Distribution of aerophilous diatom communities associated with terrestrial green macroalgae in the South Shetland Islands, Maritime Antarctica.

The establishment of diatom communities depends on environmental factors such as the type of substrate and geographic conditions that influence the dispersal processes of these organisms. The main goal of this study was to evaluate the similarity between diatom communities associated with the macroalgae Prasiola crispa (Lightfoot) Kützing in relation to spatial distance from six sampled sites located in the South Shetland Islands, Maritime Antarctica. The diatom flora associated with Prasiola crispa was represented by 23 species distributed in 15 genera. Pinnularia australoschoenfelderi Zidarova, Kopalová & Van de Vijver, Luticola austroatlantica Van de Vijver, Kopalová, S.A.Spaulding & Esposito, Luticola amoena Van der Vijver, Kopalová, Zidarova & Levkov, Pinnularia austroshetlandica (Carlson) Cleve-Euler and Psammothidium papilio (D.E. Kellogg et al.) Kopalová & Zidarova were the most abundant species in our samples, together they represented 68% of the total number of individuals collected. There was great similarity and abundance of the diatom communites among the sampled points, which resulted in the absence of a linear relationship pattern with distance between sampling points. We conclude that distance was not a factor of differentiation of Antarctic diatom communities associated with terrestrial green macroalgae. This suggests that Antarctic environments may have unique characteristics with homogeneous abiotic factors, at least in relation to this substrate.

Anthropogenic use of gallery forests in the Brazilian Pampa / Uso antropogênico de florestas de galeria do bioma Pampa Brasileiro

As effect of demographic growth in the last decades, many cities in Southern Brazil experienced a degradation process of conservation areas. In this study, semi-structured interviews and a phytosociological inventory were employed to assess the effect of anthropogenic use of tree species of the gallery forest in the Brazilian Pampa. Eighty-four informants were interviewed and listed a total of 43 tree species, belonging to 23 botanical families. Four categories of use were identified for the referenced species: firewood, medicinal, food and timber. The three most important species were Blepharocalyx salicifolius, Eugenia uniflora and Salix humboldtiana. The phytosociological inventory suggests that the anthropogenic exploitation of the gallery forests is leading some tree species to local threat and/or extinction. Aiming to preserve the gallery forests, we suggest the re-evaluation of the local people attitudes, towards a sustainable use of the gallery forests and the reforestation of the river margins with native species producing palatable fruits, enabling the exploitation of non-wood products, as well as the establishment of animal species in this environment.

Como efeito do crescimento demográfico nas últimas décadas, muitas cidades no Sul do Brasil experimentaram um processo de degradação de áreas de preservação ambiental. Neste estudo, entrevistas semi-estruturadas e um inventário fitossociológico foram empregados para acessar o efeito do uso antropogênico de espécies arbóreas de matas de galeria no Pampa brasileiro. Oitenta e quatro informantes foram entrevistados e listaram um total de 43 espécies, pertencentes a 23 famílias botânicas. Quatro categorias de uso foram identificadas para as espécies citadas: lenha, medicamento, alimento e madeira. As três espécies mais importantes foram Blepharocalyx salicifolius, Eugenia uniflora e Salix humboldtiana. O inventário fitossociológico sugere que a exploração antropogênica da mata de galeria está levando algumas espécies à ameaça e/ou extinção local. Com o objetivo de preservar as matas de galeria, sugere-se a re-avaliação das atitudes das comunidades locais, visando um uso sustentável das matas e o reflorestamento das margens de rios com espécies nativas produtoras de frutos comestíveis, possibilitando a exploração de produtos não-madeireiros, assim como o estabelecimento de animais nestes ambientes.

In situ methane and nitrous oxide fluxes in soil from a transect in Hennequin Point, King George Island, Antarctic.

The study aimed at to determine the magnitude of the methane (CH(4)) and nitrous oxide (N(2)O) flux rates in soils at Hennequin Point, King George Island, Antarctic, under different slope positions, vegetal covers and presence of skuas, as well as to evaluate the main soil and climate factors that are involved with the flux of such gases. In situ gas sampling (closed chamber method) was performed in four sites along a transect involving a skua nesting field in a moraine with 5% and 100% of surface covered by vegetal, and two poor-drained soils in the toeslope (a bare alluvium soil and a poor-drained moss field with 100% soil cover). Flux rates ranged from -0.86±0.45 to 2.75±1.52 µg N(2)O-N m(-2) h(-1) and -12.26±3.05 to 1.42±1.31 µg CH(4)-C m(-2) h(-1). The soil totally covered by vegetal in the skua field had the largest CH(4) influx rates. However, this benefic effect was counterbalanced by the greatest N(2)O efflux rates from this soil, resulting in the largest contribution to the global warming potential among the soils evaluated. Flux rates were closely related to soil temperature, but no significant relation was observed with mineral N contents and water-filled pore space. In turn, accumulated CH(4) and N(2)O emissions were closely related to the total N and total organic C stocks in the soil. Net CH(4) influx predominated even in the poor-drained soils, suggesting that the coarse soil texture avoided critical anaerobic conditions. No significant changes in flux rates were observed for sampling time along the day.