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Home Water Aquatic Species and Communities

Osgood Swamp

Status and Trend

Interpretation and Commentary

Status: Somewhat Worse Than Target
Trend: Moderate Decline
Confidence: Low

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  • Relevance - Osgood Swamp is a lake located near the base of Echo Summit, adjacent to the town of Meyers. Two separate fen sites have been confirmed on the west and south sides of the lake (Sikes et al. 2011).Fens are peat-forming wetlands that rely on groundwater input rather than precipitation. They are important sites of groundwater discharge, and may serve as indicators of shallow aquifers (Cooper 1990). Fens form slowly over thousands of years; thus, they are not easily restored once destroyed (Cooper et al. 1998). Fens have been identified by the U.S. Forest Service (SNEP 1996; USDA 2004) and in the Tahoe Science Plan, (Hymanson and Collopy 2010) as among the most sensitive habitat types in the Sierra Nevada. Fens are hotspots of biodiversity that support rare plants, insects, and small and large mammals. Vegetation in all wetland types, including fens, marshes and meadows plays an important role in recycling nutrients, trapping eroding soil, and filtering pollutants such as nitrates (Cooper and Wolf 2006).In addition, fens figure prominently in nearly all scenarios of carbon dioxide-induced global climate change because they are major sinks for atmospheric carbon (Chimner and Cooper 2006).
  • Adopted Standards - Provide for non-degradation of the natural qualities of any plant community that is uncommon to the Basin or of exceptional scientific, ecological, or scenic value. The Threshold Standard shall apply, but not be limited to, 1) the deep-water plants of Lake Tahoe, 2) Grass Lake, 3) Osgood Swamp, 4) Hell Hole, 5) Upper Truckee Marsh, 6) Taylor Creek Marsh, 7) Freel Peak Cushion Plant Community, and 8) Pope Marsh.
  • Indicator - The status and trend determination was based on a qualitative assessment of the natural qualities of a plant community. The natural qualities of a plant community include the current plant species assemblage, the health, age and ecological condition of those plant species, and the condition of the hydrologic regime.
  • Status – The two fens at Osgood Swamp are not easily accessible from the decommissioned U.S. Forest Service road on the west side of the swamp, or any of the numerous user trails surrounding the swamp. In the summer, light recreational use from local hikers and cyclists is confined to the well-established trail network. In the winter, cross-country skiing and illegal snowmobile traffic have been observed, but this is also confined to roads surrounding the swamp (TRPA 2007c).The 2006 Threshold Evaluation first noted high levels of beaver activity increasing water levels across the entire area, and causing a possible decline in conditions of the community (TRPA 2007c).Aquantitative system for ranking the ecological integrity and quality of fens in the Sierra Nevada has recently become available (Sikes et al. 2011), and was used to assess the attainment statusof fens at Osgood Swamp. In the 2010 Lake Tahoe Basin Fen Assessment, the western fen at Osgood Swamp received a Conservation Significance score of 27 out of 40, while the southern fen was one point lower (26), due to its closer proximity to Highway 50. Elements that contributed positively to the rankings include the presence of rare plants and vegetation associations, and the uniqueness of the fens in terms of pH, elevation, and geology. Elements that detracted from the score include the presence of rodent burrows at the southern site and prevalent beaver activity around Osgood Swamp that could be affecting the hydrology, and causing higher water levels than in the past.Conservation significance scores of 26 and 27 are considered high when compared to the range of scores for fens in the Tahoe Basin (18-30 points) and indicate that the natural qualities of the fens exist. However, this evaluation tool does not consider the impacts of beavers on hydrology across the entire swamp. While the two small fens may currently be in acceptable condition, beaver activity is likely altering the hydrology across Osgood Swamp, and therefore, the threshold status was determined to be “somewhat worse than target.”

