Invasive exotic species (animals as well as plants, terrestrial species as well as aquatic species) are characterized by extensive spreading capacities causing environmental damage when introduced out of their natural distribution area. The spread of invasive species is believed to be the second largest cause of current biodiversity loss worldwide. Numerous research programs have already been developed in countries (e.g. the United States of America) extensively affected by this phenomenon. Scientific concern now focuses on Europe, more recently affected by invasions. In Belgium, few data describe the characteristics and the distribution of exotic invasive species and many questions concerning processes, dynamics and consequences remain unanswered. The aim: explaining invasive success: trait analysis of species and communities. A method will be developed in order to explain invasive success based on a combination of ecophysiological traits of invaders and invaded systems. This consists of the following steps : 1. considering a suit of observed exotics with varying invasive success, including unsuccessful ones, in order to cover a wide spectrum of invasiveness and invasibility (Senecio inaequidens, Heracleum mantegazzianum, Solidago gigantea, Fallopia japonica, Rosa rugosa, Impatiens glandulifera, Impatiens parviflora, Prunus serotina, Xanthium orientale, Lathyrus latifolius and Cerastium tomentosum), 2. quantifying the invasive success of these exotics either from historical biogeographic presence/absence records (expansion rates) or from field observations, 3. regressing invasive success simultaneously on one selected invader trait and one selected trait of the invaded system, and 4. repeating step 3 for all possible combinations of invader traits and invaded-system traits. The key traits will be identified and subsequently used for the early detection of problematic species and threatened/vulnerable habitats. Furthermore, the response of invaders to competition with indigenous species will be assessed on the field by seedling monitoring and nutrient uptake estimations.