Article (Scientific journals)
Carbon stocks and isotopic budgets of the terrestrial biosphere at mid-Holocene and last glacial maximum times
François, Louis; Godderis, Y.; Warnant, Pierre et al.
1999In Chemical Geology, 159 (1-4), p. 163-189
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Keywords :
biosphere; pleistocene; isotopic fractionation; model; carbon cycle
Abstract :
[en] The carbon fluxes, stocks and isotopic budgets of the land biosphere at mid-Holocene (6 ka BP) and last glacial maximum (21 ka BP) times are reconstructed with the CARbon Assimilation In the Biosphere (CARATB) model forced with two different sets of climates simulated by the European Centre-HAMburg (ECHAM) and LMD general circulation models. It is found that the trends predicted on the basis of both sets of GCM climatic fields are generally consistent with each other, although substantial discrepancies in the magnitude of the changes may be observed. Actually, these discrepancies in the biospheric results associated with the use of different GCM climatic fields are usually smaller than the differences between biospheric runs performed while considering or neglecting the CO2 fertilization effect (which might, however, be overestimated by the model due to uncertainties concerning changes in nutrient availability). The calculated changes with respect to the present of the biosphere carbon stock range from - 132 to + 92 Gt C for the mid-Holocene and from -710 to +70 Gt C for the last glacial maximum. It is also shown that the relative contribution of the material synthesized by C-4 plants to the total biomass of vegetation, litter and soils was substantially larger at mid-Holocene and last glacial maximum times than today. This change in the relative importance of the C-3 and C-4 photosynthetic pathways induced changes in the C-13 fractionation of the land biosphere. These changes in the average biospheric fractionation resulting from the redistribution of C-3 and C-4 plants were partly compensated for by changes of opposite sign in the fractionation of C-3 plants due to the modification of the intercellular CO2 pressure within their leaves. With respect to present times, the combination of both processes reduced the C-13 discrimination (i.e., less negative fractionation) of the land biosphere by 0.03 to 0.32 parts per thousand during the mid-Holocene and by 0.30 to 1.86 parts per thousand at the last glacial maximum. (C) 1999 Elsevier Science B.V. All rights reserved.
Disciplines :
Earth sciences & physical geography
Author, co-author :
François, Louis  ;  Université de Liège - ULiège > Département d'astrophys., géophysique et océanographie (AGO) > Modélisation du climat et des cycles biogéochimiques
Godderis, Y.;  Université de Liège - ULiège > LPAP
Warnant, Pierre ;  Université de Liège - ULiège > Département d'astrophys., géophysique et océanographie (AGO) > Modélisation du climat et des cycles biogéochimiques
Ramstein, G.;  CNRS/CEA > Laboratoire des Sciences du Climat et de l’Environnement (LSCE)
de Noblet, N.;  CNRS/CEA > Laboratoire des Sciences du Climat et de l’Environnement (LSCE)
Lorenz, S.;  Universität Bremen Fachbereich > Geowissenschaften
Language :
English
Title :
Carbon stocks and isotopic budgets of the terrestrial biosphere at mid-Holocene and last glacial maximum times
Publication date :
1999
Journal title :
Chemical Geology
ISSN :
0009-2541
Publisher :
Elsevier Science, Amsterdam, Netherlands
Volume :
159
Issue :
1-4
Pages :
163-189
Peer reviewed :
Peer Reviewed verified by ORBi
Available on ORBi :
since 13 May 2010

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