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The campaign to plant a trillion trees provided an easily understood approach to reduce the threat of global warming. However, focusing on trees does not consider that a maturing forest releases carbon (C) from dying trees offsetting C intake from growth of other trees, and results in only a one-time carbon storage benefit. Under sustainable management that harvests before forest growth slows down, forest C is transferred to wood products that substitute for fossil fuel (FF)-intensive products, reducing the carbon dioxide (CO2) emissions with every harvest. Sustainably managed forests maintain growth by replanting (or regenerating), sustaining the C stored in products, as well as avoiding FF-intensive product emissions with every harvest. This paper addresses the question: Could planting more trees significantly reduce atmospheric CO2; and if so, how? Survey data from many wood-producing mills show life cycle inventory (LCI) data on C that has been tracked through every stage of processing for many different wood products specific to each United States (USA) supply region, as well as C displacement measurements when substituting wood for FF-intensive products. Results show that more and better-managed forest lands and more efficient product uses provide significant opportunities to reduce CO2 emissions, especially in highly productive forest regions. [ABSTRACT FROM AUTHOR]

Abstract: In frequent fire forests of the western United States, a legacy of fire suppression coupled with increases in fire weather severity have altered fire regimes and vegetation dynamics. When coupled with projected climate change, these conditions have the potential to lead to vegetation type change and altered carbon (C) dynamics. In the Sierra Nevada, fuels reduction approaches that include mechanical thinning followed by regular prescribed fire are one approach to restore the ability of the ecosystem to tolerate episodic fire and still sequester C. Yet, the spatial extent of the area requiring treatment makes widespread treatment implementation unlikely. We sought to determine if a priori knowledge of where uncharacteristic wildfire is most probable could be used to optimize the placement of fuels treatments in a Sierra Nevada watershed. We developed two treatment placement strategies: the naive strategy, based on treating all operationally available area and the optimized strategy, which only treated areas where crown‐killing fires were most probable. We ran forecast simulations using projected climate data through 2,100 to determine how the treatments differed in terms of C sequestration, fire severity, and C emissions relative to a no‐management scenario. We found that in both the short (20 years) and long (100 years) term, both management scenarios increased C stability, reduced burn severity, and consequently emitted less C as a result of wildfires than no‐management. Across all metrics, both scenarios performed the same, but the optimized treatment required significantly less C removal (naive=0.42 Tg C, optimized=0.25 Tg C) to achieve the same treatment efficacy. Given the extent of western forests in need of fire restoration, efficiently allocating treatments is a critical task if we are going to restore adaptive capacity in frequent‐fire forests. [ABSTRACT FROM AUTHOR]

An analysis of 2014 forest inventory data for the contiguous United States shows nearly 8 million ha of forestland that are currently defined as nonstocked after recent natural and human disturbances. It is estimated that forest regeneration on these lands could result in an additional terrestrial sequestration of 48.9 million metric tons of CO2 equivalent (CO2e) annually. Analysis across a range of seven site productivity classes indicates that approximately 58% of the total area is productive timberland, defined as capable of producing merchantable volume of ⩾1.4 m3/ha/year. It is estimated that regeneration of just the productive timberland portion of the total could produce an additional 44.4 million metric tons of CO2e annually in carbon sequestration. On National Forest System lands, more than 50% of the total potential carbon sequestration benefit from regenerating nonstocked lands could be achieved by reforesting just the top 30% of these lands in the moderate-to-high site productivity classes. On private lands, more than 70% of the total potential carbon benefit can be achieved by regenerating the most productive 30%. [ABSTRACT FROM AUTHOR]

