Striving for consistency in a national assessment: the challenges of applying a reference-condition approach at a continental scale

• DOI: 10.1899/08-081.1
• Publication Date: 2008-10-28T21:17:06Z
• Authors: Alan T. Herlihy; Steven G. Paulsen; John Van Sickle; John L. Stoddard; Charles P. Hawkins; Lester L. Yuan
• Keywords: Reference data; Ecoregion; Comparability; Sample (material); Biotic index

One of the biggest challenges when conducting a continental-scale assessment streams is setting appropriate expectations for assessed sites. The challenge occurs 2 reasons: 1) tremendous natural environmental heterogeneity exists within continental landscape and 2) reference sites vary in quality both across major regions continent. We describe process used to set multimetric index biotic integrity (MIBI) observed/expected (O/E) indices generated from predictive models assess stream condition US Wadeable Streams Assessment (WSA). was based on reference-site approach, which least-disturbed each region were establish benchmarks assessing macroinvertebrate assemblages at other Reference compiled by filtering WSA sample disturbance using series abiotic variables. Additional needed obtained state, university, federal monitoring programs. This pool potential then uniformity site comparability data. Ultimately, 1625 WSA. Reference-site data help define 9 large ecoregions that minimized naturally occurring variation associated with continental-wide differences biogeography. These as basis developing MIBI O/E reporting results. A definition nationally, but we suspect best extant ecoregions, such Northern Plains Temperate Plains, lower than ecoregions. For assessment, simple modeling approach adjust scores where gradients could be demonstrated conclusively. provided an unparalleled opportunity push limits our conceptual technical understanding how apply reference-condition real-world need. Our hope have learned enough this exercise improve next round national assessments.