Document: MAR-3-72-7

A conceptual model for land-use effects on streams: Theory and application in the southern Blue Ridge.

SCOTT, M.C.* and G.S.HELFMAN

University of Georgia, Athens, GA 30602 ¹

Abstract:
Landscapes are changing rapidly as expanding areas are appropriated for human uses, with particularly severe consequences for surface waters. Although habitat alteration has long been recognized as a primary cause of decline in stream biological condition, only recently have the linkages between terrestrial conditions in the drainage basin and habitat conditions instream been examined. Life histories of native organisms are adapted to indigenous environmental regimes, so modified habitats may be outside physicochemical tolerance ranges or may alter outcomes of species interactions. Results of these processes include altered community structure and species endangerment, signs of the worldwide biodiversity crisis. In the southern Appalachians, changes in fish assemblages are not indicated well by traditional measures such as richness or diversity indices. Historical ecology suggests that endemic species may be better indicators of stream quality in these highland systems. We hypothesized that geographically widespread, warm-water fishes would tend to replace highland endemics in more disturbed streams, where expected habitat changes included increased temperature, nutrient concentrations, and sedimentation. We linked human activities to ecological effects by empirically fitting a nested hierarchal model. We found that landscape features (primarily deforestation level) predicted 50-80% of variation in key habitat variables, and instream habitat predicted nearly 70% of variation in relative abundance of endemic and cosmopolitan fishes. Implementation of a watershed management program based on such a model would make conservation a proactive, planning-oriented exercise rather than a reactive, crisis-oriented one.

Keywords: catchment, habitat alteration, southeastern biodiversity, upper Tennessee River

This abstract is being presented at: 10:45 AM in session:
Oral Session #70: Aquatic Ecology.