Forest Harvest Residues Research Articles

Effect of Thinning and Harvest Type on Storage and Losses of Phosphorous inPinus taedaL. Plantations in Subtropical Argentina

The aim of this study was to evaluate the effect of thinning intensity and different harvest types on ecosystem P conservation in 20-year-oldPinus taedaplantation ecosystems at Misiones province, Argentina. The plantation was established in 1985, thinned at three intensities—0, 33, and 66% of basal area of control plots removed by thinning—and harvested in 2005. The nutrient content at harvest was determined for tree, shrub, and herb layers, the forest floor and upper mineral soil. Two harvest types were simulated: stem only and whole tree. Total P content was 56.8, 46.8, and 38.6 kg· ha−1for 0, 33, and 66% thinning, respectively. Total P exported by harvest was different among treatments, the highest at 0% thinning treatment. Phosphorus stability index values indicated that the P most conservative management option is 66% thinning, harvest of stem only and retention of forest floor, understory, and harvest residues.

Organic residue mass at planting is an excellent predictor of tree growth in Eucalyptus plantations established on a sandy tropical soil

Tropical plantation forests are meeting an increasing proportion of global wood demand and comprehensive studies assessing the impact of silvicultural practices on tree and soil functioning are required to achieve sustainable yields. The objectives of our study were: (1) to quantify the effects of contrasting organic residue (OR) retention methods on tree growth and soil nutrient pools over a full Eucalyptus rotation and (2) to assess the potential of soil analyses to predict yields of fast-growing plantations established on tropical sandy soils. An experiment was set up in the Congo at the harvesting of the first rotation after afforestation of a native herbaceous savanna. Six treatments were set up in 0.26 ha plots and replicated in 4 blocks, with OR mass at planting ranging from 0 to 46.5 Mg ha −1. Tree growth over the whole rotation was highly dependent on OR management at planting. Over-bark trunk volume 7 years after planting ranged from 96 m 3 ha −1 in the treatment with forest floor and harvest residue removal at planting to 164 m 3 ha −1 in the treatment with the largest amount of OR. A comparison of nutrient stocks within the ecosystem at planting and at the end of the rotation suggested that nutrient contents in OR were largely involved in the different response observed between treatments. OR management treatments did not significantly modify most of the nutrient concentrations in the upper layers of the mineral soil. Conventional soil analyses performed before planting and at ages 1 and 3 years were unable to detect differences between treatments despite large differences in tree growth. In contrast, linear regressions between stand aboveground biomass at harvesting and OR mass at planting (independent variable) showed that OR mass was an excellent predictor of stand yield ( R 2 = 0.99). A large share of soil fertility comes from organic material above the mineral soil in highly weathered sandy soils and OR mass at planting might be used in conjunction with soil analyses to assess the potential of these soils to support forest plantations.

Indirect carbon dioxide emissions from producing bioenergy from forest harvest residues

Forest harvest residues are important raw materials for bioenergy in regions practicing forestry. Removing these residues from a harvest site reduces the carbon stock of the forest compared with conventional stem-only harvest because less litter in left on the site. The indirect carbon dioxide (CO 2 ) emission from producing bioenergy occur when carbon in the logging residues is emitted into the atmosphere at once through combustion, instead of being released little by little as a result of decomposition at the harvest sites. In this study (1) we introduce an approach to calculate this indirect emission from using logging residues for bioenergy production, and (2) estimate this emission at a typical target of harvest residue removal, i.e. boreal Norway spruce forest in Finland. The removal of stumps caused a larger indirect emission per unit of energy produced than the removal of branches because of a lower decomposition rate of the stumps. The indirect emission per unit of energy produced decreased with time since starting to collect the harvest residues as a result of decomposition at older harvest sites. During the 100 years of conducting this practice, the indirect emission from average-sized branches (diameter 2 cm) decreased from 340 to 70 kg CO 2 eq. MWh ―1 and that from stumps (diameter 26 cm) from 340 to 160 kg CO 2 eq. MWh ―1 . These emissions are an order of magnitude larger than the other emissions (collecting, transporting, etc.) from the bioenergy production chain. When the bioenergy production was started, the total emissions were comparable to fossil fuels. The practice had to be carried out for 22 (stumps) or four (branches) years until the total emissions dropped below the emissions of natural gas. Our results emphasize the importance of accounting for land-use-related indirect emissions to correctly estimate the efficiency of bioenergy in reducing CO 2 emission into the atmosphere.

