Kenneth E. Skog

Methods for calculating forest ecosystem and harvested carbon with standard estimates for forest types of the United States

This study presents techniques for calculating average net annual additions to carbon in forests and in forest products. Forest ecosystem carbon yield tables, representing stand-level merchantable volume and carbon pools as a function of stand age, were developed for 51 forest types within 10 regions of the United States. Separate tables were developed for afforestation and reforestation. Because carbon continues to be sequestered in harvested wood, approaches to calculate carbon sequestered in harvested forest products are included. Although these calculations are simple and inexpensive to use, the uncertainty of results obtained by using representative average values may be high relative to other techniques that use site- or project-specific data. The estimates and methods in this report are consistent with guidelines being updated for the U.S. Voluntary Reporting of Greenhouse Gases Program and with guidelines developed by the Intergovernmental Panel on Climate Change. The CD-ROM included with this publication contains a complete set of tables in spreadsheet format.

A synthesis of current knowledge on forests and carbon storage in the United States

Using forests to mitigate climate change has gained much interest in science and policy discussions. We examine the evidence for carbon benefits, environmental and monetary costs, risks and trade-offs for a variety of activities in three general strategies: (1) land use change to increase forest area (afforestation) and avoid deforestation; (2) carbon management in existing forests; and (3) the use of wood as biomass energy, in place of other building materials, or in wood products for carbon storage. We found that many strategies can increase forest sector carbon mitigation above the current 162-256 Tg C/yr, and that many strategies have co-benefits such as biodiversity, water, and economic opportunities. Each strategy also has trade-offs, risks, and uncertainties including possible leakage, permanence, disturbances, and climate change effects. Because approximately 60% of the carbon lost through deforestation and harvesting from 1700 to 1935 has not yet been recovered and because some strategies store carbon in forest products or use biomass energy, the biological potential for forest sector carbon mitigation is large. Several studies suggest that using these strategies could offset as much as 10-20% of current U.S. fossil fuel emissions. To obtain such large offsets in the United States would require a combination of afforesting up to one-third of cropland or pastureland, using the equivalent of about one-half of the gross annual forest growth for biomass energy, or implementing more intensive management to increase forest growth on one-third of forestland. Such large offsets would require substantial trade-offs, such as lower agricultural production and non-carbon ecosystem services from forests. The effectiveness of activities could be diluted by negative leakage effects and increasing disturbance regimes. Because forest carbon loss contributes to increasing climate risk and because climate change may impede regeneration following disturbance, avoiding deforestation and promoting regeneration after disturbance should receive high priority as policy considerations. Policies to encourage programs or projects that influence forest carbon sequestration and offset fossil fuel emissions should also consider major items such as leakage, the cyclical nature of forest growth and regrowth, and the extensive demand for and movement of forest products globally, and other greenhouse gas effects, such as methane and nitrous oxide emissions, and recognize other environmental benefits of forests, such as biodiversity, nutrient management, and watershed protection. Activities that contribute to helping forests adapt to the effects of climate change, and which also complement forest carbon storage strategies, would be prudent.

Residence times and decay rates of downed woody debris biomass/carbon in eastern US forests

A key component in describing forest carbon (C) dynamics is the change in downed dead wood biomass through time. Specifically, there is a dearth of information regarding the residence time of downed woody debris (DWD), which may be reflected in the diversity of wood (for example, species, size, and stage of decay) and site attributes (for example, climate) across the study region of eastern US forests. The empirical assessment of DWD rate of decay and residence time is complicated by the decay process itself, as decomposing logs undergo not only a reduction in wood density over time but also reductions in biomass, shape, and size. Using DWD repeated measurements coupled with models to estimate durations in various stages of decay, estimates of DWD half-life (THALF), residence time (TRES), and decay rate (k constants) were developed for 36 tree species common to eastern US forests. Results indicate that estimates for THALF averaged 18 and 10 years for conifers and hardwoods, respectively. Species that exhibited shorter THALF tended to display a shorter TRES and larger k constants. Averages of TRES ranged from 57 to 124 years for conifers and from 46 to 71 years for hardwoods, depending on the species and methodology for estimating DWD decomposition considered. Decay rate constants (k) increased with increasing temperature of climate zones and ranged from 0.024 to 0.040 for conifers and from 0.043 to 0.064 for hardwoods. These estimates could be incorporated into dynamic global vegetation models to elucidate the role of DWD in forest C dynamics.

