Sequestro e discriminação isotópica de carbono em sistemas agrossilvipastoris

• Ano de defesa: 2010
• Autor(a) principal: Tonucci, Rafael Gonçalves
• Orientador(a): Garcia, Rasmo
• Banca de defesa: Ribeiro, Karina Guimarães , Bernardino, Fernando Salgado
• Tipo de documento: Tese
• Tipo de acesso: Acesso aberto
• Idioma: por
• Instituição de defesa: Universidade Federal de Viçosa
• Programa de Pós-Graduação: Doutorado em Zootecnia
• Departamento: Genética e Melhoramento de Animais Domésticos; Nutrição e Alimentação Animal; Pastagens e Forragicul
• País: BR
• Palavras-chave em Português: CO2; Pastagem; Agrofloresta
• Palavras-chave em Inglês: CO2; Pasture; Agroforestry
• Área do conhecimento CNPq: CNPQ::CIENCIAS AGRARIAS::ZOOTECNIA::PASTAGEM E FORRAGICULTURA
• Link de acesso: http://locus.ufv.br/handle/123456789/1751

The aim of this research was to evaluate the effect of different land-use systems in the soil organic carbon (SOC) dynamic. Samples were collected in six different systems at the Riacho farm, Vazante, MG, Brazil. Land-use systems chosen were: open pasture; native forest (Cerrado); old agroforestry; new agroforestry; old eucalyptus; and new eucalyptus. From each system, replicated soil samples were collected from four depths (0 10, 10 20, 20 50, and 50 100 cm); the samples were fractionated into 250 2000, 53 250, and <53 &#956;m size classes representing macroaggregates, microaggregates, and silt+clay, respectively, and their C contents and &#948;13C determined. Up to 1 m depth, the total SOC contents (Mg ha-1) in the systems were in the order: Old Silvopasture (148) &#8805; New Eucalyptus (143) &#8805; Forest (137) = New Silvopasture (130) &#8805; Old Eucalyptus(121) &#8805; Pasture (116). Pasture had the highest SOC content in the silt+clay and microaggregate fractions that represent more stable forms of C. The aggregate hierarchy and C content in different soil-size fractions suggest the likely impact of the (unknown) previous land-use on total C stock in these young systems, as well as the higher C sequestration potential of pasture and silvopastoral systems in the Cerrado. Results from &#948;13C showed that pasture and agroforestry systems had higher values of &#948;13C in whole soil and in the aggregate fractions. Soil organic carbon was mainly derivate from C4 plants in all land-use systems at all depths. At open pasture old agroforestry and new agroforestry systems C4 carbon in the microaggregate fraction at the layer of 0 10 cm corresponded to 92; 40; and 35%, respectively. At the silt+clay fraction at the layer of 50 100 cm C4 contribution to total SOC was 80; 80; and 65% in the open pasture; old agrofores tryand new agroforestry, respectively. The &#948;13C values showed a trend to increase with depth increasing suggesting that in the past (mid holocen) the vegetation placed there was basically composed by plants this C4 pathway xiii xiv and not with C3 plants as it is seen now a day. Furthers studies are need to confirm and better understand this trend. The overall conclusion of this research was that agroforestry systems placed in the Cerrado Biome has the potential to mitigate C and might be recommended as a C sinker tool to farmers.