Subtle Transitions, Dramatic Differences

Transition Zones

These subtle transition zones have characteristics of both uplands and wetlands. Peatlands began forming thousands of years ago when the climate cooled and precipitation increased, and saturated soils and partially decayed organic material began accumulating to produce and establish peat.

As glaciers retreated, fine sand was deposited, creating a subtly rolling substrate underneath the vegetation. Peat began to accumulate at a rate of 1 millimeter every 10 years in saturated low areas filling in the rolling topography.

What is a Fen?

Fens are peatlands, saturated meadows with sedges, and other grasses as well as shrubs. Groundwater seeps down through mineral soil and flows at or near the ground surface and comes into contact with plant roots. The phosphorus is slightly acidic and depends on characteristics of the vegetation.

Discover the Unique Relationships between Vegetation, Topography, Hydrology, and Climate that Allow Peatlands to Develop

Fen Layers - 450

Fen Layers - Level 1 - Climate - 450cricle 1


Climate is usually defined as the weather conditions in an area over a long period of time. Climates change over time, usually the change is very slow. The Earth has experienced many different climates over its history. There are many different factors that cause climates to shift and change.

Fen Layers - Level 2 - Wetland Plants - 450cricle 2

Wetland Plants

Wetland plants are called hydrophytes or hydrophytic vegetation. The plants grow in water or on a substrate that is at least periodically deficient in oxygen as a result of excessive water content.

Fen Layers - Level 3 - Peat - 450cricle 3


Peat is partly decayed, moisture-absorbing plant material found in wetlands. The low levels of

oxygen and acidic environment prevent the degradation of the peat.

Fen Layers - Level 4 - Sand - 450cricle 4


Sand is small, loose, gritty particles of eroded or weathered rock, varying in size from one to two millimeters in diameter.

Fen Layers - Level 5 - Groundwater - 450cricle 5


Groundwater is water that exists underground in saturated zones beneath the land surface.

The upper surface of the saturated zone is called the water table.