Characterization of the biodiversity of ornamental flora in the urban perimeter of the city of Tlemcen (Northwest of Algeria) Fatima Bendiouis 1 , Rédda Aboura 1,* , Mustapha Ainad Tabet 1 & Fatiha Barka 1 1 Laboratory of Ecology and Management of Natural Ecosystems, BP119 Department of Ecology and Environment, Faculty of Sciences of Nature and Life, Earth and Universe Sciences, University of Tlemcen, 13000 Algeria *Corresponding author, email: aredda78@yahoo.fr Biodiversity Journal, 2022, 13 (1): 25–35 https://doi.org/10.31396/Biodiv.Jour.2022.13.1.25.35 The objective of this study was to analyze and characterize the biodiversity of the orna- mental flora in the urban perimeter of the region of Tlemcen (Northwest of Algeria) in the two public gardens chosen in the city of Tlemcen. By considering in this approach the var- ious statistical indices of plant biodiversity that will allow us a better knowledge of the eco- logical potential of the environment to shelter a wide range of taxa adapted to the ecological conditions of the biotope considered. The results obtained showed a large number of species from a floristic richness point of view, including 86 ornamental species recorded in the 1 er Juin garden (Grand Bassin) and 24 in the Boujlida garden. The biogeographical origin of the inventoried species at the level of the study stations revealed a considerable number of species of the non-Mediterranean type compared to the Mediterraneanone. The calculation of the different diversity indices confirms different outstanding representatives of the plant species within their taxonomic families. The Shannon index was the values obtained of 5.24 in the garden of 1 er Juin compared to those of Boujlida with 3.72, which determined more interesting representativeness of the abundance of the species counted within their respec- tive families in the first garden by contribution to the second. The Simpson index makes it possible to note greater representativeness of all the species within the Boujlida garden with a percentage of 50% compared to that of 1 er Juin, which was only of the order of 30%. Fi- nally, we can conclude that these two gardens offer an opportunity to develop the ornamental flora of the city of Tlemcen while trying to promote the introduction of native species for sustainable preservation to ensure the sustainability of these taxa. Tlemcen, garden; inventory; ornamental; taxonomy; biodiversity; preservation. Received 12.09.2021; accepted 30.12.2021; published online 22.02.2022 KEY WORDS ABSTRACT INTRODUCTION In urban areas, public green spaces constitute ecosystems that symbolize islets of nature and its plant and animal biodiversity represent an impor- tant pole for maintaining it (Clergeau, 1996); hence the social demand for nature in the city, which has become one of the fundamental ele- ments of a better quality of life in these environ- ments (Calenge, 1997; Mathieu, 2000). Therefore, the public garden becomes a key to the devel- opment of this area where it means “a naturalistic urban space, planted, landscaped and maintained by the community for the enjoyment of all” (Pui- boube, 1996). In fact, studies have shown that these public green spaces offer their users important ecosystem services including, air purification, climate regu- lation, moderation of extreme temperatures, and intellectual stimulation (Bolund & Hunhammar, 1999), but also and especially a positive impact on the sustainability of the urban landscape by im-