Arundo donax in California's Central Coast Region
Arundo donax: Invasive Plant
Giant reed (Arundo donax) is a perrenial invasive grass native to Eastern Asia. It is a persistent rhizomatous grass with high biomass production that was introduced to other continents by humans, for building material since many years . This grass can reach up to 20 feet tall in height when healthy, with long, flat, and green leaves. It is considered an ecological threat since it spreads when its rhizomes come in contact with soil within wetlands. This grass spreads along riparian zones and lake shores, and competes with native vegetation for sunlight, water, and nutrients .
Arundo donax in the Central Coast
Arundo has been spreading through Central California watersheds, and exacerbating flood prone areas . Monterey and San Luis Obispo counties, as well as the San Francisco Bay Area, and Sacramento and San Joaquin River valleys have been impacted with proliferating stands of Arundo . Stands of Arundo change direction of water flow, change the force of the river, and increase flood risk. The thick stands of Arundo can deflect the natural flow of the river into farmland and private properties. High areas of biomass also increases the risk and severity of fires in these riparian zones, endangering native plants, and other species that find habitat in this area . Approximately 1,900 acres of the 4,160 sq miles of the Salinas Watershed were encroached with Arundo in 2008, before any control programs started treating the stands along the Salinas River as seen in Figure 2 . After the instigation of control programs, approximately 1,400 acres of Arundo remain in 2017 (pers. comm., E. Zefferman, RCDMC).
Flooding in Central Coast
The Salinas River has a long history of floods dating back to 1911, with the most recent flooding forecasted in February of 2017, after heavy rains . With high precipitation rates in the area in the winter, proliferating Arundo stalks are further exacerbating flood risks in this region.
Local Solutions to Arundo Invasion
The two groups that are addressing this encroachment of Arundo in the Central Coast region are the Resource Conservation District, Monterey County (RCDMC), and the Monterey County Water Resources Agency (MCWRA) . The Monterey County Agricultural Commissioner began treating the Arundo by implementing spraying of scattered patches in the upper watershed (pers. comm., E. Zefferman, RCDMC). In 2011 the California Invasive Plant Council (CalIPC) prepared an Arundo donax Distribution and Impact Report in agreement with the State Water Resources Control Board (SWRCB) as seen in Table 1 . In 2014 the RCDMC took over this project, and the RCDMC and DENDRA, Inc. conducted an Initial Study per the California Environmental Quality Act (CEQA) in the Salinas Watershed. The Initial Study resulted in a Mitigated Negative Declaration submitted to the California Department of Fish and Wildlife (CDFW) for the Salinas River Watershed Invasive Weed Control and Restoration Program, which is currently being implemented by the RCDMC in collaboration with the CalIPC .
The Streambed Alteration Agreement under the Initial Study clearly does not authorize "take" of any threatened species including San Joaquin Kit Fox, South-Central California Coast Steelhead, Monterey roach, Tidewater Goby, California Red-Legged Frog, sensitive plant species, California Tiger Salamander, Western Spadefoot, Pacific Pond Turtle and Foothill Yellow-legged Frog, Burrowing Owl, Least Bell's Vireo, and the American Badger. Project measures were mitigated to avoid take of these, as well as fish and wildlife that could be encountered during mowing.
Since Arundo tends to encroach in riparian zones with native plants, methods of removal will ensure avoiding natives. Species specific herbicides will be used when possible to avoid broad spectrum eradication. After removal of Arundo, native plants like willow and California sycamore are restored in regions that are prone to erosion . The rest of treated riparian areas are naturally restored (pers. comm., E. Zefferman, RCDMC). With erosion as a concern before and after Arundo control treatment around the Salinas River, the Initial Study also lists vehicular operations to be postponed 24 hours after large rain events that would make riparian region soil more prone to erosion
Arundo Control Methods
Within the Arundo Control Program, the RCDMC uses these methods of control . :
- Chemically treat with broad-spectrum and target-species specific herbicides including glyphosate, imazapyr, or triclopyr, and will be formulated for approved use nar water bodies using backpack sprayers or hand-held power sprayers .
- Removal of dead stands by mowing with attachments, by hand and carried to chippers
Future of Arundo
Since the Salinas River watershed has the second-largest infestation of California, RCDMC has implemented the Arundo Control Program in 2008, to control all Arundo by the year 2028 . Many stakeholders have been collaborating with RCDMC and private landowners in Monterey County, in order to restore native riparian vegetation. The RCDMC Control Program has been successful and treated a significant amount of Arundo since 2008 and bettered the river system with the help of private landowners, as seen in Table 2.
|Table 2. Acerage of Treated Arundo in Salinas River Watershed (pers. comm., E. Zefferman, RCDMC)|
|Year||Acerage of Arundo Treated|
Satellite Images of Salinas River Land Cover 
As seen in these Landsat 8 satellite land cover images, the Arundo invasion is under control since the start of the control programs.
- / CALIPC (California Invasive Plant Council). Arundo donax. Cal-IPC.
- / Pilu R, Bucci F, Badone FC, Landoni M. 2012. Giant reed (Arundo donax L.): A weed plant or a promising energy crop? African Journal of Biotechnology 11(38) 9163-9174.
- / Swearingen J, Bargeron C. 2016. Invasive Plant Atlas of the United States. University of Georgia Center for Invasive Species and Ecosystem Health.
- / RCDMC (Resource Conservation District of Monterey County). Salinas River Arundo and Tamarisk Control. Salinas River Watershed Arundo Control Program.
- / Wessel, Lindzi. 2016. Arundo: The invasive 'hair clog' of the Salinas River. The Californian..
- / Spencer DF, Colby L, Norris GR. 2013. An evaluation of flooding risks associated with giant reed (Arundo donax). Journal of Freshwater Ecology 28(3) 397-409.
- / CDFW (California Department of Fish and Wildlife. 2014. Notice of Determination. Salinas Watershed Invasive Non-Native Plant Control (Project). RCD Monterey. .
- / Wright, T. 2017. Forecast calls for flooding on Salinas River this weekend. Santa Cruz Sentinel Weather.
- / CALIPC (California Invasive Plant Council). 2011. Arundo donax Distribution and Impact Report. State Water Resources Control Board.
- / RCDMC (Resource Conservation District, Monterey County). 2014. Attachment E-Regulatory Documentation. Salinas River Watershed Invasive Weed Control and Restoration Program. RCDMC.
- "Salinas River." 36°21'45.24"N and 121°13'53.24"W. Google Earth. 4/2015 and 10/2016. April 5, 2018.
- Monterey County Water Resources Agency (MCWRA)
- State Water Resources Control Board (SWRCB)
- California Environmental Quality Act (CEQA)
- Resource Conservation District, Monterey County (RCDMC)
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