Connecting profitable branches to banks downstream

Posted on June 4, 2011

Along with wind-borne transport, the carriage of seeds by flowing water plays a key role in the dispersal of streamside plants.  High stream flows entrain seeds into the river channel and deposit them on banks further downstream.  In the first integrated study of riparian seed dispersal, British ecologists used aerial funnels, drift nets and Astroturf deposition mats on stream banks to assess the relative importance of wind and water in seed transport. Samples were taken every six weeks for one year at two sites on the River Frome inDorset.  The abundance and diversity of seeds deposited on the mats were greatest in winter and spring, when most high flows occurred.  In contrast, wind dispersal and the direct deposition of falling seeds dominated during low-flow periods in summer.  High flows were important in delivering a wide variety of seeds from upstream, especially to the lower parts of the stream banks, but in summer local inputs were strongest and deposition was quite even over all parts of the bank.  Because the proportion of non-local species was larger in the stream samples than in the aerial samples (49% versus 31%), water transport seemed to be the most important mechanism in introducing new species to newly created or cleared areas of riverbank. 

Reference:  Moggridge, H.L. & Gurnell, A.M.  2010.   Hydrological controls on the transport and deposition of plant propagules within riparian zones.  River Research & Applications 26, 512–527.

Posted in: plants, riparian