Wetland soils, especially those under a semi-arid climate, are among the least studied soils in the tropics. The hypersaline tidal flats on the north-eastern Brazilian coast, locally named apicum, are coastal wetland ecosystems in the peripheral portions of semi-arid estuaries. Despite their great ecological importance, they have been highly impacted by anthropogenic activities. Morphological and analytical data of six soil profiles, representative of the different coastal compartments (mangroves, apicum and coastal tablelands) of the north-eastern Brazilian coast, were examined to better understand the pedogenesis of apicum soils. The hypersaline tidal flat soils were classified as Typic Fluvaquents and Typic Sulfaquents with the following main characteristics: predominance of sand fraction (62–77%); presence of high-activity clays (>24 cmolc kg–1 clay); clay fraction comprising kaolinite, illite, smectite and an interstratified smectite/illite; exchangeable complex dominated by Na+ (ESP ≥15%); elevated levels of salinity (electrical conductivity, EC 25–44 dS m–1); alkaline pH values (7.5–9.5). The sandy texture and quartz-dominated composition of the hypersaline, tidal flat soils indicate a pedogenesis associated with the superficial addition of mineral material. This upbuilding process would have lowered the watertable (relatively to the ground level) and decreased the flooding frequency by the tides, favouring salinisation and solonisation processes at the hypersaline tidal flats. Furthermore, the still-existing hydromorphism would have promoted the maintenance of gleisation and sulfidisation. The presence of pyrite on the hyper-saline tidal flat soils further corroborates the formation of apicum soils from/over buried mangroves.

No abstract

This work aimed to test the suitability of pyrite (FeS 2 ) as a proxy for reconstructing past marine environmental conditions along the semiarid coast of Brazil. Morphological description combined with physicochemical analyses including Fe partitioning were conducted for soil depth profiles (30 and 60 cm depths) at three sites in two contrasting lagoons of the state of Ceará: a suspected former lagoon that would have been transformed into a freshwater Blake^at a site vegetated by Juncus effusus (site P1), and another lagoon with connection to the sea at sites vegetated by J. effusus (site P2) or Portulaca oleracea (site P3). Soil samples were collected in September 2010. Site P3 had more reducing conditions, reaching Eh values of -132 mV in the surface layer (0-10 cm), whereas minimum values for the P1 and P2 sites were +219 and +85 mV, respectively. Lower pyritic Fe values were found at site P1, with a degree of pyritization (DOP) ranging from 10 to 13%. At sites P2 and P3, DOP ranged from 9 to 67% and from 55 to 72%, respectively. These results are consistent with an interruption of tidal channels by eolian dune migration inducing strong changes in the hydrodynamics and physicochemical characteristics (lower salinity, oxidizing conditions) of these sites, causing the dieback of suspected former mangroves and a succession to freshwater marshes with an intermediate salt marsh stage. Together with other physicochemical signatures, pyrite can evidently serve as a useful proxy in tracking environmental changes in such ecotones, with implications for coastal management.

O Brasil abrange diversos ecossistemas, dentre eles, os manguezais, um complexo natural dotado de feições inter-dependentes e interligadas, dentre elas, a vegetação de mangue, os apicuns e os salgados. Todavia, a atual legislação ambiental brasileira no âmbito federal parece não entender e/ou considerar relevante tais características, tendo em vista a Lei Federal nº 12.651-2012 (Código Florestal) apresenta o manguezal como uma feição separada dos salgados e apicuns, caracterizando a vegetação de mangue como Área de Preservação Permanente e as demais feições, inclusive, como sendo passíveis de um “uso ecologicamente sustentável”. O trabalho apresenta conceitos científicos e fundamentação jurídica para que o manguezal seja tratado enquanto ecossistema e que seja protegido legalmente no âmbito federal sob essa premissa fundamental, sob os riscos de que mesmo a pretensa proteção setorial esteja comprometida pelas formas históricas e atuais de uso e ocupação desse ecossistema no país.

O Brasil abrange diversos ecossistemas, dentre eles, os manguezais, um complexo natural dotado de feições inter-dependentes e interligadas, dentre elas, a vegetação de mangue, os apicuns e os salgados. Todavia, a atual legislação ambiental brasileira no âmbito federal parece não entender e/ou considerar relevante tais características, tendo em vista a Lei Federal nº 12.651-2012 (Código Florestal) apresenta o manguezal como uma feição separada dos salgados e apicuns, caracterizando a vegetação de mangue como Área de Preservação Permanente e as demais feições, inclusive, como sendo passíveis de um “uso ecologicamente sustentável”. O trabalho apresenta conceitos científicos e fundamentação jurídica para que o manguezal seja tratado enquanto ecossistema e que seja protegido legalmente no âmbito federal sob essa premissa fundamental, sob os riscos de que mesmo a pretensa proteção setorial esteja comprometida pelas formas históricas e atuais de uso e ocupação desse ecossistema no país.