Nitrogen dynamics in small watersheds in the Atlantic Forest and Cerrado in Northeastern Brazil | Dinâmica de nitrogênio em microbacias na Mata Atlântica e Cerrado no Nordeste brasileiro

English. The aim of this study was to determine concentrations of nitrogen (N) in two biomes, Atlantic Forest (AF) and Cerrado (CR), at the interface between terrestrial and aquatic ecosystems. This involved evaluating N in vegetation (litterfall), soil and water in small watersheds in environmental protection areas in northeastern Brazil. Soil chemical and physical analyzes were performed and mineralization and nitrification rates were determined. The forms of organic, inorganic and particulate nitrogen in water were determined by spectrophotometry. Two collections were carried out, one in the dry season (October and November 2019) and another in the rainy season (February and March 2020), in two environmental preservation areas, Estação Veracel Private Natural Heritage Reserve - (Atlantic Forest) and Chapada Diamantina National Park (Cerrado), with five small watersheds sampled in each biome. The N concentration in litterfall was similar in both biomes, with averages of 0.69%. In relation to soil and water, N concentrations were higher in AF compared to CR, with concentrations of 0.95 ± 0.40 and 0.59 ± 0.14 µg.Ng-1 of nitrate in the soils of AF and CR, respectively, and 3.53 ± 2.51 µM of nitrate in water in AF and 0.76 ± 0.78 µM in CR.

Spanish; Castilian. The Brazilian biomes influence the biogeochemical cycles since they present a diversity of phytophysiognomies associated with the specific chemical, physical and biological characteristics of each region. The aim of this study was to verify the influence of two biomes, Atlantic Forest (AF) and Cerrado/”Campo Rupestre” (CR), on nitrogen concentrations (N) at the interface between terrestrial-aquatic ecosystems through the evaluation of N in vegetation (litterfall), soil and streamwater areas of environmental protection in northeastern Brazil. Samples were collected during the dry and rainy periods in five streams in each biome located in preservation areas. The results showed that no significant differences were observed in the production and N concentration in litterfall between the biomes. In spite of the soil and water, the N concentrations were higher in the sites located in the Atlantic Forest compared to the “Campo Rupestre”. The low moisture and low net mineralization and nitrification in “Campo Rupestre” result in lower concentrations of N in the soil. This lower concentration associated with edaphoclimatic conditions in CR was responsible for the reduction of N leaching in soil resulting in lower concentrations of N in water.

Portuguese. O objetivo deste estudo foi determinar as concentrações de nitrogênio (N) em dois biomas, Mata Atlântica (AF) e Cerrado (CR), na interface entre os ecossistemas terrestre-aquático, avaliando o N na vegetação (serapilheira), no solo e na água em microbacias em áreas de proteção ambiental no nordeste brasileiro. Foram realizadas análises químicas e físicas do solo e determinadas as taxas de mineralização e nitrificação. Na água, foram determinadas as formas de nitrogênio orgânico, inorgânico e particulado por espectrofotometria. Foram realizadas duas coletas, uma no período seco (outubro e novembro de 2019) e outra no chuvoso (fevereiro e março de 2020) em duas áreas de preservação ambiental, na Reserva Particular de Patrimônio Natural - Estação Veracel (Mata Atlântica) e Parque Nacional Chapada Diamantina (Cerrado), sendo amostrados cinco microbacias em cada bioma. A concentração de N na serapilheira foi semelhante entre os biomas, apresentando médias de 0,69%. Em relação ao solo e a água, as concentrações de N foram maiores na AF comparados a CR, com concentrações de 0,95 ± 0,40 e 0,59 ± 0,14 µg.Ng-1 de nitrato no solo de AF e CR, respectivamente e 3,53 ± 2,51 µM de nitrato na água em AF e 0,76 ± 0,78 µM em CR.