Noxious Weed Risk Assessment L 15

M N F S’ O October , Noxious Weed Risk Assessment — ❦ — L 15 R P (Signed) F J. G Forest Botanist () - [email protected] N W R A O , L R Table : Summary of Weed Risk Pre-Existing Risk Factors Risk . Adequacy of Weed Inventory Low. Known Noxious Weeds Moderate. Habitat Vulnerability Low. Vectors Unrelated to Proposed Project Moderate. Implementation Risk Factors . Habitat Alteration Moderate. Increased Vectors Moderate. Mitigation Measures Low. Anticipated Weed Response Moderate. ii I. Introduction A. A T D The purpose of this Noxious Weed Risk Assessment is to determine the risk of introducing or spreading noxious weeds through implementation of the Lassen 15 Restoration Project. In a noxious weed risk assessment, seven factors are rated for risk of introduction and spread of noxious weed species. The risks are tallied to get an overall risk for the proposed project. B. C M D The amended Sierra Nevada Forest Plan Amendment (SNFPA FSEIS, USFS ) provides direction for assessing the risk of introducing and spreading noxious weeds when planning projects. The Record of Decision for this plan amendment amework includes the following standard and guideline (ROD, pg. ): . As part of project planning, conduct a noxious weed risk assessment to determine risks for weed spread (high, moderate, or low) associated with different types of proposed management activities. Refer to weed prevention practices in the Regional Noxious Weed Management Strategy to develop mitigation measures for high and moderate risk activities. N W R A O , L R II. Weed Risk Assessment For details about the locations of project units and the proposed actions being analyzed, please consult the Environmental Assessment for this project. A. P-E R F . A W I Floristic botanical surveys for this project and other projects in the same area, in part look- ing for noxious weed infestations, took place between and . Data om previous surveys in the same areas, concurrent surveys for other projects, and other sources of infor- mation were also consulted for this assessment. Because sufficient efforts have been made to inventory known weeds on these project areas, the risk of project activities encountering and exacerbating previously unknown weed sites is considered low. K N W Two sites of spotted knapweed (Centaurea stoebe ssp. micranthos), two or three sites of Dal- matian toadflax (Linaria dalmatica), four sites of Scotch thistle (Onopordum acanthium), all California Department of Food and Agriculture List A noxious weed species; and six sites of Canada thistle (Cirsium arvense) and five sites of Mediterranean sage (Salvia aethiopis), both CDFA List B noxious weed species, have been identified within or very close to the project areas (CDFA ). Please see Table for more details. Bull thistle (Cirsium vulgare), another CDFA List B noxious weed, has been recorded om several locations within the project area, but sites have not been included in the table. Firstly, surveys for this plant were conducted by another agency in , but several sites originally identified as bull thistle have since been recognized as native thistle species such as peregrine thistle (Cirsium cymosum), which are considered beneficial components of the native flora. The author has decided to exclude these data as unreliable. Secondly, in the judgement of the author, bull thistle in the Modoc appears more a passenger than driver of disturbance, growing most thickly in heavily disturbed areas but yielding to later-seral species as time passes, provided that the disturbance does not recur. Bull thistle produces abundant wind- borne seed and consequently may be found in low concentrations across most of the Forest. N W R A O , L R For these reasons, bull thistle occurrences are equent but oen small and, in ecologically healthy areas, tend to appear and disappear om one year to the next, making treatment and monitoring unnecessary (this may be another reason that some bull thistle sites om cannot be relocated). Because of this, bull thistle is not usually mapped on the Modoc NF. The author has decided to exclude bull thistle om detailed documentation for the sake of practicality and consistency with noxious weed risk assessments undertaken elsewhere on the Forest. There are several weed sites comprising a diversity of noxious plant species, which elevate risk. However, given that surveys are tolerably complete and noxious weed sites appear to constitute less than % of the project area, the risk is not overwhelming. The risk is therefore considered moderate. H V In the aermath of large wildfires near Sugar Hill in the early to mid th century, the Forest Service implemented programmes of replanting forest in windrowed plantations, as was the custom of the time. Thus, there are areas of extensive historic soil disturbance. A diverse and healthy assemblage of native plant species characterizes nearly all treatment units visited, including the plantations, although nonnative species were more prevalent there. Some plantations appear to have been sown with nonnative range grasses. Nonnative species besides the noxious weeds listed above, such as a variety