Comparison areas, also known as reference areas or benchmark areas, are additional sampling locations established in rangeland inventory or monitoring programs to isolate the effects of land use from other natural events (especially weather factors) influencing vegetation responses. Therefore, comparison areas are usually chosen at localities with minimal management impacts, such as livestock exclosures or sites distant from water points. In other situations, fenceline contrasts reveal useful cues to separate the effects of land use from weather conditions.
Credible interpretations of land use impacts depend upon the selection of comparison areas that are representative of corresponding key areas or critical areas, partially realized by restricting sampling locations to the same range site. Problems of variability within a range site could be overcome by including multiple comparison areas, although this is seldom practical within the scope of time and budgetary constraints associated with most land evaluation programs.
References and Further Reading
Bureau of Land Management. 1996. Sampling vegetation attributes. Interagency Technical Reference, BLM/RS/ST-96/002+1730. p 6.
Smith, E.L., and G.B. Ruyle. 1991. Considerations when monitoring rangeland vegetation. G.B. Ruyle. (ed). Some methods for monitoring rangelands and other natural area vegetation. University of Arizona, College of Agriculture, Extension Report 9043. pp 2-3.
Wilson, A.D. 1984. Points of reference in the assessment of change in vegetation and land condition. Australian Rangeland Journal 6:69-74.