Changes in total carbon and nutrients in soil profiles and accumulation in biomass after a 30-year rotation of Pinus radiata on podzolized sands: Impacts of intensive harvesting on soil resources

A large proportion of plantations of radiata pine ( Pinus radiata D. Don) in southern Australia have been established on podzolized coastal sands with low nutrient reserves. Inter-rotational management of the forest floor and harvesting residues has been shown to be critical to maintain the productive capacity of these soils. In 1974 a study was initiated at the end of the first rotation to evaluate the long-term sustainability of fast-growing plantations on these podzolized sands. Growth was measured at 5, 10 and 20 years and prior to clear-felling at age 30. Soil sampling at the end of the first rotation in 1974 was repeated in 2004 prior to clear-felling to determine changes in carbon and nutrients in profiles after 30 years. Forest floor and tree biomass were measured to determine sequestration of carbon and nutrients in mature radiata pine. Productivity of radiata pine on infertile podzolized sands was either maintained at 26 m 3 ha −1 year −1 or improved from 21 to 27 m 3 ha −1 year −1 over two rotations from 1946 to 2005 and this was attributed to conservation of organic matter and nutrients through retention of litter and harvesting residues after the first rotation. Total carbon (23.4 Mg ha −1) and N (595 kg ha −1) remaining in residues and litter after harvesting compensated for losses of carbon (9.2 Mg ha −1) and N (582 kg ha −1) in soil (0–75 cm) over the rotation. Total S, P, K, Ca and Mg remaining on site after conventional harvesting (stem wood and bark) increased during the second rotation (1975–2005). Accumulation of nutrients in the above-ground biomass and soil over 30 years exceeded deposition in rainfall indicating a redistribution of S, P, K, Ca and Mg from the sub-soil to tree biomass. The net accumulation of N in biomass (201 kg ha −1) also exceeded atmospheric deposition indicating significant inputs from nitrogen fixation during the rotation. Intensive harvesting including removal of log residues and branches for biofuels but leaving foliage on site increased nutrient exports by approximately 30% but did not exceed accession of nutrients over 30 years except for N. In contrast, whole-tree harvesting including foliage increased nutrient exports by 70–150% and fertilizers are likely to be required to compensate for the additional removal of nutrients and to maintain site productivity in the next rotation.

Effets de la gestion de résidus organiques et d’un couvert de légumineuses sur la croissance de semis de pin, le lessivage des nutriments et les propriétés du sol

• The short-term effect of organic residue management on the growth and nutrition of Pinus pinaster Ait. seedlings, and on nutrient leaching and chemical properties of an acid soil was assessed through a lysimeter experiment. Treatments included absence, placement on the soil surface, and incorporation into the soil (with and without legume cover cropping) of organic residues (forest floor litter or forest floor litter plus harvest residues). • Residues placed on the soil surface enhanced seedling growth. Organic residues reduced nutrient losses (NO − , Ca and Mg) and resulted in nutrient accumulation in the soil. Harvest residues positively

The impact of feedstock cost on technology selection and optimum size

Abstract Development of biomass projects at optimum size and technology enhances the role that biomass can make in mitigating greenhouse gas. Optimum sized plants can be built when biomass resources are sufficient to meet feedstock demand; examples include wood and forest harvest residues from extensive forests, and grain straw and corn stover from large agricultural regions. The impact of feedstock cost on technology selection is evaluated by comparing the cost of power from the gasification and direct combustion of boreal forest wood chips. Optimum size is a function of plant cost and the distance variable cost (DVC, $ dry tonne −1 km −1 ) of the biomass fuel; distance fixed costs (DFC, $ dry tonne −1 ) such as acquisition, harvesting, loading and unloading do not impact optimum size. At low values of DVC and DFC, as occur with wood chips sourced from the boreal forest, direct combustion has a lower power cost than gasification. At higher values of DVC and DFC, gasification has a lower power cost than direct combustion. This crossover in most economic technology will always arise when a more efficient technology with a higher capital cost per unit of output is compared to a less efficient technology with a lower capital cost per unit of output. In such cases technology selection cannot be separated from an analysis of feedstock cost.

