Soil CO2 efflux in agroforestry and full-sun coffee systems
Data
2014-10-29
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Universidade Federal de Viçosa
Resumo
A mudança climática global tem sido atribuída ao aumento da concentração de gases de efeito estufa na atmosfera, especialmente o dióxido de carbono (CO 2 ), como resultado das atividades humanas. Para atenuar esse efeito, existe um esforço global em reduzir as emissões de CO 2 e desenvolver tecnologias para remover parte desse gás da atmosfera. A maneira mais simples e natural para remover o CO 2 da atmosfera é realizada pelas plantas através da fotossíntese. Este processo remove o carbono da atmosfera formando biomassa vegetal, a qual mais tarde será depositada no solo, maior reservatório de carbono (2500 GtC) na biosfera terrestre. O balanço de carbono no solo é resultado da deposição de biomassa vegetal e perda de carbono, especialmente como CO 2 . Portanto, o solo, no ciclo global do carbono, pode atuar como fonte ou dreno de carbono da atmosfera. Para melhor compreensão do papel do solo no ciclo do carbono não é suficiente conhecer apenas a quantidade de carbono que determinadas espécies de plantas depositam no solo, mas também como esse carbono é liberado de volta para a atmosfera. O CO 2 é liberado (efluxo de CO 2 do solo) a partir de respiração do solo, a maior fonte de CO 2 da biosfera terrestre. O efluxo de CO 2 do solo é um processo complexo que depende das características biológicas e físicas do solo, especialmente das condições de temperatura e umidade do solo. No entanto, o tipo de vegetação e as práticas agrícolas podem ser os principais componentes que controlam o efluxo de CO 2 do solo em agroecossistemas, porque influenciam as características biológicas e físicas do solo e regulam as condições de temperatura e umidade do solo. Nos sistemas agroflorestais as árvores aportam matéria orgânica no solo e o protegem contra a radiação solar direta, influenciando assim o efluxo de CO 2 do solo. O objetivo geral deste estudo foi compreender como a copa das árvores, em sistemas agroflorestais com café, afetam o efluxo de CO 2 do solo e quais os fatores controladores deste processo em comparação com café a pleno sol. Para isso avaliou-se o efluxo de CO 2 do solo (in situ), em sistemas agroflorestais com café e em sistemas com café a pleno sol em três propriedades de agricultores familiares na Zona da Mata de Minas Gerais, Brasil. O aumento nos níveis de cobertura da copa das árvores resultou no aumento da umidade do solo e na diminuição da temperatura do ar e do solo a 5 e 10 cm de profundidade. O efeito das árvores no microclima não afetou a média diária de efluxo de CO 2 do solo entre os sistemas agroflorestais e a pleno sol, mas contribuiu para que a dinâmica das emissões diárias fosse diferente entre os sistemas. No sistema agroflorestal o efluxo de CO 2 do solo foi mais estável durante o dia com menor variação entre o período de 08:00-10:00h e 12:00-14:00h e maior variação espacial do que no sistema a pleno sol. No sistema agroflorestal o efluxo de CO 2 foi explicado principalmente por variações na quantidade de nitrogênio total e carbono lábil e no sistema a pleno solo pela temperatura do solo, especialmente a 10 cm de profundidade. A análise de componetes principais mostrou que em geral o efluxo de CO 2 do solo correlacionou positivamente com a temperatura do solo a 5 e 10 cm de profundidade e negativamente com a umidade do solo. Em conclusão, as árvores em sistemas agroflorestais de café trouxeram maior estabilidade para o microclima e para o efluxo de CO 2 do solo comparado com sistemas a pleno sol.
