Spatial and temporal variability of CO2 dynamic and soil attributes in Maritime Antarctica

• Ano de defesa: 2016
• Autor(a) principal: Thomazini, André
• Tipo de documento: Tese
• Tipo de acesso: Acesso aberto
• Idioma: eng
• Instituição de defesa: Universidade Federal de Viçosa
• Palavras-chave em Português: Solos - Antárctica, Península; Dióxido de carbono; Dióxido de carbono atmosférico - Antártica, Península; Aquecimento global; Ciência do Solo
• Link de acesso: http://www.locus.ufv.br/handle/123456789/10391

Maritime Antarctica presents high sensitivity to climate change, especially by the alterations in air temperature, which modifies carbon dynamics and soil attributes in terrestrial ecosystems. Thus, variables related to soil (i.e. organic carbon, soil temperature and soil moisture), and vegetation distribution patterns, can represent climate change indicators. The objective of this work was to investigate the spatial and temporal relationship among carbon exchange, soil nutrient status and development in the main terrestrial ecosystems of Maritime Antarctica. The study was carried out at Keller and Coppermine Peninsula, in King George Island and Robert Island, respectively. Regular grids were installed to evaluate the spatial variability of general soil attributes and carbon exchange in lichens, mosses, lichens/mosses and bare soil sites along the ice- free areas. By using geostatistical techniques, spatial dependence was accessed through semivariogram and fractal dimension modeling. Soil was sampled at different soil layers to determine general soil attributes. Ecosystem respiration, net ecosystem exchange and gross primary production were determined by measuring CO 2 fluxes in situ with a closed automatic chamber system (LI-COR Biosciences, Lincoln, NE, USA), based on short and long-term measurements. Results indicate a high capacity of mosses carpets (especially by Sanionia uncinata) to act as a sink of carbon, where soil moisture is elevated. On the other hand, where guano is deposited, soil temperature is enhanced, leading to increase soil organic matter mineralization, ecosystem respiration, acting as a source of carbon to the atmosphere. Spatial dependence strongly varied among sites, where guano deposition and vegetation coverage are reported to drive the extension of spatial structure. Fractal dimension values showed great spatial relationship between organic carbon and aluminum. Soils are mainly characterized by the high amounts of bases and weak clay formation. In zones with weak ornithogenic influence, soil is acid and values of exchangeable aluminum are high, associated with elevated potential acidity. The proximity of permafrost is leading to lower soil temperatures, reducing the number of thaw days. However, under current climate warming, this site will progressively act as a source of CO 2 to the atmosphere. On the other hand, peatlands could be formed due snow/ice melting, storing large amounts of carbon. The balance of uptake and release of CO 2 needs to be further researched in Maritime Antarctica, to elucidate the current dynamic for other different ice-free areas.