The protection of rangeland health should serve as the minimum standard for management. If rangeland health is sustained then decisions about the appropriate plant community composition and production can be made depending on the desired rangeland use. Most important, the conservation of rangeland health preserves the option to change the use and management of a site as the desired resources and values change.
A one-time measure of most rangeland characteristics is only that—a picture of the situation at the time of measurement. Without a previous measurement with which the current measurement can be compared, the range manager's ability to interpret whether the management program is succeeding or failing is limited. Personnel and budget constraints and inconsistencies in the indicators measured at different times, however, have limited the number of sites where trend can be determined from comparable data collected at different points in time.
To compensate for this problem, range managers have attempted to determine apparent trend; that is, they evaluate site characteristics that indicate whether an area is improving or deteriorating. Factors such as accelerated erosion, for example, have been used to indicate a downward trend. If the soil is eroding at an accelerated rate, then the productive capacity of the site is probably being lost. The accumulation of litter is viewed as a sign of an improving rangeland because it is a sign that the amount of plant material needed to protect a site from erosion is increasing. The presence of seedlings of desirable plants was also interpreted as an upward apparent trend because those seedlings indicated that the plant composition was evolving toward the climax plant community (SCS) or potential natural community (USFS and BLM). The presence of seedlings of undesirable plants represents a downward trend. Plant vigor has also been used to judge apparent trend. Vigorous dominant plants in a climax plant community (SCS) or potential natural community (USFS and BLM) indicate an upward apparent trend, whereas the presence of weak, deformed plants indicates a downward trend.