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Effects of Management on Carbon Sequestration in Forest Biomass in Southeast Alaska
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The Tongass National Forest (Tongass) is the largest national forest and largest area of old-growth forest in the United States. Spatial geographic informa- tion system data for the Tongass were combined with forest inventory data to estimate and map total carbon stock in the Tongass; the result was 2.8±0.5PgC,or8%of the total carbon in the forests of the conterminous USA and 0.25% of the carbon in global forest vegetation and soils. Cumulative net carbon loss from the Tongass due to management of the forest for the period 1900–95 was estimated at 6.4–17.2 Tg C. Using our spatially explicit data for carbon stock and net flux, we modeled the potential effect of five management regimes on future net carbon flux. Estimates of net carbon flux were sensitive to projections of the rate of carbon accumulation in second-growth forests and to the amount of carbon left in standing biomass after harvest. Projections of net carbon flux in the Tongass range from 0.33 Tg C annual sequestration to 2.3 Tg C annual emission for the period 1995–2095. For the period 1995–2195, net flux estimates range from 0.19 Tg C annual sequestra- tion to 1.6 Tg C annual emission. If all timber harvesting in the Tongass were halted from 1995 to 2095, the economic value of the net carbon sequestered during the 100-year hiatus, assuming $20/Mg C, would be $4 to $7 million/y (1995 US dollars). If a prohibition on logging were extended to 2195, the annual economic value of the carbon sequestered would be largely unaffected ($3 to $6 million/y). The potential annual economic value of carbon sequestration with management maxi- mizing carbon storage in the Tongass is comparable to revenue from annual timber sales historically authorized for the forest.
Key words: carbon sequestration; geographic information system; climate change; forest management; Alaska.
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A paradigm shift in understanding and quantifying the effects of forest harvesting on floods in snow environments
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A well-established precept in forest hydrology is that any reduction of forest cover will always have a progressively smaller effect on floods with increasing return period. The underlying logic in snow environments is that during the largest snowmelt events the soils and vegetation canopy have little additional storage capacity and under these conditions much of the snowmelt will be converted to runoff regardless of the amount or type of vegetation cover. Here we show how this preconceived physical understanding, reinforced by the outcomes of numerous paired watershed studies, is indefensible because it is rationalized outside the flood frequency distribution framework. We conduct a meta-analysis of postharvest data at four catchments (3–37 km2) with moderate level of harvesting (33%–40%) to demonstrate how harvesting increases the magnitude and frequency of all floods on record (19–99 years) and how such effects can increase unchecked with increasing return period as a consequence of changes to both the mean (þ11% to þ35%) and standard deviation (12% to þ19%) of the flood frequency distribution. We illustrate how forest harvesting has substantially increased the frequency of the largest floods in all study sites regardless of record length and this also runs counter to the prevailing wisdom in hydrological science. The dominant process responsible for these newly emerging insights is the increase in net radiation associated with the conversion from longwave-dominated snowmelt beneath the canopy to shortwave-dominated snowmelt in harvested areas, further amplified or mitigated by basin characteristics such as aspect distribution, elevation range, slope gradient, amount of alpine area, canopy closure, and drainage density. Investigating first order environmental controls on flood frequency distributions, a standard research method in stochastic hydrology, represents a paradigm shift in the way harvesting effects are physically explained and quantified in forest hydrology literature.
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Pedoecological Modeling to Guide Forest Restoration using Ecological Site Descriptions
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the u.s. department of agriculture (usda)-natural resources conservation service (nrcs) uses an ecological site description (esd) framework to help incorporate interactions between local soil, climate, flora, fauna, and humans into schema for land management decision-making. we demonstrate esd and digital soil mapping tools to (i) estimate potential o horizon carbon (c) stock accumulation from restoring alternative ecological states in high-elevation forests of the central appalachian Mountains in west Virginia (wV), usa, and (ii) map areas in alternative ecological states that can be targeted for restoration. this region was extensively disturbed by clear-cut harvests and related fires during the 1880s through 1930s. we combined spodic soil property maps, recently linked to historic red spruce–eastern hemlock (Picea rubens–Tsuga canadensis) forest communities, with current forest inventories to provide guidance for restoration to a historic reference state. this allowed mapping of alternative hardwood states within areas of the spodic shale uplands conifer forest (scF) ecological site, which is mapped along the regional conifer-hardwood transition of the central appalachian Mountains. Plots examined in these areas suggest that many of the spruce-hemlock dominated stands in wV converted to a hardwood state by historic disturbance have lost at least 10 cm of o horizon thickness, and possibly much more. Based on this 10 cm estimate, we calculate that at least 3.74 to 6.62 tg of c were lost from areas above 880 m elevation in wV due to historic disturbance of o horizons, and that much of these stocks and related ecosystem functions could potentially be restored within 100 yr under focused management, but more practical scenarios would likely require closer to 200 yr.
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F&W Forestry Services, Inc.
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F&W is committed to helping landowners get the most from their timberland by offering customized forest management solutions tailored to your specific needs. Through our participation in academic and professional forestry cooperatives, we have access to the latest innovative research and technology. Together, we help you realize the benefits of your timberland today while conserving the resource for future generations.
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Timber Management and Prescribed Fire
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Joe Marschall (Oak Woodlands and Forests Fire Science Consortium) moderates a panel of fire professionals and timber management specialists to discuss results from research and personal experience of combining prescribed fire with timber management.
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