General Noxious Weed Risk Assessment Information
Forest Service Manual 2080 Noxious Weed Management (effective since 11/29/95) includes a policy statement calling for a risk assessment for noxious weeds to be completed for every project. Specifically, the manual states:
2081.03 - Policy. When any ground disturbing action or activity is proposed, determine the risk of introducing or spreading noxious weeds associated with the proposed action.
1. For projects having moderate to high risk of introducing or spreading noxious weeds, the project decision document must identify noxious weed control measures that must be undertaken during project implementation.2081.2 - Prevention and Control Measures. Determine the factors which favor the establishment and spread of noxious weeds and design management practices or prescriptions to reduce the risk of infestation or spread of noxious weeds.
4. Use contract and permit clauses to prevent the introduction or spread of noxious weeds by contractors and permittees. For example, where determined to be appropriate, use clauses requiring contractors or permittees to clean their equipment prior to entering National Forest System lands.
Where funds and other resources do not permit undertaking all desired measures, address and schedule noxious weed prevention and control in the following order:
1. First Priority: Prevent the introduction of new invaders,Prevention Emphasis
2. Second Priority: Conduct early treatment of new infestations, and
3. Third Priority: Contain and control established infestations.
Some points about noxious weed management are worth keeping in mind. The most important principle is that an ounce of prevention is worth a pound of cure. It is much cheaper to prevent an infestation from becoming established than to try to eliminate it once it has begun to spread, or to deal with the effects of a degraded plant community. Prevention includes both reducing the human-assisted spread of seeds and other reproductive parts into a weed-free area, and prompt eradication of the first plants that show up. (Preferably treatment occurs before plants reproduce, and especially before they reproduce several generations which may result in a locally adapted (and explosive) weed genotype; yellow star thistle in particular has been observed to follow this pattern.)
With noxious weeds, it's never a good idea to "wait and see" if a known pest will become a problem. The most aggressive species will quickly become very expensive to control. Once a priority noxious weed (particularly one on California Department of Food and Agriculture (CDFA) list A or B) is identified in an area, should be eradicated immediately, while the costs are relatively small. Hand-pulling the first plant or few noxious weed plants that show up in an area is the most efficient and effective way we have for reducing weed spread. That is why a good noxious weed inventory is so important, because inventory and initial attack can often occur at the same time.
Once noxious weeds have been identified in an area, three methods are generally used to control them: mechanical, chemical, and biological. Cultural practices may also help control weed spread.
Mechanical. The simplest and often most effective mechanical control is hand pulling or grubbing. If this is done before seed set, plants can be pulled and left in place. After seed maturity, plants, or at least seed heads, should be bagged and removed from the site and burned or otherwise disposed of. Other mechanical options include mowing and disking, which, while they may set some weed populations back, are rarely effective in eliminating noxious weeds from a site. Mowing, for instance, often produces plants that are simply shorter and more branched, but still produce seed. It is important to know how the particular weed reproduces, since some weeds reproduce by spreading rootstalks and mechanical control may not be as effective with these types of weeds.
Chemical. Chemical control usually refers to herbicide use on noxious weeds. Herbicides may kill plants on contact with the foliage (for example, glyphosphate), be pre-emergent inhibitors which do not allow seeds to germinate, or be soil-moisture activated, which kill through interaction with the root systems (for example, hexazinone). Herbicides may be selective (for instance, killing broadleaf plants but not grasses or conifers) or broad spectrum.
If you want to use chemical treatments, consider the following:
· What the target weed species isChemical controls may be controversial to some people. The Tahoe National Forest has done NEPA analysis for herbicide use for noxious weed management and the Plumas and the Lassen have not. Although the other forests do coordinate with CDFA and county agriculture commissioners to control most A-rated noxious weeds on National Forest System lands, currently, only the Tahoe is actively spraying herbicides for noxious weed control within the analysis area.
· The time of application of the chemical (related to plants' phenology and soil moisture conditions)
· Method of application (hand-spread granular materials, backpack or boomtruck sprays, or aerial application), and
· Adjacent sensitive resources (rare plants or animals, municipal watershed, riparian areas).
Selection of an herbicide or herbicides should be as target-specific as possible, so that the weeds are eliminated, but natives or other desirable plants are not. Application methods should also focus on direct application to targeted weeds. This helps maintain native plant communities and vegetative competition to resist reinfestation.
