Simulating Prescribed Fire Disturbance and Longleaf Pine Ecosystem Response

Abstract:

Longleaf pine forests of the southeastern United States depend on regular fire disturbance, currently managed in the form of prescribed fire. In order to safely administer current and future prescribed fire, land managers must consider how current conditions and management actions will drive ecosystem response in future decades. However, climate change is changing fire behavior and shifting how ecosystems respond to fire disturbance, creating large uncertainties regarding how longleaf pine ecosystems will respond to management actions. Mechanistic modeling based on the underlying physics of fire behavior and ecohydrologic response offers a means to understand fire-dependent ecosystem trajectory in climate perturbed conditions. We have developed a mechanistic disturbance and response model (DRM) that uses a physics-based approach to simulate fire behavior and hydrologic conditions that govern fuel moisture. Hydro-meteorological conditions including plant water availability and a spatially resolved canopy surface energy balance that simulates canopy microclimates provide the basis for fuel moisture, which is a first order control of fire behavior. Fire behavior and severity is then simulated by FIRETEC (a couple fire combustion and atmosphere model). The disturbance footprint, fuel consumption, and vegetation mortality is then mapped onto a longleaf pine ecosystem growth model (LLM) that 1) simulates the growth and competition of fire-dependent species setting up fuel loads for the next fire disturbance and 2) evaluates habitat suitability of species of concern based on forest structure. In this way a cycled fire disturbance and ecosystem response can be simulated. Here we demonstrate how the ecosystem trajectory differs between high prescribed fire severity versus low prescribed fire severity.