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Home Land Upland Habitat and Vegetation

Relative Abundance of Late Seral and Old Growth Forest Ecosystems for Montane, Upper Montane and Subalpine Elevation Zones

Status and Trend

Interpretation and Commentary

MONTANE ZONE


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

UPPER MONTANE ZONE


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

SUBALPINE ZONE


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

  • Relevance - This indicator characterizes the geographic extent of stands dominated by large diameter (>24” dbh) conifer trees in the Tahoe Region. Old growth forests are valued because they typically include large trees that are well spaced, and add to Tahoe’s ecological integrity by providing a greater diversity of life forms, including a variety of unique lichen, fungi, insects, vegetation and wildlife. Old forests tend to be more structurally complex and resilient to natural disturbances (wildfire) than younger forests, due to tree spacing and fire resistance of bark on mature trees, especially pines. This indicator does not measure the relative condition of this vegetation type.
  • Adopted Standards  - Attain and maintain a minimum percentage of 55% by area of forested lands within the Tahoe Region (excluding TRPA designated urban areas) in a late seral or old growth condition, and distributed across elevation zones. To achieve the 55%, the elevation zones shall contribute as follows:
    • The Subalpine zone (greater than 8,500 feet elevation) will contribute 5% (7,600 acres) of the late seral or old growth acres (61% of the Subalpine zone must be in a late seral or old growth condition).
    • The Upper Montane zone (between 7,000 and 8,500 feet elevation) will contribute 30% (45,900 acres) of the late seral or old growth acres (60% of the Upper Montane zone must be in a late seral or old growth condition).
    • The Montane zone (lower than 7,000 feet elevation) will contribute 20% (30,600 acres) of the late seral or old growth acres (48% of the Montane zone must be in a late seral or old growth condition).
  • Indicator - Percent (%) of the forested landscape dominated by large diameter (>24” dbh) conifer trees.
  • Status – The most recent data (which does not include the area affected by the 2007 Angora Fire) indicates that about 20.5% (approximately 17,280 acres) of the forested landscape is covered by stands dominated by trees >24” dbh, indicating that the region is “considerably worse than target.” According to recent mapping information, there are approximately 6,814 acres of large-tree dominated stands in the Montane zone (<7,000’), indicating that the Region is approximately 78% below the target of 30,600 acres. In the Upper Montane zone, there are approximately 9,195 acres of large-tree dominated stands, indicating the Region is approximately 80% below the target of 45,900 acres. The Subalpine zone contains about 1,269 acres of large-tree dominated stands, indicating that the Region is about 83% below the target of 7,600 acres. Consequently, the status of each zone was determined to be “considerably worse than target.”
  • Trend – The trend determination is “unknown” due to differences in mapping resolution and evaluation approach across years.

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  • Confidence 
    • Status - According to an accuracy assessment conducted on the most recent vegetation size class map by the U.S. Forest Service Remote Sensing Lab in 2009, accuracy was 60%. Therefore, a confidence of “moderate” was assigned to status.
    • Trends - Due to differences in mapping resolution and evaluation approaches for this indicator over time, there was “low” confidence assigned to trend.
    • Overall Confidence - Confidence assigned to status was “moderate” and to trend “low.” Therefore, overall confidence was assigned a “low” determination for each elevation zone.
  • Human and Environmental Drivers - Soil conditions, aspect, hill slope position, drought frequency, direct sunlight, fire suppression, climate patterns, time and natural disturbance influence the extent and distribution of large-diameter trees(Collinset al. 2011; Beardsley et al. 1999; Beaty and Taylor 2007; Scholl and Taylor2006; USDA 2000). Historical land uses, such as clear-cut logging in the late 1800s, dramatically reduced the overall extent of old growth forests in the Basin (USDA 2000). Current forest management has emphasized thinning of overstocked conifer stands, which could result in faster growth rates due to less competition for resources (D. Fournier, personal communication, 2011; USDA 2011d).
  • 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 large-diameter trees 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

Recent geographic distribution and extent of conifer stands dominated by trees >24” dbh (“old growth” forest stands; red areas in figure) in the Lake Tahoe Basin. Source: U.S. Forest Service (2007 EVEG).

 

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 11:38