PARENT SESSION
Poster Session #42: Carbon Storage.
Thursday, August 9, 2001. Presentation from 3:30 PM to 5:00 PM. Exhibition Hall

Soil CO₂ efflux and profile concentration in response to irrigation and fertilization in a 16-year old loblolly pine stand.

Anderson, Peter¹, Maier, Christopher¹, ¹

ABSTRACT- Soil CO₂ efflux rates (Sf) are the second largest carbon flux in forest ecosystems. Fertilization and to a lesser degree irrigation are increasingly being used to raise productivity in managed pine stands. Changes in soil resource availability may affect root and microbial respiration and thus Sf. To assess the affects of fertilization and irrigation on Sf, we used an automated system to measure soil surface CO₂ efflux in a 16-year-old pine plantation. These measures were conducted four times between May 21, and August 27, 2000. In addition we measured volumetric soil moisture, temperature, and soil profile CO₂ concentrations (pCO₂) at five depths from 5 to 100 cm. The four treatments were control, irrigated, fertilized, and fertilized and irrigated. Sf was significantly increased by irrigation compared to control (10 %) and fertilized (21 %) treatments. In addition, Sf in the irrigated and fertilized treatment was significantly higher than the fertilized only treatment. Mean pCO₂ ranged from 1687 ppm near the soil surface to 6995 ppm at 100 cm and was significantly higher in the irrigated treatments. Sf was significantly correlated to pCO₂ at 10 and 50 cm (r = 0.37 and .053 respectively). Our data suggest that irrigation increased soil CO₂ efflux while fertilization had little impact. In addition correlating soil CO₂ concentration with soil surface CO₂ efflux may have important implication for process modeling.

KEY WORDS: loblolly pine, soil CO₂