Santa Ynez River Tamarisk and Arundo Project

Transcription

1 Santa Ynez River Tamarisk and Arundo Project Project Summary: At 90 miles long, the Santa Ynez River is one of the longest rivers on the Central Coast of California. The river begins in, and traverses through approximately 25 miles of, the Los Padres National Forest. Three reservoirs on the river, Jameson Lake, Gibraltar Reservoir, and Cachuma Lake, store and provide the majority of the drinking and agricultural water for many of the county's cities and farms. Cachuma Lake Recreation Area is also a local county park, popular with boaters and campers. A 2008 survey for the invasive weeds Arundo donax (giant reed or also known as arundo) and Tamarix ramosissima (saltcedar or also known as tamarisk) on the Santa Ynez River conducted by the County of Santa Barbara Agricultural Commissioner's Office determined that the primary invasive plant threat to the river's plant diversity, infrastructure, and water conservation and quality is Arundo donax and Tamarix ramosissima. Otherwise, the river's riparian corridor is relatively free from other large invasive plants. In partnership with the La Purisima Audubon Society, Santa Ynez River Water Conservation District, and the Cachuma Conservation Release Board, the County of Santa Barbara Agricultural Commissioner's Office proposes to conduct an early detection and rapid response project to contain and control giant reed and saltcedar that occur sporadically along the Santa Ynez River. Removal of these two invasive plants will benefit the river by reducing the risk of erosion, flooding and fire, conserve biodiversity, and conserve water quantity and quality. Controlling the infestation at this early stage is more cost efficient before the problem becomes more serious. Non-native invasive plants threaten to expand within this relatively pristine riparian corridor. An aerial survey of the entire river conducted in September of 2008 estimated the cumulative gross acreage cover of Arundo donax and Tamarix ramosissima at 31

2 acres, and the cumulative net acreage at 13 acres. This amount is relatively low compared to the amounts found in other major river systems in Southern California. Infrastructure Benefit: Arundo donax and Tamarix ramosissima are two non-native invasive plants that are widely recognized for their detrimental impact on water quality, and water quantity, and their increasing the risk of infrastructure damage from flood, fire, and erosion. A primary goal of this project is to conserve water quantity and water quality, and reduce the risk of infrastructure damage from flooding, fire, and erosion by removing saltcedar and giant reed from the riparian corridor of the Santa Ynez River. Along the eastern half, the river meanders through a large part of its course, naturally. It travels through steep canyons, around rolling An example of the potential flood damage. hills, and across moderately managed rangeland. While the dynamics of the river has less impact in these areas, an increased presence of giant reed and saltcedar could change that by increasing sedimentation and the risk of damage from flooding and fire. Saltcedar has been blamed for increasing flooding by forming a partial barrier to floodflow, which can cause floodwater to disperse and inundate areas that otherwise would not be flooded. In other areas, with the invasion of saltcedar, there has been an apparent increase in the frequency of fire in riparian ecosystems. The river is more constrained when it travels next to vineyards, by horse ranches, and under bridges. Here the presence of giant reed and saltcedar can create flooding and erosion problems. Giant reed rhizome clumps are strong yet brittle and grow horizontally just below the soil surface. Flood flows can undermine giant reed rhizome clumps and bring down an entire bank. Errant giant reed stalks dislodged during flood flows can pile up on river bends, get caught on rip-rap or revetments, behind bridge footings, on street drains, and on fencing and create flooding problems. Giant reed is an aggressive competitor. Giant reed is well adapted to the high disturbance dynamics of riparian systems. Flood events break up clumps and deposit propagative materials (rhizomes and stem nodes) downstream. Errant giant reed stalks Page 2 of 7

