Christopher Lundberg - VSP | UCAR Visiting Scientist Programs

Figure 5: Mean (+ 1 s.e.) aboveground herbaceous standing crop of permanent study plotswithin treatment subunits (subunits 1-4) and a control marsh (C) following Phase I discharge.Bars with different letters indicate a Bonferroni-adjusted statistical differenceFour Mile Marsh provides an ideal setting for investigating carbon sequestration and greenhousegas dynamics. A nutrient gradient exists, with concentrations of nitrate, ammonium andphosphate decreasing with increasing distance from the effluent outfall (Hunter et al., 2009;Lundberg, 2008). The marsh has been divided into different subunits to investigate how variouswater management techniques, especially pulsing specific areas of the marsh, would affectseedling growth. For this project, a transect would be established within each subunit, includingthe hydrologically-isolated control subunit, for a total of five 700 m transects. A minimum offive study plots will be established along each transect to capture differences due to distancefrom effluent outfall. Each distance plot will have a 16 m 2 caged and uncaged plot. This willallow us to characterize the effect of herbivory on greenhouse gas fluxes and carbonsequestration.Plexiglas diffusion chambers measuring 0.284 m 3 with a surface area of .093 m 2 will befabricated after Faulkner et al. (1989). The top of each diffusion chamber will be constructedwith an open bottom and sampling port at the top closed with a rubber septum, through whichgases are collected using a syringe. To minimize the potential for out-fluxing of gases from thesoil due to walking and placing the bases on the marsh surface, permanent bases for chamberswill be installed prior to sample collection, and permanent boardwalks placed on the marshsurface will be used during sample collection. Chambers will be placed atop each permanentlyinstalled base. Air temperature, soil temperature and water depth will be recorded during eachsampling period. Three replicate chambers will be used at each transect-distance-herbivorytreatment plot. Samples will be analyzed for nitrous oxide, methane, and carbon dioxide. A