Validação de um modelo espectral para determinação de fluxos de CO2 em áreas do Bioma Caatinga

The development of models with high coverage and low cost are fundamental for monitoring the carbon dynamics in ecosystems. The present work analyzed, by remote sensing, the CO2 fluxes in the Caatinga Biome, verifying the potential of multispectral images in determining the CO2 dynamics in areas of preserved caatinga and in ecological succession. The Forest Carbon Sequestration Index (CO2flux) was applied for spectral modeling in 20 scenes of the OLI sensor (Landsat 8). To validate the results, the CO2flux measured in micrometeorological towers was used. According to the moment of passage of the Landsat 8 satellite, different temporal scales of the CO2flux data from the tower were used considering intervals of half, one and two hours. Normality analysis was performed using the Shapiro-Wilk test, data were subjected to Spearman correlation and then the best model was selected based on the root mean square error (RSME). The CO2flux spectral index proved to be compatible for evaluating the parameters of estimating CO2 fluxes in caatinga areas when compared with CO2 fluxes from the pixel corresponding to the location of the tower, with Spearman correlation coefficients ranging from ? = -0.8 a ? = -0.7. The proposed model presented a high correlation with the observed data (R2=0.8; RSME=1.6), showing an efficient adjustment in the evaluation of CO2 fluxes and great potential in the use of multispectral images for monitoring the CO2flux capturing the effects of seasonal changes in the dynamics of carbon fluxes.O desenvolvimento de modelos com alta cobertura e baixo custo são fundamentais para o monitoramento dos fluxos de dióxido de carbono (CO2) nos ecossistemas. O estudo objetivou validar um método para determinação de fluxos de CO2 utilizando dados multiespectrais em áreas de caatinga preservada e em sucessão ecológica. Aplicou-se o Índice de Sequestro Florestal de Carbono (CO2flux) para a modelagem espectral em 20 cenas do sensor OLI (Landsat-8). No processo de validação do modelo, dados de fluxos de CO2 medidos em superfície com o uso de torres micrometeorológicas foram utilizados. De acordo com o momento de passagem do satélite Landsat-8, foram utilizadas diferentes escalas temporais dos dados de fluxo de CO2 da torre considerando intervalos de meia hora, 1 (uma) e 2 (duas) horas. O teste Shapiro-Wilk foi utilizado para verificar normalidade dos dados, e como maioria das variáveis não apresentaram distribuição normal, os dados foram submetidos ao teste de correlação de Spearman, e em seguida foi recomendado o melhor modelo analisando o seu coeficiente de determinação (R2) e a raiz quadrada do erro médio (RSME). O índice espectral CO2flux mostrou-se compatível para avaliação dos parâmetros de estimativas dos fluxos de CO2 na caatinga quando comparados com fluxos de CO2 do pixel correspondente a localização da torre, com correlações apresentando valores variando de ? = -0,86 a ? = -0,72. O modelo proposto apresentou alta correlação com os dados observados obtendo R2 = 0,81 e RSME = 1,6, constatando um ajuste eficiente para a avaliação dos fluxos de CO2 e grande potencial no uso de imagens multiespectrais para o monitoramento do fluxo de CO2 capturando os efeitos das mudanças sazonais da dinâmica dos fluxos de carbono

MODELING OF NATURAL VULNERABILITY TO EROSION THROUGH THE GEOGRAPHIC INFORMATION SYSTEMS IN MORRO DO CHAPÉU-BA

The environment is always in permanent change keeping its proper dynamics with its own rhythms.However, when the people move themselves occupying specific locations, some transformations can take place, constituting threats for the environment and for the manhimself. These changes are related to the enviroment degradation, which has erosion as one of its most significant processes.To understand this dynamic, it is necessary to model the environment in a way that is possible to identify areas with different degrees of natural vulnerability to erosion and thus provide actions that relieve these impacts.The erosive processes are part of the lithosphere modeling system and have its intensity degree more stable or more intense according to the sum of several physical variables (lithology, leveling, landscape, rainfall and hydrography), biological variables (ecosystem- the type of the original and second growth vegetation) and anthropogenic variables (the type of human occupation and mining activities).The impact of the rain on the soil has its effects reduced because of the vegetation and so the pedogenesis is benefited and the erosive processes minimized. On the other hand, if there is no vegetation or if this is insuficient, morphogenesis becomes more intense and theerosive processes enhanced