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  • Trend Since this is the first time that the status of the fens at Osgood Swamp has been assessed based on the Conservation Significance ranking, a trend analysis of that ranking is not possible. The 2006 Threshold Evaluation determined that the condition of Osgood Swamp was declining due to altered hydrology from beaver activity (TRPA 2007c). There has been little change in recreation use at Osgood Swamp in the last five years. The U.S. Forest Service - LTBMU implemented fuel reduction treatments (hand thinning) on about 80 acres of adjacent forest in 2009, and plans to conduct mechanical treatments on an additional 75 acres in the near future. Vegetation monitoring plots have been established in the fens, but these data are not yet available (Engelhardt and Gross 2011a). In the absence of any management actions to address beaver impacts, it must be assumed that the status of Osgood Swamp continues to decline. Therefore, the trend in the condition of Osgood Swamp was assessed as “moderate decline.”
     

  • Confidence – Confidence in the status, as assessed by the Conservation Significance ranking, was moderate, lower than it is for Grass Lake or Hell Hole because field visits at Osgood Swamp were last conducted during the Region 5 fen inventory in 2006, and not in conjunction with the 2010 Fen Assessment (Sikes et al. 2011). The scoring was in relation to the status of other fens; therefore, there is a degree of uncertainty in the status score. The confidence in the trend analysis was low because of insufficient data. Therefore, confidence in the status and trend at Osgood Swamp was determined to be “low.”
  • Human and Environmental Drivers - Any condition or activity that disturbs the hydrologic regime or nutrient levels of a fen, or causes drying or changes in plant composition, is a threat to the function of that fen (Cooper 1990). Activities that threaten fens in the Sierra Nevada include timber harvest, mechanical fuel reduction treatments, road and trail construction, stock trampling, off-road vehicles, ground and surface water pumping,and water pollution (Cooper and Wolf 2006). At Osgood Swamp, illegal snowmobile use is concentrated on existing roads outside of the wetland, and a minimum 100-foot buffer around the water is enforced for adjacent mechanical fuel treatments.Currently, hydrologic modification from beaver activity is predicted to be the largest threat to this community. Extended drought and climate change could also negatively impact site hydrology and vegetation (Chimner and Cooper 2002).
  • Monitoring Approach – Two different monitoring approaches have recently been implemented at Osgood Swamp. As part of the Region 5 Fen Assessment program, a total of 135 potential fens, including Osgood Swamp, have been assessed within the Lake Tahoe Basin since 2006 (Sikes et al. 2011). Of these, a total of 47 locations have been confirmed as fens. In 2010, the U.S. Forest Servicecollaborated with the California Native Plant Society to developa quantitative system for ranking the ecological integrity and quality of fens (Sikes et al. 2011). Using this ranking system, surveyors objectively score a fen on eight different criteria on a five-point scale. The criteria include factors such as rarity, biodiversity, impacts, accessibility, and uniqueness. The Conservation Significance rank is the sum of scores for each criterion and has a maximum value of 40 points. In 2010, the Conservation Significance of the 47 confirmed fens in the Tahoe Basin ranged from a low of 18 to a high of 30.

    The second monitoring approach is part of the Region 5 Range Monitoring Program designed to quantify changes in the ecological condition of wetland plant communities (Weixelman et al. 2003). This protocol is designed to enable the user to classify meadows and wetlands according to dominant plant species, elevation, and site moisture characteristics and use a quantitative ecological condition scorecard for that meadow type. The user assigns an ecological condition of low, moderate, or high, based on plant species composition, the presence of different plant functional groups, and other hydrogeomorphic variables. The protocol provides information on the environmental conditions necessary to support certain rare species, and the monitoring design quantitatively tracks rare species abundance. In 2004, two plots and permanent photo points were established at Osgood Swamp (Engelhardt and Gross 2011a). Plots were re-visited in 2009/2010 but the data has not yet been analyzed. Due to the absence of any other available data, these quantitative data will likely form the basis of future Threshold Evaluations.

  • Monitoring Partners – U.S. Forest Service Lake Tahoe Basin Management Unit, California Native Plant Society

Links

 
  • Monitoring Plan
  • Conceptual Model

Map

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Map showing location of Osgood Swamp and surrounding area.

Additional Info

References

Additional Information

Last Updated on Tuesday, 02 October 2012 13:01