Dinâmica do nitrogênio e emissão de gases de efeito estufa em solo de manguezal no semiárido

Abstract

There are many factors that can alter the functioning of the mangrove ecosystem, however, among them, the effluent of shrimp farming, mangrove vegetation and the seasonal variation of rainfall may alter soil properties in governing the form and availability of nitrogen in the mangrove. Thus, it aimed to through three chapters evaluate the effects of these factors: 1) in the forms of nitrogen present in the soil and the fluxes of greenhouse gases (CO2 and CH4); 2) at nitrogen mineralization in mangrove soil through an experiment of wetting and drainage, similar the natural conditions of tidal changes; and 3) at distribution of fractions of organic nitrogen in the soil and the contribution of these fractions in the mineralization process. In the first chapter it was made a characterization work to determine the forms of nitrogen present in the soil and quantify the greenhouse gas fluxes (CO2 and CH4) in order to verify the mangrove forest's ability to perform their ecological functions, despite the anthropic pressure. It has been found that organic nitrogen represents 99% of the total nitrogen of soil, and the ammonium is the most abundant mineral form in mangrove soils. The CO2 flow was more constant at area that receiving the effluent from shrimp farming as a result of nutrient input coming from the effluent. The variation of the tide was the factor that more contributed to the entry of nutrients, affecting the mangrove's ability to perform their ecological functions. In the second chapter, with the results of the experiment of wetting and drainage, it was observed that the increased supply of nitrogen not reflected in a higher mineralization, on the other hand, the dry and wet seasons were the factors that most influenced the nitrogen mineralization. Nitrogen has been preserved in its organic form, indicating recalcitrance of mangrove soil. The third chapter focused determine and quantify the fractions of organic nitrogen, since most of the nitrogen in the soil is found in this fraction can be mineralized and become available. It was found that anaerobic conditions common to the mangrove, promote the degradation of recalcitrant fractions, and increased labile nitrogen fractions. It is also concluded that the dumping of effluent from shrimp farming, changes distribution the fractions of organic nitrogen in soil.