The Effect of Fire on Soil Respiration in Simulated Forests and Savannas of Northwest Georgia

Soil respiration is the second largest source of carbon flux in the global carbon cycle and a major influence on ecosystem productivity and climate change. Soil respiration is the process of carbon dioxide (CO2) evolution from soil due to metabolic processes of soil organisms including plants, microfauna, and microbes. Soil respiration rates are influenced by factors such as soil temperature, moisture, structure, and organic matter content which vary by ecosystem and are impacted by fire. Fire’s effect on soil depends on fire intensity and duration which are partly functions of fuel bed structure and composition. This study aims to investigate how fire influences soil respiration in two Georgia ecosystems, forests and savannas, that share fire as a natural disturbance, but differ in soil, microclimate, and fuel bed characteristics. We conducted two-way ANOVAs to compare soil respiration rates before and after fire in (1) forest and savanna soils and (2) forest soils with different fuel compositions. We hypothesize that low-intensity fire increases soil respiration by increasing nutrient availability to soil organisms but increasing fire intensity reduces soil respiration by killing soil organisms. We predict that fire will result in increased soil respiration rates in both ecosystems, but more so in savanna soils due to less pre-burn organic material. We also expect fuel beds burned with greater proportions of hardwood litter to reduce soil respiration rates due to slower rate of fire spread that increases soil temperatures. Soil type significantly affected respiration rate (