Tuolumne River Plan: Tuolumne Meadows Native Plant Restoration and Carbon Sequestration

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This project was selected for implementation in the 2014 Record of Decision for the Tuolumne River Plan/EIS (PEPC 14043). This project must adhere to mitigation and stipulations specified in the Final EIS/Record of Decision, specifically the ecological restoration Appendix H.

In Tuolumne Meadows changes in the native plant composition have resulted in a substantial disconnect between plant and soil processes. Researchers have recently determined that the existing vegetation provides insufficient levels of soil organic matter (i.e., soil carbon) essential to sustain the functional contribution (i.e., soil moisture, water filtration, flood retention, diverse wildlife habitat) of Tuolumne Meadows to the greater watershed. Soil carbon is critical to retaining soil water. Vegetation changes that result in an annual net-loss of carbon can cause a concurrent loss in soil water holding capacity and nutrient availability. This can set up a feedback of degradation where the loss of soil water and nutrients limits vegetation growth and ground cover, decreasing the contribution of soil organic matter, and exposing more soil organic matter to drier and more oxygenated conditions, resulting in greater decomposition and erosion, and overall net loss. As the loss of organic matter occurs, meadow soils become increasingly dry, and less capable of supporting a diverse and rich plant composition. As this feedback loop persists meadows become increasingly dry, shifting to upland vegetation types, whereby the restoration of the original wetland sedge dominated community becomes increasingly difficult (in terms of degree of manipulation required and likelihood of success). Simultaneously, meadow ecosystem function and services become compromised, and wilderness character associated with those meadow ecosystems is altered towards upland and conifer types.

This project will address the loss of soil carbon by planting two species of sedges (Carex scopulorum, C. subnigricans) in 9 acres in the west end of the Tuolumne Meadows and monitoring the carbon budget and plant success.

Key actions of the project include:

• Plant 20,000 propagules/acre over three years. The first year 1acre, the second year 3 acres, and the third year 5 acres will be planted. Soil disturbance will be up to 5" deep.
• Install temporary small mammal exclusion fence around perimeter of plots. Exclusion fence will be 18" high wire mesh with a 4" band of tin flashing along the top. The fencing will be installed with 3 ft. rebar to hold it erect and staples to hold the wire mesh to the ground.
• Small mammals that get into the exclosures will be removed with live animal traps and released nearby, outside of the exclosure.
• Seed collection of the Carex sp. will occur over approximately 10 acres within Tuolumne Meadows (429 acres).

Research objectives will require the plots within the study area to be evaluated over the period of 5 years for planting survival and tillering (formation of new shoots from rhizomes), above- and below-ground biomass production, species composition, changes in shoot density, vegetation canopy cover, bare soil and litter cover, as well as greenhouse gas flux and soil carbon accumulation. Monitoring will also include evaluation of water table depth (using existing piezometer wells), and soil redox measurements (using electrodes at depths within the soil profile). Disturbance associated with monitoring includes soil disturbance, herbage removal, and above-ground installations (i.e. data loggers, solar panels, batteries and housings).