251-2 Seasonal Variation of the Net CO2 Ecosystem Exchange Isotopic Signature Above a Corn Canopy.
See more from this Division: ASA Section: Environmental QualitySee more from this Session: Agriculture and Land Management Impacts on Soil Carbon Processes: I
Tuesday, November 4, 2014: 1:15 PM
Long Beach Convention Center, Room 103C
Stable isotopes of CO2 are powerful tools to study the carbon dioxide exchange between vegetation and the atmosphere. The development of optical sensors has allowed measurements of CO2 isotopes in the atmosphere at an unprecedented temporal resolution. The objective of this study was to study the 13CO2 composition of the net CO2 exchange (NEE) above a corn canopy. Measurements of 12CO2 and 13CO2 above and below the corn canopy were taken using a multiport sampling system connected to a tunable diode laser trace gas analyzer. The flux signature of NEE was calculated using isotopic measurements and the flux gradient technique and a Lagrangian dispersion analysis. The use of a gradient of a concentration threshold to screen half hourly period improved the estimates of flux signatures by the isotope flux ratio approach. The Langrangian dispersion analysis and the isotope flux ratio method estimates showed good agreement above the corn canopy, indicating that the former method can be a viable alternative to study the isotopic exchange within plant canopies. The 13CO2 composition of NEE showed a downward trend near the end of the growing season, which may be related to a reduction of autotrophic respiration in the soil.
See more from this Division: ASA Section: Environmental QualitySee more from this Session: Agriculture and Land Management Impacts on Soil Carbon Processes: I