Local and landscape effects on the diversity of plant communities in Swedish beaver ponds

Abstract: The European beaver Castor fiber is considered an ecosystem engineer and a key species because of its dam building behavior. Little is known about the factors affecting plant diversity in beaver impounded streams. This study aimed to investigate if local and landscape variables affect plant diversity of beaver ponds. Plant inventories were performed in 12 different ponds in three different latitudinal regions and the vegetation data collected was compiled into groups according to Raunkiear life form and dispersal traits. Landscape variables related to the catchments of the beaver ponds were processed in a geographic information system (GIS). The total plant diversity in the beaver ponds could not be explained by landscape variables while diversity of water-associated terrestrial plants grouped together with aquatic plants did show correlations with landscape variables. The median richness was the same upstream as downstream for the total plant species. All other water-associated groups, however, had greater median richness downstream the beaver pond than upstream. This study concluded that landscape variables such as total stream length in the catchment, total number of lakes in the catchment and catchment size is correlated with the diversity of aquatic and water-associated terrestrial plants in beaver ponds. It was also concluded that streams and their riparian zones have lower median plant richness upstream than downstream a beaver pond.