COLCHICUM SOBOLIFERUM, MARSILEA QUADRIFOLIA AND TRAPA NATANS VAR. NATANS IN THE DANUBE DELTA BIOSPHERE RESERVE

Rare plant species are more sensitive to anthropogenic disturbances, their effects causing a decrease in populations and the fragmentation of their habitats. Their unclear population structure often impedes conservation planning. The purpose of the study is to update the distribution and population size, identify habitat preferences, investigate limiting factors, and assess the current conservation status of three threatened taxa – Colchicum soboliferum, Marsilea quadrifolia, and Trapa natans var. natans from the Danube Delta Biosphere Reserve (DDBR). The study took place between 2019-2023. The study results showed that the taxa are rare in DDBR, and they have affinities to specific plant communities. C. soboliferum occurs frequently in Artemisio santonici-Juncetum maritimi and Agrostio maeoticae-Scirpoidetum holoschoeni subass. aperetosum maritimae, M. quadrifolia is mainly found in Typhetum angustifoliae and Artemisio santonici-Juncetum maritimi, while Trapa natans var. natans, is found in Trapo-Nymphoidetum association. The threats to the three species are overgrazing and soil compaction for C. soboliferum; water pollution, invasion of Elodea nuttallii and habitat change due to trampling for M. quadrifolia; wetland drainage, boating and silting for Trapa natans var. natans. Therefore, for all three species, changing the conservation status to endangered, protecting and restoring the actual habitats, and transplanting individuals to safer areas with similar habitats are part of the conservation plan within the DDBR area.