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

Ecosystem carbon flux under elevated CO₂ by FACE technique in southern California chaparral.

CHENG*, YUFU¹, OECHEL, WALTER¹, BRYANT, PABLO¹, HASTINGS, STEVE¹, MAJOR, JOHN¹, QIAN, YONGHAI¹, ¹

ABSTRACT- Ecosystem carbon flux was studied under elevated CO₂ treatment by Free Air CO₂ Enrichment (FACE) at 550 ppmv CO₂ in Southern California chaparral (dominated by Adenostoma faciculatum H. & A.) between 1999and 2001. By using the Clapp cuvette, we measured carbon flux in the FACE and its control (360ppmv) directly. For the daily (From 5:00 to 19:00) averaged carbon flux, for all the treatments, this ecosystem is the carbon source for the atmosphere. During the growing season (April-July), the ecosystem under elevated treatment showed less efflux then its control, while during the non-growing season, it showed higher efflux. For the average of the yearly data from April 1999 to March 2000, the daily flux also showed the same pattern, i.e., during the peak photosynthesis time, the ecosystem treated by elevated CO₂ was a greater sink or lesser source. In the growing season, the FACE ecosystem was a greater sink than its control, while during non-growing season this was reversed. Daily soil respiration and seasonal soil respiration rate are always higher in the FACE ring than in the control. Soil moisture predawn stem water potentials are also monitored to have the analysis.

KEY WORDS: elevated CO₂, FACE, carbon flux, chaparral