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  • 1
    Publication Date: 2019-07-17
    Description: Disturbance plays a major role in shaping and maintaining many of the Earth'sterrestrial ecosystems. In fact, many ecosystems depend on fire for theirvery existence. Global Change is expected to result in changed distributionof current ecosystems, changed composition of those ecosystems, and increation of new ecosystems. The International Geosphere Biosphere Program(IGBP), through the Core Projects Biospheric Aspects of the HydrologicalCycle, International Global Atmospheric Chemistry, Global Change andTerrestrial Ecosystems and International Global Atmospheric Chemistry,Biomass Burning Working Group, recognized that disturbances need to beincluded in the modeling efforts of each project. Disturbance from fire, landuse and other factors may be as important as climate change in shaping futurelandscapes (Weber and Flannigan 1998). Three main themes were recognized:impact of disturbance on carbon pools, vegetation change, and feedbacks to theatmosphere. In June 1998, a workshop was held in Potsdam, Germany to developa strategy to introduce disturbance into dynamic global vegetation models.This strategy was based on the fact that vegetation burning influencesatmospheric chemistry, that feedbacks of energy, water and trace gases tothe atmosphere are influenced by vegetation, and that changes in thecomposition of ecosystems have direct impact on the carbon pool, onbiodiversity, and on health and productivity of the land. Disturbanceincludes fire, insect, disease, drought and flooding, land conversion,land use, air pollution, and introduction of exotic species. While it willbe necessary to ultimately include all disturbances, the Potsdam workshoplimited itself to fire. This strategy is based on the fact that there areno process driven models for all disturbances, and that fire has a numberof reliable models with which to begin the process of introducing disturbanceinto dynamic global vegetation models. While this workshop limited itself tofire, a great deal of consideration was given to the fact that the modelshell must be able to include other disturbances in the future. As a result,the strategy was to focus on a hazard function which would lead to effectsof disturbance. The hazard function is basically a probability statement ofrisk of effects. This approach seems equally valid for all forms ofdisturbance.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
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  • 2
    Electronic Resource
    Electronic Resource
    s.l. : American Chemical Society
    Macromolecules 10 (1977), S. 1193-1196 
    ISSN: 1520-5835
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Plant pathology 43 (1994), S. 0 
    ISSN: 1365-3059
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Studies have shown the New Zealand flatworm to be a predator of earthworms and to be widely distributed throughout most of Ireland and Scotland. Except for one record in 1965, it had not been found in England until, in December 1992, it was positively identified from a garden centre near Manchester. Viable and empty egg capsules were also found suggesting that it had reproduced and become established in that nursery. During 1993 other confirmed reports were received from Yorkshire and East Anglia, indicating that it may be able to survive and multiply across large areas of England.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Physiologia plantarum 65 (1985), S. 0 
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Rhizosheaths (sheaths of sand grains that form around the roots of some grasses) are common in perennial grasses that colonise sandy substrates. It has been hypothesised that rhizosheaths increase water availability by increasing the efficiency of water absorption. Others have suggested that rhizosheaths act as storage reservoirs for water. In either case rhizosheaths undoubtedly play an important role in the water relations of these grasses.In an attempt to evaluate the main function of rhizosheaths, we developed a finite element cylindrical water flow model which enabled us to simulate water uptake by Oryzopsis hymenoides (Roem, and Shult.) Ricker. This model allowed us to estimate total water uptake by root systems with and without rhizosheaths and to compare these values to the extra water stored within the rhizosheath. The results of this study suggest that the presence of rhizosheaths is more important in reducing the total resistance to water flow within the rhizosphere than in enhancing water storage.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Physiologia plantarum 52 (1981), S. 0 
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Current-year shoots of Sitka spruce (Picea sitchensis (Bong.) Carr.) were removed from the forest canopy. After steady-state rates of net photosynthesis were obtained in a leaf chamber, the shoots were excised in air and removed at different times to establish a relationship between net photosynthesis and xylem water potential. The experiment was repeated at five ambient carbon dioxide concentrations.Net photosynthesis remained constant over a wide range of xylem water potential and increased linearly with ambient carbon dioxide concentration between 20 and 300 cm3 m−3. At low water potential net photosynthesis declined at each ambient carbon dioxide concentration and there was little difference in the potential (±0.05 MPa) at which zero photosynthesis was observed.There was a small increase in the CO2 compensation concentration at low xylem water potentials, but calculated mesophyll conductance still declined at low water potential after correction for this change in compensation concentration. Mesophyll conductance reached zero within the same range of water potential as net photosynthesis. The results suggested that the non-stomatal contribution to the decline of photosynthesis was approximately 30% until almost complete stomatal closure occurred.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Physiologia plantarum 45 (1979), S. 0 
