In the winter of 2022-2023, the first measures will be taken in the ‘t Zand demo forest within the LIFE Climate Forest project.

‘t Zand is owned by the municipality of Alphen-Chaam. Bosgroep Zuid Nederland has been managing this area on behalf of the municipality for several years. It is a reclamation forest on former drifting dunes, with mainly pine species (Pinus sp.) as the most important tree species in the canopy.

It has been found that forests in these dry and poor growing areas are vulnerable to the effects of climate change. The aim of the measures within LIFE Climate Forest is to strengthen the forest against climate change and other disruptions by increasing resilience. This means that a forest can better tolerate climate change and is also better able to adapt to changing circumstances. In this forest in particular, work has been going on for some time on diversity and structure, especially by allowing specific deciduous trees to continue to grow from the understory in places. In ‘t Zand we can therefore show what can be achieved in the long term with climate-smart measures.

About 10 years ago, ‘t Zand switched to tree-oriented forest management with an approach that we called forest tracking. In this management, the quality and vitality of individual trees are central and decisions about management interventions are made on a site-by-site basis. The results of this are now becoming increasingly visible. ‘t Zand has a remarkably dense shrub layer with many buckthorn, oak and birch. The quality of the oaks in particular was a reason to switch from a group rejuvenation strategy to tree-oriented forest management in those places. Under the screen of pines, oaks and occasionally a birch were selected as future trees in combination with mature pines.

Restrained measures have been taken in selected oak trees by mainly providing light directly above the crown. In this way, the oak can form a larger crown and continue to grow, greatly improving its vitality against disturbances. At the same time, the upper canopy layer of Scots pine remains as intact as possible, so that it can absorb extreme weather conditions as a kind of screen and thus maintain the forest microclimate for the layers below.

Now that the trees have been able to continue to develop for a while, it is clearly visible that the forest is developing into a mixed deciduous forest.

In ‘t Zand there are also older oak trees growing throughout the area, which are given plenty of space to take up a place in the forest canopy. The forest area is slowly developing towards a mixed forest with lots of deciduous wood. To strengthen resilience, we will continue to focus on more tree species and deciduous trees.

This oak has been selected as a future tree and has been carefully released so that it can gain vitality and grow into the crown layer.

In this demo forest we mainly want to show the longer-term effects of forest tracking and gain more experience with this methodology. We also want to gain more control over spot-by-site rejuvenation through small-scale planting or natural rejuvenation. Important objectives here are to further strengthen mixing and increase the proportion of richer litter. With a greater mix of tree species, more seed sources are present in the forest and the forest is able to adapt more quickly to future disturbances. The aim of a larger proportion of rich litter species is to make nutrients more available on these poor sandy soils.

Bosgroep Zuid Nederland will therefore do forest tracking again, during which we will assess whether the previously selected oak trees need more light again. Furthermore, we identify new opportunities for planting and natural rejuvenation. Now that we are tracking forests again, we have already noticed that these are appearing.

The challenge is to dose management interventions so that the new generation can continue to grow and the structure is strengthened, while at the same time the screen and forest climate are maintained as much as possible. Location-wise, rejuvenation is also stimulated by tailor-made interventions in the forest canopy. An additional reason for preserving the old pines is that it is still unknown how quickly the new generation of oak and birch can also function as a cost center for management. We will closely monitor the elaboration of this strategy within this project, with monitoring focused on forest structure and the required management effort.

Another point of interest is the effect of light availability on the survival of the planting. We plant under the existing forest in small groups of a few trees up to groups of 25. We optimize the light availability for each planting site, and we not only necessarily intervene in the forest canopy above the planting. We also assess whether light can penetrate sufficiently laterally. Monitoring in the coming years will provide insight into the intended results and provide guidance for future management. All this to increase the resilience of a forest ecosystem on sandy soils.

This season we are busy with forest tracking and measured management interventions in the canopy layer. We will then assess in the coming growing season which species are best to plant in which planting locations, and whether additional interventions are needed to optimize the light climate. Planting will then follow in the winter of 2023-2024. From then on, we will monitor the development in ‘t Zand and demonstrate the effects of the management measures taken for knowledge sharing and knowledge dissemination.

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