United StatesDepartment ofAgriculture

Forest Service

Technology &DevelopmentProgram

5100—Fire ManagementJuly 2001

0151 1204—SDTDC

Effective AerialReseeding Methods:Market Search Report

FORESTSERVICE

DEPA RTMENTOFAGRICULT

URE

Information contained in this document has been developed for the guidanceof employees of the Forest Service, USDA, its contractors, and cooperatingFederal and state agencies. The Department of Agriculture assumes noresponsibility for the interpretation or use of this information by other than itsown employees. The use of trade, firm, or corporation names is for theinformation and convenience of the reader. Such use does not constitute anofficial evaluation, conclusion, recommendation, endorsement, or approvalof any product or service to the exclusion of others that may be suitable.

The U.S. Department of Agriculture (USDA) prohibits discrimination in all itsprograms and activities on the basis of race, color, national origin, sex, religion,age, disability, political beliefs, sexual orientation, or marital or family status.(Not all prohibited bases apply to all programs.) Persons with disabilitieswho require alternative means for communication of program information(Braille, large print, audiotape, etc.) should contact USDA’s TARGET Centerat (202) 720-2600 (voice and TDD).

To file a complaint of discrimination, write USDA, Director, Office of CivilRights, Room 326-W, Whitten Building, 1400 Independence Avenue, SW,Washington, D.C. 20250-9410 or call (202) 720-5964 (voice and TDD). USDAis an equal opportunity provider and employer.

Ryan BeckerMechanical Engineer

USDA Forest Service

San Dimas Technology & Development CenterSan Dimas, CA 91773

July 2001

Effective AerialReseeding Methods:Market SearchReport

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IntroductionThe standard practice of reseeding wildfire-devastated areas with native seed mixes, by use ofhelicopter-borne seed buckets, presents a myriadof problems and often poor results. Seed mixestend to segregate based on size, shape, anddensity when subjected to vibratory conditions,including those associated with road-baseddelivery or the engine vibration of a motorized slinglocated at the bottom of the seed bucket. Whenseed is ejected from the bucket, it is also subjectedto air currents created by the helicopter as well asany prevailing wind.

The San Dimas Technology and DevelopmentCenter (SDTDC) studied the various causes ofpoor aerial reseeding and conducted a marketsearch for useful solutions. Several generalrecommendations for assuring rapid regenerationand stabilization presented themselves duringresearch. These recommendations appear in thesection titled, “General Native Seed Issues.” Theresearched solution proposals or current andpossible techniques for mitigating unevenness inseed distribution are first analyzed and compared.

PurposeThose responsible for rehabilitation haveencountered problems using standard reseedingpractice for dropping native seed mixtures. Unevendistribution, settling, jamming, and poorgermination are some examples of these problems.An opportunity to test two solutions arose duringthe market search. Preliminary results from thistest indicate an improvement, but further study isnecessary to confirm this supposition.

Applicable DirectivesForest Service ManualFSM 2523.03—Policy includes the relevantdirective for burned-area emergency rehabilitation,specifically Subsection 3. Compatibility with ForestPlans directs:

“Include native plant materials when possible tomeet the objectives of the burned-areaemergency rehabilitation. When practicable, useseeds and plants in burned-area emergencyrehabilitation projects that originate fromgenetically local sources of native species. Whennative materials are not available or suitable, give

preference to nonnative species that meet thetreatment objectives, are nonpersistent, and arenot likely to spread beyond the treatment area.”

“Treatments that qualify for emergency fundingprovide essential protection at minimum cost toachieve on-site soil and slope stability, runoffcontrol, and unimpaired stream channel carryingcapacities.”

“Treatments are primarily temporary measuresthat do not require maintenance or are removedafter objectives have been met.”

FSM 2520.2—Actions should be implemented withthe objective as the motivation:

“To protect National Forest System watershedsby implementing practices designed to retain soilstability, improve or maintain site productivity,secure favorable conditions of water flow, andpreserve or enhance aquatic values.”

FSM 2323.43b—Wilderness rehabilitationwatershed improvements FSM 2323.43b:

“Permit emergency burned area rehabilitationonly if necessary to prevent an unnatural loss ofthe wilderness resource or to protect life,property, and other resource values outside ofwilderness.”