Estimates of carbon stored in harvested wood products from the United States forest service northern region, 1906-2010

BackgroundGlobal forests capture and store significant amounts of CO2 through photosynthesis. When carbon is removed from forests through harvest, a portion of the harvested carbon is stored in wood products, often for many decades. The United States Forest Service (USFS) and other agencies are interested in accurately accounting for carbon flux associated with harvested wood products (HWP) to meet greenhouse gas monitoring commitments and climate change adaptation and mitigation objectives. This paper uses the Intergovernmental Panel on Climate Change (IPCC) production accounting approach and the California Forest Project Protocol (CFPP) to estimate HWP carbon storage from 1906 to 2010 for the USFS Northern Region, which includes forests in northern Idaho, Montana, South Dakota, and eastern Washington.ResultsBased on the IPCC approach, carbon stocks in the HWP pool were increasing at one million megagrams of carbon (MgC) per year in the mid 1960s, with peak cumulative storage of 28 million MgC occurring in 1995. Net positive flux into the HWP pool over this period is primarily attributable to high harvest levels in the mid twentieth century. Harvest levels declined after 1970, resulting in less carbon entering the HWP pool. Since 1995, emissions from HWP at solid waste disposal sites have exceeded additions from harvesting, resulting in a decline in the total amount of carbon stored in the HWP pool. The CFPP approach shows a similar trend, with 100-year average carbon storage for each annual Northern Region harvest peaking in 1969 at 937,900 MgC, and fluctuating between 84,000 and 150,000 MgC over the last decade.ConclusionsThe Northern Region HWP pool is now in a period of negative net annual stock change because the decay of products harvested between 1906 and 2010 exceeds additions of carbon to the HWP pool through harvest. However, total forest carbon includes both HWP and ecosystem carbon, which may have increased over the study period. Though our emphasis is on the Northern Region, we provide a framework by which the IPCC and CFPP methods can be applied broadly at sub-national scales to other regions, land management units, or firms.

Greenhouse Gas and Carbon Profile of the U.S. Forest Products Industry Value Chain

A greenhouse gas and carbon accounting profile was developed for the U.S. forest products industry value chain for 1990 and 2004−2005 by examining net atmospheric fluxes of CO2 and other greenhouse gases (GHGs) using a variety of methods and data sources. Major GHG emission sources include direct and indirect (from purchased electricity generation) emissions from manufacturing and methane emissions from landfilled products. Forest carbon stocks in forests supplying wood to the industry were found to be stable or increasing. Increases in the annual amounts of carbon removed from the atmosphere and stored in forest products offset about half of the total value chain emissions. Overall net transfers to the atmosphere totaled 91.8 and 103.5 TgCO2-eq. in 1990 and 2005, respectively, although the difference between these net transfers may not be statistically significant. Net transfers were higher in 2005 primarily because additions to carbon stored in forest products were less in 2005. Over this same period, energy-related manufacturing emissions decreased by almost 9% even though forest products output increased by approximately 15%. Several types of avoided emissions were considered separately and were collectively found to be notable relative to net emissions.

