Quantifying carbon and species dynamics under different fire regimes in a southeastern U.S. pineland

Abstract

Forests have a prominent role in carbon sequestration and storage. Climate change and anthropogenic forcing have altered the dominant characteristics of some forested ecosystems through changes to their disturbance regimes, particularly fire. Ecosystems that historically burned frequently, like pinelands in the southeastern United States, risk changes in their structure and function when the fire regime they require is altered. Although the carbon storage potential in an unburned southeastern U.S. forest would be larger, this scenario is unrealistic due to the likelihood of wildfire. Additionally, fire exclusion can have negative consequences on these forests health, biodiversity, and species endemism. There is a need, specifically for the southeast, to estimate carbon and species dynamics based on the differences between various fire regimes, and particularly the differences between prescribed fire and wildfire. These are important factors to consider given that prescribed fire is a common tool used in the southeast, and wildfires are ever more present. Field data from an experimental Pinus palustris (longleaf pine) forest of southwest Georgia were used to parametrize the forest landscape model LANDIS-II. The model simulated how carbon and species dynamics differ under a fire exclusion, a prescribed fire, and multiple wildfire scenarios. All scenarios except fire exclusion resulted in net emissions to the atmosphere, but prescribed fire produced the least carbon emissions from fire and maintained the most stable aboveground biomass compared to wildfire scenarios. Removing fire for approximately a century was necessary to obtain an average stand-level biomass greater than that of prescribed fire and net emissions less than that of prescribed fire. The prescribed fire scenario produced a longleaf pine-dominated forest, the exclusion scenario converted to predominantly oak species Quercus virginiana (live oak), Q. stellata (post oak), and Q. margaretta (sand post oak), while scenarios with intermediate wildfire regimes supported a mix of other fire-facilitator hardwoods and pine species, such as Q. incana (bluejack oak) and Pinus elliotti (slash pine). Overall, this study supports prescribed fire regimes in southeastern U.S. pinelands to both minimize carbon emissions and preserve native biodiversity.

Trade‐offs of forest management scenarios on forest carbon exchange and threatened and endangered species habitat

“…2). These results are similar to those of another study using LANDIS-II for a nearby landscape in Georgia, which suggested that prescribed fire promoted the existence of longleaf pine over hardwooddominated forests (Flanagan et al 2019). Because of the relatively minor influence of the treatments on NEE, this resulted in a strong shift on the trade-off curve toward thinning and burning being a significant benefit to TES habitat without significant influence on NEE (Fig.…”

“…Thinning and burning treatments had only minor influence under the warming scenario. Ultimately, prescribed thinning and burning provide societal services, such as supporting TES habitat or NEE under conditions of rising temperature and greater wildfire risk (Flanagan et al 2019). Below we discuss the sitespecific patterns, the role of stand entry treatments, and the impact of warming on these outcomes.…”

“…The relationship between forest management and habitat for TES species depends on many factors. Some TES species require undisturbed forests with relatively advanced stand structures (e.g., mimicking old-age forests); however, the creation of such stand structures relies on frequent low-intensity burning in some ecosystems such as in Southwestern or Southeastern US pine forests, and much less burning in the wet and cool forests of the Pacific Northwest (Flanagan et al 2019). Prior to land-use change and fireexclusion, high-frequency (years to decades), low-severity surface fires in Southwestern and Southeastern pine forests created structural heterogeneity that supported a range of conditions necessary for providing suitable habitat for TES species (Walters et al 2002, Ganey et al 2016).…”

Frequently burned loblolly–shortleaf pine forest in the southeastern United States lacks the stability of longleaf pine forest

“…A similar, recent modeling experiment utilizing LANDIS‐II showed an identical rapid (<50 yr) decline in longleaf pine and increase in hardwood dominance in the absence of fire (Flanagan et al. ). Frequent fire is not only critical to the maintenance of longleaf pine forest, but also critical to its proliferation over‐time (Brockway et al.…”

“…The clear instability and decline in longleaf pine forest under no disturbance highlight the importance of frequent fire for the maintenance of longleaf pine forest (Van Lear et al 2005). A similar, recent modeling experiment utilizing LANDIS-II showed an identical rapid (<50 yr) decline in longleaf pine and increase in hardwood dominance in the absence of fire (Flanagan et al 2019). Frequent fire is not only critical to the maintenance of longleaf pine forest, but also critical to its proliferation over-time (Brockway et al 2006).…”