The southern Brazilian grassland biome: soil carbon stocks, fluxes of greenhouse gases and some options for mitigation

Abstract

The southern Brazilian grassland biome contains highly diverse natural ecosystems that have been used for centuries for grazing livestock and that also provide other important environmental services. Here we outline the main factors controlling ecosystem processes, review and discuss the available data on soil carbon stocks and greenhouse gases emissions from soils, and suggest opportunities for mitigation of climatic change. The research on carbon and greenhouse gases emissions in these ecosystems is recent and the results are still fragmented. The available data indicate that the southern Brazilian natural grassland ecosystems under adequate management contain important stocks of organic carbon in the soil, and therefore their conservation is relevant for the mitigation of climate change. Furthermore, these ecosystems show a great and rapid loss of soil organic carbon when converted to crops based on conventional tillage practices. However, in the already converted areas there is potential to mitigate greenhouse gas emissions by using cropping systems based on no soil tillage and cover-crops, and the effect is mainly related to the potential of these crop systems to accumulate soil organic carbon in the soil at rates that surpass the increased soil nitrous oxide emissions. Further modelling with these results associated with geographic information systems could generate regional estimates of carbon balance.Keywords: pampa biome, management, soil organic matter, global warming, climate change.Campos do sul do Brasil: estoques de carbono no solo, fluxos de gases de efeito estufa e algumas opções para mitigação ResumoOs campos do sul do Brasil são ecossistemas naturais com alta diversidade e têm sido há séculos importantes para a atividade pastoril e para outros importantes serviços ambientais. Este trabalho aponta os principais fatores que controlam os processos ecossistêmicos, revisa e discute os dados disponíveis sobre os estoques de carbono no solo e as emissões de gases de efeito estufa dos solos, e sugere oportunidades de mitigação das mudanças climáticas. A pesquisa sobre as emissões de carbono e gases de efeito estufa nos campos do sul do Brasil é recente e os resultados são ainda fragmentados. Os dados disponíveis indicam que os ecossistemas campestres naturais manejados adequadamente contêm estoques importantes de carbono orgânico no solo e, portanto, sua conservação é relevante para a mitigação das mudanças climáticas. Além disso, esses ecossistemas apresentam uma grande e rápida perda de carbono orgânico do solo quando convertidos para lavouras com preparo convencional do solo. No entanto, nas áreas já convertidas, há potencial para mitigar as emissões de gases de efeito estufa por meio de sistemas de cultivo usando plantio direto e rotações de culturas baseadas em plantas de cobertura de solo. O efeito está relacionado principalmente ao potencial desses sistemas de cultivo para acumular matéria orgânica do solo em taxas que superam o aumento das emissões de óxido nitroso. O uso de modelos com...

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