title: Tracking postfire successional trajectories in a plant community adapted to high-severity fire.
abstract: In order to develop management strategies that maintain native biodiversity in plant communities adapted to high-severity fire, an understanding of natural postfire succession in the target ecosystem is essential. Detailed information on fire effects is lacking for the sand pine (Pinus clausa [Chapm. ex Engelm.] Vasey ex Sarg.) scrub of the southeastern United States, limiting our ability to decide how and when to apply prescribed fire in this ecosystem. We studied the effects of fire-severity heterogeneity on sand pine scrub following a 4700-ha wildfire in Florida's Juniper Prairie Wilderness Area (USA). We identified four levels of fire severity (unburned, low, moderate, and high) and three pre-burn stand conditions (sapling, mature, and senescent). Study plots were established in each severity-stand-class combination, and were sampled at one and two years following fire. Nonmetric multidimensional scaling (NMS) ordination was applied in order to identify differences in community composition and successional trajectories in each of the stand-class-fire-severity combinations. NMS analyses indicated a shift in dominance between the dominant understory oak species, from Quercus myrtifolia Willd. to Quercus geminata Small, as sand pine basal area increases. Our ordination and regression results showed that Q. myrtifolia was the most aggressive colonizer of postfire open space, which is an important structural and habitat component of a sand pine scrub. Successional trajectories were heavily influenced by Quercus myrtifolia Willd. and were more uniform in the mature class than in the senescent class, probably due to more consistent overstory basal area. In both mature and sapling stands, herbaceous species cover was highest in moderate-severity plots. Woody-debris load varied significantly with stand age, fire severity level, and time. Sand pine seedling recruitment was highest in mature stands burned at high severity, while sapling and senescent stands exhibited much lower sand pine seedling recruitment rates at all levels of fire severity. The observed differences in seedling recruitment are expected to influence the progressive development of vertical structure and composition in the sand pine forest, leading to community differences that will persist and influence the effects of subsequent disturbances.
authors.affiliation: School of Forest Resources and Conservation, University of Florida, 208 Newins-Zeigler Hall, Gainesville, Florida 32611, USA.
authors.forename: Johanna E
authors.initials: JE
authors.lastname: Freeman
authors.forename: Leda N
authors.initials: LN
authors.lastname: Kobziar
mesh_terms: D044822:Biodiversity; D005390:Fires; D010944:Plants / Q000145:classification*