Preventing and Managing Invasive Plants Final Environmental Impact Statement April 2005 

Appendix J-1 

The Effects of Non-herbicidal Methods of 

Invasive Plant Treatment on 

Wildlife, Fish, and Plants 

A Specialist’s Report prepared for the USDA Forest Service, 

Region 6, Invasive Plant EIS 

April, 2005 

Prepared By: Shawna L. Bautista, Wildlife Biologist 

 Linda Mazzu, Botanist 

 Jan Robbins, Hydrologist 

 Diana Perez, Forest Fisheries Biologist

 Lia Spiegel, Entomologist 
Preventing and Managing Invasive Plants Final Environmental Impact Statement April 2005 

Appendix J-2 

Non-herbicidal Methods of Invasive Plant Treatments 

Introduction 

Invasive plants may be treated or controlled by a wide variety of methods and tools. The 

effects of herbicide use are discussed in separate reports, or in the body of the EIS. Nonherbicidal methods considered in this report include, manual, mechanical, fire, cultural, 

restoration and revegetation, and biological control. In some cases, the boundary blurs 

between methods. What is considered a cultural method by some may be considered 

simply revegetation by others. 

Because this appendix may be used as a stand alone document, some of the information 

found in the EIS is repeated here. The first section describes the methods of nonherbicide control. It contains information from Chapter 3 and some additional examples 

of use in the field. The second section includes the environmental consequences; the 

majority of the second section is only found in this Appendix. 

Description of the Methods 

Manual and Mechanical 

Manual and mechanical treatments physically remove and destroy, disrupt the growth of, 

or interfere with the reproduction of invasive plants. These treatments can be 

accomplished by hand, hand tool (manual), or power tools (mechanical); and include 

pulling, grubbing, digging, hoeing, tilling, cutting, mowing, and mulching of the target 

plants. Thermal techniques such as steaming, super heated water and hot foam are also 

considered as viable treatments. 

Manual methods can be effective on small infestations if the entire root is removed. With 

new, small infestations, hand pulling can be the easiest and quickest method. Even larger 

populations, though, can be controlled with hand pulling if the workforce is available. 

The Bradley Method is one sensible approach to manual control of invasive plants (Fuller 

and Barbe, 1985). This method consists of hand weeding selected small areas of 

infestation in a specific sequence, starting with the best stands of native vegetation (those 

with the least extent of infestation) and working towards stands with the worst 

infestation. 
Preventing and Managing Invasive Plants Final Environmental Impact Statement April 2005 

Appendix J-3 

Manual methods are usually not as effective for deep-rooted or rhizomatous1 perennials 

such as leafy spurge where hand-pulling and hoeing often leave root fragments that can 

generate new plants. Hand-pulling or hoeing also disturbs the soil surface, which may 

increase susceptibility of a site to reinvasion by weeds (Brown et al., 2001; Duncan et al., 

2001). Manual methods are labor-intensive and usually ineffective for the treatment of 

large, well-established infestations of perennial invasive plants with long term viable seed 

such as knapweeds (Brown et al., 2001). Local efforts where larger community support 

or funding for hand crews exists do show promise, if efforts can be sustained (Henry, 

2004). 

The Nature Conservancy reported success with the use of manual control. (Tu et al., 

2001). Hand pulling by volunteers has successfully controlled Centaurea diffusa (diffuse 

knapweed) in the Tom McCall Preserve in northeast Oregon. Yellow bush lupine 

(Lupinus arboreus) was also controlled in coastal dunes in California by pulling small 

shrubs by hand. Larger shrubs were cut down with an ax, and re-sprouting was 

uncommon (Pickart and Sawyer, 1998). Hand pulling has also been fairly successful in 

the control of small infestations of Centaurea spp. (thistles), Melilotus officinalis (white 

and yellow clover), and Lythrum salicaria (purple loosestrife) at TNC preserves scattered 

across the country. 

Manual tools such as the Weed Wrench (www.weedwrench.com) can be used on 

herbaceous plants that have a stem or bundle of stems strong enough to withstand the 

crush of the jaws. It has been used successfully to pull acacia (Acacia melanoxylon), 

buckthorn (Rhamnus cathartica), Russian olive (Elaeagnus angustifolia), multiflora rose 

(Rosa multiflora), willow (Salix spp.), tamarisk (Tamarix spp.), bush honeysuckles 

(Lonicera spp.), Scotch broom (Cytisus scoparius), French broom (Genista 

monspessulanus), and Brazilian pepper (Schinus terebinthifolius) at preserves across the 

mainland U.S. In Hawaii, the Weed Wrench has been used to pull Strawberry guava 

(Psidium cattleianum) and small saplings of Karaka nut (Corynocarpus laevigatus) from 

the Kamakou preserve on Molokai (Hawaii) (Tu et al, 2001). 

Mowing or cutting is more effective on tap-rooted perennials such as spotted knapweed 

compared to rhizomatous perennials (Brown et al., 2001). Cutting or mowing plants can 

reduce seed production if conducted at the right growth stage. For example, a single 

mowing at late bud growth stage can reduce the number of seeds produced on spotted 

 

1

 Rhizomes are horizontally creeping, underground stems, which bear roots and leaves. Rhizomatous 

species tend to spread very quickly because of these growth structures. 
Preventing and Managing Invasive Plants Final Environmental Impact Statement April 2005 

Appendix J-4 

knapweed (Watson and Renny, 1974). Mowing can also weaken an invasive plant’s 

competitive advantage by depleting root carbohydrate reserves, but mowing must be 

conducted several times a year for consecutive years to reduce the competitive ability of 

the plant. 

Oregon Department of Agriculture staff compared mowing and pulling mature plants to 

no treatment in two western Oregon spotted knapweed infestations. They applied one 

treatment annually at the optimum time for each of four consecutive years, and concluded 

that neither method was effective in reducing population density or cover. They 

recommend consideration of pulling and mowing only, where the goal is to contain 

spotted knapweed infestations or to suppress seed production (Isaacson et al., 1997). 

Because invasive plants flower throughout the summer, it is difficult to time mechanical 

treatments to prevent flowering and seed production. Repeated mechanical treatment too 

early in the growing season can result in a low growth form that is still capable of 

producing flowers and seed (Benefield et al., 1999; Goodwin and Sheley, 2001). 

Mechanical treatments on some rhizomatous weeds, such as leafy spurge, can encourage 

sprouting and result in an increase in stem density (Goodwin and Sheley, 2001). 

