Ornithogenic soils on basalts from maritime Antarctica

Large amounts of organic matter deposited by marine birds, especially penguins, accumulate on ice-free areas of maritime Antarctica during the short austral summer. The well-known ornithogenic soils of this region are unique in Antarctica and represent important sites where phosphatization is the main soil-forming process. Most recent studies in ornithogenic soils of maritime Antarctica were conducted on andesitic areas, and no reports are available about ornithogenic soils on basaltic intrusion. The purpose of this study was to report the main chemical, physical, and mineralogical characteristics of ornithogenic soils on basaltic intrusion of Barrientos, and evaluate the effects of different nesting bird species and altitude. The amount of Mehlich-extractable P indicates a close interaction between guano and underlying soils, with different end products depending on altitude, weathering degree and nesting bird species. In the soil collected from the giant petrel's nest, the intensity of organic deposition was much lower. The lower means of Mehlich-extractable P, total organic carbon and total nitrogen in Barrientos Island showed the little influence of marine birds when compared to King George Island. On the other hand, the means of exchangeable Ca and Mg were higher due to the basaltic composition of the regional volcanoes, contrasting with the andesites, which are the commonest rock type in maritime Antarctica. Thus, the soil characteristics of the Barrientos Island are influenced by both parent material and phosphatization.