Changing riverine landscapes

1. The landscapes of large floodplain rivers are characterised by heterogeneous environments related to the interplay of flood flows, sediment transport and vegetation dynamics. 2. The large rivers of Europe, and probably most rivers throughout the forest biomes, were characterised by islands but over the period of major human interference, many have become dominated by incision and narrowing so that they are now characterised by single-thread and relatively simple channel forms. 3. Vegetation plays an active role in developing heterogeneous channel forms through (a) biotic processes such as seed dispersal, vegetative regeneration and succession and N abiotic effects such as increasing flow resistance inducing sedimentation, and decreasing bank erodibility. 4. In particular, accumulations of living driftwood (cf. dead driftwood accumulations and dispersed seedlings) accelerate sedimentation and island development. 5. River reaches with vegetated islands have a high habitat diversity. 6. The natural influences of flood disturbance, wood accumulation, vegetation growth, island development and tree die-off, cause island-dominated reaches to undergo cycles of island growth and decay that are related to cycles of aquatic habitat diversification and simplification.