Avaliação da produtividade primária bruta da caatinga do semiárido paraibano.

Abstract

The vegetation is one of the great responsible for the fixation of the atmospheric carbon dioxide (CO2), which is given by the process of photosynthesis. This excess gas in the atmosphere can cause an overheating of the same, consequently a climatic imbalance in the globe. One of the variables used to quantify the carbon that an ecosystem absorbs is Gross Primary Production (PPB), which can be estimated through remote sensing and / or through micrometeorological towers using the Eddy Covariance method. In this context, the objective of this study was to quantify and analyze the capture of CO2 absorbed by the caatinga vegetation to two microregions of the Paraiba semi-arid region, using remote sensing data from the MODIS/Terra sensor and a micrometeological tower installed in areas of conserved caatinga: Area 1 Agreste in the vicinity of Campina Grande, and Area 2 in Sumé, in Cariri, Paraíba, from 2013 to 2017. PPB was calculated by the Monteith method (1972), which uses as determinant variables the photosynthetically active radiation absorbed by the vegetation and the efficiency of light use. Then, the data were validated with those measured in the micrometeorological tower for Area 1, located in the National Institute of the Semi-Arid (INSA) and with the product MOD17A2H in Area 2. The results obtained showed a higher correlation between PPB and IVDN estimated in Area 1. It was also observed that the parameter that most influenced the PPB was precipitation, because in the period studied the caatinga had a higher emission than carbon capture, possibly caused by low precipitation and high temperatures. Although, with little condition to photosynthesize, the caatinga presented CO2 absorption, evidencing its importance for the control of greenhouse gases.