Comparative studies on turbulent fluxes measured over burned and unburned sites of a sagebrush-dominated mountain

Abstract

Fire is a major disturbance that causes rangeland change. In this study, we compared the turbulent fluxes of carbon dioxide and sensible and latent heat, measured over burned and unburned sites of a sagebrush-dominated mountain in southern Idaho during the late summer of 2006. The outcome of the investigation shows that fire altered the horizontal components of turbulence intensity (iu and iv) as well as the partitioning of radiant energy between latent and sensible heat fluxes. Average daytime Bowen ratios (β) at the burned and unburned sites were 2.03 and 1.87. On the basis of Bowen ratios determined from eddy covariance measurements of sensible and latent heat fluxes, the sensible heat fluxes were relatively more significant at the burned site than at the unburned site most of the time, and the converse was true of the latent heat fluxes. The exception to this was for the few days following heavy rainfall, when near-surface soil moisture increased the evapotranspiration at the burned site more than at the unburned site until the shallow moisture supply was depleted. By means of ratios of CO2/(H+LE), fluxes, carbon sequestration was found to be more significant at the unburned site, declining at both sites as summer progressed but declining more rapidly at the burned site than at the unburned site. © 2012 John Wiley & Sons, Ltd.