Evaluation of silvicultural treatments and biomass use for reducing fire hazard in western states

Several analyses have shown that fire hazard is a concern for substantial areas of forestland, shrubland, grassland, and range in the western United States. In response, broadscale management strategies, such as the National Fire Plan, established actions to reduce the threat of undesirable fire. Available budgets are insufficient to pay for vegetative management on all acres where fire threat is considered unacceptable. The purpose of this report is to begin to identify locations in the west where fire hazard reduction treatments have a potential to “pay for themselves” at a scale and over a long enough time to make investment in additional forest product processing infrastructure a realistic option. The resulting revenues from these activities could presumably subsidize treatment for other locations. Accordingly, we concentrate on areas where wood removed during fire hazard reduction treatments has the potential to support a forest products infrastructure. Areas for treatment were selected by the criterion where either torching or crowning is likely during wildfires when wind speeds are below 25 mph. We considered thinning treatments designed to result in either evenaged or uneven-aged stand conditions. If there are ecological limitations on basal area that is allowed to be removed and there is a need to obtain a certain amount of merchantable wood volume to help cover costs, then uneven-aged treatments appear more likely to achieve one of our hazard reduction targets. Thinning to maintain an uneven-aged structure could be more controversial because it removes larger trees, although the revenue from such treatment covers harvest costs more frequently than does revenue from thinning to maintain an even-aged structure. The removal of large trees by uneven-aged thinning may be reduced by supplementary treatments to increase torching index rather than thinning to reach a high crowning index. Treatments analyzed would treat 7.2 to 18.0 million acres, including 0.8 to 1.2 million acres of wildland urban interface area, and would provide 169 to 640 million oven-dry tons of woody biomass (e.g., main stem, tops, and limbs). About 55% of biomass would be from sawlogs. Sixty to 70% of acres to be treated are in California, Idaho, and Montana. To prepare an example estimate of annual harvest amount for the 12 selected western states, we assume acres needing treatment are divided into two parts of equal area. For half the acres, an uneven-aged treatment would be applied if at least 300 ft3 of merchantable wood is removed; for the other half, an even-aged treatment would be applied if at least 300 ft3 of merchantable wood is removed. Under this scenario, treatment of 0.5 million acres/year would generate 14.6 million oven-dry tons of biomass per year or about 29% of the current level of roundwood removals for the selected states.

Understanding the adoption of new technology in the forest products industry

In anticipating future rates of adoption of new technology in forest products, several uniquely important factors come into play. In this respect, the role of innovations imported from other industries, the effect of raw material shortages, the importance of economic factors in adoption of innovations, and the problems presented by the heterogeneity of wood raw material and finished products are discussed. The nature of the adoption process and reasons for long lags between innovation and adoption are also addressed. Certain observations carry. implications for how research and information gathering should be conducted and what priorities should be accorded activities related to technology development and research in forest products. Many times in this century, serious timber shortages have been forecast for the forest products industry. Although the economic scarcity of some wood materials is apparently increasing (the real price of sawlogs has been rising for a long time (17)), other wood materials seem unaffected (pulpwood prices have remained relatively stable over the last four decades (28)). Thus, although numerous wood-saving technological improvements are reportedly “on the shelf ” and others are adopted rapidly by the industry, slow adoption rates for some major innovations undoubtedly reflect an appropriate response to economic conditions rather than conservatism. This paper addresses the following questions: What are some of the principal and unique influences on technological change in the forest products industry that must be understood to anticipate future rates of adoption of new technology? Do these influences currently elicit appropriate rates of technology adoption? The paper has five major sections: 1) the importance of innovations imported from other industries (interindustry flow) and other countries; 2) the effect of raw material shortages; 3) the effect of the economic performance of innovations; 4) problems presented by the heterogeneous nature of wood raw material; and 5) problems presented by the heterogeneity of finished products. It is taken as axiomatic that the impact of technological change is not felt at the stage of invention or innovation, but when improved technologies are actually used in production. For this reason, we pay particular attention to the determinants of the adoption of new technologies. Interindustry technology flow Prospects for technological change in forest products are heavily shaped by 1) commitment of resources to research and development (RD and 2) developments in industries that are remote from forest products. For example, the forest products sector has made considerable use of sophisticated electronics components, including computers, lasers, and computerized axial tomography scanners (on an experimental basis). Many industries depend upon other sectors of the economy for the expansion of their technological capabilities. In the United States, five sectors account for more than 75 percent of total RD and Research Forester, Research Forester, and Forester, USDA Forest Serv., Forest Prod. Lab., One Gifford Pinchot Dr., Madison, WI 53705-2398. Research for this paper was funded by the Forest Prod. Lab. under cooperative agreement No. USDAFP-86-0877. This paper was received for publication in November 1989.

