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Development of a Hierarchical Riverine Classification System and Assessments to Help Define Conservation Targets and Potential Reference Sites

Scott P. Sowa and David D. Diamond

Missouri Resource Assessment Partnership (MoRAP), 4200 New Haven Road, Columbia, MO 65201

We developed a hierarchical classification of watersheds and stream valley segments, modeled species distributions by stream segment, and identified potential reference streams for the eastern Ozark Highlands. The classification identifies ecological drainage units (EDUs) as groups of similar sub-basins using drainage-enforced ecoregion boundaries (e.g. similar geophysical conditions) and downstream connectivity (e.g. evolutionary histories and biota). Aquatic ecological systems (AES) are groups of watersheds with similar abiotic characteristics, and these are in turn grouped into AES types. Valley segment types (VSTs) are stream segments with similar abiotic conditions. Species distributions are modeled to VSTs using decision tree analysis based on collection data and abiotic variables linked to VSTs. Conservation target streams, a subset of which may serve as potential reference streams, are identified within each EDU by selecting the best AES form each AES type based on (1) abiotic indicators and stressors developed from landscape variables and pollution information, and (2) the distribution of target biota from species distribution models. Local variables such as land cover condition are in turn evaluated for VSTs within selected AESes to establish conservation targets at finer resolution. Further field verification and research is needed to help set thresholds for assigning relative condition based on indicators, and to relate indicators to condition in a quantitative way.

Keywords: riverine classification, riverine conservation, abiotic stressors, biotic indicators, ecological drainage unit, aquatic ecological system, valley segment type

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