Tillage methods are most effective for controlling tap-rooted invasive plant species on 

small acreages and level terrain, where infestations can be revisited on a regular basis to 

remove new germinants and resprouts over time. Tillage removes all vegetation and 

should be combined with seeding or planting of desirable species. Invasive plant seeds 

may remain viable in soil for several years (Davis et al., 1993; Selleck et al., 1962) and 

often may reinfest a tilled site, thus requiring continued follow-up treatments. 

Mulching with plastic or organic materials can be used on relatively small areas (less than 

0.25 acre), but will also stunt or stop growth of desirable native species. Mulching 

prevents seeds and seedlings from receiving sunlight necessary to survive and grow, and 

can smother some established invasive plants. Hay mulch was used in Idaho to reduce 

flowering of Canada thistle (Tu et al., 2001), but most rhizomatous perennial invasive 

plants cannot be controlled by this method or by shading because extensive root reserves 

allow regrowth through and around mulch or shade materials. A new mulch made from 

wood products is currently being tested by the Forest Service and shows promise as 

having equivalent or higher erosion control potential than regular straw mulch (Forest 

Concepts, 2004). 
Preventing and Managing Invasive Plants Final Environmental Impact Statement April 2005 

Appendix J-5 

Thermal techniques are being tested or used with some success throughout Region Six by 

such agencies as Oregon Department of Transportation (ODOT), the Nature Conservancy 

and the Bureau of Land Management (BLM). ODOT has converted a mowing unit to a 

thermal heat unit for treating roadsides (Prull, personal communication, 2004). It has be 

most successful when used for maintenance treatments instead of initial treatments. The 

Nature Conservancy (Tu et al, 2002) tested the Eco-Weeder, an infrared technology 

device that uses the combustion of liquid gas to reach extremely high temperatures that 

place intense radiation directly on weeds to explode plant cells. The tool could be useful 

for small area treatments, especially on sidewalks, but the effectiveness on deep-rooted 

plants, sedges or rhizomatous grasses may not be as high. The Nature Conservancy also 

tested hot water pressure washers. The brand tested could apply hot water through a 

pressure nozzle with a wide spray or intense stream which would act as an injection 

device for below ground portions of plants. They found it effective on seedlings and 

annual plants within reach of the washer, but the effectiveness on plants with extensive 

underground roots or rhizomes would be less. Hot foam has been tested by the Nature 

Conservancy and used by the BLM effectively on puncturevine and slender false brome. 

Again, this technique is limited to the reach of the foam generator, but is an excellent 

non-chemical method. It is effective on seedlings and annuals and can be applied under 

weather conditions including wind and light rain. It has shown some success with 

perennials and an injection tool has shown some success with knotweeds (Fairchild, 

personal communication, 2004). 

Cultural Methods 

Cultural methods of invasive plant management are generally targeted toward enhancing 

desirable vegetation to minimize invasion. Common cultural treatments include planting 

or seeding desirable species to shade or out-compete invasive plants, applying fertilizer to 

desirable vegetation, and controlled grazing. 

Native plant species usually do not out-compete invasive plants in disturbed habitat. 

Herbicide application after invasive plants have emerged, followed by tillage and drill 

seeding, can be effective in establishing desirable species on some sites (Sheley et al., 

1999). This process, however, can lead to increased soil compaction (DiTomaso, 1999), 

and cannot be conducted on steep, remote, or rocky sites. 

Seeding risks introduction of non-native and/or invasive species, but use of certified 

weed-free seed reduces this risk. The magnitude of the risk varies and may be 
Preventing and Managing Invasive Plants Final Environmental Impact Statement April 2005 

Appendix J-6 

determined by seed source, cleaning practices, and other factors (see Site 

Restoration/Revegetation for more discussion). 

Fertilization has had limited use in invasive plant management. It has been used on 

hawkweed species experimentally. Soluble nitrogen fertilizer applied after herbicide 

treatment could increase the competitiveness of perennial grasses and beneficial forbs. 

This method is most effective in pastures or rangelands where nitrogen levels are not high 

enough for optimum grass performance (Rinella and Sheley, 2002). 

Grazing can be used to manage several invasive plant species successfully. Grazing 

animals prefer certain forage, and selective use of preferred forage can shift the 

competitive balance of plant communities (Crawley, 1983; Lukan, 1990). For example, 

goats and sheep have been used in various areas for controlling knapweed and leafy 

spurge. Controlled, repeated grazing of spotted knapweed by sheep has been found to 

reduce the number of 1 and 2-year old spotted knapweed plants within an infestation 

(Olson et al., 1997). Sheep have been shown to provide control for cheatgrass if grazed 

twice after winter rosettes have greened up (Mosley, 1996). Goats have been used to 

successfully control Himalayan blackberry using high stocking levels in small fenced 

areas (Peters, personal communication, 2004). Other species including gorse, bull and 

Canada thistle, scotch broom, yellow starthistle and perennial pepperweed are being 

grazed mostly by goats under different grazing strategies. Efforts for these species were 

combined with sheep grazing, herbicide treatment, biocontrols and planting competitive 

vegetation. The breed, sex, age of the animal and timing of grazing as it related to weed 

development and desired vegetation development were important factors in the design of 

an effective grazing prescription for these species (Peters, personal communication, 

2004). 

Appropriate grazing by animals preferring invasive species can shift the plant community 

toward more desired grasses (Lacey et al., 1989). Olson (1999) described three grazing 

strategies for managing weeds: (1) moderate grazing levels to minimize the physiological 

impact on native plants and to reduce soil disturbance; (2) intensive grazing to counteract 

inherent dietary preferences of cattle, resulting in equal impacts on forage species 

including weeds; and (3) multi-species grazing that distributes the impact on livestock 

grazing more uniformly among desirable and undesirable species. 

Use of grazing animals as an invasive plant management tool must be based on selecting 

the appropriate grazer for the target invasive plant species. Managers must also 

determine when, how much, and how often to graze animals to have maximum impact on 
Preventing and Managing Invasive Plants Final Environmental Impact Statement April 2005 

Appendix J-7 

the invasive plant with minimum impact on desirable plant species (Olson, 1999). 

Research has been occurring through the collaborative program BEHAVE (Behavioral 

Education for Human, Animal, Vegetation and Ecosystem Management) which includes 

partners from the Universities of Idaho, Utah, Arizona and Montana State University, and 

the National Wildlife Research Center. Studies on the relationships between animal 

condition and circumstance and their propensity to graze weedy plants is one focus as 

well as how age and body condition can affect consumption (Utah State University, 

2004). Specific research tied to this program also includes focus on providing incentives 

such as molasses to get animals to eat weeds and supplying anti-toxins to counteract the 

negative effects of weeds on animals. 