Cost structure of and competition for forest-based biomass

Biomass has become a popular alternative to satisfy expanding energy demand and as a substitute for fossil fuels and phased-out nuclear energy in Europe. The European Union White Paper stipulates that the utilization of biomass shall increase to 1566 TWh by 2010. However it is often overlooked that the forest resources are already, to a large extent, used by the forest industries. When promoting biomass for energy generation the consequences for the forest industries also need to be considered. Sweden is an excellent case study, as there are vast quantities of forest resources, nuclear power is starting to be phased out, there are restrictions on expanding hydropower and the political desire exists to “set an example” with respect to carbon dioxide emissions. This paper attempts to estimate and analyse the supply of two types of forest resource, namely, roundwood and harvesting residues derived from final harvesting and commercial thinnings. Two separate supply curves are estimated: one for roundwood and one for harvesting residues. The cost structure is based on an economic-engineering approach where the separate cost components are constructed from the lowest cost element into aggregates for labour, capital, materials and overhead costs for each forest resource. The results indicate an unutilized economic supply of 12 TWh of harvesting residues in Sweden. However, after these 12 TWh have been recovered it becomes more profitable to use roundwood for energy purposes than to continue extracting further amounts of harvesting residues.

Rail vs Truck Transport of Biomass

This study analyzes the economics of transshipping biomass from truck to train in a North American setting. Transshipment will only be economic when the cost per unit distance of a second transportation mode is less than the original mode. There is an optimum number of transshipment terminals which is related to biomass yield. Transshipment incurs incremental fixed costs, and hence there is a minimum shipping distance for rail transport above which lower costs/km offset the incremental fixed costs. For transport by dedicated unit train with an optimum number of terminals, the minimum economic rail shipping distance for straw is 170 km, and for boreal forest harvest residue wood chips is 145 km. The minimum economic shipping distance for straw exceeds the biomass draw distance for economically sized centrally located power plants, and hence the prospects for rail transport are limited to cases in which traffic congestion from truck transport would otherwise preclude project development. Ideally, wood chip transport costs would be lowered by rail transshipment for an economically sized centrally located power plant, but in a specific case in Alberta, Canada, the layout of existing rail lines precludes a centrally located plant supplied by rail, whereas a more versatile road system enables it by truck. Hence for wood chips as well as straw the economic incentive for rail transport to centrally located processing plants is limited. Rail transshipment may still be preferred in cases in which road congestion precludes truck delivery, for example as result of community objections.

Canadian Biomass Reserves for Biorefining

A lignocellulosic-based biorefining strategy may be supported by biomass reserves, created initially with residues from wood product processing or agriculture. Biomass reserves might be expanded using innovative management techniques that reduce vulnerability of feedstock in the forest products or agricultural supply chain. Forest-harvest residue removal, disturbance isolation, and precommercial thinnings might produce 20-33 x 10(6) mt/yr of feedstock for Canadian biorefineries. Energy plantations on marginal Canadian farmland might produce another 9-20 mt. Biomass reserves should be used to support first-generation biorefining installations for bioethanol production, development of which will lead to the creation of future high-value coproducts. Suggestions for Canadian policy reform to support biomass reserves are provided.

Biomass power cost and optimum plant size in western Canada

The power cost and optimum plant size for power plants using three biomass fuels in western Canada were determined. The three fuels are biomass from agricultural residues (grain straw), whole boreal forest, and forest harvest residues from existing lumber and pulp operations (limbs and tops). Forest harvest residues have the smallest economic size, 137 MW, and the highest power cost, $63.00 MWh −1 (Year 2000 US$). The optimum size for agricultural residues is 450 MW (the largest single biomass unit judged feasible in this study), and the power cost is $50.30 MWh −1 . If a larger biomass boiler could be built, the optimum project size for straw would be 628 MW . Whole forest harvesting has an optimum size of 900 MW (two maximum sized units), and a power cost of $47.16 MWh −1 without nutrient replacement. However, power cost versus size from whole forest is essentially flat from 450 MW ($47.76 MWh −1) to 3150 MW ($48.86 MWh −1) , so the optimum size is better thought of as a wide range. None of these projects are economic today, but could become so with a greenhouse gas credit. All biomass cases show some flatness in the profile of power cost vs. plant capacity. This occurs because the reduction in capital cost per unit capacity with increasing capacity is offset by increasing biomass transportation cost as the area from which biomass is drawn increases. This in turn means that smaller than optimum plants can be built with only a minor cost penalty. Both the yield of biomass per unit area and the location of the biomass have an impact on power cost and optimum size. Agricultural and forest harvest residues are transported over existing road networks, whereas the whole forest harvest requires new roads and has a location remote from existing transmission lines. Nutrient replacement in the whole forest case would make power from the forest comparable in cost to power from straw.

