Bishop Field Office
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Utilization data and residual measurements are important in evaluating the effects of grazing and browsing on rangelands. Utilization is the proportion or degree of current years forage production that is consumed or destroyed by animals (including insects). This process requires a comparison of the amount of herbage left compared with the amount of herbage produced during the year. Residual measurement is the determination of herbage material or stubble height left after a grazing or use period. Residual measurements and utilization data can be used:
- to identify use patterns,
- to help establish cause-and-effect interpretations of range trend data, and
- to aid in adjusting stocking rates when combined with other monitoring data (i.e. trend data and climatic information).
Monitored trend refers to the direction of vegetation change over time. Trend data are important in determining the effectiveness of on-the-ground management actions and evaluating progress toward meeting management objectives. Trend indicates whether the rangeland is moving toward or away from its potential Desired Plant Community (DPC) or toward or away from specific management objectives.
This trend study was established in 1969 at various locations of the Bodie Mountain allotment. Sites were permanently established and marked within critical and/or key areas. Data are recorded over a period of time at each plot and the results are then compared to detect change.
A plot frame (5x5 foot) is placed at the permanently marked location. Two photographs are taken before making any measurements or estimates. One photograph (see photo to the right) is taken close-up of the plot and the second is taken of the general landscape view from a permanently marked point. Next, a gridded frame, marked at 1 foot intervals, with sub-divided 1/16 of a square-foot sub plots, is placed on the plot frame. Observations and recordations are made for each 1/16 square-foot sub-plots. This process is repeated until the entire 5 square-foot plot has been recorded. Trend plot information is summarized to indicate whether the trend is either upward (improving), static (little/no change), or downward (declining).
The sampling process consists of:
- Identifying and grouping plant species as either grass, forb, or shrub;
- Counting seedlings and mature plants by species (seedlings/mature plants are the total number of seedlings/mature plants of the key species on the plot);
- Determining vegetation and litter cover (vegetation cover is the percent ground cover and canopy cover provided by all live vegetation. Litter is the percentage of the plot area that is covered by fallen leaves, twigs, seeds, etc.);
- Estimating composition of key species (composition is the percentage that the key species make up of the total live plant composition of the plot);
- Sketching a diagram where all the plants are located within each one square-foot sub-plot);
- Recording general observations of the site (i.e. evidence of grazing use, plant phenology, general vegetation condition).