Impacto da mudança do uso da terra e adubação nitrogenada no balanço de metano

Abstract

Pristine ecosystems exert important functions to provide the environmental equilibrium. These functions are defined as ecosystems services. Such services include the climatic regulation, which covers nutrient and greenhouse gases cycling. The CH4, second most relevant gas to the global warming, is biologically oxidized by very specialized microrganisms. Well-drained soils are the main sink of the CH4 biologically oxidized. Due to evolutionary reasons, the microrganisms that occupy the niche of ammonium oxidation are also able to oxidize CH4, and vice and versa. However, there is only energetic benefit and C assimilation when each group exerts their specific function. There is a link between biodiversity loss and loss of CH4 consumption. Thus, our hypothesis is that N fertilization results in inhibition of the soil capacity in oxidizing CH4. To test this hypothesis, the aims of this research are: compare the capacity of different soils (pristine and cultivated pairs) in consuming CH4; assess the effect of nitrogen fertilization in the capacity of the soil in consuming CH4; and identify the edaphic parameters related with the resistance of soils regarding theirs ability to consume CH4 after they receive N. Microcosms were set with soils of the Pampas, Cerrado, Caatinga and Atlantic Forest. The results indicate that soils with native vegetation don't lose the ability to consume CH4 after addition of N- (NH4) 2SO4. Soils with native vegetation can consume up to 27.22 μg.kg. soil-1.day-1, while all soils with use history didn't consume the gas, regardless the biome they come from. We conclude that the interruption of CH4 sink is related to the change in land use and not exclusively to the use of nitrogen fertilizer.