Forest Service HandbookFSH 2509.13, Amendment 2509.13-95-7, Section24—Goals of Emergency Rehabilitation Treatment:

“Emergency rehabilitation includes only thosetreatments that are immediately needed toprevent or reduce potential damages(commensurate with values at risk) due to theeffects of a wildfire on the watersheds. Eachtreatment must be directed at correcting oreffectively mitigating the adverse effect that thefire had on the watershed, as identified in theWatershed Condition Inventory (sec 23.3).”

Section 26.1—Types of Emergency RehabilitationTreatments, Land Treatments, Subsection 1,Revegetation:

“Revegetation is prescribed to be effective for thefirst or second year after treatment.Considerations for revegetation treatmentsinclude:

a. The target area to be revegetated.

b. A seed mix of species known to be effective forerosion control, adapted to the target area andcompatible with future managementobjectives.”

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Service directives dictate the focus of this marketsearch by demanding a low-cost, immediatelyavailable solution that addresses watershedstability and specifically prohibits treatmentsintended to enhance soil quality or water yield.Only treatments with proven effectiveness areallowed, further limiting the market search. Eachidentified possible solution must meet all criteria andshould also be readily available and useful withexisting equipment.

Identified ProblemsSeed SegregationRegenerating plants in their previous location is themost effective long-term treatment for wildfire-devastated areas. Inducing rapid ecosystemregeneration in these areas requires an evendistribution of the native seed mixture, so the speciemost suited to each particular microclimate will beestablished first. Any situation that may exclude themost appropriate seed from a certain area will slowregeneration and recovery of the area. SDTDC hasidentified three major contributors to seedsegregation, all of which must be mitigated to ensureeven ground distribution.

Contributor 1—Transporting SeedAs many seed distributors ship unpackaged bulkmixed seed, the seed mix generally is subjected toagitation by vibration during travel. Prepackagedseed mixes are less vulnerable to this factor, butgiven sufficient agitation, any normal packaging ofseed mix containing variously shaped and sizedseeds will segregate. A variety of factors hindersegregation and facilitate incidental remixing ofprepackaged seed. For this benefit, whenever theoption is available, premixed seed should beshipped in containers with as little open spacearound the seed as possible (e.g., full burlap sack).All seed mixtures should be visually inspected forsegregation before loading into a seed bucket orhopper.

Contributor 2—In-Bucket AgitationEven if the seed reaches the helicopter seedbucket well mixed, the bucket may create the samevibration problems as the delivery. On manyhelicopters, seeds are distributed using a gas-powered impeller. The gas engine delivers avibration to the bucket which can cause seed

segregation. Additionally, the bucket that is usuallyconnected to the helicopter by steel cables andconnectors is also capable of delivering vibrations.These contributions also depend on the amount ofvibrational damping provided by the enginemounts, the type of engine, and the amount ofvibration translated by the bucket connectionsystem. Overall effect is determined by the lengthof time the seed is exposed to vibration. It isimpossible to predict, without further study,whether this type of agitation by itself poses asignificant risk of causing uneven grounddistribution.

Contributor 3—Aerodynamic CharacteristicsOnce the seed mixture leaves the bucket, itsultimate resting place is determined by each seed’saerodynamic properties, including mass and thelocal wind conditions at the time of release. Heavy,dense seed experiences the least wind influence,while seed specifically evolved for aerialdistribution will probably follow the path dictated bythe prevailing wind at the time of release. The sidemotion of the impeller will also cause segregation,since dense seed will be slowed less by airresistance when slung perpendicular to thedirection of the flight. This causes lighter seed tooccupy a narrower swath than dense seed.

The reality is that seed is never released in idealconditions, since the prop wash of the helicopterassures chaotic airflow around the seed when theseed is dropped. The effect that windy conditionshave on seed drops can all but eliminate theintended benefits of dropping a native seedmixture. Avoiding seed drops in conditions windyenough to cause segregation is both impossibleand impractical, given the urgent nature ofreseeding efforts after wildfires. Minimizing theeffect of wind on all types of seed mixtures used bythe Forest Service is possible using the techniquesoutlined here. Determining cost effectiveness willdepend on evaluating many factors beyond thescope of this study.

Seed Removal by AnimalsSeed dropped in burned areas sometimesrepresents the only food source for many animals.Birds may easily locate the drop area and eat anyvariety they find attractive. Other animals and

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insects that survived the fire underground may beforced to feed on the dropped seed. Only if all seedsin a mixture are equally unattractive to wildlife willthe original mixture be preserved throughgermination.