Chemical control is generally more effective and cost efficient than hand-pulling when a patch of weeds has exceeded a few dozen plants, or when a weed seed bank has developed on the site. It is sometimes the only effective method for some rhizomatous or deep-rooted species.
Biological. Biological controls may be insects or disease that attack a noxious weed and kill it, reduce its reproduction, or weaken it so it is not as competitive with desirable vegetation. Bio controls should be target-specific so they will kill the intended weeds but not natives or other desirable species. The biological agent should be able to reproduce and spread quickly enough to keep up with the noxious weed invasion. Bio controls undergo rigorous testing for suitability and specificity before release.
Biological controls are not effective on small, isolated, satellite weed populations, and therefore are not suitable for reducing the spread of noxious weeds. Since a fairly large infestation is required to provide feed for the agent over several generations, and since bio controls never totally eliminate an occurrence, biological control is effective only for attempting control of large, otherwise "lost cause" infestations.
Cultural Practices. Cultural practices in this context refers to land management activities that promote vegetative conditions least conducive for noxious weed spread. For example, management practices that reduce soil disturbance, promote more soil cover (duff, litter, and desirable vegetative cover), provide for more shade, or otherwise favor desirables and natives over noxious weeds, may help slow noxious weed spread. Cultural practices fit into both the control and prevention categories.
See the following table for the general outline of a risk assessment.
|Non-proposed Action Dependent Factors|
|1. Inventory||Site-specific area, identify, map, estimate numbers/acres||Adequate ------------>
|Continue with Risk Assessment.
Complete inventory first.
|2. Known Noxious Weeds||# of A, B, or C-rated weeds, number of infestations, size||None present or adjacent ------------->
Only low priority species present ------------------------>
High priority species present ------------------------>
|Prevention high priority; no control.
Prevention high priority; control low priority.
Incoming prevention lower priority, but high priority to prevent spread within and from project area; evaluate control priority.
|3. Habitat Vulnerability||Previous disturbance, plant cover, soil cover, shade, soil type, aspect/moisture||Open habitat and/or high previous disturbance ---------->
Moderate cover, disturbance ---------->
High cover, low disturbance ---------->
|High current vulnerability.
Moderate current vulnerability.
Low current vulnerability
|4. Non-project dependent Vectors||Existing roads and trails, traffic use, livestock/ wildlife migrations, wind patterns, drainage flow direction||Abundant current
Moderate current vectors -------------->
Few current vectors ------------------------>
|High current vulnerability.
Moderate current vulnerability.
Low current vulnerability.
|Proposed Action Dependent Factors|
|5. Habitat Alteration Expected as a result of Project||Logging prescriptions, road construction, fuels prescriptions, change in grazing management or recreation use, intensity and extent of disturbance||High ground disturbance, shade and duff removal--------->
Moderate disturbance, shade and duff removal ------------------------->
Low disturbance; minimal shade and duff removal--------------->
|6. Increased Vectors as a result of Project Implementation||Road construction, facility construction, amount of project-related traffic||Road or facility construction ---------->
Temporary roads; short-term traffic increase-------------->
No access improvement; minimal project-related traffic ----------------------->
|7. Mitigation Measures||Prevention (equipment washing, weed-free materials, monitoring), control (prompt action on small infestations), cultural practices (maintain shade, minimize disturbance, design project to reduce weed flow)||No mitigation measure implemented ---------->
Implement some mitigation measures -->
Implement all mitigation measure -------------->
Moderately reduced risk.
Greatly reduced risk.
|8. Anticipated Weed Response to Proposed Action||Tally "high risk" responses in previous factors; consider mitigation if it is adopted as part of the proposed action.||Numerous high risk factors ------------->
Few high risk factors >
No high risk factors ->
|High potential for significant increased weed spread as
a result of project implementation.
Moderate potential for weed spread.
Low potential for weed spread.
|9. Costs||Consider current treatment/prevention costs
as part of the project; VS
future treatment cost of much larger infestations; OR
habitat degradation costs (Economic: forage, harvest game species, competition with timber, recreation value, fuel loadings. Ecological: TES species, visuals, watershed, biodiversity.)
|Generally, it's more economically efficient to prevent and treat small infestations than to wait until too large.|
QLG EIS Project Noxious Weed Risk Assessment
The following risk factors apply to the QLG EIS analysis area as a whole. Implementation of treatments will require site-specific analysis at a finer level. More detailed risk analysis should be done at the treatment implementation stage to determine which mitigation measures are appropriate for each activity. In general, prevention measures will apply to all projects, but control activities will depend on which noxious weeds are present in the particular project area and how large the infestation is.
