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Home Land Upland Habitat and Vegetation

Relative Abundance of the Deciduous Riparian Vegetation Type

Status and Trend

Interpretation and Commentary

Relative Abundance of Deciduous Riparian Vegetation Type


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Status: Considerabley Worse Than Target
Trend: Unknown
Confidence: Low

  • Relevance - This indicator measures the relative proportion of land covered by riparian hardwoods (known as deciduous riparian vegetation) in the Tahoe Basin. This vegetation grouping is commonly associated with moist soils adjacent to streams, springs, wetlands and small lakes (Potter 2005). Species considered to be riparian hardwood include alder, aspen, willow, cottonwood, and dogwood. The relative proportion of riparian hardwoods is important because this vegetation type enhances vegetation richness in the Basin, provides habitat for a relatively high diversity of wildlife species (including sensitive species) and is rare in the Lake Tahoe Basin (USDA 2000; Manley and Schlesinger 2001). Riparian hardwoods are also resilient to natural disturbance, such as flooding and fire (Sheppard et al. 2006). This indicator does not measure the condition or vigor of riparian hardwoods. This indicator can also be used as a proxy to assess the Common Vegetation Management Standard that calls for non-degradation of plant communities including native deciduous trees, wetlands and meadows, while providing for opportunities to increase the acreage of such riparian associations.
  • Adopted Standards  - (Relative Abundance) 1) Of the total amount of undisturbed vegetation in the Tahoe Basin – maintain at least 4% deciduous riparian vegetation, 2) A non-degradation standard to preserve plant communities shall apply to native deciduous trees, wetlands, and meadows while providing for opportunities to increase the acreage of such riparian associations to be consistent with the SEZ threshold.
  • Indicator - Percent of the landscape dominated by deciduous vegetation (percent [%]).
  • Status – The most recent data (not including area affected by the 2007 Angora Fire) indicates that about 1.4% (approximately 2,808 acres) of the land area in the Region is covered by the deciduous riparian vegetation type. The management target for this Threshold Standard sets an objective to achieve and maintain at least 7,956 acres (or 4% of the land area) of this vegetation type. Based on this target, the Region is at about 35% of the target. Consequently, a determination of “considerably worse than target” was assigned to this indicator. The non-degradation Management Standard was determined to be implemented because the agency has adopted regulatory control measures to prohibit actions that can degrade the quality of riparian vegetation. In addition, the Environmental Improvement Program (EIP) has facilitated the implementation of vegetation restoration projects designed to restore the health of deciduous vegetation.
  • Trend – The trend determination was “unknown” due to differences in mapping approach and resolution across years.

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  • Confidence 
    • Status - According to an accuracy assessment conducted by the U.S. Forest Service Remote Sensing Lab (2009) on the most recent vegetation type map, accuracy was not assessed for the riparian hardwood type. Therefore, a confidence of “low” was assigned to status.
    • Trends - Due to differences in mapping resolution and evaluation approach over time, there was “low” confidence assigned to trend.
    • Overall Confidence - Confidence assigned to status was “moderate” and to trend “low,” therefore according to rules established for this report, overall confidence was assigned a “low” determination.
  • Human and Environmental Drivers - Moist soils, direct sunlight and natural disturbance influence the abundance and distribution of riparian hardwoods. Fire suppression has allowed encroachment of shade-tolerant white fir into areas previously dominated by riparian hardwood species.
  • Monitoring Approach – Every five years, the Tahoe vegetation map is updated with new satellite data (if available) and/or modeled and calibrated using field-based Forest Inventory and Analysis (FIA) data to assess the extent of different vegetation types and associated forest structure characteristics for the Basin (USDA 2009c; Warbington et al. [no date]). For this analysis, CWHR vegetation types associated with deciduous riparian vegetation (“Montane Riparian,” “Aspen,” and “Mix Hardwood/Conifer”) were queried and enumerated from the most recently available vegetation map (U.S. Forest Service - Remote Sensing Lab Pacific Southwest Region: TMU_Strata_07 [published 2009]).
  • Monitoring Partners – U.S. Forest Service, US Geological Survey and Tahoe Regional Planning Agency

Links

 
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Map

Distribution and extent of deciduous riparian vegetation type (red areas in figure) in the Lake Tahoe Basin prior to the 2007 Angora (USDA 2009c).

 

Trend Charts

Chart data not available at this time.
 

Additional Info

References

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Additional Information

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  3. Conceptual Model:
  4. Monitoring Plan:
Last Updated on Tuesday, 13 November 2012 11:19