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  • 1
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Knowledge of carbon exchange between the atmosphere, land and the oceans is important, given that the terrestrial and marine environments are currently absorbing about half of the carbon dioxide that is emitted by fossil-fuel combustion. This carbon uptake is therefore limiting the extent of ...
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Water, air & soil pollution 70 (1993), S. 39-53 
    ISSN: 1573-2932
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract The circumpolar boreal biomes coverca. 2 109 ha of the northern hemisphere and containca. 800 Pg C in biomass, detritus, soil, and peat C pools. Current estimates indicate that the biomes are presently a net C sink of 0.54 Pg C yr−1. Biomass, detritus and soil of forest ecosystems (includingca. 419 Pg peat) containca. 709 Pg C and sequester an estimated 0.7 Pg C yr−1. Tundra and polar regions store 60–100 Pg C and may recently have become a net source of 0.17 Pg C yr−1. Forest product C pools, including landfill C derived from forest biomass, store less than 3 Pg C but increase by 0.06 Pg C yr−1. The mechanisms responsible for the present boreal forest net sink are believed to be continuing responses to past changes in the environment, notably recovery from the little ice-age, changes in forest disturbance regimes, and in some regions, nutrient inputs from air pollution. Even in the absence of climate change, the C sink strength will likely be reduced and the biome could switch to a C source. The transient response of terrestrial C storage to climate change over the next century will likely be accompanied by large C exchanges with the atmosphere, although the long-term (equilibrium) changes in terrestrial C storage in future vegetation complexes remains uncertain. This transient response results from the interaction of many (often non-linear) processes whose impacts on future C cycles remain poorly quantified. Only a small part of the boreal biome is directly affected by forest management and options for mitigating climate change impacts on C storage are therefore limited but the potential for accelerating the atmospheric C release are high.
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  • 3
    Electronic Resource
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    Water, air & soil pollution 82 (1995), S. 203-214 
    ISSN: 1573-2932
    Keywords: boreal ; forest ; transect ; ecosystem ; model ; carbon ; BOREAS ; Canada
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract The Boreal Forest Transect Case Study (BFTCS) is a multi-disciplinary ecological study organised around a 1000 km transect located in central Canada. The transect is oriented along an ecoclimatic gradient in a region likely to undergo significant environmental change within the next few decades, and crosses the climate-sensitive boreal forest biome, including the transitions north and south into tundra and grassland respectively. Originally conceived as an extension to the BOReal Ecosystem Atmosphere Study (BOREAS), the 10-year BFTCS project projects the intensive canopy-scale measurements and modelling advances obtained from BOREAS to a wider range of sites with a longer-term perspective. In addition to considering ecophysiological processes with time-frames of the order of one year or shorter, BFTCS addresses the effects of larger scale, longer term processes including vegetation succession and ecosystem disturbances. The BFTCS currently provides practical linkages among ecosystem monitoring, field experiments and regional scale modelling. It will ultimately provide a knowledge-base of key processes and their environmental sensitivities, and assessments of possible climate feedbacks, which can be used to assess the possible consequences of global change both regionally and globally.
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  • 4
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    Water, air & soil pollution 82 (1995), S. 321-331 
    ISSN: 1573-2932
    Keywords: carbon budget ; boreal forest ; CBM-CFS ; Canada ; disturbance ; future projections
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract The Canadian boreal forest covers over 300 Mha of land area. Its dynamics are largely influenced by fires and insect-induced stand mortality and to a much lesser extent by forest management. This paper analyses six scenarios of future (1990–2040) carbon (C) budgets of the Canadian boreal forest, each based on different assumptions about natural disturbances, rates of reforestation of disturbed land, and conversion of non-stocked to productive forest stands. The objective of these scenarios is to explore the range of responses to different management options. The results indicate an overall inertia of a system whose dynamics are strongly influenced by a recent 20-year period (1970–1989) of large-scale forest disturbances by fire and insects. The 50-year C budget of the six scenarios ranges from an estimated net source of 1.4 Pg C to a net sink of 9.2 Pg C. These estimates indicate the range of response to the management of the Canadian boreal forest. Although a full-scale implementation of the management activities examined here is not likely given ecological and economic realities in the Canadian boreal forest, the analyses explore the relative merits of reducing forest disturbance rates, regeneration delays, and the area of non-stocked forest land.
