INTEGRATED RESPONSE PLOT DESIGNS FOR INDICATORS OF DESERTIFICATION

The improvement of land management practices on lands susceptible to d esertification requires information on the status and condition of the existing resources as well as any change occurring in the resource co ndition over time. The Environmental Monitoring and Assessment Program (EMAP) of the U.S. Environmental Protection Agency has developed a st atistical survey design for monitoring the condition of ecological res ources on large spatial scales. EMAP-Rangelands used a uniformity samp ling study in 1993 to evaluate response plot designs for three categor ies of indicators (soils, vegetation, and spectral reflectance) to be used for monitoring ecological condition of a site. The response plot design study was developed to integrate on-site measurements for the t hree indicator categories. The study was conducted on the Colorado Pla teau in southern Utah in three rangeland resource classes (grassland, desertscrub, and conifer woodland) of differing productivity levels in an attempt to develop a common plot design for all three resource cla sses. Basic measurement units were developed to facilitate integration of data collection. Preliminary spatial analysis of the sampling stud y found considerable differences in variation patterns among the study sites and measurement categories for the indicator classes used by EM AP-Rangelands. Evidence of substantial trends in the indicator measure ments on monitoring sites relative to regional trends leads to the con clusion that nonstationary spatial models for biological processes on a monitoring site may be needed to fulfill the requirements for develo ping plot designs and indicator criteria.