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The establishment of vegetation in riparian zones is dependent upon the availability of suitable habitat and the presence of viable propagules. Studies have shown that propagules are transported by rivers (hydrochory) and deposited in the riparian zone. However, there has been no detailed integrated study of fluvial propagule transport and deposition in relation to the hydrological regime and relative to other key dispersal mechanisms, such as wind dispersal (anemochory) and direct fall from local riparian vegetation. This paper presents the findings of a 1 year study of the hydrological controls on propagule input, transport and deposition in the riparian zone along two morphologically contrasting reaches of the River Frome (UK) and the potential importance of these processes for the riparian vegetation.

Analysis of samples, taken every 6 weeks, shows that aerial seed dispersal delivered relatively few propagules to the riparian zone and was highly spatially and temporally variable. The river transported and deposited large numbers of propagules of high diversity, including many species which were not present in the local vegetation, although this varied with river water levels and with season. Winter high flows were particularly important for depositing diverse propagules into the riparian zone along with local seed production during the summer. Despite contrasts in the planform and cross profile morphology of the two study reaches, they showed great similarity in patterns of propagule deposition, which were largely driven by the inundation regime, the elevation of the sampling site, and the season of sampling. Copyright (C) 2009 John Wiley & Sons, Ltd.