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  • 5
    Electronic Resource
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    Water, air & soil pollution 82 (1995), S. 429-436 
    ISSN: 1573-2932
    Keywords: disturbance ; contagion ; temporal dynamics ; modelling approach ; spatial model ; fire behaviour ; distance-dependent fire propagation ; Succession ; sampling theory
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract Contagious disturbances are widespread and an important component of the life-cycle of the Canadian boreal forest. Models which simulate the dynamics of these forests must include a representation of disturbance influences. Spatial models differ from non-spatial models in the use of area-based rather than point-based sampling designs. Distance-dependent disturbance propagation accounts for spatial correlation among disturbed stands and its inclusion in spatial models may generate more realistic forest temporal dynamics than can be generated by non-spatial models. A comparison of results from simulations using age-dependent and distance-dependent disturbance propagation can provide further insight on the role contagion in structuring forest temporal dynamics.
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  • 6
    Electronic Resource
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    Water, air & soil pollution 82 (1995), S. 257-270 
    ISSN: 1573-2932
    Keywords: boreal Forest ; overstory ; detritus ; biomass ; field methods
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract As a contribution to the BOReal Ecosystem Atmosphere Study (BOREAS), a total of 97 sites have been surveyed in the boreal forest regions of Manitoba and Saskatchewan. The sites extend across an ecoclimatic transect through the boreal forest of central Canada, from aspen parkland to sub-arctic woodland. Sites were selected using satellite, air photograph, and forest cover map data. Each site represents a minimum 100 m by 100 m homogeneous stand, suitable for satellite imaging. Data collected at each site covers overstory (species composition, DBH, pathogens, age, etc.), understory (percent cover by species), debris, and soil characteristics. These data provide a background database for the diverse measurements of terrestrial ecology, land surface climatology, tropospheric chemistry, and remote sensing. Such data provide an important baseline for ongoing studies of the boreal forest in a region sensitive to global change. The results of this study aid integration of a variety of more detailed studies being carried out in the region and also allow comparison with other international studies of a similar nature. Sites are concentrated in two regions: north of Prince Albert, Saskatchewan, and west of Thompson, Manitoba. Additional sites are located in the area of the Boreal Forest Transect Case Study (BFTCS) between Batoche, Saskatchewan and Gillam, Manitoba. The surveyed sites were classified according to three criteria: dominant species (Picea mariana, Populus tremuloides, Pinus banksiana, or “mixed”), age (mature, immature, or young/recently disturbed), and productivity (low, medium, or high). Overstory and understory measurements were usually taken at three points within each site. Debris measurements were taken at two points, and soil measurements at one point per site. This paper focuses on overstory and debris data taken at 97 sites in 1993 and 1994. The sites are predominantly in medium and high productivity stands. Overstoiy. data, primarily from point-sampling, have been used to estimate stand basal areas, stem densities, volumes, and aboveground biomass (excluding foliage). Stand basal areas ranged from 5 m2 ha−1 to over 60 m2 ha−1. Stem densities ranged from a few hundred to over 40 000 stem ha−1. Estimates of total aboveground biomass range from a few Mg ha−1 to over 250 Mg ha−1. The Prince Albert sites tend to have greater values than Thompson for basal area, volume and biomass, but stem densities are highly variable. Detritus data show values from zero to 60 Mg ha−1. Generally, these values are small compared to aboveground biomass, but in recently disturbed sites the detrital mass can exceed aboveground biomass.
