Restoring Vegetation

After the hydrology in a peatland has been restored to a more suitable state, it is time to re-establish proper vegetation. The peatland vegetation provides the organic material to form peat and is thus an integral part of a healthy peatland. The peat-forming vegetation also lays the basis for all other mire-specific biodiversity and thus creates the basis for many of the ecosystem services provided by peatlands. Furthermore, the peatland vegetation increases water retention in the soil, soil humidity, air humidity, and slows down peat degradation.

If some remnants of peatland vegetation remain, rewetting of the area may be sufficient to allow for the vegetation to reestablish themselves. Bare surfaces, left after peat extraction, arable agriculture, or peatland fires, however, are difficult to revegetate. Peatland vegetation is unstable and relies on its own microclimate. Bare peatland vegetation is susceptible to frost, wind, and rain erosion. In this case, the application of lime, fertilizer, and a nurse crop to provide suitable conditions for revegetation with native species is required.

Peatland before (left, 2020) and after (right, 2023) restoration of vegetation in the North Pennines UK. (Pictures courtesy of Paul Leadbitter)

While some trees such as alder and willow can naturally occur in peatlands, in many cases the presence of trees is due to direct planting or invasion of trees as a result of drainage. As trees shade the lower vegetation, and increase evapotranspiration, tree and shrub removal can be an important step in peatland restoration. It is important to first address the cause of the invasion by trees (i.e. lowered water table) and then proceed to the removal of shrubs and trees. For more information on tree and shrub removal, see Thom et al. (2019).

Open water that is created after rewetting, due to height differences in peatlands used for peat extraction for example, can pose a problem for the reestablishment of peatland vegetation. If the peatland has a nutrient-rich character, this hurdle is overcome by fast growing species that quickly revegetate the open water. In nutrient poor peatlands however, wave action and lack of light hampers the revegetation of open water. In this case a framework for plant colonization such as brash or humified peat can be provided when reintroducing plants. Alternatively, wave action can be minimized by compartmentalizing the open water bodies. The best way to avoid open water that is difficult to recolonize however, is to gradually raise the water table over a long period, allowing for tussock vegetation to grow with the rising water table.