Artigo
C-14 dating and stable carbon isotopes of soil organic matter in forest-savanna boundary areas in the southern Brazilian Amazon region
Registro en:
0033-8222
Creative Commons Attribution License
Autor
Pessenda, Luiz Carlos Ruiz
Gouveia, Susy Eli Marques
Aravena, Ramon
Gomes, B. M.
Boulet, René
Ribeiro, Adauto de Souza
Institución
Resumen
This study, which was carried out in the southern Brazilian Amazon region (Rond8nia state and Humaita,
Southern Amazon state), presents and discusses the significance of carbon isotope data measured in soil profiles collected
across natural boundaries of forest to savanna vegetation. The main objective of this study was to evaluate the expansionregression
dynamics of these vegetation units in relation to climate changes during the Holocene. 14C data from charcoal, soil
organic matter (SOM) and its component humin fraction indicate that the organic matter in the studied soils is essentially
Holocene in origin. 13C data indicate that C3 type plants were the dominant vegetation at all study areas in the early Holocene,
and during the entire Holocene, in the forest sites of Central Rond8nia state and in the forest site 50 km from the city of
Humaita.13C data also indicate that C4 plants have influenced significantly the vegetation at the transitional forest and the
Cerrado (wooded savanna) sites of Southern Rond8nia state and the forest ecosystem located 20 km from the Humaita city.
These typical C4 type isotopic signatures probably reflect a drier climate during the mid-Holocene. The 13C records representing
probably the last 3000 yr show an expansion of the forest, due to a climatic improvement, in areas previously occupied
by savanna vegetation. These results and other published data for the Amazon region indicate that the areas representing
today's forest-savanna boundaries have been determined by significant vegetation changes during the Holocene. The boundary
between forest and savanna vegetation seems to be quite sensitive to climatic change and should be the focus of more
extensive research to correlate climate and past vegetation dynamics in the Amazon region.