Spatial Patterns of Frangula alnus (Rosales: Rhamnaceae): Implications for Invasive Plant Management

SIMPLE SUMMARY: Glossy buckthorn (Frangula alnus) (Rosales: Rhamnaceae) is an invasive shrub from Europe, threatening native vegetation in open and disturbed habitats. To determine the spatial distribution patterns of glossy buckthorn, the density and presence of F. alnus were recorded in 1412 transect sample points located on four sites in the Allegheny National Forest, Pennsylvania, USA. Geostatistical analyses were used to determine spatial autocorrelation among individual F. alnus samples and to measure their spatial dependency. Spatial patterns were examined using spatial analyses by distance indices (SADIE), and buffer analyses were conducted to determine the relationships between proximity to unpaved forest roads and both F. alnus density and presence. The results of this study showed that the density and presence of F. alnus decreased as the distance from the forest road increased. We also found a significant spatial aggregation of F. alnus in all four study sites. These findings imply that spatially targeted management of F. alnus would be possible by locating the patches of F. alnus and applying control measures only where needed. ABSTRACT: Glossy buckthorn (Frangula alnus) (Rosales: Rhamnaceae) is an invasive shrub from Europe that has been invading North America for over a century and threatening native vegetation in open and disturbed habitats. The treatment of F. alnus is currently restricted to the roadside, suggesting any individual F. alnus residing within the forest would be left unmanaged and would continue to spread in the area. This research was conducted to determine the spatial patterns and relationship of F. alnus with forest roads. The presence and density of F. alnus at 1412 sample points were recorded on four sites in the Allegheny National Forest, Pennsylvania, USA. Buffer analyses were conducted along roads to determine the relationship between F. alnus density and proximity to forest roads. Geostatistics and spatial analysis by distance indices (SADIE) were used to characterize the spatial pattern of F. alnus. Results of this study showed that F. alnus was spatially aggregated and resided beyond forest roads. Both the density and presence of F. alnus decreased as the distance from the forest road increased. These results imply the potential for precision management of F. alnus by locating and managing only where F. alnus presents.