The global climate change has been attributed to increasing greenhouse gas concentration, especially Carbon Dioxide (CO 2 ) in atmosphere as result of human activities. To mitigate this effect, there is a global effort to reduce CO 2 emissions and develop technologies to remove part of this gas from the atmosphere. The most simple and natural way to remove CO 2 from atmosphere is carried out by plants through photosynthesis. This process removes carbon from atmosphere creating vegetal biomass, which later will be deposited in soil, the biggest reservoir of carbon in the terrestrial biosphere (2500 GtC). The balance of carbon in the soil is the result of input of vegetal biomass and the output of carbon, especially as CO 2 . Therefore, the soil, in the Global Carbon Cycle, acts either as source or as a sink of carbon from the atmosphere. To better understand the role of soil in Carbon Cycle and to it become sink of CO 2 it is not enough to know the carbon that particular plant species can deposit in the soil, but also how this carbon is released back to atmosphere. The CO 2 is released from soil (also called soil CO 2 efflux) mainly from soil respiration, which is the biggest source of CO 2 from terrestrial biosphere. Soil CO 2 efflux is a complex process that depends on the soil biological and physical characteristics and especially on the soil temperature and moisture conditions. However, the vegetation type and the agricultural practices may be the main components to control the soil CO 2 efflux in agroecosystems, because they influence the soil biological and physical characteristics and control the soil temperature and moisture conditions. Agroforestry coffee management increases the amount of organic matter residue and the canopy’s trees protect the soil against the directly solar radiation, thus, affecting the soil CO 2 efflux. The general objective of this study it was to understand how the canopy’s trees in agroforestry and full-sun coffee systems affect the soil CO 2 efflux and which factors control it. To this end we evaluated the soil CO 2 efflux (in situ) in agroforestry and full-sun coffee systems in three different farms in Zona da Mata of Minas Gerais, Brazil. The increase in canopy cover levels from trees leads to increase soil moisture and decrease air and soil temperature at 5 and 10 cm depth. The effect of trees on microclimate did not affect the daily average of soil CO 2 efflux between agroforestry and full-sun coffee systems, but they showed different daily emission dynamics. In agroforestry system the soil CO 2 efflux was more stable during the day, presenting less variation from morning to midday and higher spatial variation than the full-sun system. In agroforestry system the variation of soil CO 2 efflux was explained mainly by total nitrogen and labile carbon and in full- sun system by soil temperature at 10 cm depth. The principal components analysis shows that in general the soil CO 2 efflux was positively correlated with soil temperature at 5 and 10 cm depths and negatively correlated with soil moisture. In conclusion, the trees in agroforestry coffee systems promoted stability to microclimate and soil CO 2 efflux compared to Full-Sun systems.
The global climate change has been attributed to increasing greenhouse gas concentration, especially Carbon Dioxide (CO 2 ) in atmosphere as result of human activities. To mitigate this effect, there is a global effort to reduce CO 2 emissions and develop technologies to remove part of this gas from the atmosphere. The most simple and natural way to remove CO 2 from atmosphere is carried out by plants through photosynthesis. This process removes carbon from atmosphere creating vegetal biomass, which later will be deposited in soil, the biggest reservoir of carbon in the terrestrial biosphere (2500 GtC). The balance of carbon in the soil is the result of input of vegetal biomass and the output of carbon, especially as CO 2 . Therefore, the soil, in the Global Carbon Cycle, acts either as source or as a sink of carbon from the atmosphere. To better understand the role of soil in Carbon Cycle and to it become sink of CO 2 it is not enough to know the carbon that particular plant species can deposit in the soil, but also how this carbon is released back to atmosphere. The CO 2 is released from soil (also called soil CO 2 efflux) mainly from soil respiration, which is the biggest source of CO 2 from terrestrial biosphere. Soil CO 2 efflux is a complex process that depends on the soil biological and physical characteristics and especially on the soil temperature and moisture conditions. However, the vegetation type and the agricultural practices may be the main components to control the soil CO 2 efflux in agroecosystems, because they influence the soil biological and physical characteristics and control the soil temperature and moisture conditions. Agroforestry coffee management increases the amount of organic matter residue and the canopy’s trees protect the soil against the directly solar radiation, thus, affecting the soil CO 2 efflux. The general objective of this study it was to understand how the canopy’s trees in agroforestry and full-sun coffee systems affect the soil CO 2 efflux and which factors control it. To this end we evaluated the soil CO 2 efflux (in situ) in agroforestry and full-sun coffee systems in three different farms in Zona da Mata of Minas Gerais, Brazil. The increase in canopy cover levels from trees leads to increase soil moisture and decrease air and soil temperature at 5 and 10 cm depth. The effect of trees on microclimate did not affect the daily average of soil CO 2 efflux between agroforestry and full-sun coffee systems, but they showed different daily emission dynamics. In agroforestry system the soil CO 2 efflux was more stable during the day, presenting less variation from morning to midday and higher spatial variation than the full-sun system. In agroforestry system the variation of soil CO 2 efflux was explained mainly by total nitrogen and labile carbon and in full- sun system by soil temperature at 10 cm depth. The principal components analysis shows that in general the soil CO 2 efflux was positively correlated with soil temperature at 5 and 10 cm depths and negatively correlated with soil moisture. In conclusion, the trees in agroforestry coffee systems promoted stability to microclimate and soil CO 2 efflux compared to Full-Sun systems.
Descrição
Dissertação de mestrado defendida na Universidade Federal de Viçosa.
Palavras-chave
Agrossilvicultura, Solo - Uso - Efeito de carbono, Solo - Respiração
Citação
GOMES, L. C. Soil CO2 efflux in agroforestry and full-sun coffee systems. 2014. 48 f. Dissertação (Mestrado em Solos e Nutrição de Plantas) - Universidade Federal de Viçosa, Viçosa-MG. 2014.