A forma de ocupação e as práticas de manejo de um solo provocam alterações, físicas, químicas e biológicas que afetam a sustentabilidade ambiental e econômica da atividade agrícola. Assim sendo, objetivou-se avaliar a dinâmica da decomposição foliar e a atividade microbiana em três sistemas de uso e manejo do solo na Microrregião do Brejo, Paraíba, Brasil. As áreas estudadas foram: Sistema Agroflorestal, mandala agrícola e floresta nativa. A taxa de decomposição foi estimada com o uso de sacolas de nylon, contendo 10 g de folhas de Gliricidia sepium, que foram dispostas na superfície do solo de cada área por um período de 56 dias. O material foliar foi coletado a cada sete dias e levado a estufa a 65°C e pesado para avaliar a perda de peso em relação ao peso inicial. A atividade microbiana foi estimada pela quantificação do dióxido de carbono (CO2) desprendido no processo de respiração edáfica, a partir da superfície do solo, e capturado por solução de KOH. O material foliar disposto na superfície do solo do Sistema Agroflorestal apresentou maior velocidade de decomposição, em relação aos demais sistemas. O sistema que emitiu maior quantidade de CO2 para a atmosfera foi a horta mandala. Os fatores climáticos, como precipitação e temperatura, influenciam na dinâmica de decomposição e na emissão de CO2 liberado pelos microrganismos edáficos.
In Brazil, soil use and occupation is largely responsible for greenhouse gas emissions, and one of the ways to monitor disturbances to ecosystems is through edaphic breathing, result of root breathing and the activity of microorganisms present in the soil. Given the above, the objective was to evaluate the microbial activity of the soil through edaphic respiration in four soil use systems. The research was carried out in four soil use systems: forest remnant area (F); agroforestry system (AFS); mandala (M) and pasture (P), belonging to the Universidade Federal da Paraíba (UFPB), Campus III, located in the municipality of Bananeiras - PB. Three samples composed of soil were collected at a depth of 0-20 cm, in each system of use, for chemical and physical analysis in order to characterize the study areas. To quantify carbon dioxide, the methodology described by Grisi was used and the CO2 captures occurred at night and during the day, for 8 months. A completely randomized design was used in a 4 x 2 factorial scheme. The lower temperatures during the night favored a higher CO2 emission; the pasture system and the AFS showed higher CO2 release in the two evaluation shifts, the forest remnant area showed less release of carbon dioxide. The microbial activity of the soil is more efficient at night; and the pasture area has higher CO2 emissions due to the lack of vegetation cover.
The changes that occur in the Caatinga vegetation cover alter the incidence of solar radiation at the surface-atmosphere interface. To monitor CO2 flows, through geotechnologies, they appear as an alternative or remote sensing. Thus, the objective of this work was to determine the carbon sequestration and the surface temperature in caatinga areas in the face of seasonal variations using data from the Landsat 8 satellite OLI and TIRS sensors. The study was carried out with a scene referring to the dry season and another referring to the rainy season, in two areas, one with preserved Caatinga vegetation and the other with agricultural intervention, both in the municipality of São José de Piranhas, Paraíba. The pre-processing of the images took place from the transformation of digital numbers for spectral radiance and then for reflectance, since the processing occurred from the application of the vegetation and temperature indices, resulting in CO2flux and surface temperature. The Caatinga was greatly influenced by rainfall, directly affecting the phenology of this vegetation. The variation in temperature and CO2flux were influenced by seasonality, in the dry season there was less sequestration and higher temperatures, while in the rainy season there was greater sequestration and lower temperatures. The multiple comparison test showed that all the variables studied showed statistical differences. Temperature and CO2flux are influenced by seasonality. Multispectral remote sensing is a tool that can assist in the study of temperature dynamics and carbon sequestration in the Caatinga biome.
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