Soil Resources Management
Soil conservation practices will be an integral part of all resource management actions and park developments. The following discussion gives guidance for soil conservation under a variety of situations that commonly occur in parks.
Soil properties influence natural and cultural resources and the physical infrastructure within parks. Therefore, a systematic inventory of soil resources facilitates effective management within each park. The NPS supports efficient inventories based upon National Cooperative Soil Survey standard terminology and techniques. (For more information about the National Cooperative Soil Survey, see Sources of Consultation, below. For a copy of the memorandum of understanding that governs soil surveys on NPS lands, see Exhibit 1, below).
Soil surveys provide an orderly, on-the-ground, scientific inventory of soil resources that includes maps showing the locations and extent of soils, data about the physical and chemical properties of those soils, and information derived from those data about potentialities and problems of use on each kind of soil in sufficient detail for park managers, planners, engineers, and scientists to apply to specific land areas of concern. Soil surveys provide the basic information needed to manage soil sustainability, and to protect water quality, wetlands, vegetation communities, and wildlife habitat. Soil surveys are the basis for predicting the behavior of a soil under alternative uses, and a soil’s potential erosion hazard, potential for groundwater contamination, and suitability and productivity for native vegetation, horticultural plants, and cultivated crops.
Prior to undertaking a soil survey, previous soil surveys for the park, if available, should be evaluated. If previous work is found inadequate for current needs, a project description is prepared. In it, existing maps of topography, geology, geomorphology, vegetation, and land use are also referenced. Because soil patterns are so intimately connected to these other themes, these maps can save much time toward the completion of the soil survey. Soil mapping scale and intensity of mapping should also be considered. When a park arranges to obtain a soil survey as a client of another agency, institution, or contractor, the park should clarify that all work is to be done in compliance with National Cooperative Soil Survey standards (For information on how to obtain existing soil surveys, or for assistance in initiating one, see Sources of Consultation, below).
A baseline soil survey (Order 3 for most applications) is one of the inventories funded through the NPS Servicewide Inventory and Monitoring Program. Parks may want to consult with the Inventory and Monitoring Program Manager about the availability of funding for their survey.
When a soil survey is conducted, the information is gathered through examination of soil profiles in the field followed by laboratory analysis of samples obtained from the profiles. Digging soil pits for description and sampling is a form of ground disturbance that requires compliance with the National Environmental Policy Act (NEPA) and the National Historic Preservation Act (NHPA). In most cases, NEPA compliance does not limit the work because the affected areas are so small. However, in areas with significant cultural resources, such as archeological sites, the NHPA consultation process may result in an NPS decision to limit digging in order to protect significant cultural resources. Near sensitive sites, working with a knowledgeable archeologist decreases the likelihood of loss, and the collaboration may yield additional insights about both cultural and soil resources in the area.
Two common problems in parks are soil compaction and soil erosion. Some soils are more susceptible to compaction and erosion than others. A soil survey in sufficient detail can provide the park with the information needed to select sites least susceptible to these types of problems. Soil surveys can be designed also with guidance on what steps may be needed to protect selected sites from compaction and erosion, or to restore sites degraded by past activities. How the soil survey is to be used needs to be included in the soil survey project specifications. A soil survey should be tailored to park information and management needs.
Facilities throughout a park can be better designed, built, and maintained with the appropriate soils information at hand. This information will assist managers with proper location and construction of the facilities, thus avoiding problems that would be expensive or impossible to correct. Park infrastructure, including buildings, bridges, and roads, may be vulnerable to damage associated with soil-related processes and must be designed accordingly. Some soils have inherent limitations that preclude facilities from properly functioning. Proper design and location of a sewage drain field is an excellent example of a facility requiring soils information.
Soil properties are intimately related to other ecological components, such as vegetation type and habitat, and affect or are related to historic resources and current park development efforts, thereby influencing many park activities. Proper landscape management, whether in natural, historic, or cultural areas, requires accurate soils information to meet the ecological requirements of plants.
Soil erosion will be maintained near natural levels to preclude both onsite degradation and off-site impacts resulting from sedimentation. A qualified soil scientist, agronomist, or geologist can estimate natural erosion levels using appropriate criteria.