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Current year shoots of Sitka spruce [Picea sitchensis Bong. (Carr.)] from the forest canopy were equilibrated in a leaf chamber. The shoots were excised in air, and removed at differing times in order to establish a relationship between stomatal conductance and xylem water potential. The experiment was repeated at five ambient CO2 concentrations. A second set of excised forest shoots, and shoots excised from 2-year- old nursery seedlings were allowed to evaporate freely in a controlled environment wind tunnel until a constant rate of transpiration was measured, to establish a relationship between cuticular conductance and xylem water potential.Cuticular conductance was estimated to be 0.012 cm s-1 at high water potential and declined linearly to 0.007 cm s-1 at −3.5 MPa. The implication of this decline in the subsequent calculation of stomatal and mesophyll conductance is considered.Stomatal conductance remained constant at water potentials above −1.4 MPa and was not affected by ambient carbon dioxide concentrations between 20 and 600 cm-3. At lower water potentials, stomatal conductance declined and approached zero at −2.5 to −2.6 MPa. The results suggest that stomatal aperture is not controlled by either ambient or intercellular space carbon dioxide concentration, and that stomatal closure at low water potential is unlikely to be mediated by carbon dioxide.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Water, air & soil pollution 70 (1993), S. 19-37 
    ISSN: 1573-2932
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract There is great uncertainty with regard to the future role of the terrestrial biosphere in the global carbon cycle. The uncertainty arises from both an inadequate understanding of current pools and fluxes as well as the potential effects of rising atmospheric concentrations of CO2 on natural ecosystems. Despite these limitations, a number of studies have estimated current and future patterns of terrestrial carbon storage. Future estimates focus on the effects of a climate change associated with a doubled atmospheric concentration of CO2. Available models for examining the dynamics of terrestrial carbon storage and the potential role of forest management and landuse practices on carbon conservation and sequestration are discussed.
    Type of Medium: Electronic Resource
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  • 8
    ISSN: 1573-8469
    Keywords: Nematoda ; tobacco ; Trichodoridae ; virus-vector
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract A virus isolated from diseased tobacco plants growing in Macedonia, northern Greece, had host range and physico-chemical properties typical of a tobravirus. Although it was serologically unrelated to any of the ten tobravirus isolates tested, it reacted in spot hybridization tests with a probe derived from RNA-1 of tobacco rattle virus (TRV) strain SYM. Therefore, the isolate probably represents a previously undescribed serotype of TRV. Male, female and juvenileTrichodorus similis nematodes recovered from the rhizosphere of the diseased tobacco plants transmitted TRV in each of three laboratory experiments. In two of these experiments 50% and 54%, respectively, of the nematodes transmitted virus toPetunia hybrida bait plants, whereas only 18% transmitted virus toNicotiana tabacum plants in a third test. Ultrathin sections of the feeding apparatus of individual nematodes, which had transmitted virus, were examined by electron microscopy. Virus particles were observed, retained as a monolayer in the apices of the oesophageal lumen and as a group of particles within a matrix in the open part of the lumen.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    European journal of plant pathology 102 (1996), S. 193-199 
    ISSN: 1573-8469
    Keywords: climate change ; Longidorus ; nematodes ; Trichodorus ; virus-vector
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Data extracted from surveys of plant-parasitic nematodes in Great Britain allowed relatively detailed maps of the geographical distribution of various longidorid and trichodorid virus-vector nematode species to be produced. These distributions are related to long-term monthly mean temperature. Recently published figures for climate change were applied to the distribution data. A potential increase in nematode associated problems due to climate change using examples of existing published data are examined and discussed.
    Type of Medium: Electronic Resource
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  • 10
    ISSN: 1573-5036
    Keywords: geostatistics ; grazing management ; 13-C ; 15-N ; resource patchiness ; ryegrass-clover pastures
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract As preparation for a below ground food web study, the spatial variability of three soil properties (total N, total C and pH) and two stable isotopes (δ13C and δ15N of whole soil) were quantified using geostatistical approaches in upland pastures under contrasting management regimes (grazed, fertilised and ungrazed, unfertilised) in Scotland. This is the first such study of upland, north maritime grasslands. The resulting patterns of variability suggest that to obtain statistically independent samples in this system, a sampling distance of ≥13.5 m is required. Additionally, temporal change (a decline of 1‰) was observed in whole soil δ15N for the grazed, fertilised plot. This may have been caused by new inputs of symbiotically-fixed atmospheric N2.
    Type of Medium: Electronic Resource
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