Genesis, properties and sensitivity of Antarctic Gelisols

According to the newest version of the US Soil Taxonomy permafrost-affected soils are Gelisols. Antarctic Gelisols in the cold deserts of the Ross Sea sector are formed under extreme conditions of low temperature and aridity. The main soil forming processes are oxidation and salinization, with almos t complete absence of organic matter. The oldest soils date from around 13 Ma. The origin of most soil salts is atmospheric, linking these soils to th ose in other parts of the world through atmospheric processes. The soils ha ve water contents in the active layer of the most arid areas <1%. With decr easing latitude or proximity to the coast in East Antarctica and the Antarc tic Peninsula, soil water contents increase and the soils support a range o f soil organisms and plant species. At latitudes less than or equal to 66 d egrees S organic matter accumulation and several other pedogenic processes such as cryoturbation, mineral weathering, brunification, acidification, po dzolization and redoximorphism occur. In addition, these soils receive nitr ogen and phosphorus from seabirds. In most places summer thaw lasts little more than six weeks; thaw depths range from around 10-100 cm. A critical fa ctor in the soil development is the albedo of the soil surface, since the a bsorbed energy controls weathering processes. The extreme fragility of the soils in the arid Ross Sea sector is largely due to the absence of structur e, cohesion, moisture and organic materials. Recovery from physical human d isturbances is in the order of hundreds to thousands of years. In East Anta rctica and the Antarctic Peninsula plant and organisms growth is similarly slow and ecosystems are susceptible to human impact. The occurrence of many old soils at high inland elevation indicates that little response to globa l climatic change would be expected there. For the much younger soils in Ea st Antarctica and the Antarctic Peninsula, when mean annual summer temperat ures are higher: responses to global change and change in sea level may be significant.