Variabilidade temporal do CO2 atmosférico e fatores de controle sobre grandes áreas de pastagens manejadas e degradadas no Cerrado Brasileiro.
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2022-06-29
Autores
Campos, Marcelo Odorizzi de
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Universidade Estadual Paulista (Unesp)
Resumo
As mudanças antrópicas no uso da terra têm contribuído para o aumento da concentração dos gases de efeito estufa (GEEs) na atmosfera. Mudar esse cenário requer ações capazes de minimizar emissões e retirar carbono da atmosfera. O estoque de matéria orgânica do solo pode ser usado como sumidouro de carbono, além de reduzir as emissões melhora também aspectos físicos, químicos e biológicos do solo. Sequestrar carbono no solo representa 25% do potencial natural do planeta em solucionar as questões climáticas, dos quais, 60% referem-se à recuperação dos estoques anteriormente perdidos, e 40% pela proteção do carbono já armazenado. Partindo da hipótese de que, sistemas de pastagens degradadas (DP) e manejadas (MP) demonstram índices vegetativos e níveis carbono estocado no solo contrastantes, este estudo objetivou compreender a dinâmica temporal da concentração de CO2 atmosféricos e outros fatores de controle sobre DP e MP no bioma do Cerrado brasileiro. Utilizando ferramentas de sensoriamento remoto e série histórica de 6 anos, foi caracterizado sob as áreas concentrações atmosféricas de CO2 (xCO2), estoque de carbono no solo (SCS (t/ha – médio 0 a 0.30 m), características vegetativas (SIF – fluorescência da clorofila induzida pelo sol, NDVI – índice de vegetação por diferença normalizada e LAI – índice de área foliar) e aspectos climáticos (LST Amplitude – temperatura da superfície terrestre amplitude e precipitação). A correlação de Pearson demonstrou que variáveis vegetativas e precipitação se relacionam negativamente, e LST Amplitude e SCS se relacionam positivamente com o xCO2. Foi observado também que LST Amplitude se destacou como potencial nova variável de impacto direto nas missões de CO2 do solo, bem como, ferramenta auxiliar para distinção de pastagens degradadas e manejadas. Exceto para o xCO2, os testes de hipótese (Teste t de Student p<0.05) demonstraram que os MP foram significativamente diferentes dos DP. Assim, MP demonstrou receber maiores índices vegetativos e volumes de precipitação, entretanto, menores valores de LST Amplitude. As análises de regressão linear (p<0.001) exibiram que os valores de SCS impactaram a concentração atmosférica de CO2 apenas sobre DP. Este resultado destaca a importância do manejo das pastagens como forma de proteger e estabilizar o carbono sobre esta atividade agricola. Assim, foi possível concluir que DP com carbono estocado no solo são as principais fontes de CO2 para atmosfera, quando comparados aos MP. Portanto, pastagens degradadas com estoque carbono orgânico no solo irão gradativamente esvaziar seus compartimentos, se não manejados, devido a exposição do carbono a metabolização microbiológica e a incapacidade vegetativa das plantas em reabastecer os compartimentos do solo.
