02655naa a2200409 a 450000100080000000500110000800800410001910000200006024501390008026000090021952015430022865000110177165000130178265000240179565000130181965000230183265000160185565000160187165300150188765300190190265300120192165300250193365300160195865300170197465300110199165300120200265300180201465300260203265300220205865300120208070000210209270000220211370000220213570000220215770000170217977300490219617870022017-04-04       1995    bl ---       0--  u    #d1 aVICTORIA, R. L.  aPast vegetation changes in the Brazilian Pantanal arboreal-grassy savanna ecotone by using carbon isotopes in the soil organic matter.  c1995  aMeasurements of the organic carbon inventory, its stable isotopic composition and radiocarbon content were used to deduce vegetation history from two soil profiles in arboreal and grassy savanna ecotones in Brazilian Pantanal. The Pantanal is a large floodplain area with grass-dominated lowlands subject to seasonal flooding, and arboreal savanna uplands which are only rarely flooded. Organic carbon inventories were lower in the grassy savanna site than in the upland arboreal savanna site, with carbon decreasing exponentially with depth from the surface in both profiles. Changes in 13C of soil organic matter (SOM) with depth differed markedly between the two sites. Differences in surface SOM 13C values reflect the change from C3 to C4 plants between the sites, as confirmed by measurements of 13C of vegetation and the soil surface along a transect between the upland closed-canopy forest and lowland grassy savanna. Changes of 13C in SOM with depth at both sites are larger than 3-4 per mil increases expected from fractionation associated with organic matter decomposition. We interpret these as recording past changes in the relative abundance of C3 and C4 plants at these sites. Mass balances with 14C and 13C suggest that past vegetational changes from C3 to C4 plants in the grassy savanna, and in the deeper part of the arboreal savanna, occurred between 4600 and 11400 BP, when major climatic changes were also observed in several places of the South American Continent. The change from C4 to C3, observed only in the ...  aBrazil  aPantanal  asoil organic matter  aIsótopo  aMatéria Orgânica  aSolo Úmido  aVegetação  aArea umida  aCarbono solido  aIsotope  aMudanca de vegetacao  aRadiocarbon  aRadiocarbono  aSavana  aSavanna  aStable carbon  aStable carbon isotope  aVegetation change  aWetland1 aFERNANDES, F. A.1 aMARTINELLI, L. A.1 aPICCOLO, M. de C.1 aCAMARGO, P. B. de1 aTRUMBORE, S.  tGlobal Change Biologygv.1, p.165-171, 1995.