Inventory and Known Noxious Weeds Present
For the QLG area as a whole, inventories are piecemeal--with some localized areas fairly well surveyed, and others not at all. Site-specific analysis will require inventory for noxious weeds.
There are numerous noxious weeds within or near the analysis area, including a high percentage of potentially very aggressive (CDFA A-rated) weeds, which contribute to a high risk factor for the area as a whole. In addition, the three Forests are surrounded by very weedy areas, which provide continuous infestation sources for the National Forest System lands. In particular, agricultural and range lands near the Forests have abundant yellow star thistle galloping toward the Forests, and infestations of other high-rated weeds like dyer's woad and knapweeds which have greatly increased near Forest lands. However, it is important to keep in mind that most infestations are small, and probably 95 percent of our three-Forest area is noxious weed free. Our main objective is to keep those habitats in that healthy condition.
On a finer scale, at the project implementation level, to maintain weed-free areas clean and to eliminate current infestations or at least keep them from spreading, it will be important to identify the units that contain noxious weeds and those that do not.
In most cases, there will be no noxious weeds. Priority, then, will be on prevention measures. On areas where there are noxious weeds, treatments should be prioritized and evaluated. (See below.)
There are many habitat types in various conditions in the analysis area as a whole. Broad vegetation types include:
Although we have little information on noxious weed spread rates in relation to such smaller-scale habitat vulnerability factors such as aspect and soil type, such factors should be evaluated on a site-specific level. Previous assumptions about elevation limits for noxious weeds have proven false. For example, yellow star thistle, once thought to be limited to elevations below 3,000 feet, has been reported at the 8,000 foot elevation.
Non-project Dependent Vectors
There are many potential noxious weed vectors within the analysis area. The three Forests are heavily used by recreation and commercial visitors. Major highways (both interstate (I-80) and intrastate (such as Highways 89, 44, 36, 32, 70, 49, 20)) run through the three Forests, as well as several county roads and an extensive Forest Service road system. The Lassen National Forest, for instance, has approximately 3,472 miles in the Forest Development Road System and 1,260 miles of State, County, and private roads on the Forest (Lassen National Forest Land and Resource Management Plan 1993 p 3-6). Abundant hiking trails (465 miles on the Lassen), OHV trails, livestock and game trailing routes, and skid trails facilitate noxious weed movement. Waterways (lakes, rivers, streams, and ditches) also contribute to the spread of weed seed and plant parts.
Seed and plant parts may inadvertently be carried on vehicles and equipment, camping gear, animals, and gravel and other fill materials. Sometimes noxious weeds are more actively (although still inadvertently) spread in forage or mulch materials, by recreational "wildflower pickers," or as a contaminant in seeding mixtures.
Habitat Alteration Expected as a Result of this Project
The Act calls for 40,000-60,000 acres of fuelbreak construction, and group selection on an average of .57 percent of the pilot project area land each year. The total for these management activities is not to exceed 70,000 acres per year. It also allows for individual tree selection, and calls for riparian restoration activities. Road work associated with these activities will also occur; up to 1,260 miles of road work is estimated for this project over a five-year period.
Defensible fuel profile zone (DFPZ) specifications call for production of a shaded fuelbreak with fairly open stands dominated mostly by larger trees of fire-tolerant species. DFPZ's will likely result in moderate shade and soil cover removal and soil disturbance. Associated landings will be highly disturbed areas. Fuelbreaks will generally be placed along roads; DFPZ arrangement will be exclusively linear in Alternative 2 and a combination of linear and areawide blocks of fuel treatments in Alternatives 3, 4, and 5 (the acreage and arrangement of DFPZ's varies between alternatives). Fuelbreak widths will vary, based on strategic importance, topography, and other conditions, but linear strips will generally be 1/4-mile wide. Areawide treatments will be much broader. Most work is likely to be done by tractor logging, machine biomass removal (feller/bunchers), and machine fuel piling. Some areas (such as within riparian zones) may involve hand thinning and fuel piling instead. Broadcast prescribed fire may also be used, either alone or more likely following thinning, to create fuelbreak conditions, and burning of piled fuels is likely with any of these treatments.
