No abstract

We determined composition and trophic structure of macroinvertebrate assemblages, and also examined how environmental factors, such as riparian forest, aquatic habitat, and vertebrate predators, influenced these assemblages in relatively undisturbed headwater streams of northeastern Ohio. Using canonical correspondence analysis, we examined the relationships between macroinvertebrate assemblages, both compositional and trophic structure, and the environment. Ordination analyses showed a distinct separation of upstream and downstream macroinvertebrate faunas, while variance partitioning suggested that this may be because of the strong effects that predatory fishes and salamanders had in upstream areas. Aquatic habitat may be a strong determinant of macroinvertebrate composition and structure in these headwater streams, though this may be a reflection of site fidelity. Riparian forest habitat also explained a large portion of variation in macroinvertebrate functional feeding guild structure, emphasizing the connection between terrestrial and aquatic ecosystems in these headwater stream systems.

Although downed wood is a significant structural component of riparian ecotones, most studies of downed wood dynamics are conducted only within the stream bankfull channel or on the riparian forest floor. We examined downed wood structural characteristics (e.g., length, volume, and decay class) across the entire riparian ecotone of seven headwater streams in mature deciduous forests of northeastern Ohio to understand the structural relationships between downed wood and riparian ecotones. Sampling was stratified by hydrogeomorphic zones that were defined by lateral position within the riparian ecotone and correspond to differing fluvial geomorphology. Most downed wood pieces sampled were small (<1 m) and with a high decay class. Downed wood pieces within the baseflow zone (within the wetted channel) were smaller and more abundant than those within the transitional zone (within the bankfull channel excluding the wetted channel). Surface contact was inversely related to aquatic influence across the riparian ecotone, with downed wood in Zone 3 (riparian area beyond the bankfull channel) having significantly higher contact than wood within the other zones. The ecotonal approach and the incorporation of hydrogeomorphic influences is an alternative approach that moves beyond traditional approaches to more holistic management of riparian forests.

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Riparian areas are diverse ecotones that provide numerous, valuable ecosystem functions. However, many riparian delineation methods use a fixed minimum width to create a riparian buffer or setback that may not adequately protect actual riparian function. A method for riparian area delineation across landscapes is presented that incorporates riparian function and moves beyond the fixed-width buffer approach. Using geospatial data and tools, riparian areas were delineated functionally for the Cuyahoga Valley National Park in northeastern Ohio and compared to fixed-width buffers in terms of extent and protection of riparian function. We suggest that functional riparian area delineation be incorporated into watershed management planning to improve protection and restoration of the valuable ecological functions provided by riparian areas across landscapes.