In recent decades, conservation objectives have driven changes to the management of some pine forests in the southeastern United States. Forest thinning and frequent burning of old‐field and plantation pine forests have resulted in an open loblolly–shortleaf pine forest community which resembles the original longleaf pine forest. It is, however, unclear how the structure, composition, and function of the loblolly–shortleaf forest compare to natural longleaf pine forest, and whether it represents an alternative stable state, or simply a transitional state. Understanding the stability of open loblolly–shortleaf pine forest is critical, particularly because several threatened and endangered species are now reliant on it for habitat. The structure and composition of loblolly–shortleaf forest and natural longleaf pine forest were compared using data from permanent forest plots at Fort Benning, Georgia, USA. To assess the stability of the loblolly–shortleaf pine forest and determine whether it is an alternative stable or transitional state, the LANDIS‐II forest landscape simulation model was used to simulate changes in forest type cover under no disturbance, and a frequent‐fire regime at Fort Benning. Under both management scenarios, nearly all loblolly–shortleaf pine forest converted to mixed hardwood forest over the course of the simulation, with most conversion occurring within 60 yr. In contrast, longleaf pine forest cover increased under frequent fire. Several important structural and compositional differences may have contributed to the instability of loblolly–shortleaf pine forest compared to longleaf pine forest. These include, among other factors, higher densities of resprouting hardwood trees and shrubs in loblolly–shortleaf pine forest, including sweetgum, a resilient broadleaf species capable of transforming ecosystem structure. These results highlight the instability of the open loblolly–shortleaf pine forest community and confirm that is a transitional state, destined for mixed hardwood forest in the coming decades under either no disturbance or frequent fire alone. Future forest planning should consider an active transition from the loblolly–shortleaf pine forest in the coming decades if open pine forest is to be conserved for wildlife and conservation objectives.

Many public land management programs in the southeastern United States have been restoring the longleaf pine forest for more than 20 years, which includes intensive treatment with fire, thinning, chemical control of competition, and tree planting. A shift to more passive management (prescribed burning alone) is anticipated once a critical level of longleaf pine has been established. It remains unclear whether this longleaf pine threshold has been reached and whether intensive management should continue at Fort Benning, Georgia. Using the Landis-II forest landscape model, changes in tree species and forest types were estimated from 2017 to 2117 under four forest management scenarios, ranging from passive (“burn only”) to intensive (“proactive”). The desired future condition includes 75% of upland forest dominated by longleaf pine (>49.5% composition). The proactive scenario resulted in the desired future forest condition, whereas reactive and passive scenarios did not. These results suggest a critical threshold of longleaf pine forest has not been reached at Fort Benning and therefore intensive management approaches are still required. This study shows that even well-established populations of longleaf pine on public lands require maintenance and continued intensive restoration to reach desired forest-wide conditions. Study Implications: The study illustrates the use of a forest landscape model to examine the implications of multiple practical forest management scenarios. Despite over 20 years of intensive longleaf pine forest restoration across the study forest, proactive management approaches remain necessary to reach desired future forest conditions. A shift to passive management at this point is expected to result in significant areas with no longleaf pine and a substantial population of hardwood forest (representing a departure from desired conditions). The main findings can be extended to other forests in the region where restoration of upland longleaf pine forest is a primary objective.