Fens

What is a fen?

Fens are peatlands with deep organic deposits and are influenced by slow, lateral water movement. Often referred to as “muskeg,” fens are the most extensive wetlands in the western boreal forest.

Ecological benefits

Known as the “green rivers: of the boreal, fens transport large volumes of water and nutrients across the landscape and help to regulate water flow
Fens help prevent downstream flooding by absorbing precipitation and run-off
Due to deep organic deposits, fens store large amounts of carbon and help moderate climate change
Provide important habitat for the threatened caribou

Types of fens

Treed fens: sparsely vegetated and stunted (<10 m) tamarack, sometimes mixed black spruce, shrubs, sedges and moss. Trees make up 25-60% of the surface area
Shrubby fens: sparse to medium density; short (<2m) shrubs (e.g. bog birch and willow) mixed with sedges and mosses. Shrubs dominate with >25% surface area
Graminoid (open) fens: dominated with sedges, mosses and hers (e.g. buckbean) often interspersed with open water.

Vegetation

Plant species reflect nutrient and moisture gradients
The plant communities of nutrient-poor fens more closely resemble those of bogs, while rich fens have more diverse and robust vegetation

Hydrology

Complex hydrology with surface, sub-surface and groundwater interactions
High water table (at slightly below the surface) with lateral water flow often connecting wetland systems vast distances

Soil

Deep peat deposits
Similar to bogs but with greater composition of sedge peat
Decomposition is slow due to the wet, cool, anoxic (oxygen-deprived) environment, resulting in the accumulation of deep organic deposits
Depending on water sources and nutrient availability, fens can be either nutrient rich or poor

Two distinct peat layers

Acrotem – living top layer (30-50cm)
Catotelm – lower, non-living layer

Types of wetlands

Canada’s wetlands can be broadly categorized into two types: organic and mineral.

Organic wetlands

Otherwise known as peatlands, these wetlands have an abundance of peat accumulation on which organic soils (excluding Folisols) are developed. These types of wetlands can include swamps, marshes, or shallow open-water wetlands.

Bogs

Bogs are peatlands that have deep deposits of poorly decomposed organic material (referred to as peat). They are elevated above the surrounding terrain and receive water and most nutrients from precipitation.

Fens

Fens are peatlands with deep organic deposits and are influenced by slow, lateral water movement. Often referred to as “muskeg,” fens are the most extensive wetlands in the western boreal forest.

Mineral wetlands

Mineral wetlands are found in locations where there is an excess of water on the surface and where there is little or no organic matter or peat due to geomorphic, hydrologic, biotic, edaphic (soil-related), or climatic causes. These wetlands are distinguished by gleysolic soils or peaty phases of these soils.

Fens

What is a fen?

Ecological benefits

Types of fens

Vegetation

Hydrology

Soil

Types of wetlands

Organic wetlands

Bogs

Fens

Mineral wetlands

Marshes

Swamps

Shallow open-water wetlands