DETERMINANTS OF SOIL BIODIVERSITY AND ECOSYSTEM FUNCTIONING IN THE ANTARCTIC DRY VALLEYS

Soil biota are exert a strong influence on ecosystem processes, and their diversity is a major component of global biodiversity. Determining how soil biodiversity is related to key ecosystem processes (decomposition, respiration, nutrient cycling) across local to landscape scales is being unraveled by studies in arid ecosystems. The determinants of soil biodiversity in the extreme soil systems of Antarctica (McMurdo LTER site), where there are no vascular plants, are determined by soil chemical and physical factors and legacies of past climates. Legacies in soil include the amount and quality of organic matter and salts derived from paleolakes, and more contemporary inputs (soil algae, cryptoendolithic biota, marine aerosols). These legacies, combined with features of the landscape (location of glaciers, elevation, soil polygons), affect the complexity and location of the soil foodweb. The diversity is low with 3 species of nematodes as the dominant soil invertebrate. Research indicates biotic distribution is predictable, with species segregating across landscape features based on soil factors. Experimental results indicate that nematode abundance and activity is limited by substrate and higher in more favorable sites (higher CO2 flux, higher soil carbon and moisture, lower salinity). Comparisons with more complex systems, including the Chihuahuan Desert (Jornada LTER site), the shortgrass steppe (SGS LTER site) and tallgrass prairie (Konza Prairie LTER site) illustrate the increasing complexity and patterning of soil foodwebs in arid systems. The effect of global change scenarios on the soil foodweb and affecting NPP, carbon and nitrogen cycling are examined using a model of soil foodwebs in an arid grassland ecosystem.