3 dislodged during flood flows can pile up on river bends, get caught on rip-rap or revetments, behind bridge footings, on street drains, and on fencing and create flooding problems. Giant reed tends to form large continuous clonal root masses that outcompete native vegetation. Giant reed is highly flammable but adapted to fire. Giant reed roots regrow quickly after a fire, before the native vegetation can respond, thus driving riparian habitat to pure stands of giant reed. Saltcedar has the potential to infest 70% - 90% of the vegetative cover, forming dense stands, substantially displacing native vegetation and reducing the value of critically important wetland complex. Saltcedar has been blamed for increasing flooding by forming a partial barrier to floodflow, which can cause floodwater to disperse and inundate areas that otherwise would not be flooded. Saltcedar is known to increase the deposition of salts on soil surface. Such deposits of salt-encrusted needles may affect water quality. Both giant reed and saltcedar are known to use more water than native vegetation. The control of giant reed and saltcedar can make more water available to native vegetation, wildlife, and livestock in a region. Land managers cite cases where springs have dried up following invasion by giant reed and saltcedar, with springs flowing again after removal. The presence of saltcedar in a habitat has been shown to dry up a habitat increasing the proportion of xerophytic plants in the habitat. Recreation benefit: The Santa Ynez River flows through the Los Padres National Forest for approximately twenty-five miles. Within the Los Padres National Forest, eight miles of the river are easily accessible by vehicles along Paradise Road. Another mile of the river is accessible by vehicle via Romero Camuesa Rd to Juncal Rd. Limited use of the rest of the river within the LPNF, except for Gibraltar Reservoir and Jameson Lake, are available to the more intrepid hiker. There are five campgrounds, five picnic areas, and two trailhead parking areas directly beside the river. The river is a major recreational resource in Santa Barbara County and is popular for swimming, camping, hiking, biking, habitat, wildlife, and fishing. The 2008 invasive plant survey indicates that saltcedar is the primary problem in the Los Padres National Forest. Cachuma Lake is a five mile long reservoir on the Santa Ynez River. Cachuma Lake Recreation Area, a county facility, is popular for camping, hiking, boating, habitat, wildlife, and fishing. Patches of saltcedar and some giant reed have been detected on the shores of Cachuma Lake. Ocean Beach Park is another county facility located at the mouth of the Santa Ynez River. Because of an active control project, giant reed and saltcedar are absent from the Santa Ynez River within Vandenberg Air Force Base. Page 3 of 7

4 Saltcedar and giant reed threaten recreation by inhibiting access to recreational sites because of their dense growth, and inhibits enjoyment of recreational sites because of their copious water use, habitat degradation, and the increase in flood, erosion, and fire risk. This project contains the threat thereby conserving recreational access and infrastructure. Saltcedar and giant reed threaten to infest the shores of Cachuma Lake This project will be operating on the shoreline and in the riparian vegetation areas of these recreational areas and will mostly not directly interact with the public. However, public access will not be restricted during the project, other than preventing access to treatment sites during the time of actual herbicide application. Biological Benefit: A primary goal of this project is the conservation of riparian habitat for birds, fish and other wildlife. Important bird species, among others, known to occur here are the southwestern willow flycatcher (SE) 1, least Bell's vireo (SE, FE), bald eagle (SE), yellow warbler (SOC), yellow breasted chat (SOC), Wilson's warbler, yellow billed cuckoo, and blue grosbeak. The southern California steelhead trout population (FE, SOC) in the Santa Ynez River watershed is part of the southern California steelhead Evolutionarily Significant Unit (ESU). Other wildlife known to inhabit the Santa Ynez River includes the Pacific treefrog, western toad, ensatina, western fence lizard, and common kingsnake. Arundo donax and Tamarix ramosissima are two non-native invasive plants that are widely recognized for their detrimental impact on biodiversity. An example of giant reed's dominance on a creek bank. Giant reed does not provide food or habitat for wildlife. Giant reed stems and leaves contain a wide array of noxious chemicals which protect it from grazing by native animals and insects. Caddisfly survival is poor when fed exclusively on giant reed leaf litter. Since caddis larvae and resulting terrestrial adult insects can be important food resources for other aquatic species, particularly insect-dependent salmonids, increasing dominance of waterways by giant reed can potentially harm populations of endangered steelhead trout. Because of its dense, vertical growth habit, giant reed does not provide prime nesting habitat, blocks access to the ground within patches and inhibits travel through the riparian corridor. Giant reed also lacks the canopy structure necessary to provide significant shading of bank-edge river habitats, resulting in warmer water than would be found with a native 1 SE = State endangered list; FE = Federally endangered list; SOC = Species of concern Page 4 of 7

