Recommended Citation Wurtsbaugh, Wayne A.; Heredia, Nick; Palacios, Patsy; Baker, Jared; Broderius, Chance; Fisher, Katie; Fuller, Jason; Pappas, G. Andrew; Smith, Christian; and Weston, Marc (2013) "A River Continuum Analysis of an Anthropogenically-Impacted System: The Little Bear River, Utah," Natural Resources and Environmental Issues: Vol. 18 , Article 1. Available at: https://digitalcommons.usu.edu/nrei/vol18/iss1/1

The 29 papers in this proceedings are divided into the main organized sessions of the 16th Wildland Shrub Symposium, including the plenary session to introduce the theme of threats to shrubland ecosystem integrity, impacts of energy development and reclamation on ecosystem function, invasive plant ecology. wildlife habitats: impacts and restoration opportunities, historical perspectives in shrublands, ecosystem threats due to fire in the Mojave Desert, and modeling and monitoring of shrubland ecosystems. An overarching goal of the symposium was to make linkages between research and management.

Aspen (Populus tremuloides) on the Gardiner Ranger District, Gallatin National Forest, have declined over the last half-century. In an attempt to reverse this trend, beaver (Castor canadensis) were reintroduced in Eagle Creek in 1991. Beaver promote aspen suckering through their dam and lodge building activities. In 2005, I assessed the long-term effects of beaver on aspen stands and the associated riparian area in the Eagle Creek Drainage. Aerial photographs taken in 1990 and 2005 were used to compare changes in riparian area vegetation where beaver were reintroduced. Aspen canopy cover decreased (P<0.05) from 43% to 25% on Eagle Creek (29 ha) between 1990 and 2005. Willow (Salix spp.) cover increased (P<0.05) from 10% to 14% and alder (Alnus incana) cover and water surface area doubled during the same period. Aspen recovery was estimated by comparing vegetative changes among control sites with <10% beaver use (n = 5), active beaver sites (n = 6), sites abandoned for 1-3 years (n = 7), sites abandoned for 4-6 years (n = 4), and sites abandoned for 7-11 years (n = 5). Thirty, 1-m plots were used to determine aspen density and one 60-m belt transect was used to calculate size-class distributions at each site. Aspen stem densities in active sites and sites abandoned by beaver for 13 years were similar (2.6/m) and increased (P=0.01) compared to all other sites (1/m). In addition, sprout and sapling densities were greater (P=0.01) in these sampling areas. However, aspen suckers were not able to grow taller than 2m on sites absent of beaver for 4-11 years, which prevented aspen recovery. Ungulate herbivory on aspen was assessed by comparing differences in 14 fenced (3 x 3m) and unfenced (3 x 3m) areas over 2 growing seasons. Growth rate of aspen suckers was greater (P=0.001) in fenced areas (32cm/year) compared to unfenced areas (0.25cm/year) due to ungulate herbivory. Total ungulate density for Eagle Creek was equivalent to 17.6 elk/km in the winter of 2005-06. Beaver activity stimulated the growth of aspen sprouts and saplings, but ungulate herbivory prevented successful aspen recovery in Eagle Creek.

Benthic organisms and substrates in Great Salt Lake, Utah, were sampled to measure selenium concentrations of prey organisms of the birds that utilize the lake for nesting and during migrations. The sampling was focused on stromatolite biostromes, as these solid reef-like structures cover approximately 23% of the oxic benthic area of the lake and are the principal habitat for brine fly (Ephydra cinerea) larvae and pupae. Samples were taken at depths of 1-5 m along two transects in Gilbert Bay where salinities ranged from 116–126 g l. Periphyton on the biostromes had chlorophyll levels of 700 mg m, and contained approximately 68% of the chlorophyll in the lake’s phytoplankton. Consequently, the biostromes represent a significant component of the lake’s primary production. A pumped-bucket sampler effectively sampled brine flies on horizontal surfaces of the biostromes, but not on the sides of the mounded ones encountered in the southern part of the bay. Brine fly larvae and pupae were far more abundant on the biostromes than on the soft substrates, with respective mean densities of 9100 m, 530 m and 240 m, on biostromes, sand and mud. Total brine fly biomass on biostromes averaged 5.9 g m, which is about 30% of the biomass present in brine shrimp (Artemia franciscana) in the water column. The mean selenium concentration in the combined organic matter-inorganic substrates of biostromes sampled in 2007 was 0.3 ± 0.1 g g dry weight. However, when the inorganic carbonates were removed with acid, the remaining organic matter had selenium concentrations of 1.0 ± 0.1 g g dry weight. Mean Se concentrations in larvae, pupae and adult brine flies were 1.3, 1.5 and 1.8 g g dry weight, respectively, but the differences were not significant. Although there was a 2500X bioconcentration factor between total dissolved Se (mean = 0.40 g l) in the overlying water and in the periphyton of the biostromes, the limited data suggested that there was little biomagnification between the periphyton and the brine flies. A review of the diets of birds utilizing Great Salt Lake and other saline lakes suggests that brine fly produced on biostromes are an important diet component for goldeneye ducks (Bucephala clangula), American avocets (Recurvirostra americana), black-necked stilts (Himantopus mexicanus) and California gulls (Larus californicus) and perhaps other birds utilizing the lake. Consequently the benthic food web may be important route for uptake of metal contaminants in these birds in Great Salt Lake. The high selenium concentrations in goldeneye ducks that feed on brine flies suggests that proposed increases in the loading of this contaminant should be reviewed carefully by managers. High mercury levels in goldeneyes suggest that the food web on the lake’s biostromes may be an important pathway for other metals into birds.

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This Article is brought to you for free and open access by the QuinneyNatural Resources Research Library, S.J. and Jessie E. atDigitalCommons@USU. It has been accepted for inclusion in NaturalResources and Environmental Issues by an authorized administrator ofDigitalCommons@USU. For more information, please contactdigitalcommons@usu.edu.