Flora der Kleingewässer im Südwesten und Zentrum Luxemburgs

Standing waters play an important ecological role in open-land habitats due to their high species and structural diversity, the occurrence of highly adapted and oftentimes rare and/or endangered species as well as the ecosystem services they provide. SICONA has been creating ponds in the southwest and centre of Luxembourg for 35 years, primarily to create habitats for endangered amphibian species. Since 2019, a systematic floristic analysis of these ponds has been carried out to document the plant species composition. A total of 229 plant species were recorded, of which 158 are closely associated with aquatic ecosystems. Among these, 54 species are considered endangered and feature on Luxembourg’s Red List or Lower Risk List. Additionally, two new species records for Nitellopsis obtusa and Potamogeton gramineus were made for Luxembourg. Most water bodies harbour between 11 and 20 species, and species number was shown to be influenced by both size and age of the water body. Species number notably decreased in older ponds in comparison to younger ones, an effect that is likely due to the early presence and consequent replacement of pioneer species. In contrast, species number increased with water body size up to an area of roughly 500 m2, after which the increase gradually slows down until reaching a maximum. Finally, the effect of pond size on species richness was only significant in younger water bodies and no longer present in older ones, highlighting the importance of succession processes in aquatic biotopes. The results emphasise the great importance of standing waters as habitats for a diversity of plant species and highlight the need for targeted protection and conservation measures. We conclude that in future projects, greater attention should be paid to the creation of multiple smaller water bodies instead of fewer larger ones, as this offers greater structural diversity and thus provides more habitats for different species at a lower expense.