Folisols

A Folisol from Calvert Island, Central Coast, BC. A thick accumulation of organic matter has formed over bedrock. (Photo Credit: Dr. Paul Sanborn, UNBC).
A Folisol from Calvert Island, Central Coast, BC. A thick accumulation of organic matter has formed over bedrock. (Photo Credit: Dr. Paul Sanborn, UNBC).

Since this website presents material focused on the forest floor of the west coast of Canada, it is important to mention a unique forest soil type, Folisol, which is commonly found in this region. Folisols are Organic soils that are not usually saturated with water for more than a few days. These soils consist of upland organic (folic) materials, generally of forest origin, that are either 40 cm or more in thickness, or are at least 10 cm thick if overlying bedrock or fragmental material (Soil Classification Working Group, 1998).

Folisols are classified within a great group of the Organic Soil order in the Canadian soil classification system. Deep Folisols (greater than 40 cm of folic material) occur frequently in cool, moist, and humid forest ecosystems, particularly on the west coast of Canada in the Coastal Western Hemlock Biogeoclimatic Subzone of British Columbia. Dominant tree species include western hemlock, western red cedar, and some amabilis fir. Folisols occur very rarely in other upland regions of Canada comprising a very minimal component of rare isolated occurrences within the soil polygon (Fox and Tarnocai, 2011).

Folisols are well to imperfectly drained, although they may become saturated after rainfall or snowmelt. They contain organic C at a level of >17% (about 30% or more organic matter) by weight in diagnostic horizons. According to the Classification Working Group (1998), folic materials qualify as Folisols if they meet the following criteria:

  1. Folic material is 40 cm or more in depth, or
  2. Folic material is 10 cm or more in depth if directly overlying a lithic contact, or fragmental material, or if occupying voids in fragmental or skeletal material, or
  3. Folic material is more than twice the thickness of a mineral soil layer if the mineral layer is less than 20 cm thick.

An important distinction of Folisols is that the L horizon is considered the parent material source made up of upland plant materials (Fox and Tarnocai, 2011).