SDE Feature Class
tree of heaven, Sapium sebiferum, environment, San Joaquin US Hydrologic Unit, tamarisk, chinese tallow, San Joaquin River, Chowchilla Bypass, salt cedar, Lepidium latifolium, Vegetation, Mud Slough, scarlet wisteria, Fresno County, Madera County, plants, California, red sesbania, Merced County, weeds, invasive species, Tamarix sp., Salt Slough, Catalpa sp., Sesbania punicea, Ailanthus altissima, Fresno Slough, perennial pepperweed, biota, Eastside Bypass, Arundo donax, giant reed
These data provide an estimate of the distribution, locations, and extent of the major invasive riparian plant species along the San Joaquin River from Friant Dam to the Merced River confluence as well as parts of major intersecting sloughs and bypasses, in June through August 2008. These data were collected for the San Joaquin River Restoration Program (SJRRP) to obtain a "snapshot" of the field conditions of the major invasive riparian plant species prior to the commencement of SJRRP interim flows on October 1, 2009, which are mandated by the Stipulation of Settlement in Natural Resources Defense Council, et al., v. Kirk Rodgers, et al., as approved by the Court in October 2006 (The Settlement). Invasive riparian plant species have the potential to substantially reduce the effectiveness of the SJRRP actions mandated by the Settlement. Invasive plant species have replaced native riparian vegetation in large portions of the SJRRP area, especially in Reach 1 along the low-flow shoreline. Invasive riparian plant species have the potential to rapidly respond to changes in the SJR and floodplain environment resulting from restoration actions, such as the release of interim and restoration flows, construction of various water control structures, fish screens and bypasses, river channel modifications, and creation of frequently inundated floodplain habitat. Among the invasive riparian plant species, red sesbania, in particular, has the greatest potential to reduce restoration effectiveness. Dispersal, growth, and physiological characteristics unique to red sesbania can substantially affect fish habitat. Unless the spread of red sesbania is controlled, achieving the restoration objectives of the Settlement may be compromised. Field observations on other California rivers have indicated that it is mainly flow that disperses red sesbania seed pods, and there is concern that SJRRP interim flows beginning in October 2009, as well as subsequent restoration flows, may facilitate the spread of red sesbania throughout the project area. See "2008 SJRRP Target Riparian Plant Species Mapping and Field Reconnaissance Survey" for a discussion of projected detrimental effects of red sesbania colonization and expansion on the project. In 2008, the current distribution, approximate locations, and in some cases estimated extent as well as other field data, of red sesbania (Sesbania punicea), arundo or giant reed (Arundo donax), tamarisk or saltcedar (Tamarix spp.), and Chinese tallow (Sapium sebiferum) were mapped along the San Joaquin River from Friant Dam to the Merced River confluence, parts of Fresno, Mud, and Salt Sloughs, as well as the Eastside and Chowchilla Bypasses at permissible access locations. Perennial pepperweed (Lepidium latifolium) was mapped, especially in the lower reaches and sloughs. Tree of heaven and Catalpa sp. were mapped opportunistically in Reach 1. Where access was allowed by canoe, kayak, automobile, and/or foot, these target riparian plant species locations were mapped using GPS units and air photo base maps; otherwise, locations of these species were estimated on the base maps and described on field data forms. Field observations were also obtained via a fixed-wing aircraft flying at low altitude. Field crews were assembled by the Department of Fish and Game, Department of Water Resources, US Fish and Wildlife Service, and Bureau of Reclamation as well as California State University, Stanislaus. The field work was coordinated by Reclamation. This mapping effort was a pilot study and first year of SJRRP invasive riparian plant species data collection. As a consequence, field data collection was not entirely consistent between the crews, with some crews utilizing GPS units only and simply mapping points, while other crews more fully implemented the protocol outlined in the scope of work, "2008 SJRRP Target Riparian Plant Species Mapping and Field Reconnaissance Survey". Given the geographic scope of the project and the compressed timeframe under which field crews were assembled and mobilized, this is an unfortunate but not unexpected artifact of a pilot study. Furthermore, limited access to the river in some reaches as well as other areas present further challenges to interpreting these data. The ground- and water-based surveys were conducted on public lands, or with the permission of private landowners. An aerial survey filled in data gaps downstream of Highway 145 and primarily revealed conditions where invasive plant species may exist. Because data were not systematically collected, they should not be analyzed or interpreted as a comprehensive sampling of the study area. Rather, these data represent our best effort at characterizing the distribution, locations, and extent of the major invasive riparian plant species along the San Joaquin River from Friant Dam to the Merced River confluence, parts of Fresno, Mud and Salt Sloughs, as well as the Eastside and Chowchilla Bypasses prior to the introduction of interim flows. In addition, despite mapping inconsistencies among crews and data gaps, these data provide value by updating the comprehensive vegetation mapping of the San Joaquin River by DWR in 2000 that included invasive species (see G.W. Moise and B. Hendrickson. 2002. Riparian Vegetation of the San Joaquin River. DWR, San Joaquin District). The invasive species included in DWR's "invasives" GIS layer are red sesbania, giant reed, blue gum, tree-of-heaven, pampas grass, and edible fig. A number of other invasive nonnative species occur, but were not systematically mapped. These species include Himalayan blackberry, white mulberry, castor bean, Lombardy poplar, and tamarisk.
The purpose of this work is to estimate the occurrence, distribution, approximate locations, and abundance of red sesbania (Sesbania punicea) and four other major invasive riparian plant species: arundo (Arundo donax), saltcedar (Tamarix spp.), perennial pepperweed (Lepidium latifolium), and Chinese tallow (Sapium sebiferum) along the San Joaquin River and some adjoining channels between Friant Dam and the confluence with the Merced River. Adjoining channels include the Chowchilla Bypass, the Eastside Bypass, and parts of Fresno Slough, Salt Slough, and Mud Slough. The location of incidental observations of additional species including catalpa trees (Catalpa sp.) and tree of heaven (Ailanthus altissima) are included with this dataset. The distribution and density of red sesbania on the five SJR reaches and bypasses of the SJRRP are currently unknown. Recent colonization and rapid spread of red sesbania in the SJR system means existing remote imagery is likely to be inadequate to accurately map the distribution and estimated abundance of this and other aggressive invasive riparian plant species. In order to develop a managment plan for the most aggressive invasive riparian plant species in the SJRRP, current knowledge of their distribution, approximate locations, and estimated abundance in the SJRRP is required.
San Joaquin River Restoration Program
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