Abstract
The dynamics of land use and land cover in watersheds of the Brazilian semi-arid region is not only influenced by human action, but also by the climatic seasonality of the region. Knowledge of the relationship between surveys of land use and land cover using geotechnology and the climatic seasonality of semi-arid regions is necessary. The aim of this study was to map and classify land use and cover in the watershed of the Orós reservoir (WSOR) with the help of geotechnology, and to identify the influence exerted by the climate on variations in the area of each class. The survey of land use and cover was carried out by means of the MAXVER method of classification of images from 2003, 2005, 2008 and 2013 from the LANDSAT 5 and LANDSAT 8 satellites. The areas of each class displayed dynamics influenced not only by human action but also by such factors as climate, topography and plant physiology. Years with high rainfall favoured classes such as thin scrub and dense scrub, with the opposite being seen in years considered as dry, when there was a considerable increase in areas of the anthropogenic class. Changes in the areas are caused by alterations in the deciduous vegetation; with leaf-fall during the dry season, these areas come to have the spectral response of areas with similar characteristics to the anthropogenic class. More-elevated regions favoured the presence of the dense-scrub class due to the microclimate and to the greater difficulty such areas present to human action.
Highlights
The conditions of forest cover are under constant change that may be subtle or abrupt, the result of both natural and anthropogenic forces (Hayes & Cohen, 2007)
Climate is seen as the conditioning element of environmental dynamics, since it exerts a direct influence on both physical and biological processes (Silva et al, 2010)
With regard to changes in ecosystems, it should be noted that the association between population growth and the development model adopted in the semi-arid region of Brazil has resulted in an increase in the pressure on natural resources due to changes in land use and cover in the region
Summary
The conditions of forest cover are under constant change that may be subtle or abrupt, the result of both natural and anthropogenic forces (Hayes & Cohen, 2007). The seasonality of regions with a tropical semi-arid climate and two well-defined seasons, one dry and one rainy, results in major changes in the landscape of dry forests Such changes are due to the poor distribution of rainfall during the year, where different rainfall indices are seen for the two main seasons, dry and rainy, resulting in a rapid response to environmental change (Batista & Santos, 2013). In this way, climate is seen as the conditioning element of environmental dynamics, since it exerts a direct influence on both physical and biological processes (Silva et al, 2010). Studies have demonstrated the negative impact that the degradation occurring over the years in the semi-arid region causes to the Caatinga Biome (Coelho et al, 2014; Pereira Filho, Silva, & CÉzar, 2013; Silva, Lima, & Mendonça, 2014; Vieira et al, 2013)
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