Relative Abundance of Deciduous Riparian Vegetation
The indicator measures the relative proportion of land covered by riparian hardwoods species which include alder, aspen, willow, cottonwood, and dogwood and are associated with moist soils adjacent to streams, springs, wetlands, and small lakes. The relative proportion of the riparian hardwoods is important as this vegetation type enhances vegetation richness in the Region, provides habitat for a relatively high diversity of wildlife species (including sensitive species) and is resilient to natural disturbances such as flooding and fire. TRPA has adopted several policies and ordinances designed to promote the conservation and protection of existing deciduous vegetation types and Environmental Improvement Program partners have implemented numerous deciduous riparian restoration and enhancement projects, restoring or enhancing aspen habitat.
Status
Estimated percent of land area occupied by deciduous riparian vegetation in the Lake Tahoe Region. Changes in the percent cover are a result of different interpretations of the baseline amount of undisturbed vegetation and changing mapping techniques/resolution, not necessarily actual changes in vegetation type. Sources: (USDA, 2010)
Data provided by the USDA Forest Service, R5 Remote Sensing Lab. Access detailed datasets on Tahoe Open Data, including, vegetation type summary, vegetation spatial data, and detailed vegetation attributes.
Evaluation Map
Vegetation Distribution in the Tahoe Region - 2010 Ecobject.
2023 Evaluation
- Status
- Considerably Worse Than Target
- Trend
- Little or No Change
- Confidence
- Low
Applicable Standard
VP5: Relative Abundance - Of the total amount of undisturbed vegetation in the Tahoe Basin: Maintain at least four percent deciduous riparian vegetation.
Key Points
- Deciduous riparian vegetation currently covers 1.3 percent of the Region, well below the four percent target.
- Projects implemented through the Environmental Improvement Program have successfully restored riparian vegetation acreage, particularly for aspen, by removing shade-tolerant white fir.
About the Threshold
This indicator measures the relative proportion of land covered by riparian hardwoods (known as deciduous riparian vegetation) in the Tahoe Region. 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 Region, provides habitat for a relatively high diversity of wildlife species (including sensitive species) and is rare in the Lake Tahoe Region (Manley and Schlesinger, 2001; Murphy and Knopp, 2010). 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.
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.The Angora Fire and more recent Caldor Fire, have created large openings where these hardwoods can expand along riparian corridors.
Delivering and Measuring Success
EIP Indicators
-
Acres of Habitat Restored or Enhanced
Since 2007, EIP partners have restored or enhanced over 1,000 acres of aspen habitat.
- Acres of SEZ Restored or Enhanced
- Linear Feet of Stream Channel Restored or Enhanced
Example EIP Projects
- Burke Creek/Rabe Meadow Riparian Restoration Project
- Riparian Vegetation and Fuels Reduction Monitoring
- Riparian Wildlife Enancement Program
Monitoring Programs
Rationale Details
- Considerably worse than target. In the most recent available data period (2017), there were 2,228 acres of deciduous riparian vegetation out of a total of 171,438 undisturbed acres, accounting for just 1.3 percent. This represents only 29 percent of the 6,858-acre target. Multiple methods have been used to evaluate the standard and nearly only have suggested that deciduous riparian cover to be well below the threshold standard. The standard has been found to be in attainment only once (2001) when the evaluation utilized aerial imagery to evaluate the standard.
- Little or no change. The Caldor and Angora fires each created openings that may allow for an expansion of the range of riparian hardwoods. Aside from the fires, no major disturbance events (e.g., fires, disease, clearing) occurred that would have significantly altered the extent of riparian vegetation communities at the regional level during the evaluation period.
Confidence Details
- Low. Confidence in the status in 2011 was assessed as low, because no accuracy assessment was available for the map of riparian hardwood vegetation. In addition, a recently released map of the SEZ in the Region estimated that the forested SEZ class (which includes deciduous riparian) is the most widely distributed SEZ type in the Region (accounting for approximately 50 percent of the Region’s SEZ) and covering 14,578 acres (6.4 percent of the Region) (Roby et al., 2015).
- Moderate. There is moderate to high confidence that, in the absence of disturbance events (e.g., fires, disease, clearing), the spatial extent of vegetation communities at the regional scale remains relatively stable over a four-year period. However, the openings created by the Angora and Caldor Fires are expected to lead to an increase in the detection of riparian hardwoods in future assessments.
- Low. If one confidence rating is moderate and the other is low, the overall confidence rating is the lower confidence rating.
Additional Figures and Resources
No photos available.
No documents available.