SIMÕES, E. M.; http://lattes.cnpq.br/7100426802449287; SIMÕES, Ewerton Medeiros.
Résumé:
In order to development the means of conservation and maintenance of water resources it is
necessary to understand the interactions between rainfall and the dynamics of vegetation in
space/time, which has been possible due to the use of NDVI. The sub-basin of the Espinharas
River undergoes great changes in its landscape, mainly caused by the expansion of anthropic
activities, therefore, it is expected to demonstrate the relationship between the NDVI and the
precipitation in the mentioned sub-basin. The aim of this paper was to verify the behavior of
the Normalized Difference Vegetation Index (NDVI) at the sub-basin of the Espinharas River
in the dry and rainy periods between 2005 and 2015, correlating it with accumulated
precipitation in each period. A dot mesh representing the geographical location of 12 data
collection platforms (DCP) was generated. From each DCP, a 5 km radius was determined, in
which 30 sampling points were randomly selected for acquisition of NDVI rates in areas of
natural vegetation. Considering the variation of the NDVI in the study area during the
analyzed period, it is possible to observe significant changes in the concentration of caatinga
vegetation from the rainy period to the dry period. The year 2005 presented the highest values
of NDVI in relation to 2015, with the highest amounts of 0.71 and 0.78 in the dry and wet
periods, respectively. In 2015, the maximum values were 0.64 and 0.61 for the dry and humid
periods, respectively. The highest values were observed in the rainy season of 2005, in the
meteorological stations of Maturéia, Salgadinho and Areia de Baraúnas. These areas are
marked by the presence of dense native vegetation found in the highest areas of the land area,
such as hillsides. Regarding the dry period, low variations in the NDVI rates were observed,
with the highest readings observed in the platforms of Maturéia, Salgadinho and Teixeira, in
the years studied. The platforms that presented the greatest reductions in NDVI values from
one year to another in the rainy season were Maturéia, Santa Teresinha and Salgadinho, with
reductions of 41.9%, 38.2% and 32.7% respectively. The most significant correlations for the
analyzed variables were established for the dry periods, with Pearson correlation coefficients
of 0.71 in 2005 and 0.48 for 2015. Such findings indicate a progressive connection between
the variables with the decrease of rainfall totals. The lowest correlations were observed in the
rainy season, with rates of 0.09 in 2005 and 0.19 in 2015. The increase in rainfall levels in the
region did not imply a progressive increase in NDVI values. It is suggested that, for new
studies in the region, a longer period of observation over the years should be explored in order
to minimize the effect of extreme situations. In addition to the accumulated rainfall, other
factors could be related, such as the steepness of the land area, temperature and soil type,
which are important factors to be considered, suggesting a combined analysis among them.
