Modelling of floating seed dispersal in a fluvial environment

Riparian revegetation is an important component of river restoration. The success of restoration efforts may be affected by outside sources of propagules (e.g. seeds dispersed by water). Water can be an important transport vector for many native and alien riparian species. However, there is limited understanding of the dynamics of seed distribution in river systems. Accordingly, we have developed a semi-empirical model of seed dispersal by water, which predicts the parameters of the dispersal kernel. The model is based on aerial dispersal and hydrological approaches, with the core parameters as a function of flow velocity. Development and calibration of the model has been carried out in the Wingecarribee River and two of its tributaries, in the Southern Highlands of New South Wales, Australia, through releases of Helianthus annus (sunflower) achenes. The model, of skewed Gaussian form with stream flow and channel dimensions as core parameters, showed good overall fit to be observed (R 2 ranging from 0.61 to 0.98) for the main river and its tributaries. This model increases our fundamental understanding of seed dispersal along rivers and is a tool that can help predict seed dispersal of native and alien plant species along waterways.

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