Seed Bridging/JammingSome seed, in bulk quantities, tends to form awoven layer due to unusual shape or appendages.This is particularly common with seeds having largeawns or bristles. This layer, or bridge, can be sostrong that both the seed composing the bridge, andother seed in the mix, may not flow through anopening. The only solution during flight is tomechanically disrupt the layer, which may beparticularly problematic when the seed is blockingthe outlet port of a flying helicopter bucket.Removing the awns is a commonly practiced option,but can sometimes hinder seed germination as wellas introduce new mixing problems. The identifiedseed treatments listed below can solve this problem.

Identified Possible SolutionsSDTDC has addressed each problem to determine aset of possible solutions and evaluate theeffectiveness of each. A market search forreasonable alternatives produced two candidates ofvarying availability, effectiveness, and cost. Otheralternatives are listed with their characteristicdrawbacks.

Seed CoatingsThe technique of coating seeds began in NewZealand. The purpose was to facilitate aerialdistribution and high germination of seed on roughterrain and unstable soil in sheep pastures. Thetechnology evolved in the United States to furtherenhance germination characteristics and facilitateground-based mechanical planting. Coating is nowa method used worldwide for enhancinggermination, facilitating accurate aerial spreading,and increasing mechanical planting efficiency.United States seed coating companies presentlyprovide planting and germination solutions forevery type of plant used by the agriculturalindustry. Two companies located in the marketsearch have developed and tested seed coatingsto ensure even aerial distribution of seed mixes.

Coatings vary in quality, thickness, ingredients,buildup characteristics, effect on germination,aqueous affinity, and animal attraction. Somecompanies distinguish coatings by using the termcoating, to refer to a thin buildup of chemicals onthe seed to add color, introduce an antifungalagent, promote or retard germination, or any otherdesirable quality. By the same standard, pelletingrefers to a coating (usually thicker) intended tosmooth irregularities in the seed, prevent clumpingor matting, increase seed mass, or generally aid inthe planting process. Pelleted seeds oftenincorporate any desired qualities of coating aswell. Most seed pelleting is done for precisionmechanical planters in the cash crop industry. Notall seed coating companies adhere to this standardnor do they offer the same alternatives for seeds.

Both coating and pelleting have demonstratedimproved seed separation and ensured even flow.Some companies offer techniques to removeexcess dust from the final coating. Whether this isnecessary in aerial seeding is unknown.

High-density coatings may offer another especiallyvaluable benefit to stand establishment andwatershed stability restoration. Since many nativeseeds are less dense than water, ungerminatedseed can be susceptible to runoff during heavyrains. Seed that is more dense tends to strike theground at a higher velocity, sometimes allowing the

Figure 1–Coatings have little effect on seed shape or size, butseed weight may be increased for relatively low cost.

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seed to bury itself in loose soil. Even when theseed does not become buried, it can better resistrunoff than seed that floats. Seed that floatsrequires negligible water flow to be displaced,while seed that is denser than water will remainstationary until the water’s ground velocity reachesthe carrying velocity for the seed. This implies thatcoated seed subjected to rainy conditions wouldexperience far less runoff and pooling thanuncoated seed does, possibly reducing the needfor runoff flow control.

Seed coating or pelleting companies are generallycontract-driven and eager to tailor their product tomeet customer requirements. Some companieswork mainly through a few seed providers, whileothers receive most of their business directly fromseed consumers. All companies listed here arewilling to produce samples of coated seed to meetthe Forest Service’s needs. All the companiesaccept large orders, with minimum orderrequirements. Turnaround time on jobs can varyfrom 1 or 2 days to several weeks.

Ballistic properties of seed is the final and mostcritical issue to resolve for even distribution. Usingthe experience of the two companies that haveengaged in ballistic tests of coated seed, theproblem can be identified as nonuniformity in seeddensity. Coatings have the sole purpose of unifyingthe densities of disparate seeds in order to unify amixed and aerially dispersed seed mixture.Companies that have identified themselves ascapable of providing density-unifying coatings holdcentral importance to this market report.

