Adriano Luis Schünemann

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.

High-resolution topography for Digital Terrain Model (DTM) in Keller Peninsula, Maritime Antarctica

High resolution topography (HRT) surveys is an important tool to model landscapes, especially in zones subjected to strong environmental changes, such as Antarctica, where landform is highly influenced by cryoclasty and permafrost melting. The aim of this work was to obtain a high accurate DTM for Keller Peninsula, Maritime Antarctica. The survey study was assessed in the 2014/2015 and 2015/2016 during the austral summer, by using Terrestrial Laser Scanner (TLS). In order to cover 8 km² of the Peninsula, the TLS equipment was installed in 81 different points. Results of the DTM generated by TLS (hereafter, HRT-DTM), and the terrain variables Aspect, Slope and Hillshade obtained were compared with previous models generated by aerophotographic survey (hereafter, APG-DTM). RMSE for the HRT and APG-DTM were 0.726 and 2.397 m, respectively. Spatial resolution of the DTMs was 0.20 m. Morphometric variables obtained from the two methods presented visual differences on the thematic maps, especially related to the Aspect. Generalization was the main process, whereas interpolation occurred for the HRT survey, being the process of choice for the APG method. A large number of points are obtained by the TLS, providing a dense cloud of points, spatially well-distributed, enabling the generalization process to obtain surface models with high performance.

Genetic Diversity and Structure of Syagrus romanzoffiana (Cham.) Glassman (Arecaceae) in Southern Brazil

The species Syagrus romanzoffiana is a monocot belonging to the family Arecaceae; it is a palm endemic to South America and is widely distributed throughout the southeast and south of Brazil, including the State of Rio Grande do Sul. To estimate the genetic diversity and structure of the species in the watersheds of Rio Grande do Sul, five simple sequence repeat markers were used to analyze 90 individuals, representing three populations. The genetic structure of S. romanzoffiana groups was evaluated through the analysis of molecular variance and a multivariate analysis based on Nei’s genetic distance. The evaluated populations showed significant intrapopulation molecular variation (FST = 0.11). The observed heterozygosity (HO = 0.17) was lower than the expected heterozygosity (HE = 0.75). These data indicate that although the number of individuals is high, the diversity is low for some indices. Our findings suggest that further studies are needed, particularly on the genetics of natural populations of S. romanzoffiana in Rio Grande do Sul State, to fully characterize their genetic diversity and structure and determine strategies and priority areas for species conservation.

Description of plant communities on Half Moon Island, Antarctica

ABSTRACT During February–March of the austral summers of 2013/14 and 2014/2015, fieldwork was performed on Half Moon Island, South Shetland Archipelago, Antarctica, to evaluate the distribution and abundance of mosses and lichens, as well as to describe and map the plant communities there. The quadrat (20 × 20 cm) sampling method was employed in a phytosociological study that aimed to describe these communities. The area was mapped using an Astech Promark II® DGPS, yielding sub-metric precision after post-processing with software. The number of species totalled 38 bryophytes, 59 lichens, only one flowering plant (Deschampsia antarctica Desv.), and two macroscopic terrestrial algae. Five types of plant communities were identified on the island, as follows: (1) fruticose lichen and moss cushion, (2) moss carpet, (3) muscicolous lichen, (4) crustose lichen and (5) moss turf.

Soil Chemical Attributes as Affected by Vegetal Cover and Seabirds in Punta Hennequin, Antarctica

is study had the purpose of evaluating the e ect of soil cover by vegetation on soil chemical attributes in a skua (Catharacta maccormicki) eld at Punta Hennequin, Shetland Island, Antarctica. Four locals along a transect were sampled, involving soils with 5 and 100% of vegetal cover (L1 and L2, respectively) with Deschampsia+Colobanthus; bare alluvium soil (L3); and poor-drained moss (Sanionia uncinata) carpet with 100% soil cover (L4). Soil samples obtained from three layers and three replicates were submitted to chemical and physical analysis. Although both L1 and L2 are in the same nesting eld, the more abundant vegetation at L2 promoted signi cantly larger (P < 0.05) total organic C (TOC) stocks in the soil than at L1 (43.08 and 9.03 Mg C ha–1, respectively, at the 0-40 cm layer). Total N stocks increased from 2.60 to 6.54 Mg ha–1 for L1 and L2, respectively. Although the presence of seabirds represents an important transfer of organic material from marine to the terrestrial environment, the di erences evidence the importance of vegetation in order to raise the soil organic matter levels. Soil pH was consistently lower in L2 than L1 about 1.0 unit for the soil layers herein evaluated, which is probably linked to the soil organic matter accumulation. Contrary to the distribution of TOC and TN contents, exchangeable P and K had no gradient along the soil pro le, evidencing that most of the P and K is native from the parent material and their input by seabirds to the soil is negligible.

Mapping and Geopositioning Methods in Ice-Free Areas Antarctica

Mapping is an activity which can register the occurrence of phenomenons related to land cover. ere are several methods of map registry. In Antarctic areas, the mapping gives importance to registry of the land cover of plants in ice-free areas. e maps are tools to understand the dynamics of plants in those areas. e Global Navigation Satellite System (GNSS) is an important tool to reach this objective, such as the plotting of georeference points in any place in the world including Antarctic locations. is study aims to contribute to the research of mapping in ice-free areas making a comparison with map builds for Hennequin Point and Keller Peninsula at King George Island, Antarctica. e study was carried out using GNSS L1/L2 and L1 receivers to record points in ice-free areas with plant coverage and post processing using speci c so ware. e post processed data were exported to CAD so ware. With the points plotted, they were connected using polylines to draw the vegetation patches. e maps obtained were overlapped to identify the growth or retraction between the patches. e resulting maps are presented. e results show di erences between the patches sampled during di erent polar years. Probably, these divergences are due to the di erent methodologies used to obtain the points in these areas. To better understand these variations, we need to produce more maps of the same place, obtained with the same methodologies or compare them using Satellite Images with high spatial resolution.