Elsevier

Applied Geography

Volume 127, February 2021, 102379
Applied Geography

Terrain units, land use and land cover, and gross primary productivity of the largest fluvial basin in the Brazilian Amazonia/Cerrado ecotone: The Araguaia River basin

https://doi.org/10.1016/j.apgeog.2020.102379Get rights and content

Highlights

  • Topography is a key structural component to understand the spatial and temporal distribution of land use and land cover.

  • Plains are the largest legally protected areas while plateaus are most vulnerable to land cover changes.

  • The geomorphologic and climatic gradients are determinant factors controlling the primary productivity of the vegetation.

Abstract

Integrity of most of tropical wetlands is threatened because they are often considered freely available resources of land and water. The Bananal, in the Araguaia River Basin, and the Pantanal in the Paraguai River Basin, are the two largest Brazilian wetlands influenced by the tropical seasonal floods. The purpose of this study is to integrate landscape structural and functional factors with the GPP dynamics over different terrain units present in the Araguaia River Basin. The study was conducted through the integration of different databases, including the topographic domains, protected areas and indigenous lands; land use and land cover map (year 2016); time series of GPP derived from the Moderate Resolution Imaging Spectroradiometer (MODIS) sensor (period of 2000–2015); Shuttle Radar Topography Mission (SRTM) digital elevation models (DEM); and precipitation data produced by the WorldClim version 2 dataset. GPP time series were processed using statistical methods of time series decomposition. The results show that, in the alluvial domains, we find grasslands (mostly), alluvial forests with the highest levels of GPP, and the largest legally protected areas. Spatial distribution of pasturelands across the entire basin is broad while croplands are concentrated mainly in geologically old and high plateaus. The time series analysis revealed the presence of intra- and inter-annual vegetation patterns and a continuous increase of GPP over time. The results contribute to the understanding of the linkages between land use changes and global carbon cycles by considering land use as a response of how the landscape is organized. The results may provide subsidies for public policies for the carbon budget equilibrium, conservation of biodiversity, and rational use of natural resources.

Introduction

Wetlands play an important role in the regional hydrological cycle and carbon dynamics, providing several benefits for local population (Mitsch et al., 2010). The integrity of most of tropical wetlands from South America, Africa, and Asia has been heavily threatened for being considered freely available resources of land and water (Junk, 2002). The main factors responsible for their degradation are deforestation, food and energy production, burning activities, and industrial pollution (Naranjo, 1995).

Approximately 20% of the Brazilian territory is covered by wetlands (Junk et al., 2014). They are under heavy pressure from agroindustry. The current Forest Code (Federal Law no. 12.561/2012) is unfriendly in terms of wetland protection (Piedade et al., 2012). The Araguaia River Basin, located in the transition region between the Amazon and Cerrado biomes, is composed of a mosaic of grass, shrubs, and trees in different proportions (Aselmann & Crutzen, 1989; Valente, Latrubesse & Ferreira, 2013). The drainage network reveals different dissection degree of the relief as well as the landforms that were developed through geological ages under various endogenic and exogenic processes (both denudation and aggradation processes) (Valente, 2007). The Araguaia River Basin contains the most geodiverse floodplain of the Cerrado and is home to more fish species than any other basin in this biome (Valente, Latrubesse & Ferreira, 2013). Therefore, it's regional landscape characterization and land use and land cover (LULC) monitoring are crucial, but so far underdeveloped, even after the signature of the Ramsar Convention in 1993 by the federal government (Junk et al., 2014). Because of the large extension of this basin, any initiative of landscape characterization and land use monitoring at a regional scale relies on remote sensing data.

Among several types of remotely sensed data available at different spatial, temporal, and spectral resolutions, we can point out (a) the Shuttle Radar Topography Mission (SRTM) data (Farr et al., 2007) that provides digital elevation models (DEM) at a spatial resolution of 30-m or 90-m regular grid; (b) the Landsat satellite (1984-present), with spatial resolution of 30 m and repeat cycle of 16 days (Roy et al., 2014) and (c) the Moderate Resolution Imaging Spectroradiometer (MODIS) sensor onboard Terra and Aqua platforms obtain spectral data from the Earth surface with the 250 m, 500 m, and 1 km spatial resolutions and temporal resolution of around one day (Justice et al., 2002). The National Aeronautics and Space Administration (NASA) provides different ready-to-use products derived from MODIS sensor, including vegetation indices, surface temperature and gross primary productivity (GPP) (Zhao, Heinsch, Nemani, & Running, 2005), among others. The aim of this study is to integrate landscape structural and functional factors with the GPP dynamics over different terrain units in the Araguaia River Basin.

Section snippets

Study area

The Araguaia River Basin is the largest basin in the seasonal tropics in Brazil and is located in the border of the states of Pará, Tocantins, Goiás, and Mato Grosso (Fig. 1). The elevation varies between 55 m and 1060 m. The dominant type of climate is Aw, according to the Köeppen's classification system (Alvares, Stape, Sentelhas, Gonçalves, & Sparovek, 2013), with dry winter (from April to September) and wet summer (from October to March), and with rainfall and temperature increasing from

Land use and land cover

The DLS, DCS, PS, and AS domains occupy 12%, 30%, 28%, and 29% of the total area of the Araguaia River Basin, respectively. The spatial distribution of LULC classes is strongly correlated with the terrain units, as has been shown in other studies in the same region (Latrubesse et al., 2019; Latrubesse & Stevaux, 2002; Valente, Latrubesse & Ferreira, 2013). In the AS domain, the original Cerrado vegetation prevails and is composed of pioneer vegetation, with distribution pattern controlled by

Final remarks

The time series decomposition showed to be a practical method of visualizing the long-term increase or decrease of GPP as well as the short-term variations of GPP, related to the seasonality in the Araguaia River Basin. The use of RGB color composites also showed to be a useful tool for understanding the spatial and temporal patterns of LULC.

Regarding dominant LULC types in the Araguaia River Basin, we found pasturelands in the entire basin, covering 40% of the total area. Croplands were mostly

CRediT authorship contribution statement

Pedro R. Martins: Conceptualization, Methodology, Software, Validation, Formal analysis, Investigation, Resources, Data curation, Writing - original draft, Writing - review & editing, Visualization, Supervision. Edson E. Sano: Formal analysis, Investigation, Writing - review & editing. Eder S. Martins: Formal analysis, Investigation, Writing - review & editing. Ludgero C.G. Vieira: Formal analysis, Investigation, Writing - review & editing. Luiz F. Salemi: Formal analysis, Investigation,

Acknowledgements

We acknowledge the Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) for a scholarship received by PRM. EES and LCGV were supported by the Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) productivity fellowships. We also acknowledge the two anonymous reviewers that have greatly contributed with highly relevant comments.

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