diversity of two tropical tree species with contrasting breeding systems was examined using direct comparison and simulation methods. Shorea leprosula is a diploid and predominantly outcrossed species, whereas Shorea ovalis ssp. sericea is an autotetraploid species with apomictic mode of reproduction. Direct comparison of adjacent natural and logged-over stands showed reduction of genetic diversity of S. leprosula, but not of S. ovalis ssp. sericea. These results clearly demonstrated that a single logging event would cause the genetic erosion of S. leprosula. However, the apomictic mechanisms and the effects of tetrasomic inheritance of S. ovalis ssp. sericea might be a way of maintaining the level of genetic diversity. These results clearly implied that outcrossing species might be more susceptible to the negative impact of logging on genetic diversity than apomictic species. Simulation studies were conducted using three approaches: (1) simulated-removal of individuals based on diameter size classes; (2) simulated-removal of individuals at random; and (3) simulated-removal of individuals in clump. The simulation study based on the first approach showed that the loss of genetic diversity was higher for the Malayan Uniform System (MUS) compared with the Selective Management System (SMS). This might suggest that SMS is more orientated towards the conservation of genetic diversity. In addition, the simulation study showed that to conserve 100% of the total number of alleles, the tolerable cutting limits of S. leprosula in the 50-ha plot of Pasoh FR should be >85 cm diameter at breast height (dbh). Comparison of simulation studies based on the second and third approaches showed that the loss of genetic diversity was more rigorous if logging activities were anticipated through extraction of trees in clump rather than to extract trees at random. Implications of the studies for conserving and managing the tropical forests are discussed.     

Evaluation of two surfacing methods on black spruce wood in relation to gluing performance

Surface quality and gluing performance of black spruce samples prepared by peripheral straight-edge knife planing and sanding were studied. Four wavelengths (1.5, 1.9, 3.1, and 6.5 mm) and four rake angles (15°, 20°, 25°, and 30°) were tested for peripheral planing. Three feed speeds (4, 10.5, and 17 m/min) and three grit size sandpapers (80, 100, and 120) were studied for sanding. The resulting surfaces were glued with an isocyanate adhesive and tested to evaluate their gluing performance (shear strength and percent wood failure). Results revealed that planing with a rake angle of 20° and wavelengths of up to 3.1 mm produced wood surfaces with adequate glueline shear strength. Sanding with 80-grit sandpaper produced the best glueline shear strength, regardless of feed speed. After accelerated aging, the loss of gluing performance was lower for the sanded samples compared with that of planed samples. In general, sanding process produced better wood surfaces for bonding with the adhesive studied.     

Greenhouse gas emissions after a prescribed fire in white birch-dwarf bamboo stands in northern Japan,focusing on the role of charcoal

Forest fires affect both carbon (C) and nitrogen (N) cycling in forest ecosystems, and thereby influence the soil–atmosphere exchange of major greenhouse gases (GHGs): carbon dioxide (CO₂), methane (CH₄), and nitrous oxide (N₂O). To determine changes in the soil GHG fluxes following a forest fire, we arranged a low-intensity surface fire in a white birch forest in northern Japan. We established three treatments, having four replications each: a control plot (CON), a burned plot (BURN), and a plot burned with removal of the resulting charcoal (BURN-CHA). Soil GHG fluxes and various properties of the soil were determined on four or five occasions during a period that spanned two growing seasons. We observed increased concentrations of ammonium-N (NH₄-N) in BURN and BURN-CHA after the fire, while nitrate–N (NO₃-N) concentration was only increased in BURN-CHA after the fire. The soil CO₂ flux was significantly higher in CON than in BURN or BURN-CHA, but there was no difference in soil CH₄ uptake between the three treatments. Moreover, the N₂O flux from BURN-CHA soil was slightly greater than in CON or BURN. In BURN-CHA, the soil N₂O flux peaked in August, but there was no peak in BURN. We found temporal correlations between soil GHG fluxes and soil variables, e.g. soil temperature or NO₃-N. Our results suggest that environmental changes following fire, including the increased availability of N and the disappearance of the litter layer, have the potential to change soil GHG fluxes. Fire-produced charcoal could be significant in reducing soil N₂O flux in temperate forests.     

