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Home Land Upland Habitat and Vegetation

Vegetation Community (Association) Richness

Status and Trend

Interpretation and Commentary

Vegetation Community Richness


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Status: At or Somewhat Better than Target
Trend: Little or no change
Confidence: High

  • Relevance - This indicator measures the number (richness) and persistence of major native vegetation communities (associations) throughout the Lake Tahoe Basin. It is not a measure of plant species richness. This measure can be used to indicate whether a major vegetation community has been lost in the Region. The vegetation community richness indicator in combination with measures of vegetation community aerial extent (acreage) and structure could provide a measure of overall vegetation community diversity.
  • Adopted Standards  - Maintain the existing species richness of the Basin by providing for the perpetuation of the following plant associations (nine communities):
    • Yellow Pine Forest: Jeffrey pine, white fir, incense cedar, sugar pine
    • Red Fir Forest: red fir, Jeffrey pine, lodgepole pine, western white pine, mountain hemlock, western juniper
    • Subalpine Forest: whitebark pine, mountain hemlock, mountain mahogany
    • Shrub Association: greenleaf and pinemat manzanita, tobacco brush, Sierra chinquapin, huckleberry oak, mountain whitethorn
    • Sagebrush Scrub Vegetation: basin sagebrush, bitterbrush, Douglas chaenactis
    • Deciduous Riparian: quaking aspen, mountain alder, black cottonwood, willow
    • Meadow Associations (Wet and Dry Meadow): mountain squirrel tail, alpine gentian, whorled penstemon, asters, fescues, mountain brome, corn lilies, mountain bentgrass, hairgrass, marsh marigold, elephant heads, tinker's penney, mountain timothy, sedges, rushes, buttercups
    • Wetland Associations (Marsh Vegetation): pond lilies, buckbean, mare's tail, pondweed, common bladderwort, bottle sedge, common spikerush
    • Cushion Plant Association (Alpine Scrub): alpine phlox, dwarf ragwort, draba

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  • Indicator - Number of vegetation associations. For this assessment, TRPA vegetation associations were compared with California Wildlife Habitat Relationship (CWHR 2011) Types (attributed in TMU_Strata_07 map, USFS 2009c) to determine which types could be considered equivalent. Using the following crosswalk table, CWHR types were used to estimate relative proportions of TRPA vegetation associations in the Tahoe Basin:
     TRPA Association California Wildlife Habitat Relationship Type
    Cushion Plant Barren
    Deciduous Riparian Aspen
    Deciduous Riparian Mixed Hardwood-Conifer
    Deciduous Riparian Montane Riparian
    Meadow Perennial Grass
    Red Fir Forest Juniper
    Red Fir Forest Lodgepole Pine
    Red Fir Forest Red Fir
    Sagebrush Scrub Bitterbrush
    Sagebrush Scrub Low Sagebrush
    Sagebrush Scrub Sagebrush
    Shrub Alpine Dwarf Shrub
    Shrub Montane Chaparral
    Subalpine Forest Subalpine Conifer
    Wetland Wet Meadow
    Yellow Pine Forest Eastside Pine
    Yellow Pine Forest Jeffrey Pine
    Yellow Pine Forest Sierran Mixed Conifer
    Yellow Pine Forest White Fir
     
  • Condition Status – Vegetation communityrichness in the Basin has been maintained. All of the major vegetation associations that were identified in the Regional Plan (1987) and U.S. Forest Service – LTBMU Forest Plan (1988) persist today and are not in immediate danger of being lost as a result of in-basin management activities. Locations of individual vegetation communities are expected to shift over time as a result of natural disturbances such as wildfire, though community richness is expected to persist through successional processes.
  • Trend – Although there has been fluctuation in the aerial extent of some vegetation communities in the Lake Tahoe Basin (Raumann and Cablk 2008), there has been no loss or gain in the total number of native vegetation communities. Consequently, it was determined that there was “little or no change” in trend for the vegetation community richness indicator.
  • Confidence - There was “high” confidence in both the status and trend for this indicator. Forest managers use best available technology and field reconnaissance to map and classify vegetation types throughout the Lake Tahoe Basin about every five years; U.S. Forest Service vegetation mapping procedures meet regional and national vegetation mapping standards (Warbington [No Date];FGDC 1997). Because vegetation communities are broadly defined and thus encompass larger spatial extents than individual habitat types, variation in the status and trend of the vegetation community richness indicator is not obvious at the relatively short time scales for which the indicator is remapped and reassessed. The accuracy assessment of TMU_Strata_07 map used for this summary was conducted by the U.S. Forest Service, Pacific Southwest Region - Remote Sensing Lab.
  • Human and Environmental Drivers - Climate, elevation, soils, aspect, geomorphology, interspecies competition, and wildlife are natural influences on pattern and expression of vegetation communities in the Lake Tahoe Basin. Fire suppression (lack of fire), and natural and human caused wildfire can also influence the distribution and extent of different vegetation communities. For example, the montane chaparral vegetation type has been decreasing in aerial extent by about 10% per decade due to fire suppression (Nagel and Taylor 2005). However, the recent Gondola (2002) and Angora fires (2007) created hundreds to thousands of acres of early successional vegetation that over time will likely be mostly comprised of shrub vegetation. Forest treatments designed to remove biomass can also influence vegetationcommunities. Treated areas in the Yellow Pine Forest have been shown to support higher intra-community plant species richness than in neighboring untreated forest (Safford et al. 2010); although this Indicator Category is not a direct measure of plant species richness, fostering intra-community species richness can potentially lead to future vegetation community richness. Trampling associated with unmanaged recreation can degrade rare high elevation plant communities, such as the cushion plant community.
  • Monitoring Approach – Satellite imagery, aerial photographs and field reconnaissance (Forest Inventory and Analysis) are used to delineate and classify vegetation types in the Lake Tahoe Basin. This information is digitized into a Geographic Information System (GIS) and subsequently analyzed to summarize vegetation community richness.
  • Monitoring Partners – U.S. Forest Service – Lake Tahoe Basin Management Unit and Pacific Southwest Remote Sensing Lab, TRPA

Links

 

Map

 

Map showing the distribution and extent of major vegetation communities (associations) in the Lake Tahoe Basin (pre-Angora Fire of 2007). Source: U.S. Forest Service - Pacific Southwest Region, Remote Sensing Lab.

 

Trend Charts

Chart data not available at this time.
Estimated proportion of land covered by different TRPA vegetation communities (associations) in the Lake Tahoe Basin (USDA 2009c).

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 11:35