Restoration of forest ponds in the Pézarches forest

Did you know?

Forest ponds are home to a rich and important biodiversity such as amphibians, insects, odonates, and hydrophytic plants. Like all wetlands, they often disappear because the forest cover closes in, and the woody vegetation that grows along their banks eventually dries them out. However, ponds are also essential for a multitude of other species like game, birds, and rodents that need them to drink, bathe, reproduce and feed.
Maintaining forest ponds with water all year round, at least during the breeding season of the species that depend on them, is essential for the balance of life in forests. Forest ponds can be natural or man-made, and their water supply can vary from rainwater, run-off or groundwater, producing permanent or temporary ponds, which dry up in summer. They are partially sheltered from sunlight, and their aquatic vegetation is generally weak. As a result, they have low concentrations of dissolved oxygen resulting from photosynthesis, which leads to an accumulation of organic matter at the bottom of the pond. As the process of degradation of organic matter is limited by the low concentrations of dissolved oxygen, which reduces the activity of decomposer micro-organisms, the pond ends up being filled in by the accumulation of organic matter and the establishment of pioneer forest plant species if no action is taken.

€60,096

collected of €231,802

26%

Participate

Overview

Our work on this restoration project has several objectives:

Locate a larger water depth in the pond when it is filled.
Limit the lack of oxygenation of the pond by reducing the layer of organic matter, like mud, to promote the growth of other hydrophytes than water lentils.
Increase the areas of wet plant formations at the water and land interface.
Enhance the site's attractiveness for fauna dependent on wet environments, especially amphibians and dragonflies, by providing more favourable habitats for these fauna.
Preserve public access to avoid closing the educational trail.

We will carry out the following work:

Strip and restore the surface horizon on the west banks of the pond, which had mesohygrophilic to hygrophilic vegetation.
Create terraces on the west banks of the pond using an excavator to create gentler slopes.
Clean the pond with an excavator, removing the mud layer to a depth of about 40 to 60 cm, depending on the sector.
Deepen the pond in specific areas with an excavator to reach a depth of about 1.5 m over an area of about 10 m2.
Remobilize and replenish the restored surface horizon using a mechanical excavator on the softest reprofiled bank sectors.

Our actions

Hydraulic and biological diagnosis (study to define the work needed to restore the ecological functions of the ponds)

Restoration work (dredging, redefinition of banks, creation of hibernaculum)

Post-works biological monitoring (N+1, N+2, N+3, N+5). This monitoring is necessary to measure the impact of the work on the environment and to adapt our management if necessary.