Grazing to manage weeds on roadsides, trailheads, and larger infestations on the forest is 

limited because of the difficulty of maintaining and managing the animals. A long-term 

commitment to small ruminant grazing is necessary for effective invasive plant 

management. Invasive plants can compensate quickly after the grazing pressure is 

removed because their seeds are long-lived in the soil, and because they can rapidly 

increase flower stem production once grazing pressure is removed (Olson et al., 1997 

cited in Sheley et al., 1999). 

Most often, though, a single method is not effective to achieve substantial control of a 

range weed. A Successful long-term management program should be designed to include 

combinations of mechanical, cultural, biological, and chemical control techniques 

(DiTomaso, 2000). 

Prescribed Fire Methods 

Use of prescribed burning for treatment of invasive plants has had limited application in 

Region Six. While fire is sometimes necessary to prompt the germination of some plant 

seeds, such as knobcone pine, fire can also cause sprouting of invasive plants, and create 

site conditions that are optimum for the spread of invasive plants. On the other hand, fire 

can sharply reduce the abundance of some species by preventing flower or seed set, 

destroying seeds, stimulating germination (for future seedling treatments), depleting 

carbohydrate reserves or killing perennating tissue (such as rhizomes, bulbs, or buds) 

(Rice, 2004). Fire can also be used to facilitate revegetation, increase herbicide efficacy, 

and remove litter to assist in emergence of desirable species (Rice, 2004). The weather, 

topography, and available fuel will determine the temperature and intensity of the 

prescribed burn this along with the timing of the treatment, largely determine how the 

burn impacts the vegetation and the abundance of particular species. Studies cited in a 
Preventing and Managing Invasive Plants Final Environmental Impact Statement April 2005 

Appendix J-8 

literature review concerning the use of fire as a tool for controlling non-native invasive 

plants provides insight on such factors (Rice, 2004). 

The effectiveness of fire as a tool is variable. Numerous research was cited in Rice 

(2004) regarding this effectiveness. Most studies focused on grassland habitats primarily 

in the Mid-west, but some valuable information for western states was included. For 

example, fire was used as a means to stimulate germination from a persistent seedbank of 

French and scotch broom species. This allows for follow-up treatments of seedlings over 

the two to three years needed for the new plants to develop seeds. Burning killed some 

seed and stimulated germination through scarification of other seeds in lab and field 

experiments (Bossard, 1993; 2000). This was more successful in drier conditions than 

wetter conditions (Parker, 2001). 

The most effective fires for controlling invasive plant species are typically those 

administered just before flower or seed set, or at the young seedling/sapling stage. This 

timing may interfere with important growth periods for native species, though. 

Sometimes prescribed burns suppress an invasive species only as a side effect. In some 

cases, prescribed burns can unexpectedly promote other invasives, such as when their 

seeds are specially adapted to fire, or when they resprout vigorously which emphasizes 

the need for repeated burning (studies cited in Rice, 2004). Burning in the fall did show 

some success in reducing cover scotch broom in western Washington, but frequent 

burning would still be required (Tveten and Fonda, 1999). 

In California’s Dye Creek and Vina Plains Preserves, prescribed burns helped control the 

spread of invasive medusahead grass (Taeniatherum caput-medusae). California’s 

Lassen Foothills Project also reported good success with >95 percent mortality of 

medusahead and yellow starthistle (Centaurea solstitialis) following prescribed burns (Tu 

et al, 2001). 

Many prescribed burn programs are designed to reduce the abundance of certain native 

woody species that spread into unburned pinelands, savannas, bogs, prairies, and other 

grasslands. Repeated burns are sometimes helpful in controlling invasive plants. 

Herbicide treatments may be required as a follow-up treatment to kill the flush of 

seedlings that germinate following a burn. 

Use of prescribed fire will also change soil chemistry and composition. Likewise, 

invasive seeds may germinate and some invasives will aggressively sprout after fire. Fire 

may encourage invasive plants even in communities that have evolved with fire. This 
Preventing and Managing Invasive Plants Final Environmental Impact Statement April 2005 

Appendix J-9 

could happen because plant communities develop not in association with fire per se, but 

with a particular fire regime. If the fire regime has been altered, vulnerability to exotic 

plant invasion increases (Keeley, 2001). Given these confounding factors, a combination 

of treatments (such as fire and herbicide or fire and manual) would be most successful. 

Flaming is a tool of use for controlling invasive plants. Flaming is done with the use of 

propane torches. Such torching tools have been available for agricultural and roofing 

use. They can be purchased as portable backpack units. Flaming destroys cell structure 

in the plant, therefore reducing its energy towards growth. It will kill most small weeds 

and will at least stunt or kill larger weeds, depending on their root system (Flame 

Engineering, no date). Flaming is limited to conditions that would be too moist to carry a 

fire. They are useful for spot burning single plants or a small population of plants with 

little disturbance to the surrounding vegetation (Tu et al, 2001). 

Spot-burning using a propane torch has been used successfully by Jack McGowan-Stinski 

in several Michigan preserves. Jack reported killing >90 percent of baby’s breath 

(Gypsophila panicula) seedlings with spot-burning. This method also kills most 

seedlings/saplings of buckthorn (Rhamnus spp.), where the adult plants have already been 

removed. In contrast, hand-pulling the seedlings requires more time and labor (Tu et al, 

2001). 

Biological Control 

The use of biological control organisms is intended to be a permanent change to the 

environment. Biological control agents are used when weed eradication is not possible. 

The agent is released to coexist with the weed while bringing the weed population down 

to acceptable levels. Biologists have long recognized the risks of introducing exotic 

organisms to control undesirable exotic plants. The first introductions on the mainland of 

the United States were in 1944 (Coulson, 2000). Safety concerns of early introductions 

centered on possible risks to agricultural or ornamental plants. Host range tests were 

conducted to ensure the potential impacts of an introduction were understood prior to 

release and that no secondary arthropods or pathogens were released in conjunction with 

the targeted ones. Current host range testing includes testing here and in the agent’s 

country of origin, choice and no-choice oviposition and feeding tests, lab and field tests, 

and tests varying environmental conditions and plant quality (Littlefield and 

Buckingham, 2004). 
Preventing and Managing Invasive Plants Final Environmental Impact Statement April 2005 

Appendix J-10 

Since the first introduction of a biological control agent, most have been regulated by the 

Plant Pest Act of 1912, Federal Plant Pest Act of 1957 and the Federal Noxious Weed 

Act of 1974. The Plant Protection Act of 2000 refined much of the previous legislation 

to directly address biological control organisms and recognize that some plant pests have 

positive effects. All legislation puts the regulation of plant pest introductions and 

interstate movement under the authority of USDA APHIS Plant Protection and 

Quarantine. In addition, the Environmental Protection Agency regulates pathogens as 

biological pesticides under the Federal Insecticide, Fungicide and Rodenticide Act of 

1972. 

