Dead wood is being used in the Jufferbeek stream near Oldenzaal in an attempt to restore the natural structure in the stream to create a good living environment for typical stream fauna.
Additionally, the wood can help increase water storage capacity and elevate the excessively lowered stream bed.
Many recovery plans for streams achieve the intended geographic benefits but fail to generate the ecological benefits. Often they do not result in the recovery of the ecosystem of the stream because the variation in flow and habitat is still lacking.
The placement of dead wood in the Jufferbeek stream near Oldenzaal is an effort to address these issues by allowing ecological recovery and improving water storage. In the spring and summer of 2006, woody material in the form of branches and trunks was placed along a 300-metre stretch of the stream.
To document the changes in the stream, three locations were sampled between 2005 and 2007. A portion upstream of the placement, serving as a control, and the wood trace itself were sampled both before and shortly after the placement of the wood samples. Changes were seen in the composition of the soil, as well as a subtle shift in the composition of the macrofauna. These are small invertebrates such as slugs and mayflies that can be seen with the naked eye and which are a good indicator of water quality.
The common practice of removing of fallen trees, branches and accumulated dead foliage from streams to promote drainage is harmful to a stream ecosystem, because:
- It compromises the environment for organisms living in the stream
- The stream water flows away too fast
- The stream bed is lowered
- The banks dry out
In a natural stream:
- One-quarter of the streambed is covered with dead wood
- Fine organic material is deposited in the sheltered areas
- These areas form excellent breeding ground for stream fauna
- The natural obstacles create stream flow variations
- Leaves and branches are food for macrofauna
- Macrofauna are in turn food for fish
This shows that dead wood is a driving factor in the form, flow and ecology of a stream.
Analysis of the samples shows that the Jufferbeek macrofauna is characteristic of a lowland stream. At the same time, the presence of another group of species indicates an imbalance. The placement of the wood brought about subtle differences in the species composition, particularly to the benefit of certain grazers (slugs) and typical stream species such as the caddis.
A few negative indicators, such as worms with a preference for sludge and sand, are less prevalent in the wood trace. Most likely, the placement of the wood has created variations in flow (faster and slower-flowing areas), creating more varied environments for different types of stream organism. Further research with dead wood, on a larger scale and with a longer research period, is called for.
- Jufferbeek Recovery Report
- Landschap Overijssel (Overijssel Land Board)
- Ministry of Agriculture, Nature and Food Quality