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  • Articles  (224)
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  • 1
    Electronic Resource
    Electronic Resource
    s.l. : American Chemical Society
    Journal of the American Chemical Society 82 (1960), S. 1413-1416 
    ISSN: 1520-5126
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    s.l. : American Chemical Society
    Journal of the American Chemical Society 82 (1960), S. 6429-6429 
    ISSN: 1520-5126
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] The distribution of sources and sinks of carbon among the world's ecosystems is uncertain. Some analyses show northern mid-latitude lands to be a large sink, whereas the tropics are a net source; other analyses show the tropics to be nearly neutral, whereas northern mid-latitudes are a ...
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  • 4
    Electronic Resource
    Electronic Resource
    Palo Alto, Calif. : Annual Reviews
    Annual Review of Environment and Resources 24 (1999), S. 571-605 
    ISSN: 1056-3466
    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract A total of 176 countries have ratified the United Nations Framework Convention on Climate Change, thereby agreeing to limit emissions of greenhouse gases that threaten to interfere with the Earth's climate. While compliance procedures are being developed, the best indicators of implementation of the Convention are the emissions inventories of greenhouse gases that member countries must submit to the Convention as part of their national communications. We review some of the first emissions inventories from non-Annex I (developing) countries. We focus on land-use change and forestry because these activities are responsible for the major emissions of carbon in many non-Annex I parties, and because they are the only activities with the potential to remove carbon from the atmosphere and sequester it on land. The review shows first, that some developing countries have already begun to reduce emissions and second, that there are significant discrepancies between the data used in the emissions inventories and the data available in international surveys. Conceptual uncertainties also exist, such as distinguishing anthropogenic from nonanthropogenic sinks of carbon, and these will require political rather than scientific resolution. We discuss several options for counting terrestrial sources and sinks of carbon in light of the Kyoto Protocol.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Palo Alto, Calif. : Annual Reviews
    Annual Review of Environment and Resources 21 (1996), S. 293-310 
    ISSN: 1056-3466
    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract The CO2 concentration of the atmosphere has increased by almost 30% since 1800. This increase is due largely to two factors: the combustion of fossil fuel and deforestation to create croplands and pastures. Deforestation results in a net flux of carbon to the atmosphere because forests contain 20-50 times more carbon per unit area than agricultural lands. In recent decades, the tropics have been the primary region of deforestation. The annual rate of CO2 released due to tropical deforestation during the early 1990s has been estimated at between 1.2 and 2.3 gigatons C. The range represents uncertainties about both the rates of deforestation and the amounts of carbon stored in different types of tropical forests at the time of cutting. An evaluation of the role of tropical regions in the global carbon budget must include both the carbon flux to the atmosphere due to deforestation and carbon accumulation, if any, in intact forests. In the early 1990s, the release of CO2 from tropical deforestation appears to have been mostly offset by CO2 uptake occurring elsewhere in the tropics, according to an analysis of recent trends in the atmospheric concentrations of O2 and N2. Interannual variations in climate and/or CO2 fertilization may have been responsible for the CO2 uptake in intact forests. These mechanisms are consistent with site-specific measurements of net carbon fluxes between tropical forests and the atmosphere, and with regional and global simulations using process-based biogeochemistry models.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Global change biology 1 (1995), S. 0 
    ISSN: 1365-2486
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Energy, Environment Protection, Nuclear Power Engineering , Geography
    Notes: Changes in land use between 1850 and 1980 are estimated to have increased the global areas in croplands, pastures, and shifting cultivation by 891, 1308, and 30 × 106 ha, respectively, reducing the area of forests by about 600 × 106 ha, releasing about 100 PgC to the atmosphere, and transferring about 23 PgC from live vegetation to dead plant material and wood products. Another 1069 × 106 ha are estimated to have been logged during this period, and the net release of carbon from the combined processes of logging and regrowth contributed 23 PgC to the 100-PgC release. Annual rates of land-use change and associated emissions of carbon have decreased over the last several decades in temperate and boreal zones and have increased in the tropics. The average release of carbon from global changes in land use over the decade of the 1980s Is estimated to have been 1.6 ± 0.7 PgC y−1 almost entirely from the tropics. This estimate of carbon flux is higher than estimates reported in recent summaries because it is limited here to studies concerned only with changes in land use. Other recent analyses, based on data from forest inventories, have reported net accumulations of carbon as high as 1.1 PgC y−1 in temperate and boreal zones. Because the accumulation of carbon in forests may result from natural processes unrelated to land-use change, estimates based on these inventories should be distinguished from estimates based on changes in land use. Both approaches identify terrestrial sinks of carbon. The argument is made here, however, that differences between the two approaches may help identify the location and magnitude of heretofore ‘missing’ sinks. Before different estimates can be used in this way, analyses must consider similar geographical regions and dates, and they must account for the accumulation and loss of carbon in forest products in a consistent fashion.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Science Ltd
    Global change biology 7 (2001), S. 0 
    ISSN: 1365-2486
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Energy, Environment Protection, Nuclear Power Engineering , Geography