Bioenergy is a significant source of renewable energy in the U.S. and internationally. We explore whether creation of localized bioenergy markets near existing military installations in the southeastern U.S. could simultaneously address military renewable energy generation objectives while reducing urban encroachment. We model the use of public–private partnerships to stimulate the creation of these markets, in which stable installation demand is paired with stable supply from surrounding landowners. We employ two economic models – the SubRegional Timber Supply (SRTS) model and the Forest and Agricultural Sector Model with Greenhouse Gases (FASOMGHG) – to assess how markets influence forest and agriculture land use, renewable energy production, and greenhouse gas (GHG) mitigation at the regional and national levels. When all selected installations increase bioenergy capacity simultaneously, we find increased preservation of forest land area, increased forest carbon storage in the region, and increased renewable energy generation at military installations. Nationally, however, carbon stocks are depleted as harvests increase, increasing GHG emissions even after accounting for potential displaced emissions from coal- or natural gas-fired generation. Increasing bioenergy generation on a single installation within the southeast has very different effects on forest area and composition, yielding greater standing timber volume and higher forest carbon stock. In addition to demonstrating the benefits of linking two partial equilibrium models of varying solution technique, sectoral scope, and resource detail, results suggest that a tailored policy approach may be more effective in meeting local encroachment reduction and renewable energy generation objectives while avoiding negative GHG mitigation consequences. [ABSTRACT FROM AUTHOR]

Changing climate and a legacy of fire-exclusion have increased the probability of high-severity wildfire, leading to an increased risk of forest carbon loss in ponderosa pine forests in the southwestern USA. Efforts to reduce high-severity fire risk through forest thinning and prescribed burning require both the removal and emission of carbon from these forests, and any potential carbon benefits from treatment may depend on the occurrence of wildfire. We sought to determine how forest treatments alter the effects of stochastic wildfire events on the forest carbon balance. We modeled three treatments (control, thin-only, and thin and burn) with and without the occurrence of wildfire. We evaluated how two different probabilities of wildfire occurrence, 1% and 2% per year, might alter the carbon balance of treatments. In the absence of wildfire, we found that thinning and burning treatments initially reduced total ecosystem carbon (TEC) and increased net ecosystem carbon balance (NECB). In the presence of wildfire, the thin and burn treatment TEC surpassed that of the control in year 40 at 2%/yr wildfire probability, and in year 51 at 1%/yr wildfire probability. NECB in the presence of wildfire showed a similar response to the no-wildfire scenarios: both thin-only and thin and burn treatments increased the C sink. Treatments increased TEC by reducing both mean wildfire severity and its variability. While the carbon balance of treatments may differ in more productive forest types, the carbon balance benefits from restoring forest structure and fire in southwestern ponderosa pine forests are clear. [ABSTRACT FROM AUTHOR]

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Use of wood biomass for energy results in carbon (C) emissions at the time of burning and alters C stocks on the land because of harvest, regrowth, and changes in land use or management. This study evaluates the potential effects of expanded woody biomass energy use (for heat and power) on net C emissions over time. A scenario with increased wood energy use is compared with a dynamic business-as-usual scenario where wood energy use is driven by its historical relationship with gross domestic product. At the national level, we projected that up to 78% of increased cumulative C emissions from increased wood burning and up to 80% of increased cumulative radiative forcing would be offset over 50 years by change in forest area loss, biomass regrowth on land, C storage in harvested wood products, and C in logging slash left in forests. For example, forest area is projected to decline in both scenarios, but 3.5 million hectares more are retained in the high wood energy-use case. Projected C offsets over a 50 year period differed substantially by US region (16% in the North, 50% in the West, and 95% in the South) not only because of differences in forest regrowth and induced investment in retaining and planting forest, but also because of shifts in competitive advantage among regions in producing various wood products. If wood systems displace coal systems that have 75% of the C emissions of wood energy systems per unit energy, then the nationwide net C emissions offset would be reduced to 71-74%. If displacing natural gas systems that have 40% of the level of wood bioenergy emissions per unit energy, the nationwide net C emissions offset would be 46-52%. [ABSTRACT FROM AUTHOR]

