Forest inventory-based assessments of the invasion risk of Pseudotsuga menziesii (Mirb.) Franco and Quercus rubra L. in Germany

Abstract In Europe, some non-native tree species (NNT) are classified as invasive because they have spread into semi-natural habitats. Yet, available risk assessment protocols often based on a few limited case studies with unknown representativeness and uncertain data quality. This is particularly problematic when negative impacts of NNT confined to particular ecosystems or processes, whilst providing valuable ecosystem services elsewhere. Here, we filled this knowledge gap assessed invasion risks two controversially discussed in Germany ( Quercus rubra L., Pseudotsuga menziesii (Mirb.) Franco) for broad forest types using large scale inventory data. For purpose, establishment success natural regeneration was quantified terms cover height classes. The current extent protected habitats investigated south-west regional Establishment most successful at sites where the abundant canopy sufficient light understory. Natural both observed 0.3% total area understory competitively inferior species, there that Douglas fir red oak cause changes composition absence management interventions. installation buffer zones regular removal unwanted could minimize such areas. Our study showed inventories can provide comparing amongst types, regions jurisdictions. information be improved by recording abundance developmental stage widespread NNT, ecosystems.