IS THAT FOREST BREATHING: SOIL RESPIRATION ACROSS A GRADIENT OF DISTURBANCE SEVERITY AND FOREST DEVELOPMENT
Julia Yang1, Chris Gough2.
1University of Kansas, Lawrence, KS, 2Virginia Commonwealth University, Richmond, VA.
In the present era of global change, the release of carbon (C) from soils is a crucial determinant of the terrestrial C sink and thus atmospheric CO2 concentrations. Past disturbances and the stage of ecosystem development may affect current ecosystem function and impact future trajectories of ecological change; however, the extent to which historical disturbances affect present-day C cycling has not been quantified for most ecosystems. Our objectives were to 1) quantify soil respiration over the course of forest development, and 2) determine whether different disturbance histories, clear-cut harvesting only versus both clear-cut harvesting and burning, affect rates of soil respiration. Our research was conducted at the University of Michigan Biological Station within a chronosequence of clear cut and burn disturbance, a chronosequence of clear cut only disturbance, and three end-member stands of varying community compositions. We measured soil respiration over the course of five weeks using a LI-6400-09 CO2 flux chamber. We expect respiration to increase with forest age because plant biomass and organic matter pools are larger; respiration to be highest in the mixed deciduous conifer forest because plant biomass is greater than in the conifer dominated forest; and respiration to decrease with higher disturbance severity because biomass and organic matter pools are smaller. We expect this last disturbance effect will persist across all stages of stand development. A better understanding of how forest age and disturbance history interact will improve our knowledge of the terrestrial C cycle and will have significant implications for forest management strategies in the future.