The appropriate statistical model for analyses to identify differences in cover between years or among sites depends on the method to determine cover that was followed, and decisions defining sample units made during preliminary planning.
Ground rules are guidelines developed to minimize the subjectivity of sampling. Ground rules should be developed before field work commences, and should be clearly included in the sampling protocol. Ground rules are especially important to maintain sampling accuracy and precision when a number of different people are involved in data collection, or when data is collected over a number of years.
Resource value ratings have been proposed as an approach to meet the demands of multiple use principles, by evaluating the suitability of the current vegetation for a specific use, such as livestock grazing, desert tortoise habitat, and recreation. Therefore, it is appropriate to assign several resource value ratings to each range site.
In 1994, the National Research Council Committee on Rangeland Classification Systems published a report addressing current methods and possible improvements to assess the status of rangeland resources. The report recommended that assessments be based on rangeland health, which embodies the degree to which the integrity of soil and ecological processes within the ecosystem are sustained. Proper functioning of these processes is assumed to ensure that rangelands have the capacity to produce commodities and satisfy values on a sustainable basis.