The Consequences of Soil Heating for Prescribed Fire Use and Fire Restoration in the South

Project Description

Soil heating resulting from prescribed burning in the southern region of the United States (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 United States.

To fill this knowledge gap, we characterized 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 evaluated 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 determined the conditions under which existing soil heating models adequately capture the relationship between reaction intensity and soil heating using a spatially explicit study design.

We acknowledge support from the Joint Fire Science Program under Project 15-1-05-5.

Purpose and Scope

Current understanding of the relationships between fuels, prescribed burning, and soil heating is limited in southern pine ecosystems, even though the southeastern region burns a higher percentage of its forests than anywhere else in the United States.

To fill this knowledge gap, we characterized relationships among fuels, fire, and soil heating in two widespread forest types of the South: pine flatwoods and pine sandhills. We then evaluated the soil heating impacts on tree stress, seed banks, and soil respiration.

Methods

Our methodology is derived from these previous Joint Fire Science Program research endeavors:

• The Influence of Prescribed Fire and Understory Fuels Mastication on Soil Carbon Respiration Rates
• Characterization of Masticated Fuelbeds and Fuel Treatment Effectiveness in Southeastern U.S. Pine Ecosystems
• Duff Consumption and Southern Pine Mortality
• Development and Validation of a Moisture-Dependent Forest Floor Fire Behavior Model

Key Findings

There is no final report available for this projects.

Project Deliverables

• Spatial and temporal variability of forest floor duff characteristics in long-unburned Pinuspalustris forests (Canadian Journal of Forest Research)
• Toward a mechanism for eastern North American forest mesophication: Differential litter drying across 17 species (Ecological Applications)
• Pine cones facilitate ignition of forest floor duff (Canadian Journal of Forest Research)
• Utility of an instantaneous moisture meter for duff moisture prediction in long-unburned longleaf pine forests (Southern Journal of Applied Forestry)
• Towards a mechanism for eastern deciduous forest mesophication: the role of litter drying (Southern Journal of Applied Forestry)