Extended Abstract (72K)10.4
Agricultural Canopy and Soil CO2 Release and Photosynthetic Recapture
Steven E. Hollinger, ISWS, Champaign, IL; and T. P. Meyers
As part of the NOAA’s contribution to GEWEX a long term energy/carbon eddy-covariance tower system was established on a no-till corn and soybean field in central Illinois. Continuous measurements of CO2 and water vapor fluxes, energy balance, and weather data have been collected from corn (1997, 1999, 2001) and soybean (1996, 1998, 2000) since August 1996. Plant growth analysis using destructive sampling techniques was also conducted during 1998, 1999, 2000, and 2001. The continuous eddy covariance measurements of CO2 fluxes from agricultural canopies provide an estimate of the Net Ecosystem Exchange (NEE). However, destructive plant growth analysis from these canopies indicate the NEE significantly underestimates the productivity of corn (Zea mays) and soybean (Glycine max) canopies. This discrepancy is a result of the eddy co-variance measurements accounting only for the CO2 that is exchanged between the canopy and the atmosphere at the height of the instruments. The atmosphere is only one source of CO2 that a canopy uses in photosynthesis, other sources include inorganic and organic CO2 from the soil (referred to as soil respiration). The CO2 that is released from the soil during daylight hours can be easily recaptured by photosynthesis and may provide a significant contribution to total canopy productivity. Total canopy productivity includes both above and below ground plant biomass. The contribution of recaptured CO2 is greater in a corn canopy than a soybean canopy. This paper will explore different methods to estimate the sources and quantity of recaptured CO2 and propose methods to more accurately estimate this important source of carbon.
Session 10, Carbon dioxide exchange Part 2
Friday, 24 May 2002, 8:30 AM-11:45 AM
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