Floods for riparian biodiversity in regulated rivers

In this project we aim to identify the magnitude and duration of floods needed to avoid invasion of terrestrial plant species into riparian zones in regulated rivers, helping to develop environmental flow measures with relevance for many regulated rivers in Sweden and world-wide.

The knowledge produced in this project will be used to discern the inundation duration needed to maintain riparian forests with deciduous hardwood trees along the regulated Dalälven river. This is done by performing (1) a laboratory experiment, (2) a field transplant experiment, and (3) a survey of tree seedling occurrence in relation to inundation duration. This information is used to (4) project the area of rehabilitated riparian forest along Dalälven in the Bredforsen reach at different magnitudes and frequencies of flow, based on a hydrological model of the reach. The project is divided into four work packages, leading to recommendations for how to implement flood pulses to maintain riparian forests of high natural values.

The four work packages are:

• Laboratory experiment assessing inundation tolerance of Norway spruce seedlings.
• Field experiment transplanting spruce seedlings to riparian zones varying in inundation duration and soil conditions.
• Distribution of tree seedlings in riparian zones in relation to inundation duration.
• Extent of riparian plant communities at different environmental-flow scenarios.