The Carbon Impacts of Wood Products

Abstract Wood products have many environmental advantages over nonwood alternatives. Documenting and publicizing these merits helps the future competitiveness of wood when climate change impacts are being considered. The manufacture of wood products requires less fossil fuel than nonwood alternative building materials such as concrete, metals, or plastics. By nature, wood is composed of carbon that is captured from the atmosphere during tree growth. These two effects—substitution and sequestration—are why the carbon impact of wood products is favorable. This article shows greenhouse gas emission savings for a range of wood products by comparing (1) net wood product carbon emissions from forest cradle–to–mill output gate minus carbon storage over product use life with (2) cradle-to-gate carbon emissions for substitute nonwood products. The study assumes sustainable forest management practices will be used for the duration of the time for the forest to regrow completely from when the wood was removed for pr...

Growth model for uneven-aged loblolly pine stands : simulations and management implications

A density-dependent matrix growth model of uneven-aged loblolly pine stands was developed with data from 991 permanent plots in the southern United States. The model predicts the number of pine, soft hardwood, and hard hardwood trees in 13 diameter classes, based on equations for ingrowth, upgrowth, and mortality. Projections of 6 to 10 years agreed with the growth of stands between the last two inventories. In 300-year simulations of undisturbed growth, softwood species were replaced by hardwoods, in accord with previous knowledge. Soft hardwood species became dominant on good sites and hard hardwoods on poor sites. Basal area oscillated over time, converging slowly towards a steady state. Changes in tree size diversity were correlated positively with basal area. Without disturbance, species diversity would decrease. For economic analysis, equations were developed to predict total tree height, sawlog length and volume, pulpwood volume, and volume of top sawtimber, as functions of tree diameter and stand basal area. Simulations of three cutting regimes showed that management would lead to a steady state faster than would natural growth. Management aimed at maintaining the current average distribution would result in size and species diversity similar to that of an unmanaged stand. From a financial point of view, the q-factor guide and a 13-in.(330-mm-) diameter-limit cut would be superior to the average current management regime. The diameter-limit regime would have the greatest effect on lowering tree size diversity and an effect on species diversity similar to that of the q-factor guide. A computer program, SOUTHPRO, was developed to simulate the effects of other management alternatives.

Comparing Life-Cycle Carbon and Energy Impacts for Biofuel, Wood Product, and Forest Management Alternatives*

The different uses of wood result in a hierarchy of carbon and energy impacts that can be characterized by their efficiency in displacing carbon emissions and/or in displacing fossil energy imports, both being current national objectives. When waste wood is used for biofuels (forest or mill residuals and thinnings) fossil fuels and their emissions are reduced without significant land use changes. Short rotation woody crops can increase yields and management efficiencies by using currently underused land. Wood products and biofuels are coproducts of sustainable forest management, along with the other values forests provide, such as clean air, water, and habitat. Producing multiple coproducts with different uses that result in different values complicates carbon mitigation accounting. It is important to understand how the life-cycle implications of managing our forests and using the wood coming from our forests impacts national energy and carbon emission objectives and other forest values. A series of articles published in this issue of the Forest Products Journal reports on the life-cycle implications of producing ethanol by gasification or fermentation and producing bio-oil by pyrolysis and feedstock collection from forest residuals, thinnings, and short rotation woody crops. These are evaluated and compared with other forest product uses. Background information is provided on existing life-cycle data and methods to evaluate prospective new processes and wood uses. Alternative management, processing, and collection methods are evaluated for their different efficiencies in contributing to national objectives.