Arundo donax in California's Central Coast Region

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Figure 1: Arundo donax (giant reed). Photo courtesy Joseph DiTomaso [1].

An environmental summary created by the ENVS 560/L Watershed Systems class at CSUMB.

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 [2]. 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 [3].

Arundo donax in the Central Coast

Figure 2: Encroachment of Arundo donax along Salinas River. Map by DENDRA Inc. [4].

Arundo has been spreading through Central California watersheds, and exacerbating flood prone areas [5]. 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 [5]. 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 [6].

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 [7]. With high precipitation rates in the area in the winter, proliferating Arundo stalks are further exacerbating flood risks in this region.

Resource Conservation Districts: RCD Monterey County

The two groups that are addressing this encroachment of Arundo in the Central Coast region are the Resource Conservation District, Monterey Bay (RCDMC), and the Monterey County Water Resources Agency (MCWRA). RCDMC is one of the special districts under California's Department of Conservation, designated to implement and monitor resource conservation projects across private and public land [8]. The mission of these special districts is to educate the public, including landowners about resource conservation in each area, as locally governed agencies. According to Division 9 of the Public Resources Code, RCD's prioritize:

  • Agricultural land conservation
  • Conservation education
  • Forest stewardship
  • Fuels management
  • Irrigation management
  • Recreational land restoration
  • Soil and water management on non-agricultural lands
  • Urban resource conservation
  • Watershed planning and management
  • Water conservation
  • Water quality protection and enhancement
  • Wetland conservation
  • Wildlife habitat enhancement

Summary Table

The following table is extracted from the California Invasive Plant Council (CalIPC) Arundo donax Distribution and Impact Report of 2011 [9]. This document was submitted to the State Water Resources Control Board (SWRCB), summarizing details of the encroachment spanning from Northern California to Tijuana. The highest levels of invasion in the Salinas have been identified to be vegetated floodplains, vegetated low terraces, and vegetated upper terraces, similar to San Luis Rey River, Santa Ana River, Santa Clara River, Santa Margarita River, and Ventura River While comparing distributions of Arundo in different watersheds, Salinas watershed Arundo patches are less continuous and less connected than the others across the state [9].


Arundo acreage in central California by hydrologic unit according to 2011 Distribution and Impact Report [9].
Hydrological Unit Total Area (Acres) Treated Arundo (Acres) Untreated Arundo Total Arundo Percent Treated
Salinas 2,272,492 106.4 1,225.3 1,331.7 8%

RCDMC Arundo Control Program

Since the Salinas River watershed has the second-largest infestation of California, RCDMC has implemented an Arundo Control Program in 2008, to eradicate all Arundo by the year 2028 [4]. Many stakeholders have been collaborating with RCDMC and private landowners in Monterey County, in order to restore native riparian vegetation. Phases I-III have successfully taken off since the start of the program, and have eradicated a significant amount of Arundo and bettered the river system with the help of private landowners. Methods of eradication are as follows:

  • 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 [10].
  • Removal of dead stands by mowing with attachments, by hand and carried to chippers

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 will be restored in these regions[10].


Phase I: 2008

50 acres of Arundo were removed between King City and the Monterey/San Luis Obispo county line.

Phase II: 2014

109 acres of Arundo were removed in private land between Greenfield and King City.

Phase III

Planned to treat an additional 350 acres downstream of Phase II.

before and after google earth images

References

  1. / CALIPC (California Invasive Plant Council). Arundo donax. Cal-IPC.
  2. / 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.
  3. / Swearingen J, Bargeron C. 2016. Invasive Plant Atlas of the United States. University of Georgia Center for Invasive Species and Ecosystem Health.
  4. 4.0 4.1 / RCDMC (Resource Conservation District of Monterey County). Salinas River Arundo and Tamarisk Control. Salinas River Watershed Arundo Control Program.
  5. 5.0 5.1 / Wessel, Lindzi. 2016. Arundo: The invasive 'hair clog' of the Salinas River. The Californian..
  6. / 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.
  7. / Wright, T. 2017. Forecast calls for flooding on Salinas River this weekend. Santa Cruz Sentinel Weather.
  8. / RCD (Resource Conservation District). 2017. Resource Conservation District Assistance. State of California Department of Conservation.
  9. 9.0 9.1 9.2 / CALIPC (California Invasive Plant Council). 2011. Arundo donax Distribution and Impact Report. State Water Resources Control Board.
  10. 10.0 10.1 / CDFW (California Department of Fish and Wildlife. 2014. Notice of Determination. Salinas Watershed Invasive Non-Native Plant Control (Project). RCD Monterey. .

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Disclaimer

This page may contain student work completed as part of assigned coursework. It may not be accurate. It does not necessary reflect the opinion or policy of CSUMB, its staff, or students.