A model for unsteady-state gas flow in the longitudinal direction of wood

The longitudinal unsteady-state flow of compressible fluids in wood is modeled on a basis of series elements of differing permeabilities and three zones acting in parallel. Two of these zones having widely differing permeabilities are capable of varying degrees of intermixing while a third low-permeability zone is isolated from the other two. A good agreement between theoretical and experimental results was achieved by the appropriate selection of the parameters.This research was supported by the National Science Foundation, Grant No. ENG 69-0056-A03.     

Psychometric charts for use with normal and high temperature drying of wood

Kiln drying of timber sometimes makes use of air at well above 100 °C and at very high humidities. The psychometric charts of Carrier and Mollier do not normally accommodate such air states and so they are not useful. Charts are given herein which use the axes ln r and ln p_s where r is the relative humidity and p_s is the pressure of water vapour at saturation. Such charts accommodate the above conditions without difficulty and fit tidily onto a rectangular sheet. The values of p_s are not shown but they are expressed as a function of dry-bulb temperature, which is shown on the charts. Charts are given for normal and high temperature ranges, and to display different properties we have chosen to use separate charts rather than to fit too much information on a single chart. Received 8 May 2000     

Connection of growth and wood density with wood anatomy in downy birch grown in two different soil types

Soil affects the anatomy of downy birch wood (Betula pubescens), which raises the question whether the growth of this species differs between mineral and peat soils. The aim of this study was to compare growth, density and structure of xylem of B. pubescens between trees grown in different soils. Both growth and density differed between trees grown in different soils. All measured anatomical characteristics, except double thickness of fibre walls, percentage vessel area and ray number, showed differences between the soil types: the cell dimensions were larger and numbers smaller in trees grown in mineral soil. In peat, high growth rates decreased the wall:lumen ratio of fibres in maturing wood, while no such correlation was observed in trees grown in mineral soil at any studied cambial age. In addition, axial parenchyma may have a different role in trees grown in different soils, as the rapid growth decreased and increased axial parenchyma in mineral and peat soil, respectively. The characteristics affecting wood strength were more similar between trees grown in different soils than those affecting water conductance. The observed differences between trees grown in different soils emphasise rapid growth particularly at young ages and shorter reasonable rotation period in mineral soil.     

A comparison of harvesting productivity and costs in thinning operations with and without midfield

Mechanised thinning operations can be carried out in the forest where skid roads are provided on which harvesters and forwarders can move. In the transition to continuous cover forestry (CCF) it is better to keep a thinner network of skid roads in the forest. Instead of tracks for harvesters and forwarders, these areas can be used for younger generations of trees. Moreover, fewer skid roads in the forest environment make the stand more natural. Fewer skid roads were introduced in this research as an alternative thinning operation with midfield¹ (MF) to the most popular mechanised thinning operation with skid roads² (SR). The aim of this paper is to analyse the productivity and economic aspects of thinning operations based on harvesters and forwarders, where there are different distances between skid roads. In both of the operations, harvesters and forwarders were used, but in the MF operation a chainsaw was additionally used to cut trees beyond the reach of the harvester boom. The distances between skid roads in the MF operation were 35–38 m, while in the other they were 18–20 m. The research was carried out in premature pine stands in a flat terrain in Poland. Bigger productivity and lower costs were found in the MF thinning operations. In the younger 44-year-old stand, the average harvester (Timberjack 770) productivity (in operational time) in the MF operation was 5.87 m³h⁻¹ and in the SR operation 4.52 m³h⁻¹; forwarding provided by the Vimek 606 6WD achieved a productivity of 5.03 and 4.52 m³h⁻¹, respectively. In the older 72-year-old stand, the Timberjack 1270B productivity was 11.53 m³h⁻¹ in MF and 8.70 m³h⁻¹ in SR; the Timberjack 1010B forwarder achieved 11.22 m³h⁻¹ (MF) and 8.84 m³h⁻¹(SR).The costs of harvesting and forwarding 1 m³ of wood were lower in the MF operations. In the younger stand, harvesting costs were 5.78 €/m³ (MF) and 6.72 €/m³ (SR) while forwarding costs were 1.94 and 2.18 €/m³ respectively. In the older stand, harvesting costs were 5.58 €/m³ (MF) and 6.78 €/m³ (SR); the forwarding costs were 2.65 €/m³ (MF) and 3.41 €/m³ (SR).     

