Submitted to: First Interagency Conference on Research in the Watersheds
Publication Type: Proceedings
Publication Acceptance Date: 8/20/2003
Publication Date: 9/15/2003
Citation: Holifield, C.D., Emmerich, W.E., Moran, M.S., Bryant, R., Verdugo, C.L. 2003. Estimating regional daytime net carbon dioxide flux using remotely sensed instantaneous measurements. Proceedings First Interagency Conference on Research in the Watersheds. Oct. 27-30, 2003, Benson, AZ., pp. 517-521. Interpretive Summary: Atmospheric carbon dioxide (CO2) is steadily increasing as a result of the world=s increasing use of fossil fuels and wood biomass. However, the impact of increases in CO2 on the global carbon cycle is unclear. Semiarid grasslands comprise a large portion of the world=s rangeland ecosystem and may play a significant role in the carbon cycle. Many of the studies being conducted around the world to understand the role of grasslands in the carbon cycle are performed on the small scale of a few hundred meters. However, larger, regional scale measurements are needed for examining the global carbon cycle. Remote sensing has the potential to provide these measurements. Regional estimates of point in time net CO2 flux can be obtained from the Water Deficit Index (WDI),derived from Landsat satellite imagery. In this study, point in time estimates of net CO2 flux were converted to daytime estimates (6 a.m. to 6 p.m.). The study showed that it was possible to obtain reasonable large-scale estimates of daytime net CO2 flux for semiarid grasslands in southeastern Arizona, and illustrates the potential of this tool in determining the role played by semiarid grasslands in the carbon cycle.
Technical Abstract: Atmospheric carbon dioxide (CO2) is steadily increasing as a result of the world=s increasing use of fossil fuels and wood biomass. However, the impact of increases in CO2 on the global carbon cycle is unclear. Semiarid grasslands comprise a large portion of the world's rangeland ecosystem and may play a significant role in the carbon cycle. In a previous study, regional estimates of instantaneous net CO2 flux were obtained by using a Water Deficit Index (WDI) derived from satellite imagery over a five-year period (1996-2000) covering a grassland site in the Walnut Gulch Experimental Watershed (WGEW). In this study, a linear relationship (R2 = 0.95) was found to exist between instantaneous and daytime net CO2 flux estimates, where daytime is the period from 6 a.m. to 6 p.m. This linear relationship was used to convert instantaneous estimates of net CO2 flux to daytime estimates, and maps depicting spatially distributed daytime net CO2 flux were generated for WGEW. Remote sensing offers a viable means of obtaining regional estimates of daytime net CO2 flux in semiarid grasslands.