2023 SYRCL's Invasive Weed Crew Takes on the Challenge • SYRCL

written by: Seaera M. Moe, SYRCL’s Forest Restoration Crew Lead

Since 2019 the South Yuba River Citizens League (SYRCL) has built a partnership with the US Forest Service (USFS) to confront the challenges posed by invasive weeds in the Yuba River Watershed. Non-native invasive plants (NNIP) present significant concerns, including their capacity to outcompete native plants and escalate the risk of high-severity fires by acting as ground and ladder fuels. Unlike native plants which are more selective and sensitive in an ecosystem, NNIPs thrive where there’s disturbance and lack biological control to keep them at bay.

Scotch broom (Cytisus scoparius), one of our target invasive weeds, is particularly problematic due to its high flammability and dense growth that forms an impenetrable barrier for wildlife. Moreover, it boasts a long-lived seedbank, with seeds remaining viable for up to 30 years. Its high resprout potential enables it to effectively outcompete native conifers and shrubs. Other high priority invasives include yellow star-thistle (Centaurea solstitialis), rush skeletonweed (Chondrilla juncea), spotted knapweed (Centaurea stoebe ssp. micranthos) and annual grasses such as medusahead (Elymus caput-medusae) and barbed goatgrass (Aegilops triuncialis). All of these species disrupt our native ecosystems, impacting pollinators, wildlife, and fire behavior.

Medusahead
Yellow Star-Thistle

As part of ongoing efforts in forest restoration, the SYRCL invasive weeds crew was busy this past field season treating and monitoring over 250 sites and 50,000 plants throughout the Tahoe National Forest (TNF). Working to reduce high fire risk in our beloved watersheds, the crew performed a variety of tasks. Manual and mechanical operations included hand-pulling, weed-whacking, weed-wrenching, flagging and monitoring existing infestations, and mapping new ones. In tandem with the seasons, the crew carefully timed their efforts with the phenologies (“the timing of growth events, including major biological changes in plant growth and development throughout the season”) of target invasives to ensure treatment occurred at the most appropriate stage of the plants’ development. For instance, annual grasses are very weather-dependent and optimally treated when weed-whacked, but precise timing is critical—treat too early, and regrowth is likely; treat too late, and there’s a risk of seed dispersal. Treatment type varies from species to species and factors such as plant life cycles, weather, elevation, and infestation size all play an important role in how each site is handled.

Under the guidance of TNF’s west zone district botanist and range specialist Chelsea Morgan, SYRCL also assisted the TNF botany crew with rare plant surveys in the American River Ranger District. The TNF botany crew focused on three key species for the 2023 field season: Van Zuuk false bindweed (Calystegia vanzuukiae), Layne’s butterweed (Packera layneae), and Sierra blue grass (Poa sierrae). Notably, Layne’s butterweed, a California endemic, is the only plant in the TNF west zone that’s federally listed as a threatened species. Van Zuuk false bindweed and Sierra blue grass (also a California endemic) are federally sensitive species (FSS). All of these species fall under the “California Rare Plant Rank 1B,” indicating a significant population decline in the last century. These classifications exist to ensure populations of threatened species can be prioritized and monitored to increase their resilience in the face of climate change. The data we collect during rare plant surveys aids in preventing these botanical gems from going extinct. Invasive weed management and rare plant surveys go hand-in-hand in promoting rare plant populations by preventing NNIPs from encroaching on their limited geographic ranges.

Beyond these primary responsibilities, SYRCL actively engaged in cross-training events with various TNF crews, including the wildlife crew, archaeology crew, timber crew, and east zone botany crew. These collaborations are always a lot of fun and allow different departments to share their knowledge and passions, network, and see what other projects are happening within our forest. Several noteworthy events marked these collaborations, such as “Frog Friday” during which we assisted the wildlife crew in surveying for foothill yellow-legged frogs in Greenhorn Creek. Other activities included participating in wetland restoration efforts to enhance red-legged frog habitat, rebuilding a fence to protect Blackjack Fen from cattle grazing and trampling, and “Boca Weed Day” where we helped remove the highly invasive musk thistle (Carduus nutans) at Boca Historic Townsite in the Truckee watershed.

The SYRCL team takes pride in the extensive work accomplished to contribute to the restoration and protection of our watershed. By monitoring and treating over 130 acres in the Yuba and American River Ranger Districts, the SYRCL team has effectively opened up usable habitat for native biodiversity and significantly reduced the negative effects of NNIPs. For Californians, these efforts of ongoing management provide a valuable safety net in terms of wildfire mitigation as well as maintaining the beauty and integrity of the ecosystems in our backyard. The impact of our work is significant; however, the persistence of invasive species will require ongoing management. We look forward to the 2024 field season where we can continue our efforts!