USDA-APHIS-PPQ must approve each step in the importation and release of new 

biological control agents into the United States. Permits for entry into the U.S. must be 

obtained prior to importation. New agents are imported into approved containment 

facilities after USDA inspection. After further testing, applications for release are 

submitted to the Technical Advisory Group (TAG). The TAG reviewers examine the 

information on taxonomy of target plant and agent, the test plants used, host range tests, 

and impact to nontarget plants. TAG then makes a recommendation to APHIS for or 

against immediate release. If TAG recommends release, the researcher must submit an 

application to APHIS requesting a permit to release the agent into the environment. In 

accordance with the National Environmental Policy Act and the Endangered Species Act, 

the application to APHIS must be accompanied by an Environmental Assessment and 

Biological Evaluation. APHIS is responsible for ensuring the introduction of new 

biological control agents into the United States is in compliance with NEPA and ESA 

(Horner, 2004). 

The use of pathogens for weed biological control is regulated somewhat differently from 

arthropods. Exotic pathogens must be screened and tested just as arthropods are. If the 

pathogen, endemic or exotic, will be applied to more than 10 acres (cumulative in the 

United States), or if it is formulated for commercial use, it is subject to EPA regulation 

(USDA, 2003). 

Regulation and testing for biological control releases has changed as public values have 

changed. McFadyen (1998) conducted a review of those working with biological control 

of weeds and came up with a list of 5 species introduced into the United States that are 

now known to damage natives. All of these species were originally introduced from 

1946-1969 and the effects on nontarget plants were anticipated for these insects from host 

range testing conducted at the time. Pemberton (2000), in a similar review, established 
Preventing and Managing Invasive Plants Final Environmental Impact Statement April 2005 

Appendix J-11 

that of 117 biological control organisms established in the United States and the 

Caribbean, only 1 uses a native plant unrelated to the target weed. This is an insect 

introduced to Hawaii in 1902 without host specificity testing. This insect is now 

suspected of being more of a generalist than originally thought. All of the agents now 

known to impact nontarget plants were approved for release when native plants were not 

generally valued as they are today. These releases would not be allowed under current 

protocols. 

Site Restoration/Revegetation 

Site restoration or revegetation is part of any long term strategy to reduce invasive plants. 

Determining the need for active restoration/revegetation versus passive restoration 

(allowing plants on site to fill in a treated area) is the first choice when addressing this 

need. Passive restoration may be appropriate where treated sites leave only small gaps of 

bare ground and native vegetation on site can provide adequate seed source to fill in such 

gaps. 

Promoting the establishment of desirable plant communities through the manipulation of 

species composition, plant density, and growth rate is a critical component of invasive 

plant management (Masters et al., 1996; Masters and Nissen, 1998; Masters and Shelly, 

2001; Brooks et al., 2004). Three components of succession could be manipulated; site 

availability, species availability, and species performance (Cox and Anderson, 2004). 

Although single control tactics, such as treatment with herbicides, may eliminate or 

suppress invasive species in the short term, the resulting gaps and bare soil create niches 

that are conducive to further invasion by the same or other undesirable plant species. On 

degraded sites where desirable species are absent or in low abundance, revegetation with 

competitive grasses, forbs, and legumes may be necessary to direct and accelerate plant 

community recovery, and achieve site-management objectives in a reasonable timeframe. 

A two step approach, using a model of ‘assisted succession’ was used to accelerate 

recovery in sagebrush steppe invaded by cheatgrass. The first step was to convert a site 

from annual to perennial domination. The second step in the process was to insert native 

species into the stable perennial matrix using such seedbed techniques as tilling or 

treatment with herbicide (Cox and Anderson, 2004). 

The selection of appropriate species for revegetation is dependent on a number of factors, 

including management objectives and site characteristics such as soil texture, 

precipitation/temperature regimes, and shade conditions. Seed availability and cost, ease 
Preventing and Managing Invasive Plants Final Environmental Impact Statement April 2005 

Appendix J-12 

of establishment, seed production, and competitive ability are also important 

considerations and, as a consequence, resource managers in the western United States 

have historically relied on introduced species that have been selectively bred and 

marketed for these attributes. 

Some success has been found using crested wheatgrass as in the ‘assisted succession’ 

model discussed above (Cox and Anderson, 2004). Success in establishing native species 

varied by precipitation patterns and seed bed preparation in plots dominated by crested 

wheatgrass verses cheatgrass. The study was based in the Great Basin in sagebrush 

steppe and covered only two years of measurements. While success was shown in 

amount of native species to germinate and establish when crested wheatgrass was the 

dominant species, this success was tied to seed bed preparation that created niches for 

native species development. Crested wheatgrass was not expected to be eliminated with 

such a strategy, but diversity, structure and function of the resulting community was 

considered more similar to the original native community. The use of crested wheatgrass 

may therefore only be appropriate under very specific, controlled situations where native 

plant community restoration is not a high priority. 

Numerous annual or sterile cereal grasses could be used instead of the above persistent 

non-natives. For example, cereal wheat, barley, annual ryegrass or sterile wheatgrass 

have been used in restoration efforts. In the case of wildfire recovery (Burned Area 

Emergency Rehabilitation (BAER) programs, some studies are being done to assess the 

success of seeding with these species. 

In order to conserve and enhance the biodiversity and sustainability of wildland 

ecosystems, numerous authorities and policies are in place to promote the use of native 

species in restoration and revegetation. There is debate among restoration practitioners 

on how close in distance and genetics a seed source should be to the restoration site 

(Kaye, 2001). The definition of what is ‘local’ varies and should be defined through 

specific project objectives. Genetically similar seed may have an advantage because it is 

from locally adapted plants, but could be more costly than using seed from a broader 

genetic pool such as a watershed or even an ecoregion that can be used for many projects. 

The successful use and incorporation of native species, in revegetation of impacted sites 

will require extensive ecological and biological knowledge and expertise in order to meet 

both short-term objectives of attaining adequate amounts and levels of competitive plant 

cover, and long-term objectives of physical and biological site recovery. Although 

agency knowledge and experience base is growing, education and training is still needed. 
Preventing and Managing Invasive Plants Final Environmental Impact Statement April 2005 

Appendix J-13 

There is also a critical need for research efforts that more broadly explore the array and 

combinations of native grasses and forbs that may be useful in restoration/revegetation. 

The effects of the timing, as well as the rate and methods of seeding on sites previously 

infested with invasive plants, have also not been fully examined for most species. 