Coatings that may be of use to the Forest Servicefor aerial reseeding of wildfire-damaged, erosion-sensitive land must ensure uniform grounddistribution. The seed coatings must not increaserisk of removal by animals or increase stress causedby the local or global environment. Nearly all coatingcompanies have custom-tailored coatings to meetForest Service needs except ground distribution.The techniques they presently use will work with thewide range of seeds used in reseeding.

The most economically feasible coating method,high-density coating, generally costs between 30and 50 cents per coated pound (before packagingand delivery costs). According to coating companies,weight gain for good ballistic improvement is usuallydouble the original seed weight, meaning that thecoating cost in terms of the original delivered seedweight is generally 70 cents to $1 per uncoatedpound. Commonly used native seed species rangein cost from approximately $1 to over $20 per pound.Average seed cost per project is roughly $5 to $15per pound. Full consideration of the cost for eachresearched method is discussed later.

Coating offers a possible solution for providing evendistribution characteristics with only slightly greatereffort or time commitment than regular uncoatedseed. This is the targeted benefit of the marketsearch, but other benefits from the operation affectthe technique’s worth. The enhanced ballisticcharacteristics of the seed cause it to strike theground at a higher velocity when it is dropped from ahelicopter, allowing it to penetrate the surface andgain more contact with the ground. This canenhance germination and speed site recovery.Certain coatings can also offer hydrophilic propertiesthat speed water absorption and germination. Othersoffer hydrophobic (water repellent) properties thatmay be advantageous in extremely wet situationswhere excess water may slow germination.Hydrophilic coatings would probably be more useful.

Coating generally meets all Forest Servicerequirements. The relatively small weight concessionof coating, to unify density, is the technique’sgreatest asset. The techniques described show howthis consideration can adversely affect a solution’sutility. As coating companies work on a contractbasis through seed suppliers, with properpreparation seed supply used to rehabilitate a sitewill not be excessively delayed by the coatingoperation. This is most easily arranged when prioragreements are made with a dedicated native seedsupplier who has a working relationship with acoating company. Seed ordered for rehabilitation canthen be specified as coated seed, avoiding addinganother step for the contracting officer.

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Hydroseeding/HydromulchingHydroseeding or hydromulching began in the late1970s. Seed is distributed in a slurry form combinedwith processed woodchip fibers and other optionalenhancements. Fertilizer and a tackifying agent areoften added to speed the growth and prevent seed/slurry runoff or pooling. Hydroseeding andhydromulching are defined differently by somebusinesses.

Hydroseeding is sometimes defined as spreadingmulch concentrations less than 3,000 pound per acre,or a coverage insufficient to offer a dedicated layer ofmoisture protection to the ground. The mulch cover stillhydrates the seed and traps any incidental moisture,but it is considered insufficient to offer erosionprotection itself or prevent dehydration in constantly dryconditions.

Hydromulching is spreading mulch concentrationsgreater than 3,000 pound per acre. At or above theseconcentrations, the mulch is supposed to form a linkedmatrix, making a crude blanket over the ground. Theblanket absorbs the initial shock of any incident waterdroplets and then absorbs the water itself before it everreaches the ground. In addition to the fertilizer that maybe added to the slurry, the wood fiber itself provideslong-term fertilization as it decomposes.

The water/wood fiber suspension is generally thickenough to prevent segregation of the seed mixtures,and the high water/fiber to seed ratio eliminatessegregation due to wind conditions. Hydroseeders withmodern equipment have never encountered problemswith uneven ground distribution of seed mixes.

The main drawback of hydroseeding is that it requires alarge amount of water to create the slurry. This causesthe ratio of seed weight to cargo weight to be extremelylow. While targeted seed counts per acre are notdifficult to achieve, the increase in weight associatedwith each load of seed means that the number of tripsrequired to seed a single acre may be more than thenumber required for conventional seeding.

A conventional seed bucket will typically hold enoughseed to cover several acres at the desired applicationrate. Carrying the same weight, the helicopter wouldhave to make many trips dropping slurry to achieve thedesired application rate on a single acre.

Due to its generally specialized application, informationon animal reaction to hydroseed-applied seed isunavailable. It is likely, however, that the seedattractiveness to animals is minimized by the rapidgermination of the seed. If low quantities of slurry areapplied and germination is about the same as for plainseed, current hydroseeding technology offers nobenefits or solutions to seed removal by animals.

