Anthropogenic disturbances to streams have been shown to cause channel instability resulting in increased sedimentation and altered substrate composition. I studied effects of two such disturbances (logging and bridge construction) on habitat among three phases (pre-, during-, and post-disturbance) for two southern Jefferson County (Kansas) intermittent streams. From autumn 2001 to spring 2004, I seasonally sampled six habitat variables (thalweg depth, bank full width, percent bank exposed, riparian thickness, geometic mean, and substrate compaction) along 100 m benchmarks upstream from, at the site of, and downstream from disturbance locations. Using repeated-measure analysis of variance with a sequential Bonferroni correction of a = 0.05 and Tukey's studentized range test for pairwise comparisons, all six variables differed significantly at both the logging location and the bridge construction location among phases, whereas no variables differed significantly upstream from or downstream from either disturbance among the three phases. Results show that both logging and bridge construction can have adverse effects on stream habitat characteristics, and for intermittent streams, the disturbances might be localized due to lack of flow.

Keywords: logging, bridge construction, stream habitat, sedimentation, Plum Creek, Mud Creek, Jefferson County, Kansas.

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Anthropogenic disturbances to streams can cause negative effects to habitats and associated faunas. Two such stream disturbances are logging (Moring 1982; Davies and Nelson 1994) and bridge construction (Barton 1977; Wellman, Combs and Cook 2000). Both of these disturbances reduce the riparian area of streams, leading to alterations in physicochemical conditions several kilometers downstream from the disturbance with resultant effects on fish (Crispin, House and Roberts 1993; Weaver and Garman 1994), and macroinvertebrate assemblages (Davies and Nelson 1994; Young, Hinch and Northcote 1999). The riparian area is vital to the interrelationships between instream habitat and physical features of streams (Talmage, Perry and Goldstein 2002), and the removal of this area can lead to rises in mean stream temperatures, reductions in hydraulic roughness, increases in mean water velocities, modifications in riffle-run-pool sequences, and alterations in channel structures from reduced input of woody debris (Crispin, House and Roberts 1993; Young, Hinch and Northcote 1999). In addition, removal of streamside vegetation increases sediment loads in streams and occludes interstital spaces in substrate; during periods of no flow, the streambed can become exposed, which allows sediment to dry in these spaces and remain compacted when the water flows again (Bulger and Edds 2001). Thus, sedimentation reduces habitat diversity for aquatic assemblages (Moring 1982; Berkman and Rabeni 1987), and possibly alters primary productivity and/or allochthonous inputs that affect the rest of the food chain (Wood and Armitage 1997).

Intermittent streams typically are small, headwater streams that flow during part of the year and remain in permanent pools the rest of the year. These unique environments are essential to stream ecosystem structure and function by providing critical habitat for aquatic assemblages (Zale et al. 1989). Modification of intermittent streams through anthropogenic disturbances (e.g. sedimentation) is highly deleterious to these sensitive habitats, and can have adverse effects on the stream's biota. However, little work has been done on the...