Estudo do comportamento dos fluxos de calor e massa no bioma caatinga na região semiárida da Paraíba.

Abstract

Arid and semi-arid environments correspond to 1/3 of the terrestrial surface, in these localities water is an important and limiting element for vegetation growth and ecosystem biomass productivity. The semiarid region in Brazil comprises around 11.5% of the national territory, where 76% of this was originally composed by the Caatinga biome, with water deficit as a striking feature, average rainfall less than 800 mm and high temperatures of annual averages ranging between 25oC and 30oC. Research on the dynamics of mass and energy fluxes in these environments have not received much attention, although they are especially vulnerable to environmental change. And, techniques such as eddy covariance (EC) have contributed to estimating the magnitude and patterns of turbulent exchanges between the ecosystem and the atmosphere. In this micrometeorological study, for an area of dense Caatinga (DC) and another of sparse Caatinga (SC) belonging to the National Institute of the Semiarid (INSA) in Campina Grande - PB, during the 2013 and 2014 years, it was observed that the albedo (α) and the net radiation (Rn) were more intense in the SC compared to DC, since the magnitude of incident short wave radiation was higher in this area. It was found that most of the net radiation it converted to sensible heat flux (H), mainly during the dry period in the SC, followed by the latent heat flux (LE) and much smaller partition in soil heat flux (G), usually about 50% for H and 20% for LE. Through the energy balance closure, it was verified that the turbulent fluxes (H + LE) were underestimated in relation to the available energy to the surface (Rn-G), being that in the DC this discrepancy was greater and reaching more than 30%. The ecosystem at the two study sites acted as CO2 sinks, sequestering more than 700 gC/m2 and 550 gC/m2 for DC and SC, respectively.