Abstract
Non-native invasive plant species can influence ecosystem functioning over broad spatial scales, but most research on ecosystem impacts has focused on the plot level covering sampling units of only a few square meters or less. We used a multi-scale approach to analyze structural and leaf chemical vegetation traits depending on the presence of nonnative American black cherry (Prunus serotina) in a mixed deciduous forest at the plot level and at the forest stand level. Trait data were derived from remotely sensed maps of leaf area index (LAI), wood volume as well as canopy leaf nitrogen concentration (N-mass), phosphorous concentration (P-mass) and N:P ratio. Differences in these traits were compared between invaded and non-invaded areas at the plot level using 264 sampling units with a size of 25 m x 25 m and in 4119 forest management units (mean area: 7.6 +/- 5.1 ha). Observed patterns between invaded and non-invaded areas were similar at both spatial scales. Invaded areas were characterized by less wood volume, indicating that lower standing biomass promotes the occurrence of P. serotina. In contrast, LAI did not differ between invaded and non-invaded areas. Furthermore, the presence of P. serotina trees had an impact on the chemical composition of the forest canopy by decreasing leaf N:P. While for P-mass, we found no differences in between invaded and non-invaded areas, for N-mass we observed an invasion effect, though only at the plot level. Using remotely sensed trait data proved valuable to evaluate the spatial relevance of invasion impacts over large areas.