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  • 7
    Electronic Resource
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    Journal of radioanalytical and nuclear chemistry 110 (1987), S. 245-252 
    ISSN: 1588-2780
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract Fission track analysis (FTA) has been used to investigate the biological uptake of uranium. Examination of fission track maps of black spruce twigs (from areas of uranium mineralization and mill tailings) shows uranium to be concentrated in the inner bark while decreasing in the outer bark of the twigs. Track clusters in the bark, too large to be uraniferous airborne particulate matter, are identified as being associated with resin canals in the twigs. The results of this work help clarify the mechanisms by which uranium is incorporated in black spruce twigs. The observation of decreasing uranium content with the increasing age of black spruce twigs by an earlier worker, can now be explained by the relative reduction in volume of the uranium enriched inner bark with age.
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  • 8
    Electronic Resource
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    Journal of radioanalytical and nuclear chemistry 123 (1988), S. 133-147 
    ISSN: 1588-2780
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract A study has been carried out of the uptake of uranium and other radionuclides by plants growing on abandoned tailings from an uranium mining operation. Assay methods included instrumental neutron activation analysis, delayed neutron counting, fission track imaging, and counting of natural radioactivity. Care was taken to avoid contamination of the plant material and a number of methods are described to identify such contamination. All plants observed showed high uptake of radionuclides, compared to plants studied from naturally uraniferous and control areas. Graminoid (grass-like) plants showed significant uptake in the above-ground parts while woody plants showed exceedingly high uranium accumulation in the root portions. These results have significance in determination of the spread of radioactive material from such sites.
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  • 9
    Publication Date: 1988-07-01
    Print ISSN: 0236-5731
    Electronic ISSN: 1588-2780
    Topics: Chemistry and Pharmacology , Energy, Environment Protection, Nuclear Power Engineering
    Published by Springer
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  • 10
    Publication Date: 2002-05-01
    Description: This study compared three estimates of carbon (C) contained both in the surface layer (030 cm) and the total soil pools at polygon and regional scales and the spatial distribution in the three prairie provinces of western Canada (Alberta, Saskatchewan, and Manitoba). The soil C estimates were based on data from (i) analysis of pedon data from both the Boreal Forest Transect Case Study (BFTCS) area and from a national-scale soil profile database; (ii) the Canadian Soil Organic Carbon Database (CSOCD), which uses expert estimation based on soil characteristics; and (iii) model simulations with the Carbon Budget Model of the Canadian Forest Sector (CBM-CFS2). At the polygon scale, good agreement was found between the CSOCD and pedon (the first method) total soil carbon values. Slightly higher total soil carbon values obtained from BFTCS averaged pedon data (the first method), as indicated by the slope of the regression line, may be related to micro- and meso-scale geomorphic and microclimate influences that are not accounted for in the CSOCD. Regional estimates of organic C from these three approaches for upland forest soils ranged from 1.4 to 7.7 kg C·m2 for the surface layer and 6.2 to 27.4 kg C·m2 for the total soil. In general, the CBM-CFS2 simulated higher soil C content compared with the field observed and CSOCD soil C estimates, but showed similar patterns in the total soil C content for the different regions. The higher soil C content simulated with CBM-CFS2 arises in part because the modelled results include forest floor detritus pool components (such as coarse woody debris, which account for 412% of the total soil pool in the region) that are not included in the other estimates. The comparison between the simulated values (the third method) and the values obtained from the two empirical approaches (the first two methods) provided an independent test of CBM-CFS2 soil simulations for upland forests soils. The CSOCD yielded significantly higher C content for peatland soils than for upland soils, ranging from 14.6 to 28 kg C·m2 for the surface layer and 60 to 181 kg C·m2 for the total peat soil depth. All three approaches indicated higher soil carbon content in the boreal zone than in other regions (subarctic, grassland).
    Print ISSN: 0045-5067
    Electronic ISSN: 1208-6037
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
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