In Alternatives 2-4, group selection will occur on about 8,700 acres per year across the three Forests. Group selections are small (generally less than two acres) clearcuts where all merchantable trees are removed (after CASPO basal area and diameter limit restrictions have been met). The area may then be site-prepped (slash piled and/or burned) and either replanted with conifers or allowed to reseed naturally from the adjacent timber stand or residual large trees. Since each group selection is a small area, and large total acreages are mandated by the Act, the number of group selections will be very high. Access routes to each group selection may include skid trails, existing roads, and/or new temporary or permanent roads. Habitat alteration within group selections, access routes, and landings will be very high, while the surrounding stand (unless it is within a DFPZ) will not be altered.
Apart from DFPZ and group selection units, individual tree selection will be used for thinning units; CASPO restrictions will apply. There will be an estimated 5,800-6,800 acres per year of individual tree selection in the pilot area. Habitat alteration in the thinning units will likely be similar to DFPZ's, except that the resulting stands are likely to have more cover than a DFPZ. Hazard trees will also be managed, causing localized disturbance and habitat alteration.
Watershed restoration projects focus on road maintenance, improvements, and obliteration, integrated with stream and meadow restoration projects. The extent of these activities has yet to be determined, but in comparison to DFPZ and group selection activities, habitat alteration for restoration activities is likely to be more localized (since acreage targets are not specified).
Road construction, reconstruction, temporary roads, heavy maintenance, and relocation, in particular, and obliteration, to a lesser degree, will cause major habitat alteration in their immediate and adjacent areas. Roads produce a recurring disturbed area highly conducive for noxious weed growth. Road work is estimated at 168 to 252 miles per year for Alternatives 2-4.
Increased Weed Vectors as a Result of this Project
As access into specific project areas is improved, road construction, reconstruction, temporary roads, heavy maintenance, and relocation will increase the number of vectors for bringing weed seed into the pilot area. Road obliteration will cause a decrease in the long-term weed spread vectors. In Alternatives 2-4, over a five-year period, 820-960 miles are estimated in the former categories and 200-300 miles in the latter category. The net result would be an increase in potential weed vectors from roads in the pilot area.
Since the Act calls for up to 70,000 acres of timber and fuels management per year in the analysis area, there will be a significant temporary influx of equipment and workers for these projects. This will result in a short-term increased potential for the introduction and spread of weed seed and plant parts. Mitigation (see below) may reduce this risk.
Riparian restoration and any other revegetation or restoration work associated with this project may have similar increased vector risks from equipment and crews coming on site, although the scale is likely to be much smaller. Revegetation and erosion control materials, such as seed mixes, rooted stock, mulches, fill, and gravels also have the potential for introducing noxious weeds into an area. Again, rigorously applied mitigation measures will reduce or eliminate this risk.
There are no changes expected in state or county roads, visitor use, grazing, or wildlife migration patterns as a result of the QLG project, so no change in weed vectors from these factors is expected.
For the QLG EIS, mitigation measures proposed for noxious weed management range from inventory, control, prevention, to monitoring are:
Inventory project area: Inventories across the QLG area are incomplete. In order to more accurately assess the site-specific risk and control measures necessary, surveys should be done on the individual project level.Anticipated Weed Response to the Proposed Action
Evaluate control of existing noxious weeds: Promptly treating small, isolated patches of noxious weeds in or near a project area is highly effective and efficient in reducing the risk of weed spread due to project activities. Options for treating larger existing patches should be evaluated on a site-specific basis. Site-specific NEPA documentation will be needed for control activities; generally this will be done as part of the pilot implementation projects' NEPA.
Prevention/Equipment washing: Requiring clean off-road vehicles and equipment is effective in reducing the risk of weed introduction into an area.
Prevention/Weed-free material: Requiring weed-free road fill, gravel, mulches, and seed sources is effective in reducing the risk of weed introduction.
Monitoring: Monitoring for new infestations of noxious weeds during and following project implementation, and prompt treatment of any noxious weeds found, is effective in halting the spread of new weeds into an area.
