The consequences of soil heating for prescribed fire use and fire restoration in the South
Soil heating resulting from prescribed burning in the southern region of the US (the South) has potential immediate and long-term impacts. Where fire is being restored to long-unburned sites, the duration and depth of soil heating may be substantial, affecting seed banks, soil carbon cycling, and root and rhizosphere systems. Where fire has been used frequently, effects on soil qualities are assumed benign, but this is not empirically proven. Current understanding of the relationships between fuels, prescribed burning, and soil heating is limited in southern pine ecosystems, even though the region burns a higher percentage of its forests than anywhere else in the US.
To fill this knowledge gap, we first propose to characterize the relationships among fuels, fire, and soil heating in two widespread forest types of the South: pine flatwoods and pine sandhills. Second, to quantify second-order effects with clear management implications for ecosystem sustainability, we will evaluate soil heating impacts on tree stress, seed banks, and soil respiration. Below-ground soil processes are integrated in soil respiration, which indicates the combined biological and physical consequences of soil heating, and is a critical component of ecosystem carbon budgets. Overstory tree retention and diverse understory vegetation are principal goals for restoration of these ecosystems, and are likely to be influenced by soil heating.
Finally, to ensure our science products are actionable, we will determine the conditions under which existing soil heating models adequately capture the relationship between reaction intensity and soil heating using a spatially explicit study design. Our methodology is derived from our previous JFSP research endeavors (JFSP 10-1-01-16 to Kobziar et al.; 11-3-1-21to Kobziar and Godwin; 01-1-3-11 to Hiers, Varner, et al.; 10-1-08-05 to Dugaw, Varner, et al.). We propose to meet the research needs identified in these previous studies by addressing the consequences of soil heating across contrasting soils and fuel conditions. Our three-tiered approach will enable us to provide recommendations to managers and answer the question, Under what conditions should fire managers in the South be concerned about soil heating, and why?