Correlations between vegetation layers during post-fire restoration in southwestern Oregon

In recent years, goals of post-fire restoration, especially on federal lands in the western United States, have changed from rapid tree regeneration to a combination of management goals that include forest regeneration, maintenance of species diversity, and retaining or accelerating late seral habitat characteristics. To meet these restoration goals, mixed species plantings with limited manual vegetation control is typically implemented after wildfires on federal lands in southwestern Oregon. We investigated how these restoration practices impacted relationships between three vegetation layers (bryophyte, herbaceous, and shrub). A Mantel test indicates weak but positive relationships (r=0.17 - 0.24, p<0.000) between bryophyte layer dissimilarities and herb and shrub layer dissimilarities. Herbaceous layer dissimilarities have positive and moderately strong correlations with shrub layer dissimilarities (r=0.5, p=0.0000). However, Nonmetric Multi-Dimensional Scaling demonstrated that, while communities of different layers align along a common gradient, the ordering of plots along the gradient is not consistent between layers. Our data suggest that this may be due to differential responses of the layers to restoration practices and environmental factors. As demonstrated by the correlations, the reduction of the shrub layer caused by manual vegetation control may impact lower vegetation layers. If the manual vegetation control is delaying the shrub succession, it may alter succession of the entire plant community. However, the plant community composition and environmental factors are likely to interact in determining the responses of different layers to restoration practices.