Using Estimates of Natural Variation to Detect Ecologically Important Change in Forest Spatial Patterns: A case study, cascade range, eastern Washington

Using hierarchical clustering techniques, we grouped subwatersheds on the e astern slope of the Cascade Range in Washington State into ecological subre gions by similarity of area in potential vegetation and climate attributes. We then built spatially continous historical and current vegetation maps f or 48 randomly selected subwatersheds from interpretations of 1938-49 and 1 985-93 aerial photos, respectively, and attributed cover types, structural classes, and potential vegetation types to individual patches by modeling p rocedures. We estimated a natural range of variation (NRV) in spatial patte rns of patch types by subwatersheds and five forested ecological subregions . We illustrate how NRV information can be used to characterize the directi on and magnitude of vegetation change occurring as a consequence of managem ent.