Restoring forests on poor sandy soils

Restoration Story by Silke Jacobs & Lisa Raats

When visiting the Dutch SUPERB demo area at the end of January, one could see a grayish dust cloud coming from a helicopter that was flying over the forests. The helicopter was covering the forest soil with rock dust: a much-needed measure in forests growing on dry sandy soils.

The forests in the Dutch demo area depend on very degraded sandy soils which are poor in nutrients, dry and have a low pH, meaning stronger acidity. This is not what the trees are hoping for in terms of environmental conditions. While walking around, one can notice that the trees, mostly Scots pine, are quite small both in height and diameter. They are longing for a healthy forest soil.

Within SUPERB, Bosgroep Zuid Nederland will implement measures to make the forests more vital and healthier. The aim is to treat approximately 60 hectares of forests owned by 16 private forest owners. It was a huge task to track these people and involve all of them in the project.

But after this hard work and conducting research, one of the restoration measures has finally started. The helicopter is thus spreading the rock dust in the area. Rock dust contains nutrients that the forest soil could use and gradually releases calcium, magnesium and potassium.

We had a great viewpoint to see the actual restoration activities being carried out by the helicopter. It was impressive to watch! The route flown by the helicopter can be visualized after the flight and we have been told that it is very accurate thanks to a skilled pilot.

The helicopter stayed in the air the whole time we watched it, except during a short break to refuel. It has also lowered so that a shovel could add the rock dust again to its basket for another flight spreading dust over the forest.

In the picture above you can see the big pile of rock dust that still needed to be spread. After flying a couple of hours, everything was gone and it’s time for the rock dust to do its work within the soil.

Alongside the use of rock dust, another implemented measure includes planting rich litter tree species in this area. The intention is for species such as hazel, lime and maple to gradually become more prominent contributors to the leaf composition in the litter layer. As these leaves decompose, they release nutrients into the soil, replenishing the system with essential elements over time. Additionally, this results in a more diverse forest in terms of species composition.

The experiences gained from both restoration actions and involving forest owners and other stakeholders can be valuable for future forest restoration projects, especially considering the prevalence of other degraded sandy forest soils in the Netherlands.