Analogies between mineral sediment and vegetative particle dynamics in fluvial systems

The geomorphological significance of interactions between vegetative particles and fluvial processes is illustrated at different spatial scales. At the catchment scale, ribbons of mineral and vegetative particles are transferred downstream with inputs continuously supplied throughout the river's course. Individual particles experience phases of mobilisation, transport and deposition. As a result, along larger rivers, down-river changes are typically seen in the size and type of mineral sediment and vegetative particles, and also the species composition of the vegetative particles. Coupled with downstream changes in hydroclimatological conditions within a river's active zone, marked downstream changes in interactions between fluvial processes, vegetation propagules and landforms can result. At the patch scale individual vegetative particles (particularly aggregate particles) deposited on exposed riverine sediments create local hydraulic complexity that induces the scour and deposition of sediment and further plant propagules, resulting in a suite of distinctive landforms which may support many plant species. Within individual reaches, patch-scale interactions between mineral sediment and vegetative particles are moderated or sieved by the form of the reach and its flow patterns, so that the integration of patch-scale effects can support the development of different landforms in different locations.