Research/Evaluate Restoration of NE Oregon Streams: Effects of Livestock Exclosures (Corridor Fencing) on Riparian Vegetation, Stream Geomorphic Features and Fish Populations; Final Report 2002.

Abstract

(Cover and this Figure are the Middle Fork John Day River at Phipps meadow in grazed (cover) and exclosed reaches (above). SIGNIFICANT FINDINGS OF RESEARCHCorridor fencing to exclude livestock grazing along Interior Columbia Basin streams is a widely used approach to restore salmonids and their habitats. Yet few studies have quantified the ecosystem response to this treatment. Vegetation, geomorphic features, and fish populations were sampled in 11 riparian/stream ecosystems in Northeast Oregon. At each stream we sampled two paired reaches -a reach grazed by livestock and one exclosed by fencing. The following are the highlights of this study. Vegetation• We found significant differences in the cover, composition and structure of vegetation in all grazed/exclosed reaches. In the majority of exclosed reaches there were increases in the cover of forbs, shrubs, and sedges. Exposed bare ground was more extensive in grazed reaches.• Wetland indicator scores, based upon streamside vegetation composition, indicate that cessation of livestock grazing results in a shift to more mesic wetland riparian vegetation. 3• Species adapted to herbivory and drier environments were more abundant in grazed riparian areas.• Plant species diversity and richness were higher in exclosed stream reaches.• Composition of shrubs varied between streams. In 88% of the streams where exclosures were over 5 years old, the cover of riparian obligate shrubs (e.g., willows, alder, etc.) was greater in exclosures, with the greatest differences in exclosures over 20 years old Geomorphology• Considering all sites together, livestock exclusion resulted in statistically significant improvements in channel geomorphology. The channels in the exclosed reaches are narrower, deeper, and have more pool area than the channels in the grazed reaches.• At the level of individual sites, in most cases the exclosed reach was clearly narrower, deeper and had more pool area than the grazed reach at the same site.• We did not detect any differences between fenced and grazed reaches in maximum pool depth or residual pool depth.• Geomorphic response to livestock exclusion appears to be influenced by multiple factors, including age, vegetation cover, hydraulic conditions, and site geomorphology. Younger exclosures show less vegetation difference with the paired grazed reach and are less likely to show geomorphic adjustment. Other conditions, such as stream power, channel constraint and sediment supply may also limit the effectiveness of restoration projects. Fish• Densities of young-of-the-year redband trout (Oncorhynchus mykiss) were significantly greater in exclosed reaches compared to grazed reaches. Moreover, the effects of fencing were negatively associated with the dominant warmwater fishes, redside shiners (Richardsonius balteatus) and speckled dace (Rhinichthys cataractae), which are relatively uncommon in the best trout habitats.• Conversely, we could not detect significant differences in densities of combined juvenile and adult life stages of salmonids between e...

Global Review of the Physical and Biological Effectiveness of Stream Habitat Rehabilitation Techniques

“…Rinne (1999) found that in most studies, the experimental design or duration was inadequate to effectively determine significant changes in fish numbers due to grazing removal or reduction. In a study of Oregon streams, Kauffman et al (2002) reported that livestock exclusion yielded improvements in vegetation, stream morphology, and density of age-0 rainbow trout Oncorhynchus mykiss but not in density of adult or juvenile rainbow trout. Kauffman et al (2002) suggested that the lack of juvenile or adult response was attributable to the short reaches sampled in their study.…”

“…In a study of Oregon streams, Kauffman et al (2002) reported that livestock exclusion yielded improvements in vegetation, stream morphology, and density of age-0 rainbow trout Oncorhynchus mykiss but not in density of adult or juvenile rainbow trout. Kauffman et al (2002) suggested that the lack of juvenile or adult response was attributable to the short reaches sampled in their study. Medina et al (2005) reported on three long-term case studies in the southwestern USA and found that in all three cases, results were inconclusive due to study design limitations, species interactions, upstream or watershed-scale effects, introduction of exotic species, and fisheries management (stocking and changes in fishing regulations).…”

Do trout respond to riparian change? A meta‐analysis with implications for restoration and management

“…less nutrient filtration, less shading) and reduce fish growth and abundance (Summers, Giles & Stubbing, 2005;Saunders & Fausch, 2012). Removing livestock may also alter channel geomorphology, improve water quality and increase terrestrial food supply (Kauffman, 2002;Opperman & Merenlender, 2004;Saunders & Fausch, 2012). These changes may consequently increase the suitability of streams for trout.…”

Stream Fish Responses to Grazing Exclosures

“…-Physical dimensions of exclosed and unfenced reaches compared in sampled northeastern Oregon streams (modified fromKauffman et al 2002).…”

“…-Numbers of experimental reaches sampled in northeastern Oregon streams; at these reaches, mean values of vegetation variables differed by 5% or greater between exclosed and contiguous unfenced reaches. The total number of exclosed-unfenced reach pairs examined was 11 (modified fromKauffman et al 2002).…”