Continuous Measurement of Carbon Dioxide Evolution From Partitioned Forest Floor Components

Loss rates of organic detritus in ecosystems can be determined by measuring rates of CO_2 release from decomposing organic substrates. We used an open system employing inverted boxes and an infrared gas analyzer (IRGA) to obtain continuous measurements of CO_2 evolution from the floor or a mixed mesophytic forest. Plexiglass sheets were used to partition respiratory activity of two litter horizons (01 and 02) and soil. Root respiration rates were determined with a differential respirometer. We compared the open system with a closed system in which KOH was used as the CO_2 absorber. Respiration measurements with KOH were 63% of IRGA values at 20 degrees C and 90% at 12 degrees. Flow rates (28 to 340 liters hr — 1) had no effect on rates of CO_2 evolution. Nighttime CO_2 evolution rates were generally higher day — 1. Preliminary data indicate annual CO_2 evolution of 3.8 kg m — 2 (48% from litter, 17% from soil, and 35% from roots). This estimate is equivalent to 2.3 kg m — 2 organic mass catabolized, assuming a carbohydrate substrate, which is 11% higher than independent estimates of the organic detritus annually available for catabolism.