Environmental Consequences 

Effects to Native Plants 

Manual, Mechanical 

The removal of invasive plants using manual or mechanical techniques could directly 

affect native plants and plant communities. Direct negative effects would be 

unintentional removal or trampling of flowers, fruits, or root systems of native plants, but 

should be minimal with properly trained crews. Vigor could be reduced in individuals 

due to damage. The removal of individuals could also directly affect remaining native 

plant community components negatively by reducing native seed production (if methods 

such as mowing are used), creating soil disturbance, and opening the canopy (understory, 

shrub layer or overstory depending on the species). Hand-pulling trials conducted on 

spotted knapweed in western Montana and on diffuse knapweed in west-central Colorado 

were 35 percent and 0 percent effective, respectively. The treatments were completed 

twice per year for two consecutive years, were found to significantly increase bare 

ground, and were expensive (Duncan et al., 2001). Test plots established on Blue 

Mountain (Lolo National Forest) and the Lee Metcalf National Wildlife Refuge near 

Stevensville, Montana, measured effects of hand-pulling on spotted knapweed. Spotted 

knapweed covered 76 percent and 53 percent of the two sites, respectively. Hand-pulling 

provided 100 percent flower control and 56 percent plant control at Blue Mountain, but 

resulted in an increase in bare ground from 2.7 percent to 13.7 percent during the first 

year after treatment (Brown et al., 2001). 

Indirect effects from these changes include microsite shifts such as reduction in 

productivity, reduction in soil moisture, disruption of mychorrhizal connections and 

increase in surface temperatures. All of these indirect effects could lead to a shift in 

species composition further away from a native community. One possible scenario is that 

the removal of one invasive species would only encourage another invasive to take its 

place. This could occur through various means of introduction (windblown seeds, human 

transport etc.). 
Preventing and Managing Invasive Plants Final Environmental Impact Statement April 2005 

Appendix J-14 

Communities would be affected positively by providing the space for increased growth in 

community size. One possible scenario is that removal of invasives will encourage native 

seed dormant in the soil to germinate due to less competitive conditions. Dremann and 

Shaw (2002) documented the success of converting live oak woodland from 99 percent 

exotic species cover to 85 percent native plant cover through a strategy of timed 

manual/mechanical removal that released the native seed bank. No reseeding was 

necessary. 

Cultural 

Grazing affects native plants much the same way as manual or mechanical methods. 

Individual plants can be eaten, uprooted, or trampled leaving bare space for re-invasion. 

While grazing to manage weeds on roadsides, trailheads, and larger infestations on the 

forest may be limited because of the difficulty of maintaining and managing the animals, 

grazing has also been proven to be a useful tool for invasive plant control. For example, 

goats and sheep have been used in various areas for controlling knapweed and leafy 

spurge. Controlled, repeated grazing of spotted knapweed by sheep has been found to 

reduce the number of 1 and 2-year old spotted knapweed plants within an infestation 

(Olson et al., 1997). Appropriate grazing by animals preferring invasive species can shift 

the plant community toward more desired grasses (Lacey et al., 1989). When not 

properly controlled, however, grazing or other actions of grazing animals (wallowing, 

pawing up soil) can cause significant damage to a system, and promote the spread and 

survival of invasive weeds. Overgrazing can reduce native plant cover, disturb soils, 

weaken native communities, and allow exotic weeds to invade. In addition, animals that 

are moved from pasture to pasture can spread invasive plant seeds (Tu et al, 2001). 

Invasive plants can compensate quickly after the grazing pressure is removed because 

their seeds are long-lived in the soil, and because they can rapidly increase flower stem 

production once grazing pressure is removed (Olson et al., 1997 cited in Sheley et al., 

1999). 

Prescribed Fire 

Use of prescribed fire will affect native plant communities in a similar manner to 

mechanical and manual treatments, but will also change soil chemistry and composition. 

The litter and duff layer including thatch would be reduced, allowing natives a better 

opportunity for seed germination. Likewise, invasive seeds may germinate and some 

invasive plants will aggressively sprout after fire. High temperatures or smoldering 

conditions could kill seeds of not only invasive plants, but also natives; and could 
Preventing and Managing Invasive Plants Final Environmental Impact Statement April 2005 

Appendix J-15 

damage important mychorrhizal connections. Therefore, the timing of prescribed burns 

is important to consider. This timing may interfere with important growth periods for 

native species. 

Fire may encourage invasive plants even in communities that have evolved with fire. 

This could happen because plant communities evolve not in association with fire per se, 

but with a particular fire regime. If the fire regime has been altered, vulnerability to 

exotic plant invasion increases (Keeley, 2001). Given these confounding factors, a 

combination of treatments (such as fire and herbicide or fire and manual) would be most 

successful. 

Biological 

Even though control agents are reviewed and approved by APHIS prior to release in this 

country, there is a slight risk that an approved agent the Forest Service releases may 

unintentionally affect native plants or animals. There also remains the possibility that 

regardless of what the Forest Service does, unapproved agents or agents known to affect 

non-targets will spread from neighboring lands to National Forest lands. 

There are very few post-release studies on the effects of biocontrol introductions on 

nontarget plants or animals (D. Simberloff and P. Stiling 1996, Howarth 2001). Perhaps 

the most relevant studies of direct non-target effects concern the thistle seedhead weevil, 

Rhinocyllus conicus, introduced into North America for the control of Eurasian thistles in 

the genus Carduus, primarily musk thistle, C. nutans (Zwolfer and Harris 1984, Turner et 

al., 1987, Louda et al. 1997). The original releases were made in Canada in 1968 and 

releases in both the U.S. and Canada continue today. Approval for the release of this 

insect was granted knowing that the weevil’s host range included three native North 

American thistle genera. At that time, there was little concern for possible negative 

impacts on native thistles. In addition, female egg-laying behavior was expected to 

restrict the weevil’s host range. Current evidence shows this weevil continues to expand 

it’s geographic and host range, which now includes a close relative of the federally listed 

threatened Pitcher’s thistle (Cirsium pitcheri) (Louda et al. 1997). Recent research rebuts 

the idea that the host-specificity of this weevil has changed since the original testing 30 

years ago (Arnett and Louda, 2002). 

Rhinocyllus conicus would not be approved for release by the current standards used by 

USDA APHIS. Agents known to affect non-targets with a likelihood of encountering 

those non-targets if introduced are no longer approved for release (USDA, 2003). APHIS 
Preventing and Managing Invasive Plants Final Environmental Impact Statement April 2005 

Appendix J-16 

modified the testing process in the mid-1980’s to include more potential hosts in host 

specificity testing. APHIS continues to work on refining regulations and procedures for 

introducing biological control agents (Andres et al., 2000). 

