Chemical and biological properties, formation, occurrence and classification of Spodic Cryosols in a terrestrial ecosystem of East Antarctica (Wilkes Land)

Soils with the morphological features of podzols are widespread in coastal East Antarctica. Neither the World Reference Base of Soil Resources (WRB) nor Soil Taxonomy (ST) adequately classify these soils, so we recommend the addition of Spodic Cryosol at the second hierarchical level in WRB and Spodorthel at the great group level of ST. We divide the Spodic Cryosols into ornithogenic and non-ornithogenic Spodic Cryosols based on inorganic chemistry, soil organic matter composition and microbiology. The occurrence of Spodic Cryosols depends on parent materials, soil texture, surface pattern, solar energy input and vegetation patterns. Antarctic Spodic Cryosols form on solid rocks, outwash sediments and abandoned penguin rookeries, and represent 20% of the soil-landscape of Wilkes Land, with one-third ornithogenic and two-thirds non-ornithogenic. Ornithogenic Spodic Cryosols are related to tectonically uplifted abandoned penguin rookeries. odic Cryosols contain large amounts of carbon and nitrogen. During pedogenesis iron complexed with organic matter in the topsoils has been altered to oxides and crystalline iron minerals, but aluminium remains almost entirely 100% organically bound throughout the profile. Meltwater and a moss cover are essential for podzolization on the non-ornithogenic sites, and at the ornithogenic sites, the chemically aggressive solution from dissolved guano has bleached the uppermost AE horizon and translocated iron and aluminium into the subsoil. The low salinity suggests that downward leaching exceeds upward transport by evaporation. Intensity of podzolization is determined by microclimate, soil microbial effects and parent materials. The permafrost table may cause precipitation of organic matter in the subsoil. Mg and P levels are high. The P level is very high in the ornithogenic soils. K, P, pH, base saturation (BS) and bacterial colonization reflect the influence of guano. In the AE horizon of ornithogenic soils colonization by lichens and/or mosses depresses bacterial activity. The mean C/N ratio of approximately 11 and the abundance of carboxylic carbon compounds probably derive from organic acids and oxidized carbohydrates. Migration of organic acids, non-humified carbohydrates and N-containing compounds is suggested as the main mechanism of podzolization.