Les facteurs déterminants des invasions végétales en friches industrielles urbaines et péri-urbaines wallonnes

Abstract

Industrial wastelands are disturbed habitats within a highly anthropized landscape, and yet they remain understudied. Environments that have been disturbed or regularly disturbed are particularly susceptible to plant invasions. In total, 1.411 floristic observations of invasive species were gathered from opportunistic geodatabases for all industrial wastelands catalogued in Charleroi, Liège and Mons’s urban areas. This survey sampled 479 plots of 20m², displaced in 9 sites in Charleroi and 9 sites in Liège, to record occurrence, cover, and density of 139 invasive species from Belgium and neighboring countries’s blacklist, alert list and monitoring list, and Europe’s monitoring list. The invasive species with the higher occurrence are Buddleja davidii (32,6% of invaded plots) Senecio inaequidens (15,9%), Robinia pseudoacacia (10,2%), species of the genus Œnothera (9,0%), and Fallopia japonica (7,7%). Communication routes density in a direct pressure radius (100m) influences positively sites’s species richness of invasives. For each of the most occurring species, landscape variables were tested on the occurrence with a “stepwise” type regression. Distance to the nearest stream influences negatively Buddleja davidii’s occurrence, showing an inverse exponential curve. Time since abandonment influences Œnothera’s occurrence, higher for wasteland abandoned for a period of 10 to 20 years. Time since abandonment influences also Robinia pseudoacacia’s occurrence, higher for wastelands abandoned for less than 10 years or more than 50 years. Most invaded ecotopes are “bare soils” ecotopes (of which 68,24% of plots are invaded). The most invaded substrate is gravel (of which 76,54% of plots are invaded).