Skip to main content
ARS Home » Pacific West Area » Burns, Oregon » Range and Meadow Forage Management Research » Research » Publications at this Location » Publication #138741
Title: ANNUAL CARBON DIOXIDE FLUXES ON NATIVE SAGEBRUSH RANGELAND IN EASTERN OREGON

Author
item Angell, Raymond
item Svejcar, Anthony
item Bates, Jonathan - Jon
item GILMANOV, TAGIR - UNIVERSITY OF S. DAKOTA

Submitted to: Agricultural and Forest Meteorology Conference Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 3/1/2002
Publication Date: 5/20/2002
Citation: ANGELL, R.F., SVEJCAR, A.J., BATES, J.D., GILMANOV, T.G. ANNUAL CARBON DIOXIDE FLUXES ON NATIVE SAGEBRUSH RANGELAND IN EASTERN OREGON. AGRICULTURAL AND FOREST METEOROLOGY CONFERENCE PROCEEDINGS. 2002.

Interpretive Summary: Eastern Oregon sagebrush steppe vegetation is characterized by an understory of herbaceous grasses and forbs with an overstory that includes several shrub species. The most common species is Wyoming big sagebrush. This community type is one of the largest contiguous plant assemblages in the continental United States. Little is known regarding the dynamics of CO2 flux over these rangelands. We established a study at the Northern Great Basin Experimental Range in 1995 to determine the magnitude of CO2 flux on an ungrazed sagebrush-steppe that is representative of large areas of the northern Great Basin. Bowen ratio/energy balance was used to obtain 20-minute summaries of energy, H2O, and CO2 fluxes. We will discuss CO2 fluxes in this presentation and will use the ecophysiological convention in which positive fluxes are toward the surface. Maximum CO2 assimilation rate measure on our site was about 0.5 mg CO2 m-2 s-1, usually between 15 may and 1 June. Maximum respiration rate also occurred within the same time period and averaged about -0.4 mg CO2 m-2 s-1. Daily uptake peaked in late May most years at about 9 g m-2 d-1. Our site was a moderate sink during most seasons, however in 1996 we measured a net loss of CO2 from the surface, apparently a result of freezing nighttime temperatures in mid June. Below-average precipitation was received in 2000, and during that year the site again became a source for CO2. The dataset illustrates the high variability of CO2 uptake associated with northern Great Basin ecosystems. This variability most likely results from the extreme inter-annual variation of precipitation and temperature that occurs in this ecosystem. These data suggest that this site is a sink for CO2 during average to wet years, but becomes a source during drought or after a disturbance such as a late frost.

Technical Abstract: Eastern Oregon sagebrush steppe vegetation is characterized by an understory of herbaceous grasses and forbs with an overstory that includes several shrub species. The most common species is Wyoming big sagebrush. This community type is one of the largest contiguous plant assemblages in the continental United States. Little is known regarding the dynamics of CO2 flux over these rangelands. We established a study at the Northern Great Basin Experimental Range in 1995 to determine the magnitude of CO2 flux on an ungrazed sagebrush-steppe that is representative of large areas of the northern Great Basin. Bowen ratio/energy balance was used to obtain 20-minute summaries of energy, H2O, and CO2 fluxes. We will discuss CO2 fluxes in this presentation and will use the ecophysiological convention in which positive fluxes are toward the surface. Maximum CO2 assimilation rate measure on our site was about 0.5 mg CO2 m-2 s-1, usually between 15 may and 1 June. Maximum respiration rate also occurred within the same time period and averaged about -0.4 mg CO2 m-2 s-1. Daily uptake peaked in late May most years at about 9 g m-2 d-1. Our site was a moderate sink during most seasons, however in 1996 we measured a net loss of CO2 from the surface, apparently a result of freezing nighttime temperatures in mid June. Below-average precipitation was received in 2000, and during that year the site again became a source for CO2. The dataset illustrates the high variability of CO2 uptake associated with northern Great Basin ecosystems. This variability most likely results from the extreme inter-annual variation of precipitation and temperature that occurs in this ecosystem. These data suggest that this site is a sink for CO2 during average to wet years, but becomes a source during drought or after a disturbance such as a late frost.