Questions: What are the effects of fire on the relationships between community composition and environment? Does fire affect β-diversity and rates of species turnover along spatial and environmental gradients? Do these effects differ among functional groups?
Location: Linville Gorge, in the southern Appalachians of western North Carolina, USA.
Methods: We sampled all vascular plants in 20 plots (200 to 400 m2) before and after a wildfire. We used Non-metric Multidimensional Scaling to compare pre- and post-fire relationships between community composition and elevation, fire history, and topographic moisture. We compared Whittaker's βw and quantified rates of species turnover along geographic and environmental gradients for all plants, trees, shrubs, and herbs. Randomization tests were used to determine whether rates of species turnover changed after the fire.
Results: Correlations between community composition and environmental variables generally increased after fire. The largest increase was for elevation, reflecting its potential to influence fire severity. βw decreased only slightly and the only statistically significant change in species turnover rates occurred for herbs over geographic distance.
Conclusions: Large changes in community composition occurred after fire due to immigration of herbaceous species. Community-environment correlations increased but β-diversity did not change because fire effects and immigration were influenced by the same environmental gradients that structured vegetation pre-fire. Results differed for herbaceous species that responded to environmental but not spatial gradients post-fire. Dispersal limitation and community resilience through resprouting or regeneration from serotinous cones in dominant woody vegetation maintain β-diversity and species turnover after fire.
Nomenclature: Kartesz (1994).