Soil, Water, and Air Program

Soil Resources

Soil properties determine the types of ecosystems that can be supported and the suitability of the soil for selected land uses. The Soil, Water, and Air Program may initiate specific soil surveys to determine soil properties and suitability for a specific land use. In the United States, the National Cooperative Soil Survey program sets the standards for soil surveys. The Bureau of Land Management (BLM) is a cooperator in this program. To adequately support good management of lands and resources, an inventory and understanding of the resources are necessary. Currently, there are only four completed soil survey reports for BLM managed lands in Alaska.

Cover page for the Soil Survey of the Delta River Area, AlaskaOne is the very broad, reconnaissance type Exploratory Soil Survey of Alaska published in 1979. One is a planning level soil survey for part of the Seward Peninsula. Another, more detailed soil survey, is available for the Gulkana Wild and Scenic River corridor  (1999). In addition, the detailed survey of the Delta Wild and Scenic River Corridor  (2005) is now available on the internet.

The Delta and Gulkana surveys were initiated by BLM and conducted by the Natural Resources Conservation Service, the lead agency in the National Cooperative Soil Survey program. A lot more work on soils needs to be done before management responsibilities can be met with confidence. The soils program also deals with such things as project siting, erosion control and revegetation.

Photograph of a soil profile, from the top surface down through horizons and including some parent material (that is pedogenically unaltered and similar to that in which the soil formed). This soil is Kuslinad loamy; mixed, nonacid Histic Pergelic Cryaquept found in the Gulkana River Corridor.

This is a soil profile, from the top surface down through horizons, including some parent material (pedogenically unaltered and similar to that in which the soil formed). This soil is Kuslinad loamy-mixed, nonacid Histic Pergelic Cryaquept found in the Gulkana River Corridor.
(photograph courtesy of Mark Clark, Soil Scientist, NRCS)

Scientist standing on an esker during a field investigation of glacial lake outburst potential in the Taiya River watershed, Skagway, Alaska Anchorage Field Office. 2004
Standing on an esker (a long narrow ridge of sand
and gravel left from glacial meltwater) during a field
investigation of glacial lake outburst flood potential
in the Taiya River watershed, Skagway, Alaska.  
Anchorage Field Office, 2004. 

Welcome to the earths interface, the world of that natural body we call soils, formed from parent material (geologic matrix) as it is altered by the climate over time and influenced by topographic position and biological activity. Unique profiles develop during the action of soil forming processes.

The alteration of the fresh geological material starts at the exposed surface as a result of the integrated activity of the soil forming factors. With time the soil forming processes become active deeper and deeper below the surface. As these processes progress, the results of their actions are expressed in changes of appearance and other characteristics in horizontal layers from the surface down into the profile.

The soil profile then includes the surface down through the genetic horizons (horizontal layers), and into and including some unaltered parent material. Chemical and physical characteristics of soil profiles and their horizons are used for classifying the soils.

Additional material will eventually be added to this site. In the interim, to learn more about soils, please follow the accompanying links.


(Soil Formation)

Podzolization is a general term referring to those processes by which soils are depleted of metallic cations (alkaline materials), become acidic, and have developed leached (the removal of soluble or other constituents by percolating a liquid) surface layers and lower horizons (layers) of accumulation. Podzolization is fully active only where there is acid leaching from a surface layer of organic material. So there must be an accumulation of organic material above the mineral body (i.e., fresh inorganic, geologic material). This type of organic material accumulation occurs under timber in cool and humid regions.

Graphic of typical soil horizons including the Organic (O1,Oa), A, B,C, &R layers

Figure showing a hypothetical soil profile featuring all the soil horizons.
Where permafrost prevails, the soil solum is thin. Permafrost is the condition where material remains frozen throughout the year. The active layer above thaws during the warm season, which is where soil formation occurs. The rate of soil formation is slow at low temperatures and the active layer is cool even in the summer. Thus, the solum develops slowly.

The conifer needles and other organic debris reaching the mineral body surface are relatively low in metallic cation concentration and on decomposition, principally by fungi (microscopic plants), they give rise to acid products. As the acids generated in the organic layer are moved downward by percolating water into the mineral body below, the acids dissolve alkaline earth carbonates (lime such as calcite and dolomite) along with other soluble salts which then move downward in solution. Once carbonates have been removed from the upper part of the mineral body, the hydrogen ions of percolating acid waters replace many of the metallic cations on the cation exchange complex (positively charged cations can exchange for each other on the surface of negatively charged clay particles.). The metallic cations move downward in solution, and the upper part of the mineral body becomes acid. Under acid conditions, many iron and aluminum compounds are unstable; therefore, minerals containing these compounds break down. The iron and aluminum oxides are carried downward. Since quartz is fairly stable under acid conditions, it remains behind as a residue in the upper part of the mineral body. (During intermediate stages, quartz may form just a residual coating of mineral particles as the particles are weathering and losing iron, aluminum and other less resistant materials.) Thus, the upper layer of the mineral body becomes leached and is left in a
highly acid and siliceous state (i.e., high
amount of quartz and quartz-like materials).

The leached materials, colloidal organic materials, metallic cations, clays, and iron and aluminum oxides, accumulate at lower depths. Still deeper, there remains some unweathered, or only slightly altered, portions of the mineral body. At least four distinct layers have developed: (1) the mat of organic material overlying the mineral body; (2) the leached, acid and siliceous upper layer of the mineral body; (3) the zone of accumulation below the leached layer; and (4) the unweathered portion of the mineral body or the remaining parent material below the zone of accumulation. Soil morphologists have chosen to label each of these layers. The organic mat is called the "O horizon;" the leached layer is the "A horizon;" the zone of accumulation is the "B horizon;" and the remaining parent material is the "C horizon."

Back to Top