The current technology of aerial reseeding alsorequires special equipment. One company has built areasonable base of experience with the process, butthe helicopters used are designed for large liquidtransport and dropping, as with fire retardants. Adaptingother helicopters to handle the slurry could prove costly,time-consuming, and ultimately impractical.

Figure 2–Aerial hydroseeding enables precise application onalmost any terrain but the amount of material requiredneccessitates expensive, specialized equipment.

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Organic Mulch PelletsTwo companies offer a direct solution for achievinguniform distribution of seed mixtures. Gluingmixtures of seed to organic mulch pellets, providesa premixed product that guarantees no seedseparation. The pellets are certified weed-free andmade from compression- and heat-formed greenwaste material. Unique Forest Products uses urbanwaste for material while Elk Grove Milling relies onfarm residue. The diameter of the base pellet usedvaried from 5/32 to 5/8 inches. The length mayalso vary as required.

Attaching seeds to each size pellet hasadvantages and disadvantages from both theproduction and the consumer standpoint. The 1/4-inch-diameter pellet has worked well in the past forattaching seed mixtures, while the 5/32-inch-diameter pellet maximizes the seed to cargoweight ratio. Larger seeds attach poorly to any sizepellet, while small seeds present accurate ratioproblems. Although many different adhesives areavailable, each company uses a standard adhesiveunless unusual conditions dictate otherwise. Inaddition, Elk Grove Milling uses a calciumcarbonate dust coating on seeds to prevent pelletsfrom sticking to each other. Elk Grove Millingprovided pellets for burn area reseeding beforeSDTDC began research but never attempted toattach a variety of seeds to pellets.

The pellet itself offers multiple benefits to the seed.It is hydrophilic, and when exposed to water, thepellet rapidly expands and opens from the directionof the incoming water. In the case of rain orsprinklers, this property causes the seed attachedto the outside of the pellet to contact the groundafter rain while gaining a cover layer of mulch ontop. The mulch adequately retains water and offersnutrients to the seed. In seeding lawns, the mulchlayer has proven effective enough to form apseudo ground cover for the grass, allowing thegrass to form a layer of sod on barren, rockyground. Unique Forest Products offers nutrientenrichment for their pellets. The composition of thepellet may be modified to suit particular groundconditions.

Previous aerial reseeding projects demonstratedno difficulties with bridging or plugging of thepellets, probably due to the uniformity in size,shape, and density. The finished pellets alsodiscourage animal consumption for two reasons.The calcium carbonate dust coat, applied by ElkGrove Milling, masked the smell of the seed, andboth companies use a pellet that is composed ofnonnutritious organic waste. Animal consumptionhas never been noticed in any pellet application.

On average each pellet receives an equal mixtureof seeds. The uniformity in both size and density ofeach pellet ensures that the seed mixture willneither segregate due to agitation nor differ inballistic characteristics.

One major concern with the overall effectiveness ofthe technique is seed retention of the pellet. Theglues used are reportedly quite strong, but whetherthe glue can retain all seeds equally duringagitation is unknown. A mixture of varying seedsizes requires a large pellet to maintain anaccurate ratio on each pellet, but larger pelletsincrease cargo weight for the same quantity ofseeds.

Differential Metering Bucket, Mixing BucketSpeculation that a modified bucket could assist inachieving even distribution led to research intobucket designs. Although buckets with an effectivemixing device, such as an auger within the hopper,

Figure 3–Organic Mulch pellets (far rignt hold seeds of any sizeon their surface but to achieve uniform coverage only a fewseds may be attached to each pellet. The resulting cargo weightrequires many more helicopter trips to deliver the entirepayload.

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or separate compartments and variable-aperturespouts, can ensure that accurate mixtures leavethe bucket, each type has its drawbacks. Neitherensures that all seeds travel equal horizontaldistances in the air or fall at the same rate. Themixing bucket may also harm the seed as someauger devices subject the seed to a grinding orshearing force. Careful calibration of the meteringsystem is also required to ensure that each type ofseed flows out in its proper ratio. Bucketcompartments should also be considered. The bestnumber of compartments for the bucket is bothcritical to cost considerations and very difficult topredict, since only one major fire may require awide variety of seed mixtures. Because somecompartments may be unusable when seeding witha mixture containing an odd variety of seeds thehelicopter will not be fully loaded.

