PARENT SESSION
Poster Session #11: Elevated CO₂.
Monday, August 6, 2001. Presentation from 3:30 PM to 5:00 PM. Exhibition Hall

Increased soil respiration under elevated CO₂ at the Nevada Desert FACE Facility.

Wells, Christina ¹, Pataki, Diane², Schorran, David³, Cheng, Weixin⁴, Cogar, Crystal ¹, Nowak, Robert¹, ^{1 2 3 4}

ABSTRACT- Soil respiration provides an integrative measure of belowground respiratory activity and is an essential component of ecosystem carbon budgets. It has been suggested that increased primary production and greater belowground carbon allocation under elevated atmospheric [CO₂ ] will drive higher rates of soil respiration. We tested this hypothesis at the Nevada Desert Free-Air CO₂ Enrichment (FACE) Facility using a continuous, open flow gas exchange system that monitors the diurnal time course of soil CO2 flux in ambient (350 ppm CO₂ ) and elevated (550 ppm CO₂ ) rings. Soil CO₂ flux at the NDFF typically ranges from -0.25 to 1.5 umol/m2/sec and exhibits a strong diurnal pattern. During the 1999-2000 season, net daily soil CO₂ flux ranged from -3.10 ± 3.363 to 29.59 ± 1.37 mmol/m2/day. There was a consistent trend toward higher soil CO₂ flux in elevated rings, and this effect was most pronounced when temperatures were high (F = 5.70, P = 0.0179, temperature*CO₂ interaction). Small differences in net daily CO₂ flux resulted in large differences in total soil CO₂ losses over time: when net daily CO₂ flux was summed over the 1999-2000 season, elevated ring soil averaged approximately twice the CO₂ loss of ambient ring soil.

KEY WORDS: soil respiration, FACE, elevated CO2, Mojave