Patterns and dynamics of vegetation recovery following grazing cessation in the California golden trout habitat

Abstract

Abstract. In 1978, the Golden Trout Wilderness area was established to protect the California golden trout (Oncorhynchus mykiss aguabonita)-a vulnerable subspecies of the rainbow trout that is endemic to California-and its habitat, which is currently restricted to a few streams within high-elevation meadows in the Sierra Nevada Mountain Range. Because of the deleterious effects of livestock grazing on riparian vegetation in the golden trout habitat (occurring since the 1800s), meadow restoration activities were initiated in 1991, including cattle exclusion. There has been renewed discussion about re-opening these public lands to livestock grazing, and impact assessment studies are needed to inform decision makers about the potential consequences. Thus, we estimated the recovery potential of the golden trout habitat by measuring the height of riparian vegetation within areas that have been grazed vs. closed to grazing ("rested") since 1991. We found that cattle exclusion is effective at favoring riparian vegetation growth, but that vegetation recovery from grazing could take several decades in these sensitive habitats as some "rested" areas have yet to recover to full vegetation height, even after 25 yr of rest.

Response of Riparian Vegetation, Instream Habitat, and Aquatic Biota to Riparian Grazing Exclosures

“…Complete willow recovery, especially when planted as part of a restoration program, can take 25 years even when livestock are excluded, as was shown for high‐elevation meadow streams in the Sierra Nevada mountains in California (Nusslé et al. ). This highlights the importance of environmental context and growing conditions on vegetation response.…”

“…Studies that do have a temporal dimension usually only have field data from a few years over a longer timeframe (Nusslé et al. ). In contrast, much satellite imagery is collected every few days, and some satellite programs have been in place now for decades.…”

“…When unsuccessful, overgrazed riparian vegetation can take over 25 years to recover (Nusslé et al. ).…”

Using a Mechanistic Model to Develop Management Strategies to Cool Apache Trout Streams under the Threat of Climate Change

“…Plants can regrow through grazer (livestock and elk) exclusion alone, but this requires several decades for full recovery in some systems (Nussle et al. ) and specific shading requirements may not be met. Shade can also be provided by artificial techniques, such as shade cloth and felled vegetation (Kiffney et al.…”

The Relationship Between Measures of Annual Livestock Disturbance in Western Riparian Areas and Stream Conditions Important to Trout, Salmon, and Char

“…For example, if livestock grazing resulted in excessive streambank alteration or limited vegetation height at the end of the grazing season, then high-flow events between the grazing seasons would increase erosion along the disturbed banks (Trimble and Mendel 1995) and further degrade stream habitat conditions (e.g., reduced bank angles and fewer undercut streambanks) the following year. In contrast, if livestock grazing near the stream minimized disturbance and protected aboveground vegetation, channel conditions would either be maintained or trend toward conditions that fostered trout and salmon populations (Nusslé et al 2017).…”