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Carbon debt and carbon sequestration parity in forest bioenergy production
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The capacity for forests to aid in climate change mitigation efforts is substantial but will ultimately depend on their management. If forests remain unharvested, they can further mitigate the increases in atmospheric CO2 that result from fossil fuel combustion and deforestation. Alternatively, they can be harvested for bioenergy production and serve as a substitute for fossil fuels, though such a practice could reduce terrestrial C storage and thereby increase atmospheric CO2 concentrations in the near-term. Here, we used an ecosystem simulation model to ascertain the effectiveness of using forest bioenergy as a substitute for fossil fuels, drawing from a broad range of land-use histories, harvesting regimes, ecosystem characteristics, and bioenergy conversion effi- ciencies. Results demonstrate that the times required for bioenergy substitutions to repay the C Debt incurred from biomass harvest are usually much shorter (< 100 years) than the time required for bioenergy production to substitute the amount of C that would be stored if the forest were left unharvested entirely, a point we refer to as C Sequestration Parity. The effectiveness of substituting woody bioenergy for fossil fuels is highly dependent on the factors that determine bioenergy conversion efficiency, such as the C emissions released during the har- vest, transport, and firing of woody biomass. Consideration of the frequency and intensity of biomass harvests should also be given; performing total harvests (clear-cutting) at high-frequency may produce more bioenergy than less intensive harvesting regimes but may decrease C storage and thereby prolong the time required to achieve C Sequestration Parity.
Keywords: bioenergy, biofuel, C cycle, C sequestration, forest management
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Domesticated Nature: Shaping Landscapes and Ecosystems for Human Welfare
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Like all species, humans have exercised their impulse to perpetuate and propagate themselves. In doing so, we have domesticated landscapes and ecosystems in ways that enhance our food supplies, reduce exposure to predators and natural dangers, and promote commerce. On average, the net benefits to humankind of domesticated nature have been positive. We have, of course, made mistakes, causing unforeseen changes in ecosystem attributes, while leaving few, if any, truly wild places on Earth. Going into the future, scientists can help humanity to domesticate nature more wisely by quantifying the tradeoffs among ecosystem services, such as how increasing the provision of one service may decrease ecosystem resilience and the provision of other services.
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Characteristics, distribution and geomorphic role of large woody debris in a mountain stream of the Chilean Andes
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The paper presents an analysis of amounts, characteristics and morphological impact of large woody debris (LWD) in the Tres Arroyos stream, draining an old-growth forested basin (9·1 km2) of the Chilean Southern Andes. Large woody debris has been surveyed along a 1·5 km long channel section with an average slope of 0·07 and a general step–pool/cascade morphology. Specific wood storage is very high (656 –710 m3 ha−1), comparable to that recorded in old-growth forested basins in the Pacific Northwest. Half of the LWD elements were located on the active floodplain, and around two-thirds of LWD elements were found in accumula- tions. Different types of log jam were observed, some heavily altering channel morphology (log-steps and valley jams), while others just line the channel edges (bankfull bench jams). Log-steps represent approximately 22% of all steps, whereas the elevation loss due to LWD (log-steps and valley jams) results in 27% loss of the total stream potential energy. About 1600 m3 of sediment is stored in the main channel behind LWD structures, corresponding to approximately 150% of the annual sediment yield.
Keywords: large woody debris; channel morphology; valley jams; log-steps; Andes; stream sediment: sediment traps
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Invited Review: Quantifying surface albedo and other direct biogeophysical climate forcings of forestry activities
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By altering fluxes of heat, momentum, and moisture exchanges between the land surface and atmosphere, forestry and other land-use activities affect climate. Although long recognized scientifically as being important, these so-called biogeophysical forcings are rarely included in climate policies for forestry and other land management projects due to the many challenges associated with their quantification. Here, we review the scientific literature in the fields of atmospheric science and terrestrial ecology in light of three main objectives: (i) to elucidate the challenges associated with quantifying biogeophysical climate forcings connected to land use and land management, with a focus on the forestry sector; (ii) to identify and describe scientific approaches and/or metrics facilitating the quantification and interpretation of direct biogeophysical climate forcings; and (iii) to identify and recommend research priorities that can help overcome the challenges of their attribution to specific land-use activities, bridging the knowledge gap between the climate modeling, forest ecology, and resource management communities. We find that ignoring surface
biogeophysics may mislead climate mitigation policies, yet existing metrics are unlikely to be sufficient. Successful metrics ought to (i) include both radiative and nonradiative climate forcings; (ii) reconcile disparities between biogeophysical and biogeochemical forcings, and (iii) acknowledge trade-offs between global and local climate benefits. We call for more coordinated research among terrestrial ecologists, resource managers, and coupled climate modelers to harmonize datasets, refine analytical techniques, and corroborate and validate metrics that are more amenable to analyses at the scale of an individual site or region.
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Predicting a change in the order of spring phenology in temperate forests
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The rise in spring temperatures over the past half-century has led to advances in the phenology of many nontropical plants and animals. As species and populations differ in their phenological responses to temperature, an increase in temperatures has the potential to alter timing-dependent species interactions. One species-interaction that may be affected is the competition for light in deciduous forests, where early vernal species have a narrow window of opportunity for growth before late spring species cast shade. Here we consider the Marsham phenology time series of first leafing dates of thirteen tree species and flowering dates of one ground flora species, which spans two centuries. The exceptional length of this time series permits a rare comparison of the statistical support for parameter-rich regression and mechanistic thermal sensitivity phenology models. While mechanistic models perform best in the majority of cases, both they and the regression models provide remarkably consistent insights into the relative sensitivity of each species to forcing and chilling effects. All species are sensitive to spring forcing, but we also find that vernal and
northern European species are responsive to cold temperatures in the previous autumn. Whether this sensitivity reflects a chilling requirement or a delaying of dormancy remains to be tested. We then apply the models to projected future temperature data under a fossil fuel intensive emissions scenario and predict that while some species will advance substantially others will advance by less and may even be delayed due to a rise in autumn and winter temperatures. Considering the projected responses of all fourteen species, we anticipate a change in the order of spring events, which may lead to changes in competitive advantage for light with potential implications for the composition of temperate forests.
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Resources Planning Act (RPA) Assessment Webinar: U.S. Forest Fragmentation and Land Cover Patterns
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Forest fragmentation continues even as total forestland area remains relatively stable.
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Forest Service Report Highlights Restoration Progress Made Despite Growing Challenges
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The U.S. Forest Service has increased the pace and scale of forest restoration by nine percent since 2011, according to a report released today. The significant progress comes in the face of mounting challenges to the agency including record droughts, longer wildfire seasons and the increasing percentage of the agency’s budget spent fighting wildland fires.
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Where the Not-So-Mighty Chestnut Still Grows
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A recent study by U.S. Forest Service, university, and state agency researchers provides baseline information on contemporary populations of American chestnut needed to support restoration of the tree to the forests it once dominated.
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Managing Forests for Birds Video Series
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A new video series by the Ohio Bird Conservation Initiative highlights the importance of proper forest management in improving a diversity of habitat for birds and other wildlife.
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Bringing Back Diversity in Eastern Forests for Landowners, Wildlife
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What do biologists look for in a healthy forest? A diversity in the ages and composition of trees and occasional breaks in canopy to allow sunlight to reach understory plants.
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