As a rule of thumb, no human action should increase cumulative soil loss beyond the soil loss tolerance value for each soil in the NPS unit soil survey, and the maximum acceptable rate of erosion should not exceed the rate of soil formation over the long term. The most sensitive soils tend to be those that are shallow, and those in chemically limiting, cold, or dry environments.
In general, the potential to yield off-site sediment tends to be positively correlated with the depth of soil (sediment availability), soil texture (transportability), and the transport energy (wind, water, gravity) at a given site. These factors can be taken into account to estimate an erosion potential at a given site, in conjunction with other important factors, such as vegetation cover and disturbances such as plowing or fire.
Potential adverse off-site impacts of sediment upon other resources can be managed as necessary. Examples of measures appropriate for erosion control are the use of vegetative cover at Civil War earthworks, trail maintenance and fire line rehabilitation, watershed erosion-proofing and restoration, and crop rotations on agricultural lands.
"Erosion" refers to a broad class of processes, several of which go beyond the normal scope of soil science. Mass erosion is often addressed by specialists other than soil scientists, especially if mass erosional events are deep-seated. Some examples of mass erosion include landslides, earthflows, debris slides, debris flows, and debris torrents. A person with the specialized expertise to understand and manage these types of events may have a title such as engineering geologist, geotechnical engineer, or watershed restoration specialist. "Soil" most often refers to primarily the upper part of unconsolidated material covering the earth's surface, and it is this upper part that is mapped in soil surveys and best known by soil scientists. (See sections on Geologic Resource Management and Disturbed Lands Restoration in this Reference Manual).
Effective soil management practices will be followed to ensure protection of the soil resource. Baseline and follow-up monitoring help ensure that human actions are not adversely affecting terrestrial ecosystems through increased compaction, erosion, deposition, or other processes. Soil management in a park's natural areas cannot be relegated to a "non-management" status since human actions in developed areas may affect the resource within the natural area through accelerated runoff and erosion rates, lack of vegetative cover, land use patterns, etc. Therefore, an inventory of the soil resources in all park natural areas should be conducted, followed by monitoring at an appropriate frequency. The soil survey can be used to identify those areas of the park where soils are susceptible to erosion or other disturbance. Wetlands, highly erodible, or other sensitive soils that are easily damaged by human activity can receive special focus in a monitoring program. If adverse impacts are found, appropriate soil management practices can be put in place, which may include limiting public access to sensitive areas. A qualified soil scientist can be enlisted to ensure that appropriate soil management practices are used.
In cultural landscapes, an active soil management program helps ensure that the horticultural requirements of the landscape plantings are met, and that adverse impacts of human activity upon landscape plants and soils are minimized. The increased visitation often associated with cultural landscapes can lead to soil compaction and subsequent plant stress. Plant stress in compacted areas results from increased mechanical impedance to root penetration through the soil matrix, reduction in soil oxygen available for root respiration and growth, and lack of nutrient uptake. These plants are then subject to a host of other problems, such as disease, dieback, and insect infestations.
In areas of heavy visitation, soil management may require reduction or amelioration of soil compaction. Another part of the solution may be to confine traffic to specific paths hardened for heavy use. A qualified soil scientist can provide expertise on what actions to take to solve soil compaction problems. (See Sources of Consultation, below).
Several cultivation practices have been developed that can help conserve soil stability and fertility in a park setting. Alternative soil conservation techniques such as crop selection, crop rotation, minimum tillage, grassed waterways, mulching, contour farming, strip farming, terracing, and the use of various soil amendments can be weighed when designing a land use plan for a park's historic district where the interpretive program calls for using agricultural tillage practices. Appendix 7 of DO/RM 53 Special Park Uses provides further guidance on this topic.
Occasionally a manager may find it necessary to import soil into the park from an outside source. Erosion repair, site restoration, and road or building construction are examples where this need might occur. Soil should be imported only as a last resort. Seemingly subtle differences in soil physical and chemical characteristics often lead to profound differences in what natural vegetation develops. Soil is a natural "seed bank" of organisms. Viable seed, arthropods, fungi, and bacteria will almost inevitably be transported along with any soil that is brought into or moved around within a park. Thus, soil importation can introduce nonnative species and new cultivars or races, altering the gene pool in a park.
