Environmental effects on the CO2 flux and CO2—Water flux ratio of Alfalfa

✍ Scribed by Dennis D. Baldocchi; Shashi B. Verma; Norman J. Rosenberg

• Publisher: Elsevier Science
• Year: 1981
• Weight: 538 KB
• Volume: 24
• Category: Article
• ISSN: 0002-1571
• DOI: 10.1016/0002-1571(81)90042-x

✦ Synopsis

Environmental effects on the CO2 flux (Fc) and CO2--water flux ratio (CWFR) of alfalfa (Medicago sativa L.) were studied using micrometeorological techniques. The study was conducted in the east central Great Plains of North America. F c was dependent on solar radiation, turbulent mixing and air temperature. The response of F c to increasing irradiance was described by a diminishing returns curve. Increasing turbulent mixing caused a reduction in the boundary-layer resistance to CO2 transfer and increased light penetration into the canopy; both factors caused F c to increase. Under high irradiance, F c decreased with increasing air temperature in the range 23--32°C. This effect was due to both soil plus root and dark respiration increasing with air temperature. Fc was not limited by plant water potentials ranging between --7 and --17 bar. That alfalfa is relatively drought-tolerant is indicated by the fact that no significant stomatal closure seemed to have occurred at water potentials as low as --17 bars. CWFR was correlated with net radiation. Sensible heat advection, however, reduced CWFR since this additional source of energy contributed only to evapotranspiration.