Soil surface CO₂ flux is the second largest terrestrial ecosystem carbon flux.  As the demand for wood fiber increases, forest management activities may change soil C storage, as evidenced by soil surface CO₂ flux.  This study characterizes the differences in soil surface CO₂ flux following additions of forest canopy gaps simulating group selection harvests and mechanization within plots simulating ground disturbance following logging. The experiment was carried out in the Flambeau River State Forest, Rusk County, WI.  The study area (45^˚ 37’ 24.51” N, 90^˚ 47’ 7.72” W) is representative of the Great Lakes State forest region in age structure and composition.  Treatments were implemented in the winter of 2006-2007.  Tracked harvesters were used to create the canopy gaps. In the mechanization control treatment plots, the harvesters moved throughout a plot but did not cut the trees. Soil surface CO₂ flux was measured throughout growing seasons pre- and post-treatment. 

Results/Conclusions

Post-treatment soil respiration differed significantly among treatments with harvested gap plots having higher soil surface CO₂ fluxes especially during in the middle of the summer when water demands were great.  Soil surface CO₂ flux did not differ significantly between the control and mechanization treatment throughout the growing season.  Mean post-treatment soil surface CO₂ flux was 4.19 μmol m^-2 s^-1 for both mechanized and control plots but harvested gap plots had a mean flux of  4.54 μmol m^-2 s^-1 and had greater range of soil CO₂ fluxes. Soil moisture did differ significantly among treatment throughout the growing season (p<0.001) with gap plots having significantly greater soil moisture.  Soil surface CO₂ flux was positively correlated to soil moisture (p<0.001) and negatively correlated to the following (p<0.001): temperature at 2 and 10 cm, air temperature, and relative humidity.  The results of this study signify the importance of understanding the influence of overstory management on soil carbon storage and the subsequent soil surface CO₂ flux.