Six Years of COSubscript2/Subscript Flux Mea

Authors: A B Frank

Publish Date: 2003/12/04

Volume: 33, Issue: 1, Pages: S426-S431

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Abstract

The large area occupied by temperate grassland ecosystems makes it important to determine their strength as a carbon sink The Bowen ratio/energy balance BREB technique was used to determine CO2 fluxes over a moderately grazed mixedgrass prairie at Mandan North Dakota USA over a 6year period from 1996 to 2001 Aboveground biomass and leaf area index LAI were measured about every 21 days throughout the growing period Root biomass was determined to 11 m depth in midJuly each year Peak aboveground biomass typically occurred between midJuly to early August and ranged from 782 kg/ha in 1998 to 2173 kg/ha in 1999 Maximum LAI ranged from 04 in 1998 to 09 in 1999 Root biomass ranged from 118 Mg/ha in 1997 to 174 Mg/ha in 1996 Maximum daily CO2 fluxes generally coincided with periods of maximum LAI and aboveground green biomass The average time period for CO2 uptake was 5 May to 3 October Annual CO2 fluxes ranged from a low of 13 g CO2/m2 in 1998 to a high of 247 g CO2/m2 in 2001 nearly a 20fold difference and averaged 108 g CO2/m2 The cumulative annual flux over all 6 years was 646 g CO2/m2 or 176 g CO2C/m2 These results indicate that the strength of the carbon sink for this moderately grazed prairie site is about 30 g CO2C/m2/yr which is quite small but considering that the site was grazed and still remains a sink for carbon it is significant

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