Aboveground stand-level biomass estimation: a comparison of two methods for major forest species in northwest Spain

Context

The scaling-up approach (which requires the use of individual tree biomass equations and data) is one of the most commonly used methods for estimating stand biomass at a local scale. However, biomass prediction over large management areas requires more efficient methods.

Aims

Two methods of estimating aboveground stand biomass were developed and compared: stand biomass equations (SBE) including observed stand variables, and SBE including biomass expansion factors (BEF) and stand volume.

Methods

Two types of systems of additive equations were fitted simultaneously for components and total aboveground stand biomass, to ensure additivity. Inherent correlations among biomass components were also taken into account in the fitting process.

Results

The systems explained a high percentage of the observed variability. The SBE systems that included observed stand variables provided more accurate estimates than those that included BEF and stand volume. However, the latter were found to be more precise for stem wood and total aboveground biomass prediction.

Conclusions

Both approaches provide a direct link between forest inventory data, outputs from whole-stand growth models, and biomass estimates at stand level. Taking into account that the inventory effort is similar for both alternatives, the choice of which to use will depend on the data available and on the relative importance of the biomass components for the end-users.     

Evaluation of intra-ring wood density profiles using NIRS: comparison with the X-ray method

Key message

Pith-to-bark wood density profiling is interesting in forestry science. By comparing it with the X-ray method, this study proved that a fiber optic NIR spectrometer with a high-precision displacement system could accurately measure intra-ring wood density with a spatial resolution of 0.5 mm.

Context

Most near-infrared spectroscopy (NIRS) studies for wood density determination use samples that have been pulverized beforehand. Attenuation of ionizing radiation is still the standard method to determine wood density with high spatial resolution. However, there is evidence that NIRS could be an accurate and affordable method for determining intra-ring density in solid wood strips.

Aims

In this study, we research whether the results published for intra-ring density predictions in wood can be improved when calibrated with X-ray microdensitometry.

Methods

The measurements were made using a fiber optic probe with a separation between measurement points of 0.508 mm in a range between 1200 and 2200 nm. A total of 4520 density points were used to create partial least squares regression (PLSR). X-ray densitometry data were used as reference values. Twenty PLSR calibrations were randomly executed on 31 samples collected from 28 Pinus radiata D. Don trees.

Results

Upon selecting 20 latent variables, the R ² value was 0.873 for the training group and 0.895 for the validation group, while RMSEP values are 43.1 × 10^?3 and 47.1 × 10^?3 g cm^?3 for the training and validation groups, respectively. The range error ratio (RER) was 13.7.

Conclusion

The RER was high and almost in the range suggested for quantification purposes. Results are superior to wood density studies in the literature which do not employ spatial resolution and to those found in studies using hyperspectral imaging.

     

Comparison analysis of nonlinear segmentation methods for selected wood features in sugar maple

Two classification methods, a feed-forward neural network and a fuzzy logic algorithm, were used for the automatic identification of CT images for selected wood features in sugar maple, one of the most important hardwoods in eastern Canada. Three wood characteristics were selected for automatic identification together with the background as a default. Local features, such as position and local pixel values were used as the neural networks inputs. The fuzzy sets consisted of four different possible pixel values and four possible distances from the center of the log. The fuzzy method used in this study was of the Mamdani type. Five sugar maple logs were randomly selected for this study. One of the logs is used for the training of the neural network and the others for validation and comparison. The structure of the neural network was optimized and was used for the segmentation of the other logs. An efficiency function, consisting of the number of pixels correctly labeled, was defined for the evaluation of the segmentation process. This study shows that a segmentation based on a fuzzy method has better capabilities for generalization than one based on a feed-forward method.     