The bucket alone can offer no solution to theproblem of unpredictable wind conditions. Severalhelicopter pilots have recommended using shorttethers connecting the bucket to the helicopter,small helicopters, and wide-open gangs(minimizing bridging problems as the seed flows tothe impeller) to minimize ground segregation. Withthe gangs wide open, distribution density can onlybe controlled by the helicopter’s speed. Pilots mustconsider the flow rate of the particular bucket usedin each situation to determine the appropriatespeed necessary for achieving target seed density.Swath width differences may be minimized byflying low to the ground, but this may reduce theoverall swath width, leading to more passes withthe helicopter and more flight time.

Suspension/FillersSome reseeding operations utilize material such asrice hulls or sand to create a suspended mixture ofseed in the seed bucket. The primary benefit of thetechnique is the availability and cost of thenecessary materials. It also offers benefits for seedparticularly prone to bridging or rapid settling. Thecentral drawback to the technique is its inability tooffer a solution to wind segregation. Althoughcomponents are capable of significantly slowingvibrational segregation, they cannot eliminate it.The technique can only ensure little segregationover an extended flight and cannot significantly

affect aerodynamic segregation. The technique’sorigin was not apparent, nor were therecommended application rates documented.

Alternative Delivery PracticesSome agencies discussed their practice ofrequesting that seed mixes be delivered to them inbags or other packages after they discovered thatthe mixes remained mixed when delivered this way.While the technique offers the benefit of minimizingsegregation due to automobile-related vibration, theissue of in-bucket agitation and aerodynamicsegregation are not addressed. While helpful tooperators, this technique alone cannot solve theproblem.

Market Report—Seed Coating CompaniesSeed coating in the United States has been drivenby two major markets, each seeking differentadvantages from coating. Several companiesattempt to service both markets, but all thecompanies identified in this report derive themajority of their profits from one of the markets, ifnot from a single type of seed.

Companies offering low-volume, high-weight buildupcoatings generally cater to the ranching and fodderindustry. Alfalfa and clover are the most commonlycoated seed types in this category. The seedsthemselves are generally of moderate cost, and thecoatings provide soil and nutrient enhancement forthe germinating seed. Clover and legume seedsgenerally have inoculants added to the coating to aidin stand health.

The two companies involved in this market report,CelPril and Seedbiotics, coat millions of pounds ofseed per year. CelPril has manufacturing facilities inManteca, CA, and Hermiston, OR, as well as severalsales and distribution offices around the UnitedStates. It operates in cooperation with a sistercompany in France that supplies coated seedworldwide. Together the sister companies have over60 years of experience in seed coating technology.

Since Seedbiotics began operation in 1989, it hasexperienced a steady 20 percent annual salesgrowth. The company now coats several millionpounds of seed per year with significantcontributions from native and nonnative grasses.

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Manufacturing facilities in Caldwell, ID, and St. Joseph, MO, supply seed throughout the United States andrecently worldwide. Other smaller businesses fill the market needs unmet by these companies. Only thesetwo companies participated in this study.

Companies coating for the cash crop market address completely different product demands and havedeveloped completely different technologies to suit the market. Most individual coating orders for cash cropseeds, such as lettuce and tobacco, involve very low quantities of seed. Of the palletizing companiesidentified in this report, Incotec and Harris Moran represent the largest and oldest. Table 1 combines bothmarkets and identifies the current capabilities of each business.

The companies bearing a question mark in the Coating column have identified the availability of a high-density coating applicable for using standard pelleting machinery. This coating is different from the standardpelleting coat as well as from the coatings used by Seedbiotics and CelPril. In general, the more items inwhich the company has experience (as shown by the table), the greater their interest in this particularproject.

Coating companies catering to cash crop farmers must meet exacting germination and seed separationstandards in a fairly narrow range of conditions. The high volume, low-weight specialized coating of mostcompanies is designed to insulate the seed from temperatures as high as 140 °F, provide seeds of almostexactly the same size and shape for easy mechanical planting, leach water to the seed quickly to speedgermination, and provide fungicide for the seed and plant. Because of the relatively small quantity of seedeach company coats and the wide variety of special enhancements the coating must provide, the cost ofthis procedure is much higher than that of other coating processes.

