Abstract

Mapping vegetation types through remote sensing images has proved to be effective, especially in large biomes, such as the Brazilian Cerrado, which plays an important role in the context of management and conservation at the agricultural frontier of the Amazon. We tested several combinations of optical and radar images to identify the four dominant vegetation types that are prevalent in the Cerrado area (i.e., cerrado denso, cerradão, gallery forest, and secondary forest). We extracted features from both sources of data such as intensity, grey level co-occurrence matrix, coherence, and polarimetric decompositions using Sentinel 2A, Sentinel 1A, ALOS-PALSAR 2 dual/full polarimetric, and TanDEM-X images during the dry and rainy season of 2017. In order to normalize the analysis of these features, we used principal component analysis and subsequently applied the Random Forest algorithm to evaluate the classification of vegetation types. During the dry season, the overall accuracy ranged from 48 to 83%, and during the dry and rainy seasons it ranged from 41 up to 82%. The classification using Sentinel 2A images during the dry season resulted in the highest overall accuracy and kappa values, followed by the classification that used images from all sensors during the dry and rainy season. Optical images during the dry season were sufficient to map the different types of vegetation in our study area.

Highlights

  • The Cerrado biome is considered as being among the most extensive and diverse ecosystems in the Neotropics and is a hotspot in the context of biodiversity [1]

  • In order to overcome the lack of studies using both sensors to discriminate vegetation types, the aim of this study is to evaluate the use of optical and radar remote sensing for mapping the different types of vegetation in the transitional area between the Cerrado and Amazon biomes

  • The two different combinations used for classifications, Sentinel 2A with ALOS-PALSAR 2 dual polarimetric and Sentinel 2A with ALOS-PALSAR 2 full polarimetric, showed similar high overall accuracy of 0.99 and 1, respectively

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Summary

Introduction

The Cerrado biome is considered as being among the most extensive and diverse ecosystems in the Neotropics and is a hotspot in the context of biodiversity [1]. The Cerrado biome is the second largest complex vegetation present in Brazil and occupies about 200 million hectares, of which the largest territory is in the state of Mato Grosso [3] This large distribution of the Cerrado biome in Brazil covers three main vegetation types: grassland, savannas, and forest formations, which results in indeterminate boundary and a gradient of biomass, height, and tree cover. The amount of biomass and carbon storage is differently distributed in the biome, depending on the vegetation type and soil [8,9,10] This large biodiversity and floristic heterogeneity in Cerrado was and is decreasing due to deforestation since the 1980s, which can lead to a loss or decrease in ecosystem services [11]

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