Contact Information: NSF AMS Accelerator Facility NSF AMS Accelerator Facility Ph.D project: Elevated Atmospheric CO2 Impacts Carbon Dynamics in a C4-Sorghum-Soil Agroecosystem- An Application of Stable Carbon Isotopes (õ13C) in Tracing the Fate of Carbon in the Atmosphere-Plant-Soil Ecosystem Arizona Maricopa Free-Air Carbon Dioxide Enrichment
(FACE) Experiment |
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Seasonal Soil Respiration and Soil CO2 under Elevated CO2
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Free Air-CO2 Enrichment (FACE) of C4-Sorghum: Biochemical Composition and Decomposition of Sorghum Tissues Grown Under Elevated CO2Department of Soil, Water and Environmental Sciences
The Unversity of Arizona Li Cheng Biochemical composition of sorghum tissue grown under elevated CO2
was determined in Free-Air CO2 Enrichment (FACE) experiment
during the 1998-1999 growing seasons at Maricopa, Arizona, USA. Sorghum
samples were collected from FACE (560 ppmv CO2 ) wet (well-watered)
and dry (water-limited), and Control (360 ppmv CO2) wet and
dry plots at the end of 1999 growth season. Elevated CO2 increased
cellulose and lignin by 40% and 5%, respectively, while total non-structural
carbohydrates and amino acids were reduced by 8% and 7%, respectively.
Phenolics were significantly higher in FACE roots, but not significant
different in FACE leaves and stems. Water stress modified the CO2
effects, especially for uronic acids that were increased in FACE-wet by
7% and reduced in FACE-dry sorghum tissues by 3%. The C/N ratio in sorghum
tissues was not affected by CO2, but was substantially lower
under water stress. Laboratory incubation of soil amended with sorghum
tissues showed the decomposition rate of FACE sorghum tissues was on average
14% lower than control sorghum tissues after 30 day incubation; consequently,
23% more new organic carbon was left in the incubated soil amended with
FACE sorghum tissues based on isotope mass balance. The results confirm
the slower decomposition of FACE plant tissue reported in literature apparently
due to biochemical changes in the plant tissue. |
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