Modelling long-distance floating seed dispersal in salt marsh tidal channels

Seed dispersal is a primary factor influencing plant community development in salt-marshes. However, studies on seed dispersal in marsh-channel system are relatively scarce, and relevant mathematical modelling is particularly lacking. In this study, we developed a one-dimensional advection-dispersion model to explore the patterns of long-distance floating seed dispersal in tidal channels. Oscillatory tidal current velocity and water depth were assumed to represent the tidal effects. An exponential decay coefficient was introduced to account for the loss of floating seeds due to water-logged deposition and retention by trapping agents along the channel banks. An analytical solution in integral form was derived using the method of Green's function. The developed model was applied to simulate floating Spartina densiflora seed dispersal in a real tidal channel. Seed floating duration and seed collection data reported in the literature were used for model calibration and validation. The leptokurtic seed dispersal kernel in the marsh-channel system was quantified for the first time using the predicted spatio-temporal distribution of deposited and retained seeds. The range of the long-distance floating seed dispersal and its distribution concentration that have important implications for salt marsh protection and restoration activities were evaluated through statistical parameters such as the centroid displacement and the variance of the floating seed cloud and floating seed concentration contours. The developed model provides a useful tool for ecological management of tidal marshes, as data on the long-distance floating seed dispersal are rarely available and hard to gather.