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United States Department of Agriculture

Agricultural Research Service


item Herrick, Jeffrey
item Tugel, Arlene - USDA-NRCS
item Shaver, P - USDA-NRCS
item Pellant, M - USDI-BLM

Submitted to: Soil Quality Information Sheets
Publication Type: Government Publication
Publication Acceptance Date: May 1, 2001
Publication Date: May 1, 2001

Interpretive Summary: Interpretive summary not required for government publications.

Technical Abstract: WHAT ARE INDICATORS? Indicators are key soil or plant community characteristics sensitive to environmental change. They reflect complex ecosystem processes too difficult or expensive to be measured directly. They provide information about the current status of rangeland ecosystems. Trends from indicators measured regularly provide clues about the response of the system to anagement. Soil quality indicators complement vegetation indicators and may be qualitative or quantitative. SOIL QUALITY INDICATORS USED ON RANGELANDS. Soil properties¿Physical, biological, and chemical soil properties are included. Some properties, such as bulk density, reflect limitations to root growth, seedling emergence, and water infiltration. Other properties, such as the diversity and activity of soil biota, reflect the availability of both water and nutrients to plants. Soil organic matter and soil aggregate stability reflect a combination of physical, biological, and chemical processes. Soil surface features¿Pedestals, exposed plant roots, rills, gullies, wind scours, and soil deposition reflect such processes as runoff and erosion. These indicators are commonly assessed qualitatively. Spatial patterns and variability¿The distribution and cycling of water and nutrients in rangeland soils are affected over both short and long distances by such processes as erosion and deposition. The kinds, amounts, and spatial distribution of living plants and decaying residue on the soil also affect nutrients and water. Accordingly, as the distribution of soil organic matter becomes less uniform, resource availability declines in some patches and increases in others. HOW ARE INDICATORS SELECTED? The indicators chosen depend on the functions to be assessed or monitored and the scale (e.g., management unit, ranch, watershed, or region) at which the information is needed. Rangeland ecosystem functions include maintaining soil and site stability; distributing, storing, and supplying water and plant nutrients; and supporting a healthy plant community. Good indicators are strongly related to the function and scale of interest; sensitive to change; compatible with time and resource availability and technical expertise; and relatively easy to observe or measure in a reliable manner. Assessment estimates or measures the functional status of ecological processes. The assessment must start with understanding the standard to be used for comparison. For assessments of rangeland, the ecological site description is used as a standard at the site scale. Information from the ecological site description should be supplemented, if possible, with data from local reference sites. The optimum time and location for making assessments depend on the objectives. Potential objectives include selection of sites for monitoring, gathering inventory data used in making decisions, identification of areas at risk of degradation, and targeting management inputs. The timing of assessments also depends on seasonal cycles. Some soil properties are highly variable on a daily, seasonal, or yearly basis in response to changes in both temperature and moisture. For example, the total amount of organic matter in a soil is relatively insensitive to seasonal changes, whereas rills can become less apparent, depending on the length of time and conditions since the most recent major storm. Careful site selection helps to ensure assessment sites are truly representative of the area of interest. The sites should be on the same soil and in the same landscape position as the area they represent. Offsite features, such as roads, homesteads, and other areas of recent or historic disturbances, can have significant impacts and should either be avoided or noted. The management history of the site can aid in interpretation. Monitoring identifies changes in the resource through the orderly collection, analysis, and interpretation of quantitative data. It must be conducted over time at permanently marked locations and include baseline data if it is to ascertain the trend of the change in the functional status of the resource. Monitoring is often designed so measurements can be made consistently by more than one observer. Reference data or standards may be used to establish management goals and aid in interpreting the monitoring results. Site selection for monitoring depends primarily on the objectives, which include: evaluating and documenting the progress toward management goals; detecting changes that may be early warnings of future degradation; and, determining the trend for areas in desired condition at risk or with potential for recovery. If the objective is to determine progress or trend, sites representative of the management unit should be selected. If the objective is to provide an opportunity to modify management before degradation occurs, the most vulnerable sites should be selected. Detected changes must be real and must occur rapidly enough for land managers to correct problems before undesired and perhaps irreversible loss of soil quality occurs. The monitoring plan should include the proper measurement frequency, which either limits or captures seasonal variability, as dictated by the objectives.

Last Modified: 5/23/2015
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