Montmorency Forest, France, June 2021
The planting campaign for 1,000 perennial trees on 1.15 ha in Montmorency Forest ended in February 2020. Over this area, 80% sessile oaks and 20% wild cherry trees have replaced the chestnut trees affected by ink disease.
Ink disease has been in the soil for centuries and is caused by two fungi – Phytophthora cambivora and Phytophthora cinnamomic – that are spread by water in the soil and cause necrosis of the chestnut tree roots. The leaves of the chestnut tree wilt and dry out, causing the branches to gradually die from top to bottom. Black spots then appear on the trunk and roots. Susceptible trees die quickly (one to five years) in the case of a serious attack.
This disease has developed in Ile-de-France over recent years due to climate change, leading to a lack of frosts in winter plus wet springs that have waterlogged the soil, thus providing ideal conditions for multiplication and movement of the ink in the soil.
This disease now affects all chestnut groves in north-western France and no treatment exists to eradicate it.
To limit its spread, and ensure Montmorency Forest remains safe for walkers, technicians from the French National Forest Office (Office National des Forêts, ONF) carry out sanitation cutting among the diseased chestnut trees, replacing them with species more resilient to climate change.
In June 2021, the A Tree for You team and a member of its scientific committee visited the plantation plots with Matthieu, ONF forestry technician, and Alban, ONF Sponsorship and Sponsorship Manager.
On the planted plots, the recovery rate (number of living trees one year after planting) is 84%, which is higher than the expected 80%. The protective fencing around each young plant has helped shield them from wild animals. They will be removed within 15 years, once the trees are big enough to no longer be vulnerable.
Plot 104 is located near Château de la Chasse. Since planting, a lot of vegetation and spontaneous companion species (trees growing naturally without being planted) have appeared on the plot, without disturbing the young plants.
Natural growth of ash, hornbeam, birch, willow, holly, and chestnut grow alongside the planted sessile oak and wild cherry tree species. For the chestnut trees, only natural growth from a chestnut tree is retained since it doesn’t seem to carry the disease. Other chestnut shoots, from the stumps of cut trees, will be removed since they do carry the disease.
On the ground, rich biodiversity is emerging, including several herbaceous plants such as hanging sedge (Carex pendula), eagle fern (Pteridium aquilinum), purple foxglove (Digitalis purpurea), bramble (Rubus sp. ), water pepperweed (Persicaria hydropiper), hemp-nettle (Eupatorium cannabinum), rushes (Juncus sp.), burdock (Arctium), common heather (Prunella vulgaris) and various small geraniums (especially Geranium robertianum).
The ONF and its technicians in the field are working daily to slow down health crises in French forests and protect public forests. Work groups are also exploring the species best suited for replanting in light of climate change. This is a long-term project whoseresults will only be visible in several years to come
To give you an idea, the A Tree for You team went to visit a plot planted over thirty years ago, where a first thinning opreation was carried out in 2018.
Vegetation and natural growth of other tree species are increasing in the cleared undergrowth.
Bringing hope to French forests!
Next steps on the planted plots: the first thinning operation will take place in the summer of 2021 to facilitate tree growth by removing unnecessary competition in the vicinity.