    Notes: The amount of carbon released to the atmosphere as a result of deforestation is determined, in part, by the amount of carbon held in the biomass of the forests converted to other uses. Uncertainty in forest biomass is responsible for much of the uncertainty in current estimates of the flux of carbon from land-use change. In the present contribution several estimates of forest biomass are compared for the Brazilian Amazon, based on spatial interpolations of direct measurements, relationships to climatic variables, and remote sensing data. Three questions were posed: First, do the methods yield similar estimates? Second, do they yield similar spatial patterns of distribution of biomass? And, third, what factors need most attention if we are to predict more accurately the distribution of forest biomass over large areas?   The answer to the first two questions is that estimates of biomass for Brazil's Amazonian forests (including dead and belowground biomass) vary by more than a factor of two, from a low of 39 PgC to a high of 93 PgC. Furthermore, the estimates disagree as to the regions of high and low biomass. The lack of agreement among estimates confirms the need for reliable determination of aboveground biomass over large areas. Potential methods include direct measurement of biomass through forest inventories with improved allometric regression equations, dynamic modelling of forest recovery following observed stand-replacing disturbances, and estimation of aboveground biomass from airborne or satellite-based instruments sensitive to the vertical structure plant canopies.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Science Ltd
    Global change biology 5 (1999), S. 0 
    ISSN: 1365-2486
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Energy, Environment Protection, Nuclear Power Engineering , Geography
    Notes: The net emissions of carbon from forestry and changes in land use in south and southeast Asia were calculated here with a book-keeping model that used rates of land-use change and associated per hectare changes in vegetation and soil to calculate changes in the amount of carbon held in terrestrial ecosystems and wood products. The total release of carbon to the atmosphere over the period 1850–1995 was 43.5 PgC. The clearing of forests for permanent croplands released 33.5 PgC, about 75% of the total. The reduction of biomass in the remaining forests, as a result of shifting cultivation, logging, fuelwood extraction, and associated regrowth, was responsible for a net loss of 11.5 PgC, and the establishment of plantations withdrew from the atmosphere 1.5 PgC, most of it since 1980. Based on comparisons with other estimates, the uncertainty of this long-term flux is estimated to be within ±30%. Reducing this uncertainty will be difficult because of the difficulty of documenting the biomass of forests in existence 〉40 years ago. For the 15-y period 1981–1995, annual emissions averaged 1.07 PgC y–1, about 50% higher than reported for the 1980s in an earlier study. The uncertainty of recent emissions is probably within ± 50% but could be reduced significantly with systematic use of satellite data on changes in forest area. In tropical Asia, the emissions of carbon from land-use change in the 1980s accounted for approximately 75% of the region’s total carbon emissions. Since 1990 rates of deforestation and their associated emissions have declined, while emissions of carbon from combustion of fossil fuels have increased. The net effect has been a reduction in emissions of CO2 from this region since 1990.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Science Ltd
    Global change biology 9 (2003), S. 0 
    ISSN: 1365-2486
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Energy, Environment Protection, Nuclear Power Engineering , Geography
    Notes: The carbon balance of the world's terrestrial ecosystems is uncertain. Both top-down (atmospheric) and bottom-up (forest inventory and land-use change) approaches have been used to calculate the sign and magnitude of a net terrestrial flux. Different methods often include different processes, however, and comparisons can be misleading. Differences are not necessarily the result of uncertainties or errors, but often result from incomplete accounting inherent in some of the methods. Recent estimates are reviewed here. Overall, a northern mid-latitude carbon sink of approximately 2 Pg C yr−1 appears robust, although the mechanisms responsible are uncertain. Several lines of evidence point to environmentally enhanced rates of carbon accumulation. Other lines suggest that recovery from past disturbances is largely responsible for the sink. The tropics appear to be a small net source of carbon or nearly neutral, and the same uncertainties of mechanism exist. In addition, studies in the tropics do not permit an unequivocal choice between two alternatives: large emissions of carbon from deforestation offset by large sinks in undisturbed forests, or moderate emissions from land-use change with essentially no change in the carbon balance in undisturbed forests. Resolution of these uncertainties is most likely to result from spatially detailed historical reconstructions of land-use change and disturbance in selected northern mid-latitude regions where such data are available, and from systematic monitoring of changes in the area of tropical forests with satellite data of high spatial resolution collected over the last decades and into the future.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Science Ltd
    Global change biology 11 (2005), S. 0 
    ISSN: 1365-2486
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Energy, Environment Protection, Nuclear Power Engineering , Geography
    Notes: The long-term net flux of carbon between terrestrial ecosystems and the atmosphere has been dominated by two factors: changes in the area of forests and per hectare changes in forest biomass resulting from management and regrowth. While these factors are reasonably well documented in countries of the northern mid-latitudes as a result of systematic forest inventories, they are uncertain in the tropics. Recent estimates of carbon emissions from tropical deforestation have focused on the uncertainty in rates of deforestation. By using the same data for biomass, however, these studies have underestimated the total uncertainty of tropical emissions and may have biased the estimates. In particular, regional and country-specific estimates of forest biomass reported by three successive assessments of tropical forest resources by the FAO indicate systematic changes in biomass that have not been taken into account in recent estimates of tropical carbon emissions. The ‘changes’ more likely represent improved information than real on-the-ground changes in carbon storage. In either case, however, the data have a significant effect on current estimates of carbon emissions from the tropics and, hence, on understanding the global carbon balance.
    Type of Medium: Electronic Resource
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