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Peat Bog Restoration - Part 2/3 - Sphagnum Peat Harvesting

Some Sphagnum peat bogs are forested while others are not. Depending upon its geological age, Sphagnum peat bogs may or may not have higher plants growing on their surface. Higher plants include Tamarack, Spruce and plants from the genera Ericacea (blueberry, cranberry, rhododendron, ...). In all cases, harvesting Sphagnum peat moss begins with diverting the water within the peat bog. This is done by digging a series of ditches within a section of the bog to channel the water and lower the water table. Maintaining the proper level of water in the bog is important, since introduction of air will accelerate the decomposition of the lower vegetative peat layers of the bog. Careful attention is necessary to maintain an optimum level of water for management of the peat, however enough water must be removed to allow equipment to operate on the bog surface without ‘sinking’.

Water management alone can take up to one year. Once the water table is lowered to a manageable level, equipment can enter the peat bog to prepare its surface. If present, trees are cut and used to make roadways within the bog, then large stumps and smaller vegetation are removed. In years past, the surface containing live Sphagnum moss was rototilled to loosen the surface and scraped off. Today, this layer is carefully removed for use at restoration sites. This live Sphagnum moss is harvested and used to propagate Sphagnum plants in peat bogs that are no longer harvested. (This will be further discussed in the third part of this series) Once the surface is rototilled to loosen the compacted layer, large tractors pull specialized harrows to comb the surface and ‘roll’ the loosened peat so sun and air can dry the Sphagnum peat moss.

Once dried to the optimal level, the blonde to light brown fibrous Sphagnum peat moss is harvested with large vacuum harvesters (Figure 1). This equipment drives across the bog surface drawing the dried Sphagnum peat moss into a large canister that holds approximately 1,800 ft3. It only takes 10 minutes for a harvester with a 25 foot-wide suction path to fill its canister. After filling, the harvester unloads the Sphagnum peat moss into large piles, which are later transported to the factory for screening, grading, quality monitoring and packaging.

Vacuum harvester

Figure 1: "Vaccum harvester"

 

The size and depth of a Sphagnum peat bog determines the number of years peat moss can be harvested. The upper layers of the peat bog possess blonde fibrous peat, which is the youngest peat, geologically speaking. As bog layers are harvested, the degree of decomposition and humification increases, as does the age of the Sphagnum peat moss. Older peats are darker in color and possess shorter fiber. Shallow bogs are harvested for up to 7-10 years. Some deep bogs may be in production for over 50 years. In most cases, the upper layers of fibrous peat moss are harvested for horticultural purposes leaving behind the short fiber, dark brown layers.  These peatlands are sometimes claimed for agriculture and forestry purposes. However, when local and regional biodiversity are desired, methods are used to restore peat bogs to functional ecosystems. These sites are restored to natural Sphagnum peat moss accumulation, indigenous plant material and wildlife.

Peat Bog Restauration - Part 3/3 - Sphagnum Peat Restoration

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