W artykule przedstawiono charakterystykę nowego stanowiska Salvinia natans (L.) All. w Kotlinie Sandomierskiej. Znajduje się ono w dolinie niewielkiego cieku, gdzie bobry zbudowały kilka tam, doprowadzając do powstania rozlewiska. W latach obserwacji (2008–2009) roślina tworzyła duże zgrupowania o powierzchni od 300 m2 do 1500 m2. Ze względu na walory florystyczno-faunistyczne zaproponowano utworzenie na tym terenie użytku ekologicznego
The floating watermoss is an aquatic fern from the family of Salviniaceae. This fern is strictly protected as an endangered species and is included on the Red list of vascular plants of Poland with the assigned endangered category of V. The occurrence sites of Salvinia natans (L.) All. in the Sandomierz Basin are generally concentrated along the rivers Wisła and San, where the species is usually associated with an oxbow lake and ponds in the vallyes of these rivers. The new location of the floating watermoss was discovered in the mesoregion of the Lower Wisłoka Valley within the Sandomierz Basin. This location is situated in the Tuszyma Forest District, in ATPOL FF-41 grid. It is situated on a small watercourse where beavers are responsible for backwaters by building a cascade of dams. Four forest formations and an open adjacent area (65 ha) are inundated by this backwater. The largest number of places with floating watermoss were located in the largest beaver pond and in the old draining canal flooded due to beavers’ activity. The plant formed large patches (from 300 to 1500 m2) during the observation period (2008–2009) with cover-abundance of 100%. In the places with the most abundant occurrence of this species, 280–310 specimens were found over 1 m2 of water surface. The abundant occurrence of the floating watermoss in the beaver pond indicates that there are good conditions for the development of this species. Perhaps, this due to high eutrophic status of this reservoir, good direct sunlight, and wind protection by a wide zone of reeds. At the same time, the ephemeral nature of the beaver pond poses a threat to the existence of this site with the floating watermoss. Therefore, it is suggested that the site should be protected for floral and faunal reasons.