Prevention/Cultural practices: In some cases, designing the project to maintain shade, maximize desirable vegetation and soil cover, minimize soil disturbance, and reduce potential weed vectors can be moderately effective in slowing the spread of noxious weeds. Since the QLG project direction is spelled out in the Herger-Feinstein Act, however, prescribing treatment and acres fairly specifically, we have less latitude for project design than usual. Minimizing soil disturbance and maximizing shade and cover while still meeting DFPZ and group selection objectives to the extent practical is a worthy goal, but the actual result on the ground for this project is not likely to be very effective in reducing potential weed spread.
Overall, high risk factors include a large number of particularly nasty noxious weeds present in the analysis area, moderately high level of previous disturbance, an abundance of weed vectors, moderate to high habitat alteration proposed from this project, and temporarily and permanently increased vectors, resulting in a cumulative high potential for the project to increase noxious weed spread. These risks may be reduced substantially by application of the proposed mitigation measures.
The expected weed response will vary somewhat depending on the specific action. In DFPZ's, a somewhat open stand (moderate habitat vulnerability), often adjacent to roads (high introduction potential) creates the potential for greatly increased weed spread both linearly (down the length of the DFPZ) and laterally into the modified (and from there into the unmodified) timber stand or other vegetation zone. DFPZ's located in or near riparian areas may cause weed spread into this sensitive habitat and would be particularly degrading. Since such a large acreage (25,000-60,000 acres per year for Alternatives 2-4) and span are involved, this may result in a significant increase in noxious weed spread as a result of this project. Application of mitigation measures will reduce this risk.
Group selections will create localized disturbed areas highly conducive to noxious weed growth. Collectively, since there will be so many group sites, these pockets could contribute to an increase in noxious weeds, depending on what weeds are in the localized area, and what are brought in by project activities. Access routes for group selection areas will also have a great influence on the spread of noxious weeds between group selection areas, and into other forest areas. Again, mitigation measures can reduce this anticipated effect significantly.
Individual tree selection thinnings will result in a weed response similar to DFPZ's except with somewhat less risk since the resulting stand is likely to be higher in canopy cover than in DFPZ's, and units are not necessarily arranged linearly and associated with roads.
Riparian restoration projects will produce localized disturbance from heavy equipment and prescribed burning within RHCA's where these activities are being used to meet riparian objectives, and a temporary increase of traffic (from work crews) and associated potential weed vectors. This will result in an increased risk of weed spread into this very sensitive habitat. Mitigation measures will reduce this risk.
Road work will result in an increase in noxious weeds due to both the habitat modification and increased vectors for weed introduction. Mitigation will reduce the short-term risk of project-related introduction, but longer-term risks from increased access and consequent disturbance will continue.
Treatment activities (control of existing noxious weed occurrences) implemented as part of project activities will result in a decrease in noxious weed spread and infestation. This is most effective for small, isolated patches of noxious weeds in or near the specific project area.
Costs and Benefits
It is generally difficult to produce meaningful figures in a cost/benefit analysis for noxious weed prevention since it requires assumptions on the rate of weed spread, future control costs, habitat vulnerability, and other factors that are difficult to determine, and it requires attaching monetary values to resources which are not readily appraised. However, in general, it is much cheaper to prevent infestations and treat small, new infestations than to attempt to treat large outbreaks. Wildfire initial attack makes a good analogy, except that noxious weeds will never burn themselves out.
Treatment costs cannot be estimated at this time, since we do not know how many acres of noxious weeds currently occur in any site-specific project area. However, noxious weed patches targeted for treatment are likely to be small; a major eradication project for a large area would be beyond the scope of this document and require its own analysis. The emphasis on treatment with the QLG project would be to prevent small, isolated patches from spreading as a result of QLG activities.
Prevention measures proposed for this project, such as equipment cleaning, use of weed-free material, and selected cultural practices, will result in an undetermined increased cost for project implementation. These increased costs are not anticipated to be prohibitively expensive, and need to be weighed against anticipated benefits.
Benefits for keeping an area noxious weed-free include economic factors, since weed-free land has a higher appraisal value for forage, harvest game species, commercial timber growth, recreation, and reduced fire risk. Ecological factors are more difficult to quantify but are at least as important, since noxious weeds degrade Threatened, Endangered, Sensitive, and rare species habitat, visuals, watershed values (by increased erosion), and biodiversity. The cost of current treatment and prevention would also be weighed against the future cost of treating a much larger infestation and future land degradation if prevention measures or control of small patches are not undertaken now.
Table G-2 Noxious Weeds in Quincy Library Group Bill Area National
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