Many of the accumulations of smooth stones on the Durance riverbank at Lauris are partially vegetated. Although the zoom shots are not clear enough to permit plant identification, it is clear that there are micro-habitats supporting different combinations of perennial and annual plants, each having distinct distribution patterns. These communities would seem to vary according to their relative position to the water level (and therefore frequency of submersion), and the size of the stones in the substrate.
Jessica's Nature Blog 