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Larval salamanders and channel geomorphology are indicators of hydrologic permanence in forested headwater streams
JOHNSON, B. R., K. M. FRITZ, K. A. BLOCKSOM, AND DAVID M. WALTERS. Larval salamanders and channel geomorphology are indicators of hydrologic permanence in forested headwater streams. ECOLOGICAL INDICATORS. Elsevier Science Ltd, New York, NY, 9(1):150-159, (2009).
Research will provide States, Regions and Tribes with methods, guidance and indicators for correctly assessing the biological integrity of headwater streams, wadeable streams, large rivers and wetlands. It will enable the use of biological assessments and biocriteria in State and Tribal water quality standards programs to manage aquatic resources nationwide. Research in this task will assist in meeting the States 303d listing and 305b reporting requirements and in the development of TMDLs. In addition, the availability of indicators with known sensitivity and specificity will move the agency toward meeting it's goals of the Environmental Indicators Initiative.
Regulatory agencies need rapid indicators of hydrologic permanence for jurisdictional determinations of headwater streams. Our study objective was to assess the utility of larval salamander presence and assemblage structure and habitat variables for determining stream permanence across a large geographic area. We sampled four core forests (61 sites in Indiana, Kentucky and Ohio) in spring (April-May) and summer (August-September) over a two-year period. Sites in each forest were selected to cover a gradient of permanence, from perennial to ephemeral. Salamanders were collected by both benthic core sampling and timed visual search on each site visit. Classification and regression tree (CART) models were used to identify indicators of seasonal permanence at core sites that were then tested using data collected from six satellite forests (52 sites) located nationwide. Southern two-lined salamanders, Curycea cirrigera, were numerically dominant and were the only sepcies included in CART models. Salamander diversity declined with distance from the Appalachians and strong longitudinal changes in assemblage composition were evident within streams. Abundance of E. cirrigera was positively correlated with watershed area, whereas dusky salamanders, Desmognathus spp., and spring salamanders, Gyrinophilus porphyriticus, comprised a greater proportion of salamander communities at intermittent sites within their range. Spring and summer CART models incorporated E. cirrigera abundance and measures of channel geomorphology to accurately classify approximately 80% of core sites as either ephemeral, intermittent, or perennial. When applied to validation data from national satellite forests, correct classification rates were >85% for intermittent and ephemeral sites, but were only 20% for perennial sites. These findings suggest that larval plethodontid salamanders and habitat variables can be valuable predictors of headwater stream hydroperiod, but indicators are largely limited to the regional scale.