Mediterranean wetlands are currently subjected to habitat loss and degradation derived from pollution, climate change, eutrophication and the occurrence of exotic species as the most important threats, affecting numerous taxonomic groups. Different tools are being used to assess water quality conditions in these environments, including physicochemical measurements and biological indicators (fish, invertebrates, and diatoms). We aim to study the diversity and ecology of the diatom assemblage inhabiting the RAMSAR site Oubeïra Lake in northeastern Algeria, contributing to the catalogue of diatoms recorded for Algeria. The identification of the morphological characters allowed us to make an inventory of 18 genera of diatoms belonging to 13 families of diatoms. Navicula and Cymbella resulted in the most abundant genera in the two studied stations during February, June, and August over two years (2017, 2018). The diatom community is structured, with a diversity index (H) equal to ~2.30.

<p><strong>Background:</strong> Despite its ecological importance, the study of Algerian alder forests has been largely neglected, even though they represent the largest ones of their kind in North Africa. Moreover, few measures have been taken towards the protection of these ecosystems.</p><p><strong>Questions: </strong>How many species are present in the Algerian alder forests? What is the effect of soil properties on species richness and diversity of inventoried plants?  Is its spatial patterns a result of soil variables variation?</p><p><strong>Studied species: </strong>Polypodiopsida, Gymnospermae, and Angiospermae.</p><p><strong>Study site and dates:</strong> El-Kala Biosphere Reserve (KBR), El-Tarf province, northeastern Algeria, from January 2016 to February 2017.</p><p><strong>Methods:</strong> Twenty-eight localities were sampled using the relevé method. Soil samples were taken from three points at each site. The relationship between species richness and soil factors was statistically evaluated using multiple linear regression and multivariate statistical analysis.</p><p><strong>Results:</strong> The inventory showed a total of 352 species that belong to 236 genera and 89 families. According to NMDS results, black alder forests were classified into two groups (marshy and the hilly, and the fluvial forests), in relation to plant species richness. No linear relationships between species richness and soil parameters were observed, except for OM (<em>P</em> =  0.013).</p><p><strong>Conclusion:</strong> The present study allowed us to perform an inventory of plant species present in alder forests and to understand its distribution among different habitat types, as well as those factors that affect its zonation. For this ecosystem, our study revealed that vegetation diversity is related to the variation of soil variables.</p>

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