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Registro Completo |
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Biblioteca(s): |
Embrapa Pantanal. |
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Data corrente: |
05/11/1996 |
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Data da última atualização: |
03/04/2017 |
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Autoria: |
BIRD, M. I.; FYFE, W. S.; PINHEIRO-DICK, D.; CHIVAS, A. R. |
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Título: |
Carbon isotope indicators of catchment vegetation in the Brazilian Amazon. |
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Ano de publicação: |
1992 |
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Fonte/Imprenta: |
Global Biogeochemical Cycles, v.6, n.3, p.293-306, Sept. 1992. |
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Idioma: |
Inglês |
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Conteúdo: |
Particulate organic carbon (POC) samples from rivers draining wholly forested catchments in the Amazon Basin exhibit carbon isotope values (13C) of generally between -27 and - 30%. These values are distinct from those of POC from rivers draining nonforested (grassland/woodland) catchments, which are generally higher -26%. The difference is due to the presence in the nonforested regions, of grasses which assimilate carbon via the C4 photosynthetic pathway (average 13C =~-13%), rather than the C3 pathway (average 13C =~-28%) utilized by forest vegetation, and to negligible utilization of low-13C respired carbon dioxide in regions of open vegetation. A change in the area of the Basin covered by closed forest will lead to modification in the carbon isotope composition of exported POC as a result of changing (1) the proportion of C4 carbon in the total biomass (2) the relative proportion of the total POC derived from upstream, high-altitude (Andean) sources, (3) erosion rates, and (4) productivity. All of these factors will tend to reinforce each other in their effect on the carbon isotope composition of POC exported from the Basin, with a decrease in foirest area leading to an increase in the 13C value of POC (and vice versa). There is a sufficient difference between the 13C values of POC exported from forested and non-forested catchments to elucidate past vegetation and therefore climatic changes in the Amazon Basin (and other tropical river basin), using the 13C record in POC from either terrestrial or offshore sedimentary sequences. The carbon isotope composition of POC in rivers draining recently deforested regions indicates that the isotopic composition of coarse (>63 um) riverine POC will respond to vegetation changes in a catchment within years to decades, whereas the 13C value of fine-grained (<63 um) riverine POC may take longer to respond. MenosParticulate organic carbon (POC) samples from rivers draining wholly forested catchments in the Amazon Basin exhibit carbon isotope values (13C) of generally between -27 and - 30%. These values are distinct from those of POC from rivers draining nonforested (grassland/woodland) catchments, which are generally higher -26%. The difference is due to the presence in the nonforested regions, of grasses which assimilate carbon via the C4 photosynthetic pathway (average 13C =~-13%), rather than the C3 pathway (average 13C =~-28%) utilized by forest vegetation, and to negligible utilization of low-13C respired carbon dioxide in regions of open vegetation. A change in the area of the Basin covered by closed forest will lead to modification in the carbon isotope composition of exported POC as a result of changing (1) the proportion of C4 carbon in the total biomass (2) the relative proportion of the total POC derived from upstream, high-altitude (Andean) sources, (3) erosion rates, and (4) productivity. All of these factors will tend to reinforce each other in their effect on the carbon isotope composition of POC exported from the Basin, with a decrease in foirest area leading to an increase in the 13C value of POC (and vice versa). There is a sufficient difference between the 13C values of POC exported from forested and non-forested catchments to elucidate past vegetation and therefore climatic changes in the Amazon Basin (and other tropical river basin), using the 13C record in POC ... Mostrar Tudo |
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Palavras-Chave: |
Amazon Basin; Bacia Amazonica; Carbono organico; Sediment. |
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Thesagro: |
Sedimento; Vegetação. |
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Thesaurus Nal: |
particulate organic carbon; vegetation. |
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Categoria do assunto: |
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Marc: |
LEADER 02574naa a2200253 a 4500
001 1789890
005 2017-04-03
008 1992 bl --- 0-- u #d
100 1 $aBIRD, M. I.
245 $aCarbon isotope indicators of catchment vegetation in the Brazilian Amazon.
260 $c1992
520 $aParticulate organic carbon (POC) samples from rivers draining wholly forested catchments in the Amazon Basin exhibit carbon isotope values (13C) of generally between -27 and - 30%. These values are distinct from those of POC from rivers draining nonforested (grassland/woodland) catchments, which are generally higher -26%. The difference is due to the presence in the nonforested regions, of grasses which assimilate carbon via the C4 photosynthetic pathway (average 13C =~-13%), rather than the C3 pathway (average 13C =~-28%) utilized by forest vegetation, and to negligible utilization of low-13C respired carbon dioxide in regions of open vegetation. A change in the area of the Basin covered by closed forest will lead to modification in the carbon isotope composition of exported POC as a result of changing (1) the proportion of C4 carbon in the total biomass (2) the relative proportion of the total POC derived from upstream, high-altitude (Andean) sources, (3) erosion rates, and (4) productivity. All of these factors will tend to reinforce each other in their effect on the carbon isotope composition of POC exported from the Basin, with a decrease in foirest area leading to an increase in the 13C value of POC (and vice versa). There is a sufficient difference between the 13C values of POC exported from forested and non-forested catchments to elucidate past vegetation and therefore climatic changes in the Amazon Basin (and other tropical river basin), using the 13C record in POC from either terrestrial or offshore sedimentary sequences. The carbon isotope composition of POC in rivers draining recently deforested regions indicates that the isotopic composition of coarse (>63 um) riverine POC will respond to vegetation changes in a catchment within years to decades, whereas the 13C value of fine-grained (<63 um) riverine POC may take longer to respond.
650 $aparticulate organic carbon
650 $avegetation
650 $aSedimento
650 $aVegetação
653 $aAmazon Basin
653 $aBacia Amazonica
653 $aCarbono organico
653 $aSediment
700 1 $aFYFE, W. S.
700 1 $aPINHEIRO-DICK, D.
700 1 $aCHIVAS, A. R.
773 $tGlobal Biogeochemical Cycles$gv.6, n.3, p.293-306, Sept. 1992.
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Registro original: |
Embrapa Pantanal (CPAP) |
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