Effects of organic matter removal on the soil food web: Forestry practices meet ecological theory

We examine the long-term effects of removing forest harvesting residues (above-ground whole-tree harvesting; WTH) in the soil food web, using data from two different experiments on slash removal and addition in Sweden. Removal of harvesting residues had negative effects on the abundances of animals at higher trophic positions and on more mobile animals. Predators such as gamasid mites, spiders and staphyliniid and cantharid beetles decreased by 30–50% after WTH at both sites. Microbidetritivorous dipterans and fungivorous Collembola decreased at the pine site, but not at the more productive spruce site. Enchytraeids and nematodes were usually not affected by WTH. No differences in fungal and bacterial biomass were found. The removal of organic matter had fairly long-term, of the order of decades, effects on the soil food web. The effects were quantitative rather than qualitative. No functional groups disappeared after WTH. Our findings do not support the hypothesis that soil food webs are entirely donor-controlled. The more pronounced effects of WTH at higher trophic positions indicates that the major interactions in the food webs we have studied are reciprocal, i.e., that consumers to some degree control the density of their resources.

96/05009 Screw compressor capacity regulated by stepless speed control

The power cost and optimum plant size for power plants using three biomass fuels in western Canada were determined. The three fuels are biomass from agricultural residues (grain straw), whole boreal forest, and forest harvest residues from existing lumber and pulp operations (limbs and tops). Forest harvest residues have the smallest economic size, 137 MW, and the highest power cost, $63.00MWh−1 (Year 2000 US$). The optimum size for agricultural residues is 450MW (the largest single biomass unit judged feasible in this study), and the power cost is $50.30MWh−1. If a larger biomass boiler could be built, the optimum project size for straw would be 628MW. Whole forest harvesting has an optimum size of 900MW (two maximum sized units), and a power cost of $47.16MWh−1 without nutrient replacement. However, power cost versus size from whole forest is essentially flat from 450MW($47.76MWh−1) to 3150MW($48.86MWh−1), so the optimum size is better thought of as a wide range.None of these projects are economic today, but could become so with a greenhouse gas credit. All biomass cases show some flatness in the profile of power cost vs. plant capacity. This occurs because the reduction in capital cost per unit capacity with increasing capacity is offset by increasing biomass transportation cost as the area from which biomass is drawn increases. This in turn means that smaller than optimum plants can be built with only a minor cost penalty. Both the yield of biomass per unit area and the location of the biomass have an impact on power cost and optimum size. Agricultural and forest harvest residues are transported over existing road networks, whereas the whole forest harvest requires new roads and has a location remote from existing transmission lines. Nutrient replacement in the whole forest case would make power from the forest comparable in cost to power from straw.

A Carbon Budget for Forests of the Conterminous United States

The potential need for national‐level comparisons of greenhouse gas emissions, and the desirability of understanding terrestrial sources and sinks of carbon, has prompted interest in quantifying national forest carbon budgets. In this study, we link a forest inventory database, a set of stand‐level carbon budgets, and information on harvest levels in order to estimate the current pools and flux of carbon in forests of the conterminous United States. The forest inventory specifies the region, forest type, age class, productivity class, management intensity, and ownership of all timberland. The stand‐level carbon budgets are based on growth and yield tables, in combination with additional information on carbon in soils, the forest floor, woody debris, and the understory. Total carbon in forests of the conterminous U.S. is estimated at 36.7 Pg, with half of that in the soil compartment. Tree carbon represents 33% of the total, followed by woody debris (10%), the forest floor (6%), and the understory (1%). The carbon uptake associated with net annual growth is 331 Tg, however, much of that is balanced by harvest‐related mortality (266 Tg) and decomposition of woody debris. The forest land base at the national level is accumulating 79 Tg/yr, with the largest carbon gain in the Northeast region. The similarity in the magnitude of the biologically driven flux and the harvest‐related flux indicates the importance of employing an age‐class‐based inventory, and of including effects associated with forest harvest and harvest residue, when modeling national carbon budgets in the temperate zone.