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United States Department of Agriculture

Agricultural Research Service

Title: Carbon Dioxide Flux, Biomass, and Radiometric Reflectance of Northern Great Plains Grasslands.

Authors
item Frank, Albert
item Karn, James

Submitted to: Journal of Range Management
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: September 25, 2002
Publication Date: July 1, 2003
Citation: FRANK, A.B., KARN, J.F. CARBON DIOXIDE FLUX, BIOMASS, AND RADIOMETRIC REFLECTANCE OF NORTHERN GREAT PLAINS GRASSLANDS. JOURNAL OF RANGE MANAGEMENT. 2003. v. 56(4). p. 382-387.

Interpretive Summary: Native grasslands sequester atmospheric carbon dioxide and store carbon in the soil. Methods for extending site specific carbon dioxide flux (carbon dioxide flux is a measure of carbon dioxide sequestration) measurements to a regional scale for determining the total amount of carbon dioxide sequestered by grasslands lacking. Objectives of this study were to evaluate the relationship between the normalized difference vegetation index (NDVI) calculated from spectral reflectance data obtained with hand held radiometers and carbon dioxide flux (carbon dioxide flux is a measure of carbon dioxide sequestration) calculated from Bowen ratio/energy balance measurements. Measurements of carbon dioxide flux were made during the plant growing season over a nongrazed prairie, grazed prairie, and a shrub dominated prairie site near Mandan, ND. Measurements were also made of evapotranspiration, green biomass, leaf area index. Correlations were highly significant between NDVI and carbon dioxide fluxes, evapotranspiration, green biomass, and leaf area index. Regression analysis showed a strong nonlinear relationship for NDVI vs. biomass (R2 0.83) and leaf are index (R2 0.77), and between NDVI and carbon dioxide flux (R2 0.51) and evapotranspiration (R2 0.81). The relationships between NDVI and carbon dioxide flux, evapotranspiration, biomass, and leaf area index for these three grassland sites that differed in management were generally quite similar suggesting that NDVI has good potential for use in predicting carbon dioxide sequestration for grasslands in the Northern Great Plains. Drought conditions in 1999 caused a slight disconnect between NDVI and carbon dioxide fluxes.

Technical Abstract: Native grasslands are a sink for atmospheric CO2 sequestration, but ways for extending site specific CO2 flux measurements to a regional scale are needed. Objectives of this study were to evaluate the relationship between the normalized difference vegetation index (NDVI) calculated from spectral reflectance data obtained with hand held radiometers and CO2 flux calculated from Bowen ratio/energy balance (BREB) measurements for assessing ecosystems CO2 fluxes for semiarid grasslands. Measurements of CO2 flux were made during the plant growing season over a nongrazed prairie, grazed prairie, and a shrub dominated prairie site near Mandan, ND. Measurements were also made of evapotranspiration (ET), green biomass, and green leaf area index (LAI). The NDVI was evaluated to determine the utility of using canopy radiometric reflectance for estimating CO2 fluxes. Correlation coefficients for NDVI with vegetation parameters of biomass and LAI for each site and year exceeded 0.84 in 1999, 0.74 in 2000, and 0.91 in 2001; with CO2 fluxes correlations exceeded 0.51 in 1999, 0.65 in 2000, and 0.67 in 2001; with ET correlations exceeded 0.69 in 1999, 0.76 in 2000, and 0.70 in 2001. Regression produced a nonlinear relation between NDVI and both biomass (R2 0.83) and LAI (R2 0.77) and a nearly linear relationship between NDVI and CO2 fluxes (R2 0.47) and ET (R2 0.55). The relationships between NDVI and biomass, CO2 flux, and ET for the three grassland sites which differed in management and vegetation were generally quite similar suggesting that NDVI has good potential for use in predicting canopy CO2 flux rates for the semiarid grasslands in the Northern Great Plains.

Last Modified: 7/25/2014
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