Spread of alien invasive plant species in Blekinge County, Sweden : Alien invasive plant species distance to buildings and preferences for different land use type

Abstract: Invasive species are a threat to biodiversity, economy and human health. The distribution and spread of invasive species needs to be studied to make good management plans. Invasive plant species mostly came to Sweden as ornamental plants and later spread into the local fauna. This study aimed to investigate if observations of invasive plant species were still mainly near residental gardens, and if they were observed in a specific land use type. The analysis was made on four different invasive species (L. polyphyllus, I. glandulifera, H. mantegazzianum and R. japonica) in Blekinge County, Sweden. Species observations were obtained from the Swedish Agricultural University’s (SLU) species database “artportalen” on SLU:s “artdatabanken”. ArcGIS was used to measure the distance between species observations and the nearest buildings and identify the land use type for each point. Randomized points within Blekinge County were used as a comparison. The result showed a statistically significant difference in distance between the observed- and randomized points for all four species. (L. polyphyllus observed mean distance 10.7 meters, randomized mean distance 46.7 meters. I. glandulifera observed mean distance 9.1 meters, randomized mean distance 47 meters. H. mantegazzianum observed mean distance 7.1 meters, randomized mean distance 44.5 meters. R. japonica observed mean distance 5.8 meters, randomized mean distance 46.8 meters.). There was also a statistically significant difference in land use type distribution between the invasive species and the randomized points. The most common land use type occupied by the invasive plants studied was open landscapes. This could also explain the proximity to buildings, since the species spread from gardens into open landscapes such as roadsides. It is also likely that soil that contained seeds and/or rhizomes was used in constructions, keeping the species close to buildings. In conclusion, it seems that invasive plant species are often found close to buildings and in open landscapes, which means observations and management should focus on these areas.