Nutrient and thermal regime, microbial biomass, and vegetation of antarctic soils in the Windmill Islands region of East Antarctica (Wilkes Land)

In the antarctic summer of 1996, permafrost-affected cold soils close to th e Australian Casey Station in the Windmill Islands region (Wilkes Land) wer e investigated to determine in what way the thermal and nutrient regimes in the antarctic soils an related to microbial biomass and vegetation pattern s. The soils are characterized by a high content of coarse mineral particle s and total organic carbon (TOC) and a low C/N ratio (mean 11). Despite the low pH values (mean 4.0) the soils are rich in nutrients due to an input f rom seabirds (existing or abandoned nesting sites) and an eolian distributi on of line-grained soil material in the landscape. Vegetation influences TO C storage and the cation exchange capacity in the uppermost soil horizons, whereas total N and most nutrient levels are not affected by the vegetation , but by seabird droppings. The present nutrient level does not affect plan t adaptation, because the K, Mg, and la contents are often extraordinarily high. This suggests that nutrient supply is not a limiting factor, whereas microclimate effects, such as moisture availability and ground-level wind s peed, have a primary influence on plant growth. Soil-surface temperature me asurements indicate a strong variability in microclimate due to small-scale variations in geomorphological surface features. Bacteria art, found in al l soil horizons, bur not algae and yeast. Soil microbial counts are weakly correlated to the C/N ratios and soil surface temperatures. High TOC and cl ay contents probably improve the soil water-holding capacity and TOC contri butes to the microbial food supply. The investigated microbial parameters a re weakly correlated to the present vegetation carpet, the lowest counts ar e found in the soils with scattered or no vegetation cover.