Natural Resources: Soil

The stewardship of water, soil, and air resources is a basic requirement for the national forest land management activities. Riparian (streamside) areas on the Daniel Boone National Forest are of importance to many wildlife, fish, and plant species. The Forest Service manages these areas to maintain streamside function, values and resources. In addition to the wildlife and plant species that thrive here, riparian areas are also essential for flood control, providing clean water and erosion control, and as a place for forest visitors to enjoy.

Soils
Currently about 90 different soils have been mapped and classified on the Forest and are included in
280 mapping unit delineations, representing one or more soils. The dominant kinds of soils on the Forest, their location and extent, can be described in such brief and general terms as: deep, fineloamy and fine-silty soils occurring on alluvial bottoms and terraces, on about four percent of the forest; moderately deep to deep, fine-loamy, coarse-loamy and loamy-skeletal soils occurring on gently sloping to steep side-slopes and deep, fine-loamy soils in coves, on about 73 percent of the forest; and moderately deep to deep fine-loamy, fine-silty, fine, and clayey textured residual soils appearing on ridgetops and upper ridge crests, on about 23 percent of the forest. Productivity, as related to tree growth, ranges from about 10 cubic feet/acre/year on shallow (<20 inches to bedrock), loamy-skeletal soils, usually in association with rock outcrops, to greater than 133 cubic feet/acre/year on deep (>40 inches to bedrock), well-drained soils found in flood  plains, terraces, benches, toe slopes and coves. Shallow soils comprise less than one percent of the Forest and occur as either minor soils in a mapping unit name or as inclusions described in the mapping unit description, but not included in the mapping unit name.

Soils forming from mixed alluvial materials (e.g., limestone, quartzose sandstone and shale and siltstone) on terraces and flood plains are predominately well-drained, fine-sandy loam, loam and silt loam soils with high moisture availability and moderate fertility. Less extensive soils are somewhat poorly drained or have a fragipan, which restricts root growth and permeability.

Riparian area soils, gravelly and cobbly loams, fine sandy loams, and sandy loams, developing from moderately coarse and coarse textured sediments, yield higher quality aquatic habitats (stable stream banks, clean, open-graded substrates, lower turbidities) than silt loam and loamy textured soils developing from silty alluvium (less stable stream banks, higher sediment yields, silty substrates, and increased turbidity). Soils in riparian areas generally exhibit distinct features that are influenced by flooding and/or a water table. Riparian soils will typically have free water (water table) available for plant use at some time during the growing season.

Soils on ridges are forming in weathered residuum from acid shale, siltstone, and sandstone, and to a limited extent, limestone, and carbonaceous shale and siltstone. They are mostly  moderately deep-todeep, well-drained, loam, silt loam, and silty clay loams with moderate fertility.

Soils on upland slopes are usually formed from colluvial materials of mixed mineralogy, derived from a variety of rock types. In cove positions, deep, well-drained silt loam and sandy loam soil have developed, offering highly productive growing sites. Soils on steep upper slopes range from moderately deep to shallow. They are well drained with the gravelly and channery silt loam and sandy loam textures commonly associated with rock outcrop. These soils generally have severe erosion potential from exposed or bare soil areas and a greater risk of slope failure.

Soils in midslope and toe or lower slope positions are usually deep, well-drained, gravelly silt loams. Those below prominent sandstone cliffs are usually sandy loams.

Soils on the forest east of the Highland Rim (the Eastern Karst Plain subsection, the Knobs and Cliff subsections to the north), with the exception of the broader river valleys, have basically 40 to 80 percent quartz with some mica in the sand and silt size fraction.

In the area of the Knobs subsection, soils have less than 60 percent quartz and mica minerals. Soils in the broad river bottoms along the Upper Cumberland and the Licking Rivers have sand and silt content comprised between 40 and 80 percent quartz.

Current Conditions Soil Erosion: Erosion caused an annual loss of more than 86 million tons of soil from Kentucky lands from 1992 to 1996, according to the 1997 National Resource Inventory (USDA NRCS 1997), making it the state’s most serious land management problem. Most people recognize, however, that well-managed forests are one of the most effective means of protecting watersheds.

Forests cover about one half of Kentucky’s 25 million acres. However, vegetation management activities statewide, and particularly on the DBNF, generate a relatively small percentage of the total sources of non-point source pollution. Sheet and rill erosion in forests is of minor consequence.

Channel and gulley erosion, though, is estimated to account for about two-thirds of the erosion and sediment yield problems in forested watersheds. Much of this is associated with roads. Most erosion and sediment yields originate from poorly maintained roads, many of which are not under Forest Service or other government jurisdiction, or from roads and skid roads associated with old logging operations on intermingled private property.

In contrast, the land use generating the greatest loss of soil within the state is mining. In the mountains of eastern Kentucky, nearly 38 million tons of soil was eroded from 5 million acres from 1992 to 1996, according to the 1997 National Resource Inventory (USDA NRCS 1997). Eighty-seven percent of this loss comes from about 158,000 acres, 60 percent of which was strip mined for coal.

The biggest factor contributing to the amount of soil loss by erosion is the amount of bare soil created by an activity. With exposure comes the potential for soil movement through and off the areas where the disturbance occurs. Other important factors in soil erosion include soil texture, organic matter, infiltration/permeability rates, and slope. The highest sediment yields occur during the larger rainfall events. Since about 80 percent of estimated annual runoff and peak flood events occur from December through May, soils are more susceptible to erosion during this period.

Slope disturbances produced by construction of roads, skid roads, and log landings, etc., can potentially initiate or accelerate existing soil mass movement by undercutting or loading a slope, or disrupting established drainage patterns. Internal soil strength and external  factors (e.g., root systems, ground water supplies, bedrock type) are important aspects of slope stability. Of particular concern are soils developing from shale’s of these following formations or formation members: Beattyville, Hartselle, Magoffin, Pennington, Nada-Cowbell, and Nancy. These shale’s weather to plastic clays, which increases the risk that soils will slump when subjected to a rapid rise in groundwater or concentrations of overland flow.

Slope stability on the Forest is of concern where soils are forming from soft incompetent shale’s on steep slopes. These readily weather to plastic clays that are sensitive to disturbance or disruption of the hydrologic balance (e.g., a rapid rise in ground water). In many areas on the forest, topographic, lithologic, or structural conditions are particularly susceptible to landslides and debris flows when disturbed by road construction/reconstruction or logging. Such incipient slope failures can exert a tremendous impact on soil and water resources and cause serious economic losses due to blocked streams, degraded water quality, and loss of soil productivity. Accordingly, those engaged in locating, designing, constructing and maintaining roads, planning timber sales, and mineral development, etc., should be aware of how slope and groundwater interact with various sensitive soils and geologic formations. Not all landslides can be prevented, but they can be controlled, thus minimizing adverse effects to soil productivity and the benefits, functions and values of riparian areas and wetlands as well as water quality and aquatic habitats.

Author: Soils Staff
Last Updated: March 31, 2005