Submitted to: International Rangeland Congress
Publication Type: Abstract Only
Publication Acceptance Date: December 19, 2002
Publication Date: July 26, 2003
Citation: FRANK, A.B. CARBON DIOXIDE FLUXES OVER A GRAZED MIXED-GRASS PRAIRIE. INTERNATIONAL RANGELAND CONGRESS. African Journal Range and Forage Science 20(2):156. 2003. Technical Abstract: Temperate grasslands ecosystems occupy vast areas worldwide that are important in the global carbon cycle, but annual CO2 flux data for these grasslands are limited. The CO2 Bowen ratio/energy balance technique was used to measure CO2 fluxes over a moderately grazed mixed-grass prairie site from 24 April to 26 October in 1996, 1997, 1998, 1999, 2000 and 2001 at Mandan, ND, USA (latitude 46°46'N, longitude 100°55'W, elevation 518 m). The site is mostly cool season grass species with a complement of warm season grasses. Annual precipitation averages 404 mm. Average CO2 flux for the 175 day period over the six years was 860 g CO2 m-2 when radiation exceeded 25 W m-2 and when radiation was less or during the night period CO2 flux averaged 448 g CO2 m-2. Net CO2 fluxes for the 175 day growing period averaged 376 g CO2 m-2. Yearly fluxes ranged from 377 g CO2 m-2 in 2001 to 655 g CO2 m-2 in 1999. Dormant season fluxes measured with soil chambers in 1999 were 265 g CO2 m-2. Peak fluxes coincided well with periods of peak standing biomass and varied from late June to mid July. These results suggest Northern Great Plains mixed-grass prairie grasslands can be a small sink for atmospheric CO2 even when defoliated at proper grazing intensities.