Peatland restoration

Restoration of Sphagnum-dominated peatlands

Since 1992, the Peatland Ecology Research Group, in collaboration with the Canadian Sphagnum Peat Moss Association, has developed a restoration method for Sphagnum-dominated peatlands where peat is extracted for horticultural substrate production: the Moss Layer Transfer Technique (MLTT). This method is now widely applied in North America, but also in South America, Japan, Australia and Europe.

Peatland Restoration Guide (Quinty and Rochefort 2003).

The restoration method has been revised in 2019 and 2020: Booklets of the revised method (Chapter 3).

Moss Layer Transfer Technique

The objective of the Moss Layer Transfer Technique is, in the short term, to re-establish a plant cover typical of Sphagnum-dominated peatlands, which will allow the restoration of the long-term peat accumulation function, the ability to sequester carbon.

The restoration method consists of 8 steps:

1 - Planning

1. Planning

Any restoration project must begin with careful planning, in order to describe the pre-restoration site conditions and the specific objectives of the restoration. It is at this stage that a restoration plan is developed, which details each of the operations to be carried out and the resources to be mobilized to do so.
Good planning also includes a comparison with the reference ecosystem.

2 - Site preparation

2. Site preparation

The peatland surface is reprofiled and undesirable pre-existing vegetation is removed. Particular attention is paid during this step to re-establish the ecohydrological connectivity of the peatland with its adjacent environment by restoring a natural gradient between the two environments.
This step is intended to improve the conditions for the establishment of plants that will be reintroduced later and to ensure an equal distribution of water.

3 - Plant harvesting

3. Plant harvesting

This step involves the harvesting of plant material from an intact peatland, called a donor site, in order to reintroduce it in the site to be restored. Using machinery, the top 10 cm of the moss layer is harvested. This contains seeds, rhizomes and diaspores of a multitude of species, especially Sphagnum mosses, the small non-vascular plants that are responsible for peat accumulation in bogs. Sphagnum communities of the subgenus Acutifolia, such as Sphagnum rubellum and S. fuscum are targeted. In natural peatlands, they form hummocks and are more drought resistant than depression species.

4 - Plant spreading

4. Plant spreading

The harvested plant material is spread evenly at a ratio of 1:10 over the bog to be restored, meaning that 1 m² of harvested vegetation is spread over 10 m² of the peatland to be restored.
This step must be carried out with great care since plant fragments are very sensitive to environmental conditions. Also, it is important to spread just the right amount of material: too thin a layer could compromise and slow down the establishment of a moss layer, while too thick a layer would prevent the plant fragments from accessing light and water.

5 - Mulching

5. Mulching

The addition of a straw mulch helps protect the mosses from wind and heat, and creates a microclimate that is favorable to their establishment. The effect is temporary as the straw decomposes after about four years. It should be noted that Sphagnum mosses have no root system and are therefore very sensitive to environmental conditions. Once established, however, they do not require mulch.

6 - Fertilization

6. Fertilization

The restored peatland is then fertilized, usually with a small dose of phosphate rock pellets, to favour the germination and establishment of companion plants for the Sphagnum. Polytrichum strictum, in particular, is one of the first plants to become established after disturbance in a peatland. It is said to be a "pioneer" plant. Polytrichum has pseudo-roots called rhizoids, which stabilize the peat. It is also considered a companion plant, since by reducing the impact of frost heaving, it favours the establishment of other plant species.

7 - Rewetting

7. Rewetting

After fertilization, we are finally ready to "rewet" the peatland. The return of typical water conditions (e.g., a stable, near-surface water table) is essential for the recovery of the Sphagnum carpet. Drainage channels, which had been dug during peat extraction activities, are therefore blocked with peat. Thus, water from precipitation can collect again in the peatland.

8 - Monitoring

8. Monitoring

Monitoring is essential to determine whether corrective measures need to be applied to the site and eventually whether the restoration is a success or a failure. In this regard, peatlands restored by the Canadian horticultural peat industry are unique research sites for researchers and students from universities across Canada. Various aspects of the return of ecosystem functions are studied from an ecological perspective, such as biodiversity, hydrology or carbon cycle.

Other restoration and rehabilitation options

Fen restoration

Where the residual peat is not characteristic of a Sphagnum-dominated peatlands, but rather a fen, restoration efforts should be made to restore a fen. It has been shown that the Moss Layer Transfer Technique is not directly applicable to fens and must be adapted. Its adaptation is currently the subject of several research projects at PERG.

Sphagnum farming

Sphagnum-dominated peatlands can also be used for Sphagnum cultivation, which aims to produce non decomposed Sphagnum fibres on a cyclical and renewable basis. The biomass produced can be used for various purposes, as a substitute for peat in horticultural substrates, as floral moss for orchid cultivation, as donor material for peatland restoration, etc. The cultivation of Sphagnum mosses and its optimization has been studied for a few years at the PERG.