Floristic diversity, composition and invasibility of riparian habitats with Amorpha fruticosa: A case study from Belgrade (Southeast Europe)

Amorpha fruticosa L. represents one of the most dangerous invasive neophytes spreading quickly in many countries and cities of southeastern Europe where it aggressively penetrates into newly invaded sites and establishes permanently. It prefers moist and periodically flooded terrains, being therefore a serious threat for fragile wet habitats. Considering this, the main aim of this research was to determine the floristic diversity, composition and level of invasibility of urban and suburban riparian forests and open habitats with domination of A. fruticosa at the mouth of the Sava and Danube Rivers in Belgrade, and to assess the impact of all invasive neophytes in the analyzed habitats. Two hundred fifty seven (257) relevés, made according to Braun-Blanquet (1964) methodology, were subjected to different statistical analyses. The obtained results showed that urban wet habitats with domination of A. fruticosa were differentiated into 7 coenological groups, with the total of 222 registered taxa, out of which 29 (13.06%) were invasive neophytes. These coenoses are developed within willow and poplar habitats, wet lowland meadows and reedbed habitats. We found a direct negative correlation between the change in the number of species and the proportion of invasive species i.e. their coverage indexes in the analysed stands. The identified coenological group with domination of Rubus caesius and A. fruticosa represents the most dangerous hotspot of invasive species, which might seriously threaten native species and their urban riparian habitats, as well as similar habitats downstream.