While little studied, there are a few examples of indirect effects on nontargets resulting 

from biological control introductions. Callaway, DeLuca and Belliveau (1999) found the 

reproductive output of native Festuca idahoensis planted with spotted knapweed 

(Centaurea maculosa) was lower when the introduced root moth, Agapeta zoegana, had 

attacked neighboring knapweed. A study of native deer mouse (Peromyscus 

maniculatus) diets found introduced knapweed gall flies were the primary food item for 

most of the year and over 80 percent of the winter diet (Pearson et al., 2000). These 

studies illustrate ways agents can indirectly affect their new communities and also ways 

their communities may change agent effectiveness. Increased emphasis on prerelease 

ecological testing may reduce these indirect effects. The International Code of Best 

Practices for biological control of weeds provides further guidelines for practitioners 

involved in redistribution that, when followed, will reduce these indirect effects. 

Site Restoration/Revegetation 

While planting or seeding will provide the positive effect of covering bare ground to 

reduce the chances of re-invasion and enhance a native plant community, species 

composition could be negatively affected by inappropriate choices during revegetation or 

restoration. First, the choice to revegetate when not necessary may occur; secondly, a 

material that may be inappropriate for specific site conditions could be chosen. With 

sterile wheatgrass, Keeley (2003) found that seeding with cereal wheat, at high seeding 

rates, reduced invasive species after two years. The study also found decreases in species 

richness and ponderosa pine seedlings. The dense stands of wheat did appear to reduce 

erosion, but left thick thatch which increased fire hazard at least initially. Such studies 

suggest determining if seeding is necessary and the amount of seed per acre considered 

crucial for reducing disruption to ecosystem processes. 

Although some introduced species will continue to be used in site restoration, the 

extensive past use of highly competitive and persistent non-natives (e.g., smooth brome, 

orchardgrass, timothy, and crested wheatgrass) has had adverse impacts on the diversity 

and health of our native forest, rangeland, and aquatic ecosystems (Romo, 2005; Bartos 

and Campbell, 1998; Brown, 1995; Covington and Moore, 1994; Cetwyler, 1971; 

Kaufmann et al., 1994; Kay, 1994; Lesica and DeLuca, 1996; Mills et al., 1994). 
Preventing and Managing Invasive Plants Final Environmental Impact Statement April 2005 

Appendix J-17 

The use of crested wheatgrass in assisted succession experiments is showing some 

success under specific conditions (Cox and Anderson, 2004). On the other side of the 

argument, crested wheatgrass is considered invasive in the native prairies of 

Saskatchewan where experiments to determine its invasiveness and guidance for 

controlling the species have has been published (Romo, 2005; Saskatchewan Watershed 

Authority Fact Sheet, no date). Studies linking invasiveness of the species with 

environmental factors are pending publication (Henderson and Naeth, 2004; Hansen and 

Wilson, 2004). 

Effects to Wildlife 

Wildlife species may be adversely affected by invasive plant treatment methods. All 

treatment methods have the potential to disturb, temporarily displace, or directly harm 

various wildlife species. Successful control of invasive plant infestations provides longterm benefits by restoring native habitat. Treatment of larger infestations may create 

more disturbances for longer periods than small infestations, but the specific amount and 

duration is largely dependant upon specific treatment method. Several techniques can 

create bare ground, which may reduce cover and expose certain species to increased 

predation. Large tracts of bare ground can alter migration and dispersal of some species 

(Semlitsch, 2000). The likelihood of these effects depends on the size and distribution of 

bare ground created. 

The effects of the invasive plant treatment are also relative to the size and locations of 

existing and future invasive plant infestations. Treatments of infestations along disturbed 

roadsides are not likely to substantially affect terrestrial wildlife populations, since this 

vegetation type does not provide essential habitat for native wildlife species, and it 

consists of long, narrow areas spread over large distances. Adverse effects to individuals 

using the roadside vegetation at the time of treatment could occur. 

Treatments of moderate infestations may pose the greatest risk to native wildlife. In 

moderately infested areas, enough native habitats may remain to support some native 

wildlife, and the infestation may be large enough to require more intensive and extensive 

treatment techniques. Very large infestations and monocultures of invasive plants do not 

support native wildlife populations and the presence of native wildlife in these areas is 

greatly reduced in comparison to native habitat (see Duncan and Clark, 2005). 

Manual 
Preventing and Managing Invasive Plants Final Environmental Impact Statement April 2005 

Appendix J-18 

Manual treatments can result in trampling of non-target plants and animals and create 

bare ground. The degree of threat and effect from manual treatments depends on the 

number of workers present and the size of the area being treated. Because manual 

techniques are slower than mechanical or chemical methods, the duration of disturbance, 

caused by the presence of people, may be longer in the treatment area. The slower pace 

of work allows animals in the area to leave and reduces the risk of direct harm from 

trampling. Bare ground is likely to be patchy in distribution with this method and less 

likely to interfere with animal movement or dispersal. 

Mechanical 

Some mechanical treatments may crush small mammals, reptiles, amphibians, or eggs of 

ground-nesting birds. Hand-held mechanical equipment, like chainsaws and string 

trimmers, can be used very selectively on target plants and may be less likely than larger 

equipment to directly harm wildlife. Use of vehicle-mounted mechanical equipment 

(mowers, tractors with disks or hammer flails, bull dozers with brush rakes, etc.) is much 

less selective and more likely to directly harm small wildlife species. Vehicle-mounted 

equipment is most often applied to monocultures of invasive plants on gentle slopes or 

road verges, and even though those areas do not provide preferred or suitable habitat for 

most native wildlife, adverse effects from disturbance or crushing are still possible. 

Mechanical treatments may produce more bare ground, reducing cover, exposing more 

soil to erosion, potentially disrupting dispersal or foraging patterns of small animals, and 

possibly exposing some to increased predation as a result of decreased cover. 

Mechanical methods generate more noise than other treatments, except for aerial 

applications, and have a higher likelihood of disturbing species that are secretive or 

sensitive to noise. 

Cultural 

Livestock grazing conducted to reduce invasive plant populations while increasing native 

plant populations, would provide long-term beneficial effects to wildlife. Grazing would 

also cause short-term disturbance similar to mechanical methods, resulting in more bare 

ground and decreased cover for wildlife. Fertilization may increase competitive 

advantages of native plants and improve forage quality and quantity, contributing to 

improved wildlife habitat. However, in naturally nutrient-poor soils, fertilization may 

give the competitive advantage to invasive species (Brooks, 1999), which would further 

degrade wildlife habitat. Off-site movement of fertilizer can have substantial adverse 

effects to aquatic wildlife habitat and may have toxic effects to some species as well. 
Preventing and Managing Invasive Plants Final Environmental Impact Statement April 2005 

Appendix J-19 

Prescribed Fire 

Prescribed burning may cause mortality to animals lacking the ability to escape and 

would reduce cover and food provided by intermixed native plants. Fires can produce a 

large amount of bare ground that may fragment habitat or expose small animals to 

increased predation. Smoke from prescribed fires could temporarily disturb nesting birds 

and other wildlife long distances down wind from the project area. 

