We quantified soil respiration as an index of microbial biomass. Plots were sampled on
21 June 1999 and subsequently processed following the protocols described above. Each soil
sample was placed in a respiration flask and moistened to near field capacity with double
distilled H2O. Flasks were equilibrated to a 24°C and sealed with an air-tight lid. After one
hour, initial CO2 measurements were made by sampling 5 ml of air from each flask that was then
injected into a closed circulating infrared gas analyzer (CID-310, CID Inc., Vancouver, WA).
Flasks were returned to the growth chamber and sampled again after 15-20 hours. Specific mass
of the soil was determined from measurements of wet mass, dry mass, and water content of each
sample. Mass-specific respiration rates (μL CO2 g-1 h-1) were then calculated by subtracting
initial CO2 measurements from final CO2 readings on an adjusted dry weight basis.