Resumo Trabalho

RELATIVE INFLUENCE OF NDVI IN THE ORGANIC MATTER CONTENT OF SEMIARID SOILS

Autor(es): DAVID BRUNO DE SOUSA TEIXEIRA e orientado por CARLOS ALEXANDRE GOMES COSTA

Soil organic matter (SOM) is an important indicator of soil quality, being directly influenced by the carbon deposition of the present vegetation. The objective of this study was to evaluate the influence of vegetation density on soil organic matter contents. For this, deformed soil samples were collected in the 0-10 cm layer for each of the three Soil and Vegetation Association (SVA) areas, SVA1, SVA2 e SVA3, in the Aiuaba Experimental Basin (12km²), Ceará, Brazil, and the organic matter content (OMC) was determined from laboratory analysis. The vegetation density was estimated from orbital images obtained by TM-LandSat 8 satellite, from which the Normalized Difference Vegetation Index (NDVI) was calculated using the reflectance values of the bands 4 (red) and 5 (near infrared). The SOM contents were correlated with the NDVI values obtained for each of the pixels in the used image where the samples were collected and the coefficients of determination were obtained. The soil analysis showed higher values and a greater amplitude of the soil organic content in the Hypochromic Luvisol area (SVA2). Results showed a good correlation between a greater presence of vegetation and the presence of organic material in the initial soil layer, presenting a positive correlation when observed SVA1 and SVA2 areas. Despite these good correlation, aspects related to the physiology of the vegetation as well as the inherent features of the present soils should be considered. In conclusion, vegetation indexes obtained by orbital images, such as NDVI, by itself, do not make possible a reliable estimation of the OMC, but can be a good indicator of the levels of organic matter in semi-arid soils when associated to analysis of the vegetation behavior.

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