Biological 

Biological control methods will not directly affect native wildlife species; however, 

recent studies have found that native rodents may take advantage of the food source 

provided by biological control agents (Pearson et al., 2000). Biological control methods 

that reduce invasive plant populations, increase native plant populations, and provide a 

supplemental food source are indirectly beneficial to wildlife. Any biological control 

agents that affected native plant species could adversely affect wildlife. 

Site Restoration/Revegetation 

Reseeding or revegetation to increase competition with invasive plants can cause shortterm disturbance to wildlife similar to manual or mechanical treatments, depending on 

specific methods used. If native or non-native, non-invasive forage species are used in 

restoration or competitive plantings, increased food and native habitat could benefit 

wildlife. Restoration activities have the potential to restore important wildlife habitat 

faster than natural or passive revegetation. 

Effects to Soil 

The intensity and extent of non-herbicide treatment effects to soil productivity will vary, 

depending on treatment type and extent of area treated; soil characteristics such as 

texture, moisture, and depth of the organic layer; as well as climate and hydrologic, 

chemical, and biological properties. Vegetation prevents soil erosion and subsequent loss 

of soil productivity. 

Manual and Mechanical 

Manual and mechanical treatments that disturb soil, such as grubbing and pulling, when 

carried out over a large area, may cause a significant local soil disturbance. Manual and 

mechanical treatments are expected to cover relatively small areas, with effects to soil 

productivity localized to the treatment area, though some soil may be moved off-site 

through wind or water erosion. 
Preventing and Managing Invasive Plants Final Environmental Impact Statement April 2005 

Appendix J-20 

Wheeled or tracked machinery can compact soil. Soil compaction eliminates soil pores 

and so reduces water infiltration, plant growth, and increases the potential for runoff, and 

erosion. One pass of heavy equipment over wet soil can cause enough compaction to 

reduce tree growth, and the effects of this compaction can last for decades (Perry, 1994). 

Best management practices minimize effects of wheeled or tracked machinery to soil 

productivity due to compaction. 

Cultural 

Potential impacts of grazing on soils include increased bare ground, increased erosion, 

decreased litter layer, increased compaction, decreased infiltration, and decreased 

fertility. Careful management of the grazing animals can significantly reduce the effects 

of grazing on soil productivity. 

Prescribed Fire 

The risk of harm to soil productivity from prescribed fire is low to high, depending on 

soil and climate conditions during burning and fire intensity. Prescribed burning has the 

potential to bare large areas of soil, and thus increase surface erosion. High intensity fire 

may cause the formation of a hydrophobic surface layer on the soil. A hydrophobic 

surface layer repels water and increases erosion by increasing the volume of surface flow 

during rain events. High intensity fires are not generally used to treat invasive plants. 

Depending on fire intensity, significant amounts of the nitrogen, phosphorus and 

potassium content of vegetation burned in a fire is volatized (Perry, 1994), and is no 

longer available to take part in soil nutrient cycling processes. After a fire, decomposing 

roots of dead plants and the mineral content of ash add a significant nutrient pulse to the 

soil. If some vegetation and soil microbes remain, these nutrients can be captured for 

cycling in the new plant community. If the soil biotic community is heavily impacted by 

high intensity fire, the nutrient cycling ability of the soil may be reduced and nutrients 

may be lost to surface or ground water. 

Stendell, et al. (1990) studied the mycorrhizal community in a ponderosa pine forest in 

the Sierra Nevada Mountains before and after a low intensity fire. They found and eightfold reduction in mycorrhizal biomass in the litter and organic layers, but no reduction in 

mycorrhizal biomass in mineral layers. Grogan, et al. (2000) studied the effect of a 

severe fire on mycorrhizal community in a bishop pine forest in northern California. 

They found that after 11⁄2 years, all regenerating pine seedlings were associated with at 

least one mycorrhizal fungus, although the mycorrhizal fungi present in the burned forest 
Preventing and Managing Invasive Plants Final Environmental Impact Statement April 2005 

Appendix J-21 

differed from those present in neighboring unburned forest. Another study, in Scots pine 

stands in a Swedish boreal forest found that low intensity wildfires had little effect in the 

mycorrhizal fungal community (Jonsson, et al., 1999). In general, research indicates that 

a functional mycorrhizal fungi community is present in the soil after fire, even severe 

fire. Freidman’s study (1989) on soils that had shifted from fungal dominance to 

bacterial dominance suggests that if natural regeneration of the plant community does not 

take place on the burned area, native vegetation should be planted quickly to provide 

suitable hosts for the mycorrhizal fungi. 

Prescribed fire as a treatment for invasive plants is expected to be a very small portion of 

the prescribed fire program in Region Six. Implementing prescribed fire as outlined in 

the National Fire plan should minimize negative effects to soil productivity. 

Biological 

Most biological treatment agent complete their life cycles above ground, and these 

organisms are not likely to directly affect soil productivity. Biological treatment 

organisms that spend at least a portion of their lives below ground may affect soil 

processes. The root moth Agpeta zogana, introduced as a biological control of spotted 

knapweed (Centaurea maculosa), appeared to cause a reduction in the reproductive 

output of the native Festuca idahoensis planted with the spotted knapweed, indicating a 

reduction in soil productivity (Callaway et al., 1999). 

Site Restoration/Revegetation 

The risk of harm to soil productivity from planting or seeding is unlikely to low. Planting 

or seeding native or non-invasive species is likely to occur over small areas. Manual 

methods are generally used for planting and seeding, though hand carried power tools are 

sometimes used. Planting and seeding will protect soil from surface erosion. 

The risk of harm to soil productivity from fertilization, done in conjunction with seeding 

or planting, is low to moderate. Fertilization can change soil properties and these 

changes may not be easily reversed. For instance, fertilization and watering of a 

shortgrass steppe ecosystem led to invasion by the non-native Kochia coparia (Vinton 

and Burke, 1995). Kochia coparia continued to dominate 20 years after fertilization and 

watering stopped. Fertilization projects are likely to be small and affect small areas, so 

effects are likely to be minor and localized. Best management practices minimize 

negative effects. 
Preventing and Managing Invasive Plants Final Environmental Impact Statement April 2005 

Appendix J-22 

The risk of harm soil productivity from mulching is unlikely to low. Mulch application is 

likely to be manual and affect small areas. Mulching prevents soil erosion, protecting 

soil productivity. Decay of the mulch could temporarily affect nutrient cycling. 

