Shiells-Sommers Riparian Restoration Implementation Project

The proposed project is a second phase of restoration for the 140-acre Shiells-Sommers Property, owned by The Nature Conservancy (TNC), and located approximately 1.5 miles east of Fillmore, California. Immediately neighboring the property downstream is a California Department of Fish and Wildlife (CDFW) owned Ecological Reserve where $3.2 million has been spent removing the invasive bamboo-like grass, arundo (Arundo donax). The Shiells-Sommers Property encompasses approximately 0.9 linear miles of the Santa Clara River, and is dominated by braided riparian scrub, and emergent riparian woodland and wetland habitats.

Efforts to remove invasive arundo have been staged in phases across the property since the mid-2000’s and are ongoing. Impacts from arundo and other dominant invasive species like short-pod mustard (Hirschfeldia incana), thistles (Cirsium vulgare, Carduus pycenocephalus), perennial pepperweed (Lepidium latifolium), salt cedar (Tamarix spp.), castor bean (Ricinus communis), carnation spurge (Euphorbia terracina) and others, coupled with the effects of prolonged drought, have delayed a native dominated community from emerging passively in this riparian-wetland habitat.

The proposed project would be implemented by The Nature Conservancy, University of California Santa Barbara, and the Santa Clara River Conservancy. This second phase of restoration would build on the investment made to control arundo, both on the TNC property and the downstream CDFW Ecological Reserve, and would address the ecological degradation of this valuable riparian habitat using active restoration practices. An assessment of the property would be made to identify areas severely (>50%) or moderately (20-50%) dominated by invasive plant cover, currently estimated to approximate 75 acres. Areas with the most severe invasive plant cover would be mowed to remove the dense accumulation of thatch that is currently restricting native plants from recolonizing the site. Invasive plant regrowth in these mowed zones would be treated for 3 years. While mitigating invasive plant growth, a selection of native species would be actively planted to jumpstart the ecological structure and function currently missing in these riparian areas. Moderately infested areas would use a combination of treatments to remove invasive plant cover and to restore a selection of native riparian species. Project objectives would include reducing absolute invasive plant cover below 20% and increasing relative native plant cover to 50% as well as enhancing native structural diversity (i.e., riparian trees, shrubs, and herbaceous understory) throughout the Shiells-Sommers Property.