Background: Forest fuel treatments have been proposed as tools to stabilize carbon stocks in fire-prone forests in the Western U.S.A. Although fuel treatments such as thinning and burning are known to immediately reduce forest carbon stocks, there are suggestions that these losses may be paid back over the long-term if treatments sufficiently reduce future wildfire severity, or prevent deforestation. Although fire severity and post-fire tree regeneration have been indicated as important influences on long-term carbon dynamics, it remains unclear how natural variability in these processes might affect the ability of fuel treatments to protect forest carbon resources. We surveyed a wildfire where fuel treatments were put in place before fire and estimated the short-term impact of treatment and wildfire on aboveground carbon stocks at our study site. We then used a common vegetation growth simulator in conjunction with sensitivity analysis techniques to assess how predicted timescales of carbon recovery after fire are sensitive to variation in rates of fire-related tree mortality, and post-fire tree regeneration. Results: We found that fuel reduction treatments were successful at ameliorating fire severity at our study site by removing an estimated 36% of aboveground biomass. Treated and untreated stands stored similar amounts of carbon three years after wildfire, but differences in fire severity were such that untreated stands maintained only 7% of aboveground carbon as live trees, versus 51% in treated stands. Over the long-term, our simulations suggest that treated stands in our study area will recover baseline carbon storage 10-35 years more quickly than untreated stands. Our sensitivity analysis found that rates of fire-related tree mortality strongly influence estimates of post-fire carbon recovery. Rates of regeneration were less influential on recovery timing, except when fire severity was high. Conclusions: Our ability to predict the response of forest carbon resources to anthropogenic and natural disturbances requires models that incorporate uncertainty in processes important to long-term forest carbon dynamics. To the extent that fuel treatments are able to ameliorate tree mortality rates or prevent deforestation resulting from wildfire, our results suggest that treatments may be a viable strategy to stabilize existing forest carbon stocks. [ABSTRACT FROM AUTHOR]

Forests play a key role in the global carbon cycle, and programs aimed at mitigating greenhouse gas emissions through the protection and enhancement of forest carbon stocks are growing in number. Adding greenhouse gas mitigation as a management objective presents managers with a considerable challenge, because data and guidelines are scarce. Long-term inventory datasets have the potential to serve as a useful resource, providing data on carbon accumulation over time, as well as offering insight on strategies for managing forests for the objective of climate mitigation in the face of changing climate and disturbance regimes. We present long-term estimates of carbon accumulation developed from biometric measurements from two northern hardwood forests in the northeastern USA. The Bartlett Experimental Forest in central New Hampshire, USA, stored an estimated net average annual 0.53 tC/ha/yr between 1932-2001, for an increase of 50% in carbon stock per unit area; there were significant differences in accrual rates between age classes (38% for old unmanaged stands and 78% for younger unmanaged stands). The Kane Experimental Forest in northwestern Pennsylvania, USA, exhibited a 140% increase in carbon stored per unit area between 1932 and 2006, with an average annual accumulation rate of 0.89 tC/ha/yr. While both forests have experienced management activity and natural disturbances and differ in species composition, the average age of the forests is an important factor driving the differences in net accumulation rates. [ABSTRACT FROM AUTHOR]

Higher tree density, more fuels, and a warmer, drier climate have caused an increase in the frequency, size, and severity of wildfires in western U.S. forests. There is an urgent need to restore forests across the western United States. To address this need, the U.S. Forest Service began the Four Forest Restoration Initiative (4FRI) to restore four national forests in Arizona. The objective of this study was to evaluate how restoration of ~400,000 ha under the 4FRI program and projected climate change would influence carbon dynamics and wildfire severity from 2010 to 2099. Specifically, we estimated forest carbon fluxes, carbon pools and wildfire severity under a moderate and fast 4FRI implementation schedule and compared those to status quo and no‐harvest scenarios using the LANDIS‐II simulation model and climate change projections. We found that the fast‐4FRI scenario showed early decreases in ecosystem carbon due to initial thinning/prescribed fire treatments, but total ecosystem carbon increased by 9–18% over no harvest by the end of the simulation. This increased carbon storage by 6.3–12.7 million metric tons, depending on the climate model, equating to removal of carbon emissions from 55,000 to 110,000 passenger vehicles per year until the end of the century. Nearly half of the additional carbon was stored in more stable soil pools. However, climate models with the largest predicted temperature increases showed declines by late century in ecosystem carbon despite restoration. Our study uses data from a real‐world, large‐scale restoration project and indicates that restoration is likely to stabilize carbon and the benefits are greater when the pace of restoration is faster. [ABSTRACT FROM AUTHOR]