ARS | Publication request: CARBON DIOXIDE FLUXES OVER GRAZED NATIVE PRAIRIE AND A PASCOPYRUM SMITHII PASTURE.

Submitted to: International Rangeland Congress
Publication Type: Proceedings
Publication Acceptance Date: December 23, 1998
Publication Date: N/A

Interpretive Summary: This study is associated with the ARS Carbon Dioxide Flux Network involving 11 rangeland research locations in the USA. The goal overall is to determine the role of grasslands in the global carbon cycle. The objectives were to compare carbon dioxide fluxes over a grazed native prairie and a seeded western wheatgrass pasture on the Northern Great Plains at Mandan, North Dakota. Carbon dioxide fluxes were measured in 1996 and 1997 from mid April to November using Bowen ratio-energy balance methods. Peak green biomass occurred in mid July and averaged 133 and 170 g/m2, peak LAI averaged 0.47 and 0.54, and root biomass to 30-cm depth averaged 1116 and 657 g/m2 for the native prairie and western wheatgrass pastures, respectively. Net carbon dioxide fluxes averaged -292 and -131 g/m2 (negative flux is toward the soil), for the native prairie and western wheatgrass pasture, respectively. The greater flux for the native prairie than western wheatgrass pasture was attributed to greater total biomass production and species diversity. Based on these data, the native prairie has greater potential as a sink for carbon dioxide than the seeded western wheatgrass pasture, although both pastures produced a positive carbon balance, even when grazed.

Technical Abstract: This study is associated with the ARS Carbon Dioxide Flux Network involving 11 rangeland research locations in the USA. The goal overall is to determine the role of grasslands in the global carbon cycle. The objectives were to compare carbon dioxide fluxes over a grazed native prairie and a seeded Pascopyrum smithii (Rybd) Love (western wheatgrass) pasture on the Northern Great Plains at Mandan, North Dakota. Carbon dioxide fluxes were measured in 1996 and 1997 from mid April to November using Bowen ratio-energy balance methods. Both sites were on a fine-silty, mixed Typic Haploborolls soil. Peak green biomass occurred in mid July and averaged 133 and 170 g/m2, peak LAI averaged 0.47 and 0.54, and root biomass to 30-cm depth averaged 1116 and 657 g/m2 for the native prairie and P. smithii pastures, respectively. Midday soil carbon dioxide efflux measured about every 21 days averaged 13 and 14 g/m2/d for the native prairie and P. smithii pasture, respectively. Net carbon dioxide fluxes averaged -292 and -131 g/m2 (negative flux is toward the soil), for the native prairie and P. smithii pasture, respectively. The greater flux for the native prairie than P. smithii pasture was attributed to greater total biomass production and species diversity.