There are several options when importation of soil is necessary and unavoidable. One option is to have the soil sterilized to destroy seeds and any plant disease organisms and arthropods that might be contained in it. Obviously, this would be a prohibitively expensive option for large-scale projects. Care should be taken in making this decision based on the intended use of the soil. If the soil is going to be used for development (i.e., road fill, building site material), then soil sterilization may be a viable option. However, if the soil is to be used for natural habitat restoration, soil sterilization may not be a beneficial action. Sterilization, while removing harmful organisms from soil, may also destroy beneficial and sometimes essential soil organisms.
Other actions include approximating imported soil properties to key native soil properties such as texture, color, structure, clay type, organic matter and nitrogen content, and pH. Selecting a soil source in a similar setting from as close to the park as possible will help ensure that soil properties are similar. At a minimum, in order to collect appropriate soil, the collection site should be matched to the target site in terms of its surface and subsurface texture, parent material, basic landform type and position, and the target site’s existing or former natural vegetation. It is therefore recommended that use of local sources of soil be a selection factor in contracting specifications, especially when the contract is written by other agencies such as the Federal Highway Administration and state highway departments. Sources of the proposed soil need to be inspected in advance to ensure adequacy of the soil and freedom from nonnative plants and nonnative arthropods.
No hazardous materials contamination should be present in soil imported into parks. A clause can be included in the contract or purchase order used to obtain topsoil to preclude this possibility. The Environmental Protection Agency has established the Pollutant Priority List of analyses for soil and water materials, which can be used to identify potential problems. These testing procedures will be followed if suspicion arises concerning a park soil or a specified soil being brought into a park.
Soil properties can have a dramatic affect on the success of any park development. Unstable soil slopes, poorly drained soils, permafrost, expansive soils, soils with poor water retention, etc., all have limitations for certain uses. These limitations are inherent and not easily overcome. Such factors must be taken into account in any design or construction. Therefore, it is imperative that soil survey information be obtained and used early in the planning and design phase of any NPS project. (See Sources of Consultation, below).
Within the NPS, expertise on soil survey, soil management, erosion control, soil ecology, agronomy, and revegetation techniques can be found in the Natural Resources Program Center and the resource management staffs of several parks with active restoration programs. Soil scientists stationed in parks can consult on a variety of soil management problems. The Soil Scientist located in the Natural Resource Program Center in Denver can locate these experts as needed. The Denver Service Center can provide advice on the implications of soils in land use planning.
The U.S. Department of Agriculture's Natural Resources Conservation Service (NRCS), universities, and university extension services have varied expertise in the interpretation of soil surveys and investigation of specific soil management problems. The NRCS is the lead agency for conducting soil surveys in the United States and its services can be obtained through interagency agreement. If a park soil survey is conducted under contract with private industry or universities, the NRCS should at least be involved in providing quality assurance and correlating and reviewing the products.
Through a national memorandum of understanding (see Exhibit 1, below), the NPS is a member of the National Cooperative Soil Survey (NCSS), a nationwide partnership of federal, regional, state, and local agencies and institutions under the leadership of the NRCS. The purpose of this partnership is to work together to cooperatively investigate, inventory, document, classify, and interpret soils for understanding, managing, conserving, and sustaining the nation's limited soil resources. Pursuant to the memorandum of understanding, regions and parks are encouraged to also seek partnerships with local, state, and regional governments in order to share information and costs of soil surveys and promote efficiency. More information pertaining to the National Cooperative Soil Survey, and its standards, can be obtained at the following website, http://www.soils.usda.gov/ or at local USDA Natural Resources Conservation Service offices.
Additionally, the U.S. Forest Service and the Bureau of Land Management frequently have soil scientists or agronomists on their staffs who can provide consultation to nearby parks. These other land management agencies frequently have completed soil surveys for their lands that can serve as a base for conducting soil surveys on park lands.
State agricultural universities also have soil scientists and agronomists on staff and often conduct surveys in conjunction with research and sometimes in areas not covered by the above agencies.
Independent laboratories are usually available locally for the analysis of physical and chemical properties of soils, although the cost of independent laboratories is usually greater than that of state or federal laboratories.
Collecting soil samples for scientific purposes must be authorized by the park superintendent in accordance with NPS regulations at 36 CFR § 2.5. The mechanism for scientific sample collections is the Research and Collection Permit required by 36 CFR § 2.5, discussed in this Reference Manual in Research Administration and Collections.Soil Resources Management Table of Contents | RM#77 Table of Contents