Abstract
This study aimed to analyze fragments of rangelands through spectral responses and land cover change by livestock in regions of the Caatinga biome through remote sensing. For spectral behavior, the surface reflectance bidirectional (SRB) and spectral indexes of vegetation were used to verify the ragelands seasonality. Land cover change detection of Ouricuri and Tauá through Landsat-8 images with a 16-day revisit interval, were processed in the Google Earth Engine platform (GEE) and software Quantum GIS version 2.18 (QGIS). In the GEE platform, annual mosaics and stacking of the spectral bands were generated for the classification of images, and in sequence the production of thematic maps in QGIS. The analysis of land cover change considered the classes: thinned Caatinga, conserved Caatinga, herbaceous vegetation, bare soil, water and others. The analysis of the spectral responses showed that the vegetation monitored in Ouricuri presented higher SRB in the infrared band and lower SRB in the red and blue bands, and that caused the pasture to produce higher vegetation indexes than the other locations. Through validation, it was observed that in Tauá, there was an overall accuracy of 91% and Kappa index of 89%, and in Ouricuri there was an overall accuracy of 90% and Kappa index of 86%, indicating excellent correctness of the classification model. The classification model proved to be effective in verifying the temporal and spatial land cover change, making it possible to identify places with the vegetation that was most affected and susceptible to degradation and generation of political support to minimize damage to the Caatinga Biome.
Highlights
The Brazilian semiarid region is mostly located in a depression, with the predominance of stable air masses, and it has a unique environment in which rainfall is difficult to o ccur[1]
The rangelands located in Tauá had similar behavior regarding the surface reflectance bidirectional (SRB) of the band ρb[4], it was observed that Caatinga TD144 presented higher SRB values when compared to Caatinga TD280
Considering the rangelands monitored in Tauá (TD280 and TD144), the NDVI, EVI, mSAVI2, and LAI indexes were able to distinguish the rangeland during the rainy season, and the rangeland with the lowest woody density (TD144) presented the highest indexes, SAVI and NDWI were not able to differentiate the two rangelands
Summary
The Brazilian semiarid region is mostly located in a depression, with the predominance of stable air masses, and it has a unique environment in which rainfall is difficult to o ccur[1]. In this Brazilian region, the predominant vegetation is the Caatinga, presenting a great floristic diversity as the result of some managements of the v egetation[2], which is composed of plants adapted to the dry climate. Remote sensing tools have significant potential to monitor vegetation dynamics, and it allows the verification of events such as the beginning or peak of vegetation growth. The choice of the most adequate vegetation index to represent the vegetation requires basic studies, which relate the variability of the structural conditions of the vegetation with the bidirectional reflectance factors of the surface of the different channels or spectral bands
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