Do Landscape Structure and Socio-Economic Variables Explain the Solidago Invasion?

Abstract

Biological invasions are considered a major threat to biodiversity on a global scale. In this study, we examined the effect of landscape structure and socio-economic variables on the invasion pattern of alien Solidago species. Field data were collected in a set of 309 sampling plots, regularly placed on the intersecting lines of a 10 × 10-km grid, in south-western Poland (Silesia, Central Europe). Landscape characteristics and average values of socio-economic variables, such as human population density and total income per capita, were calculated. To examine the effect of landscape structure across different spatial extents, the landscape characteristics were analysed for three different buffers (radius: 500 m, 2 km and 5 km). A model explaining the pattern of the invasion was developed using a univariate, binary classification (decision) tree. The results show that both landscape structure and density of human population explain the spatial pattern of the invasion by alien Solidago species. The pattern was mostly shaped by the presence of unsuitable (forests) and suitable (roadsides) habitats for Solidago. The influence of percentage forest cover and road length was the strongest at the small spatial extent (radius = 500 m). The sum of linear elements length, percentage of urban areas and human population density calculated at the large extent (radius = 5 km) significantly improved the model. However, the predictive ability of these variables was less accurate. The model can be used by local authorities and land managers for modelling/predicting the hazards of invasion and elaborating a landscape-level system of Solidago control.