Spatial-temporal dynamics of islands in a sandy, braided river: the role of riparian vegetation

What is it about?

River Tiétar is a braided system on sandy substrate where vegetated islands are formed. Islands are formed along incised areas where willow seeds accumulate, germinate, and get established, and where moisture remains during summer. Willow seedlings increase the roughness, favoring accumulation of sand, and when this process is maintained in time, a vegetated island may arise. Island formation starts with the establishment of a single pioneer species (Salix salviifolia), and if the island resists subsequent floods, it continues with the colonization of other species (Fraxinus angustifolia, Celtis australis, Sambucus nigra) as part of an ecological succession.

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Why is it important?

Overall, intensive flow regulation is promoting woody vegetation coverage increase and exotic plant species invason, that are progressively destruying the braided structure of the river.