Anthropogenic changes in land use have contributed to an increase in the concentration of greenhouse gases (GHGs) in the atmosphere. Changing this scenario requires actions able to minimize emissions and remove carbon from the atmosphere. The stock of soil organic matter can be used as a carbon sink, in addition to reducing emissions, it also improves physical, chemical and biological aspects of the soil. Sequestering carbon in the soil represents 25% of the planet's natural potential to solve climate problems, whereas 60% refer to the recovery of previously lost stocks, and 40% to the protection of carbon already stored. Based on the hypothesis that degraded (DP) and managed (MP) pasture systems show contrasting vegetative indices and carbon levels stored in the soil, this study aimed to understand the temporal dynamics of atmospheric CO2 concentration and other control factors on DP and MP in the Brazilian Cerrado biome. Using remote sensing tools and a 6-year historical series, was characterized under the areas atmospheric concentrations of CO2 (xCO2), soil carbon stock (SCS t/ha – mean 0 a 0.30 m), vegetative characteristics (SIF – solar-induced chlorophyll fluorescence, NDVI – normalized difference vegetation index and LAI – leaf area index) and climatic aspects (LST Amplitude – land surface temperature amplitude and precipitation). Pearson's correlation showed that vegetative variables and precipitation are negatively related, and LST Amplitude and SCS are positively related to xCO2. It was also observed that LST Amplitude stood out as a potential new variable of direct impact on soil CO2 emissions, as well as an auxiliary tool for distinguishing degraded and managed pastures. Except for xCO2, the hypothesis tests (Student t-test p<0.05) demonstrated that the MP were significantly different from the DP. Thus, MP showed to receive higher vegetative indices and precipitation volumes, however, lower LST Amplitude values. Linear regression analyzes (p<0.001) showed that SCS values impacted atmospheric CO2 concentration only on DP. This result highlights the importance of pasture management as a way to protect and stabilize the carbon on this agricultural activity. Thus, it was possible to conclude that DP with carbon stored in the soil are the main sources of CO2 for the atmosphere, when compared to MP. Therefore, degraded pastures with organic carbon stock in the soil will gradually lose their compartments, if not managed, due to carbon exposure to microbiological metabolism and the vegetative inability of plants to replenish soil compartments.
Anthropogenic changes in land use have contributed to an increase in the concentration of greenhouse gases (GHGs) in the atmosphere. Changing this scenario requires actions able to minimize emissions and remove carbon from the atmosphere. The stock of soil organic matter can be used as a carbon sink, in addition to reducing emissions, it also improves physical, chemical and biological aspects of the soil. Sequestering carbon in the soil represents 25% of the planet's natural potential to solve climate problems, whereas 60% refer to the recovery of previously lost stocks, and 40% to the protection of carbon already stored. Based on the hypothesis that degraded (DP) and managed (MP) pasture systems show contrasting vegetative indices and carbon levels stored in the soil, this study aimed to understand the temporal dynamics of atmospheric CO2 concentration and other control factors on DP and MP in the Brazilian Cerrado biome. Using remote sensing tools and a 6-year historical series, was characterized under the areas atmospheric concentrations of CO2 (xCO2), soil carbon stock (SCS t/ha – mean 0 a 0.30 m), vegetative characteristics (SIF – solar-induced chlorophyll fluorescence, NDVI – normalized difference vegetation index and LAI – leaf area index) and climatic aspects (LST Amplitude – land surface temperature amplitude and precipitation). Pearson's correlation showed that vegetative variables and precipitation are negatively related, and LST Amplitude and SCS are positively related to xCO2. It was also observed that LST Amplitude stood out as a potential new variable of direct impact on soil CO2 emissions, as well as an auxiliary tool for distinguishing degraded and managed pastures. Except for xCO2, the hypothesis tests (Student t-test p<0.05) demonstrated that the MP were significantly different from the DP. Thus, MP showed to receive higher vegetative indices and precipitation volumes, however, lower LST Amplitude values. Linear regression analyzes (p<0.001) showed that SCS values impacted atmospheric CO2 concentration only on DP. This result highlights the importance of pasture management as a way to protect and stabilize the carbon on this agricultural activity. Thus, it was possible to conclude that DP with carbon stored in the soil are the main sources of CO2 for the atmosphere, when compared to MP. Therefore, degraded pastures with organic carbon stock in the soil will gradually lose their compartments, if not managed, due to carbon exposure to microbiological metabolism and the vegetative inability of plants to replenish soil compartments.
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Palavras-chave
Mudanças Climáticas, Sensoriamento remoto, Climate changes, Remote sensing, Sistema de pastagem, Serviços ecossistêmicos, Dioxido de carbono atmosferico, Carbon