of annual bromes, were discovered in many areas but generally in low concentrations. Since the native plant community appears to be relatively intact, despite known disturbances in the past such as grazing, logging, tree planting, and wildfire, the habitat vulnerability is judged to be low. V U P P Roads crisscross the general project area. Noxious weeds are oen found close to roads; of the noxious weeds sites listed in Table are associated with roadsides. Forest Road is considered a relatively well-traveled road within the Forest, although it does not carry nearly the traffic volume of local paved highways that would represent a high risk om vectors. Roads are conduits for vehicles, which are very effective weed vectors (Von der Lippe & Kowarik ). Vehicles may belong to Forest Service staff, range permittees, firewood gatherers, recreation- ists, or other members of the general public. Vehicles may not be clean and ee of weed- transporting debris, and may bring weed seeds om long distances away. The Lassen Creek Campground is located in the northwest of the project area. Concen- trations of noxious weeds associated with the site of the former Crane Creek Lumber Co. occur about ½ mile to the northwest of the campground. Forest visitors to the campground may encounter noxious weeds and inadvertently contribute to their spread by hiking through infestations that have produced viable seed. During the warmer seasons of the year, permitted cattle graze the Lassen Allotment, within N W R A L R O , which the proposed activity units are located. Livestock can serve as vectors for noxious weeds by carrying around seeds or other propagules on their hooves, their fur, or by ingesting and later depositing viable seed (Vavra et al. ). They may spread existing infestations further, or introduce weeds om off-Forest. The permitted cattle are owned by a ranch in Lake City. Local herbivorous wildlife may also act as vectors in a similar way, although they are not as effective vectors as cattle (Bartuszevige & Endress ), perhaps due to different digestive biology. Existing vector risks are, therefore, posed by Forest visitors and by livestock. The area is neither so remote as to minimize the risk om visitors, nor so highly visited as to pose a high risk. Livestock numbers and seasons of use are subject to permit conditions, meaning that while they are vector risks, their presence on the Forest is managed. The cattle live on a nearby ranch and thus are not a great risk for introducing novel weed propagules om great distances away. The risk of vectors unrelated to the proposed project introducing or spreading noxious weeds is therefore considered moderate. B. I R F . H A In pile-and-burn units, slash would be piled and the piles would be burnt. While more quickly eliminating excess fuels, burn piles will result in scatterings of small, intensely disturbed spots of denuded and sterilized soil. These spots are favorable habitat for nonnative species such as noxious weeds (Haskins & Gehring ). Removing some overstory canopy would reduce shading, which may favor noxious weeds which are adapted to more open sun. Replanting a few open areas within plantations would similarly reduce weed risk in those areas, provided that tree density is managed in the future to prevent a fuels hazard. The proposed actions may also alter the habitat for the better by reducing the threat of large-scale intense wildfire, which could create extensive contiguous areas of the open primary- successional habitat that is favored by our noxious weeds (Alba et al. ), through fuels reduction treatments and fuel-break creation and maintenance. According to the soils report for this project, “[v]egetation treatment activities associated with the proposed action are expected to result in limited compaction and soil displacement.” Plans to redistribute topsoil in old plantations, however, may cause more extensive localized soil disturbance. Given these factors, the risk of habitat alteration due to project implementation is considered moderate. N W R A O , L R . I V Mechanized timber harvesting equipment, masticators, fire suppression traffic, graders, back- hoes, and worker transportation vehicles would come onto the forest in order to implement the project. Some of this equipment, such as the masticators, may also effectively spread weeds that are already found within the project area. Besides the people and equipment required to implement the project, no other increased vectors can be foreseen. The risk om increased vectors, considering mitigation measures requiring equipment cleaning before entering the project area, as well as mitigation measures preventing project activities and equipment om interacting with known sites, is considered moderate. M M These mitigation measures are to be integrated as features of the project design for noxious weeds. Known noxious weed sites will be flagged with yellow and black checkered flagging (and, where possible, treated) prior to implementation and avoided by project activities whenever it would be possible while still achieving the project’s desired conditions.

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