5 gallery forest of Populus or Salix. As a result, riverine areas dominated by giant reed tend to have warmer water temperatures, which results in lower oxygen concentrations and lower diversity of aquatic animals, including fishes. This lack of streambank structure and shading has been implicated in the decline of native stream fishes and may also result in increased ph in the shallower sections of the river due to high algal photosynthetic activity. In turn, high ph facilitates the conversion of total ammonia to the toxic unionized ammonia form which further degrades water quality for aquatic species and for downstream users. Most birds do not use saltcedar in high proportions compared with native plant communities. Frugivores and insectivores, abundant in native riparian vegetation, almost completely avoid saltcedar. Studies showed that several species, including common flicker, yellow-bellied sapsucker, porcupine and beaver, had a higher affinity for the cottonwood-willow association. With the exception of desert woodrat and desert cottontail, no native mammal species are known to feed upon saltcedar. Saltcedar is known to increase the deposition of salts on soil surface. Such deposits of salt-encrusted needles can inhibit other plant species germination. Although certain wildlife species may find saltcedar beneficial to their survival, the encroachment of saltcedar has most certainly altered the native habitat that was apparently of great benefit to wildlife. Although the southwestern willow flycatcher can nest in saltcedar, infestations have a negative impact on most other birds that would normally use the native vegetation. Method: Arundo donax and Tamarix ramosissima are not easily controlled without the use of herbicides. This project proposes to use herbicides to eradicate Arundo donax and Tamarix ramosissima in the bed, and on the banks, and immediate overbanks along the entire length of the Santa Ynez River. Applicators will use handheld application equipment. The treatment of giant reed in the first year is estimated to take 4 weeks, and saltcedar treatment is estimated at 6 weeks. The amount of time needed will decrease with each subsequent year. Good control is expected to take 5 consecutive years of treatment. Monitoring is appropriate for 10 years. On most sites this project will use a helicopter to transport applicator personnel to treatment sites. Applicators using handheld equipment will be shuttled to treatment sites. Efficient use of the helicopter is realized when more than one applicator is available and applicators can be shuttled alternately to infested sites. A helicopter has the advantage in the many roadless areas that are a part of this project. Some sites will be treated by applicators and crews that access the site via trucks. Truck and foot access will be used where helicopter access will upset livestock. Giant reed will be treated by cut stump or foliar treatments with glyphosate or imazapyr herbicide. The method will be determined by site conditions. Cut stump is more directed and the preferred method around sensitive sites. Foliar treatment is more effective and economical and will be used when appropriate. The foliar method of giant reed control is the first choice. When necessary, giant reed foliage will be isolated from surrounding native vegetation, although there will be some damage to grasses and other annual vegetation immediately surrounding a patch. The project will use aquatic registered brands of glyphosate or imazapyr, when necessary. Page 5 of 7

6 On sensitive sites, cut stump treatment of giant reed can be utilized. Cut stump treatment involves cutting the giant reed down, and quickly applying undiluted glyphosate or imazapyr to the cut stump. Cut stump treatments allow for very little offsite overspray. Sensitive sites are primarily those areas where people will be involved and where the project will be able to effectively deal with the leftover giant reed cuttings. Saltcedar will be treated by foliar, basal bark or frill treatment with either glyphosate, imazapyr, or triclopyr. Basal bark and frill treatments will be the preferred method. Both have the advantage of very little offsite overspray. Imazapyr and triclopyr are more effective and will be used when appropriate. However, the Los Padres National Forest's Environmental Assessment only allows the use of glyphosate within their jurisdiction. Several exotic insect herbivores have been discovered feeding on giant reed in California. Three in particular, a stem-boring wasp (Eurytomidae: Tetramesa romana), a stem-feeding shootfly (Chloropidae: Cryptonevra sp.), and an aphid (Aphididae: Melanaphis donacis) are present in the Santa Clara watershed in neighboring Ventura County. This project proposes to support research to conduct trial sleeve-release tests to confirm establishment and prepare for open releases of giant reed biocontrols on the Santa Ynez River and Santa Barbara County. Leaf feeding chrysomelid beetles, Diorhabda elongata, have recently been shown to be highly successful in Tetramesa romana Photo courtesy of Tom Dudley controlling saltcedar in certain areas. This project proposes to support a study of the minimum requirements and performance of the saltcedar leaf beetle in Santa Barbara County. Most patches will be treated with herbicides and left intact to degrade naturally. Because of the dynamic nature of the Santa Ynez River, re-vegetation will not be conducted. Native recruitment is lower in re-created habitat than in natural regenerating habitat. The best way to address habitat loss in southern California riparian systems is through a comprehensive program of eradication of A. donax, T. ramosissima, and other invasive plants, and relying on natural physical processes, especially flood dynamics, for the recovery of native natural communities and species. Worst case scenario: Giant reed and saltcedar prefer riparian habitats. A riparian habitat is a distinct habitat susceptible to invasion. The invasion process occurs in three phases, introduction, colonization, and naturalization, over time and area invaded. The introduction of a plant into a habitat is the time to attempt eradication. Colonization can occur exponentially, until naturalization, at which time eradication is impractical. The Santa Ynez River infestation is perhaps in the colonization phase. Now is the time to act to prevent naturalization of giant reed and saltcedar on the Santa Ynez River. Page 6 of 7

7 References: Bell, G Ecology and Management of Arundo donax, and Approaches to Riparian Habitat Restoration in Southern California, In: Brock, J. H., et al (Eds.): Plant Invasions: Studies from North America and Europe. Blackhuys Publishers, Leiden, The Netherlands, pp Dudley, T.L. personal communication Dudley T.L Arundo donax In C.C. Bossard, J.M. Randall, & M.C. Hoshovsky, (Eds.), Invasive Plants of California's Wildlands, pp Berkeley and Los Angeles California: University of California Press Page 7 of 7