阔叶林不同采育方式生态经济效益的试验研究

本文通过对阔叶林三种不同采育方式定性分析与定量研究,在符合林业可持续发展的基础上得到初步结论:采用皆伐后不炼山,人工促进天然更新所获得的生态经济效益最好,这为今后溪口林业采育场的阔叶林采伐更新提供了科学依据、对南方集体林区类似条件的经营单位提供了参考。     

Utilization of polar metabolite profiling in the comparison of juvenile wood and compression wood in loblolly pine (Pinus taeda)

Juvenile wood (JW) of conifers is often associated with compression wood (CW), with which it is sometimes believed to be identical. To determine whether JW and CW can be distinguished metabolically, we compared gas chromatographic profiles of 25 polar metabolites from rooted cuttings of a single loblolly pine (Pinus taeda L.) clone raised in controlled environment chambers and subject to three treatments: (1) grown erect with minimal wind sway (control); (2) swayed by wind from oscillating fans; and (3) with 30-cm growth increments successively bent at an angle of 45 degrees to the vertical. Profiles were compared by principal component analysis. Substantial increases in abundances of coniferin and p-glucocoumaryl alcohol separated immature JW-forming xylem tissues of the control trees from the CW-forming xylem of the bent and swayed trees.     

Optimizing CNC wood milling operations with the use of genetic algorithms on CAM software

Main focus of this paper is to introduce an appropriate methodology and create a Genetic Algorithm that optimizes wood milling operations, since wood is one of the primary materials used in both structures and musical instruments building. Mechanical properties of wood were considered in the cutting process modeling on CAM software as far as machining parameter values are concerned. Key machining parameters are explained along with their effect on the final product. The proposed Genetic Algorithm was specifically built for wood milling applications and its operators are examined in detail. The undertaken quality characteristics were minimum machining time and optimal surface quality, thus covering both productivity and quality goals at the same time. As a case study, a novel custom 3D CAD model of an electric guitar body was introduced, on which the proposed optimization methodology was implemented, so as to reveal its efficiency and effectiveness.     

Overview of the use of ultrasonic technologies in research on wood properties

Two ultrasonic technologies, acoustic emission and acousto-ultrasonics, are reviewed in terms of characteristics and applications to wood and wood-based materials. The background is given on the two technologies, including the effect of wood on wave propagation and sensitivity to defects and other properties. The factors that affect wave injection and processing are reviewed for each technology. Four applications are given as examples: particleboard springback, creep/creep-rupture, adhesive curing, and deterioration detection. Recent developments in the technologies are discussed. Received 30 September 1999     

Development of two reverse transcription‐PCR methods to detect living pinewood nematode,Bursaphelenchus xylophilus,in wood

Pinewood nematode, Bursaphelenchus xylophilus, is an inhabitant of native pine species of North America, where its presence in trees is non‐pathogenic. By contrast, the introduction of this nematode to forests overseas has devastated some pine stands and is recognized as a pest of phytosanitary concern by some countries' National Plant Protection Organizations. The ability to detect B. xylophilus in internationally traded wood products is crucial to reduce the spread of this organism. Current molecular techniques for the detection of B. xylophilus rely on the presence of genomic DNA and thus will detect both living and dead nematodes without differentiation. The detection of dead nematodes could lead to unnecessary trade disruption. Therefore, accurate techniques for the detection of and differentiation between live and dead B. xylophilus are critical. We have developed an endpoint RT‐PCR assay and a SYBR Green 1 real‐time RT‐PCR assay, both of which selectively identify living pinewood nematode by detecting the presence of Hsp70 mRNA as a viability marker. Both of these assays may help overcome or resolve disputes involving the detection of pinewood nematode at the port of entry and can also be used to evaluate the efficiency of wood treatment procedures.     

A comparison of two stand table projection methods for young Eucalyptus nitens (Maiden) plantations in Chile

The study compares two methods of stand table projection based on data from young Eucalyptus nitens (Maiden) plantations in Chile. The projected diameter distributions were estimated using the methods proposed by Nepal and Somers (1992) [For. Sci. 38 (1992) 120] and Cao and Baldwin (1999) [For. Sci. 45 (1999) 506]. The evaluation compared the observed and estimated diameter distributions for different projection intervals, using the Kolmogorov–Smirnov test and an error index called ‘relative discrepancy’. The evaluation showed that both methods are suitable for application in the Eucalypt plantations. However, the method proposed by Nepal and Somers proved to be more accurate, especially when the projection period extends over 4 years or more. Expected error and bias for the observed and estimated total and merchantable volumes at stand level were also evaluated. The observed error and bias were relatively low for both methods; however, some differences were detected when the volume distributions were analyzed at diameter class level.