The formation of peat moss

The process of forming peat moss, which takes place over centuries, consists in the accumulation and fossilization of vegetation debris in wetlands called peatlands. In Canada, these wetlands developed following the retreat of the last glaciers and are now between 5,000 and 10,000 years old.

Steps in peatland formation

The physical and chemical composition of peat depends on several factors such as the type of vegetation, the climate, the acidity of the water and the extent of diagenesis. Peat is comprised mostly of water and ash (80% to 90%) and of decomposed organic matter. Nature needs about a century to make peat moss five centimetres thick. Sphagnum growth rates can reach 2 to 12 centimetres per year, depending on peatland characteristics. However, since plant residues are decomposed and compacted as they accumulate, peat accumulation is limited to about 0.5 to 1 mm per year.

The different types of peat

In its natural state, peat is a light, spongy and fibrous substance whose colour varies from pale to dark brown and even to black according to its age and carbon content.

The younger the peat, the paler its shade and the lower its carbon content. Conversely, peat becomes darker as it ages, and its carbon content rises up to 60%. This is the reason it has been used as fuel for centuries in some countries, notably in Scotland and Ireland.

Pale blond peat

• Product of recent, incomplete decomposition of sphagnum.
• Fibrous and may hold water 700 times its volume.
• Once it has dried, it is hard to rehydrate.
• Poor in nutrients, but it can easily absorb those from a fertilizer.

Brown peat

• Product of intermediate decomposition.
• Ability to hold less water than blond peat.
• Poor in nutrients.

Black peat

• Product of more ancient decomposition.
• Constitutes an intermediate stage in the formation of coal.
• Pasty, it contains no fibre.
• High carbon content (> 60%) explains why it is used as fuel in some countries where wood is scarce.
• Is found in ombrotrophic peatlands (bog).

Diagenesis - The processes that transform sediment into solid rock.

Von Post Scale(H1 à H10) : Degree of decomposition: The closer peat approaches H10, the more decomposed it is.