Effects to Fish and Aquatic Invertebrates 

The intensity and extent of treatment effects to fish, aquatic invertebrates, and their 

habitat will vary, depending on amount of area treated; soil type, proximity of the 

treatment to water, hydrologic regime and weather conditions during and after treatment; 

temperature, channel morphology and large woody debris; and biota present in surface 

water. 

Riparian vegetation is important to preventing or slowing introduction of sediment, 

particularly fine sediment, to streams. Loss of vegetation in riparian areas during 

treatment may temporarily increase fine sediment, turbidity, or sedimentation in a stream. 

Stream shade provided by riparian vegetation prevents increased water temperature due 

to solar radiation. Where invasive plants prevent the growth of trees or other native 

vegetative cover, invasive plant treatment may restore shade in the long term. 

Alternately, treatment could result in temporary loss of shade and increased stream 

temperatures. 

Manual and Mechanical 

Manual and mechanical treatment effects to riparian function, water quality, and aquatic 

biota depend on soil properties, climate, distance to surface water, and the extent of the 

mechanical treatment. Manual and mechanical treatments are expected to cover 

relatively small areas within watersheds. Manual and mechanical treatments within 

riparian areas that disturb soil, such as grubbing and pulling, carried out over a large area, 

may lead to increased erosion and stream sedimentation. Sedimentation may adversely 

affect fish by covering eggs or spawning gravels, reducing prey availability, or directly 

harming fish gills. In lower intensity non-native plant infestations, non-target vegetation 

left on the treatment site can reduce the potential for erosion and subsequent sediment 

delivery to streams or other water bodies. 

The risk of harm to aquatic ecosystems due to fine sediment production from manual 

treatment or use of motorized hand tools is low, and short-term, resulting in effects likely 

to be localized and minor. Best management practices at the site-specific scale are likely 

to prevent long-term negative effects. Depending on the scale of treatment, large riparian 
Preventing and Managing Invasive Plants Final Environmental Impact Statement April 2005 

Appendix J-23 

areas treated with motorized hand tools may moderately increase the risk to aquatic 

environments. 

The risk of harm to aquatic environments from use of wheeled or tracked machinery will 

vary, depending on the extent of treatment area and proximity to aquatic environments. 

Soil compaction within riparian areas can prevent the establishment of native vegetative 

cover. Best management practices at the site-specific scale will minimize effects of 

wheeled or tracked machinery to riparian and aquatic ecosystems due to soil compaction. 

Cultural 

The use of livestock, primarily sheep or goats, to control invasive plants, is a relatively 

new treatment that has gained attention recently (Olson et al., 1997). The treatment of 

invasive plants by grazing animals requires a highly specialized operation, often 

involving animals that are “trained” to forage on the target plant, and usually involving 

temporary fencing to keep the animals within the target area (Peters, personal 

communication, 2004). The livestock species, grazing intensity, and management of the 

grazing animals used to treat invasive plants are different from grazing for other 

purposes. Also, the specific use of livestock in this type of control effort has not been 

utilized extensively in riparian areas or near aquatic ecosystems. Careful management of 

livestock used as a treatment tool can significantly reduce the effects on riparian areas 

and aquatic environments. 

Fertilizer is used to promote native plant species at the expense of invasive plant species, 

but has been done infrequently in the region, and is not likely to have large-scale effects. 

Fertilizer use near streams could produce localized adverse effects if the fertilizer was 

introduced into the water via runoff. Seeding is not likely to have adverse effects to 

aquatic ecosystems. 

Prescribed Fire 

The risk of harm to riparian function, water quality, or aquatic species from prescribed 

fire depends on fire intensity, timing, and land form, among other factors. Prescribed 

burning has the potential to bare large areas of soil, and thus increase both surface erosion 

and sedimentation of streams. High intensity fire may cause the formation of a 

hydrophobic surface layer on the soil. A hydrophobic surface layer repels water and 

increases erosion by increasing the volume of surface flow during rain events. 

Groundwater recharge may be reduced in areas with hydrophobic soils. 
Preventing and Managing Invasive Plants Final Environmental Impact Statement April 2005 

Appendix J-24 

Heavy runoff from burned areas can increase water pH, indirectly affecting aquatic biota. 

Effects to watersheds are dependent on the extent and intensity of the fire. Prescribed fire 

as a treatment for invasive plants has been rarely used, and is expected to be a very small 

portion of the invasive plant program in Region Six. Implementing prescribed fire as 

outlined in the National Fire plan consultation with regulatory agencies should minimize 

effects to the aquatic environment (Northwest National Fire Plan Consultation Process, 

www.or.blm/fcp/documents/salmonids). 

Biological 

Biological controls, targeted to a single species of invasive plant, are unlikely to result in 

adverse effects to riparian function, water quality, or aquatic species. Biological controls 

act very slowly, often taking a decade or more to substantially reduce the invasive plant 

population. Therefore, indirect effects to water quality and aquatic species are unlikely. 

Site Restoration/Revegetation 

Negative effects to fish and aquatic ecosystems from planting or seeding are unlikely. 

Planting or seeding native or non-invasive plant species is likely to occur over small 

areas. Manual methods are generally used for planting and seeding, though hand carried 

power tools are sometimes used. Planting and seeding in riparian areas will speed 

establishment of vegetative ground cover, preventing fine sediment introduction to 

streams. 

Fertilization done in conjunction with seeding or planting, may result in minor and 

localized effects. Depending on fertilizer type, application method, soil type, weather 

during and after application, and proximity to surface water, nutrients can be delivered to 

streams. High nutrient loads in water bodies can lead to algal blooms, increased 

biological demand, water chemistry effects, and changes in biota. Ammonia, a common 

ingredient in fertilizers, is listed in both Oregon and Washington with specific water 

quality criteria for 303(d) lists. Fertilization projects are likely to be small and affect 

small areas within watersheds. Best management practices at the site-specific scale will 

minimize effects from fertilizer use in riparian areas. 

Mulch application is likely to be manual and any risk of harm riparian function, water 

quality, or aquatic species from mulching is unlikely. A significant amount of mulch, or 

decayed mulch, would have to enter a water body in order to impact the aquatic 

ecosystem; a scenario that is unlikely to occur. The use of mulch for restoring sites 
Preventing and Managing Invasive Plants Final Environmental Impact Statement April 2005 

Appendix J-25 

previously infested with invasive plants is unlikely to negatively affect riparian areas or 

aquatic ecosystems. 

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