PARENT SESSION
Oral Session #25: Soil Ecology: Microbial and Invertebrate. Presiding: W. Parsons.
Tuesday, August 7, 2001. 8:00 AM to 12:00 PM. Hall of Ideas G.

CO₂ flux from Antarctic Dry Valley soils: Cross valley comparisons and relationship to soil biota.

Parsons, Andrew¹, Barrett, John², Blecker, Steve¹, Catapano, Kathleen², Porazinska, Dorota¹, Virginia, Ross², Wall, Diana¹, ^{1 2}

ABSTRACT- The McMurdo Dry Valleys in Antarctica are one of the coldest and driest ecosystems on the planet. No higher plants are present, and organic carbon content of the soil is typically <0.1 mg g^-1. The diversity of soil invertebrate communities is extremely low. We are interested in determining the physical and biological controls on soil respiration. We measured diel CO₂ flux (using a LiCor 6400 infra-red gas analyzer) and soil temperature, at sites in 3 lake basins in Taylor Valley, for 2-3 days at each location during the austral summer. In addition, soil chemical properties and invertebrate abundance were determined. Flux rates were low for all sites, with maxima less than 0.2 mol m^-2 s^-1. At two sites, soil temperature was the important determinant of both the rate of CO₂ evolution from the soil, and the direction of flux. The third site had no biological activity, no net positive CO₂ flux was measured even when soil temperatures were positive and rising. At this site invertebrate populations were virtually non-existent. At the two sites with measurable CO₂ flux, when temperatures were dropping, (about 1°C hr^-1), CO₂ was taken up by the soil. The mechanism of this uptake appears to be physical rather than biological, based on laboratory experiments using irradiated soil. The net CO₂ flux measured was a combination of biological CO₂ production and uptake by the physical process. We use our data to model the physical uptake based on temperature change, and as a result we can estimate CO₂ production by soil biota.

KEY WORDS: extreme environment, respiration