A review of hydrochory (seed dispersal by water) with implications for riparian rehabilitation

Working alongside natural regeneration processes is an important part of an ecosystem approach to long-term, self-sustaining, riparian rehabilitation. Hydrochory (seed dispersal by water) is a key influence on such rehabilitation and has received limited attention. This review of hydrochory suggests it is the relationships between hydrology, fluvial geomorphology and seed biology which determine seed deposition and germination. In-stream geomorphic and hydraulic diversity are important for both seed transport and seed retention in fluvial systems. Woody debris and flotsam are important for longdistance seed dispersal, especially for seeds without specialised floating phenology. Lateral connectivity between the channel and floodplains, as well as timing of seed release, for example with receding flood flows, influence whether seeds are transported to sites with favourable germination conditions. Not all hydrochory is desirable, such as the spread of invasive plant species in New Zealand. It is clear that much more attention should be given to hydrochory to better align riparian management with natural ecosystem processes and improve the longterm outcomes of riparian rehabilitation.