Market Report—Hydroseeding CompaniesOf the hydroseeding companies contacted during this market search, who had experience in applying nativeseed mixtures in hydroseed slurries, only one had performed aerial reseeding of large tracts of land in harshterrain. Erickson Air-Crane has applied hydroseeding slurries to relatively large areas of land on minereclamation sites several times. All the sites received hydroseeding treatment after other rehabilitationtechniques failed. In one situation, hydroseed revegetated a hillside where a previous reforestation effortleft a plantation consisting of 10-year-old, 2-foot-tall pine trees, jokingly referred to as the bonsai forest. Thesoil of the site was so acidic that the revegetation effort required the application of 1 ton of lime per acre tomake the land arable.

Hydroseed application on all the sites selected was based on the failure of previous revegetation efforts.The technique costs a tremendous amount per acre when applied in the recommended quantities, and therelative benefits dissipate quickly when application rates dip much below the recommended amount. One

Company Coating Pelleting Burn Experience Aerial Experience Trees Grasses Flowers Treat mixSeedbiotics x x x x xCelpril x x x x xIncotec x x xSynergene x x x xSeedTechnologies ? xSeedDynamics ? x x xElk GroveMilling x x x xHarris Moran x x

Table 1—Markets and current capabilities of each business.

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blanket estimate received from a hydroseedingcompany who contracts with Erickson Air-Cranelisted the recommended application rates as 16tons per acre with a cost, not including materials,of $85 to $125 per ton. Typical application rate ofseed alone on Forest Service reseeding areasaverage 2 to 4 pounds per acre. One load of seeddropped from a conventional bucket theoreticallycovers hundreds of acres, while many trips of aheavy-lift helicopter are required to hydroseed asingle acre. The cost of hydroseeding could not bejustified on any large general rehabilitation project.

Market Search for BucketsTwo different types of seed segregation related toaerial application, classified as either preflight orinflight, were identified. To achieve the goal ofapplying a uniform seed mixture to the burnedland, the different segregation patterns must beeliminated. While the coatings identified providedthe most promise for solving the inflightsegregation problem, they may still leave theseeds vulnerable to preflight segregation. Thissegregation may be eliminated by providing amixing system within the bucket.

Bucket manufacturers are interested in the projectbut have performed no prior research on thisproblem. The California Department of Forestry(CDF) developed and produced several mixingbucket models designed specifically for nativeseed mixtures. One helicopter bucket manufactureris also willing to produce a prototype mixing bucketfor Forest Service inspection. Individuals whoworked on the development of the CDF bucketshave offered to loan buckets to SDTDC for studyand test. In short, solving preflight segregationwherever it occurs will be possible, but until inflightsegregation is eliminated, it is impossible to saywhether new technology needs to be developed toavoid poor ground distribution caused by preflightsegregation.

Field Test—Kirk Fire in the VentanaWilderness and Los Padres National ForestA large and particularly fast-moving fire decimatedmuch of the northern Los Padres National Forest,including large parts of the Ventana Wildernesslate in the summer of 1999. Rob Griffith, the manin charge of the rehabilitation effort, submitted the

proposal to study alternative distribution methodsof native seed mixtures several years before.During correspondence, Griffith learned about thedifferent techniques being studied and asked ifSDTDC wished to conduct a small trial on someland designated for reseeding within the burn area.Preparations soon began with coated seed andseed attached to organic mulch pellets ready fortest drops by the third week in November.

During the preparations, SDTDC arrangedshipment from the native seed supplier, to thecoater, then back to the field office, as well as tothe mulch pellet provider and back. Having SDTDCsolely responsible for this position madecoordination much easier. Any widespread use ofthese techniques will need to be arranged duringthe prefire season to ensure that all burned areaemergency rehabilitation team members, seedsuppliers, seed treaters, and equipment operatorsare aware of the necessary steps involved in theoperation. Other requirements, such as those forseed and treatment labeling, will need earlydissemination as well.

Three hundred six acres, divided into sevenseparate plots, received aerially applied seed forthe test. Five received seed coated by CelPril, onereceived organic mulch pellets supplied by UniqueForest Products, and one received seeds with nocoating at all. Data gathered revealed that both thecoated and uncoated seed still experiencedsegregation. The organic mulch pelletsexperienced problems as well. During the first loadthe pilot kept the bucket’s opening partly closed.Upon return for a reload, it was discovered thatonly half the load had been expelled. During thenext pass the pilot completely opened the bucket,but the copilot noticed that at this setting, thetorque generated by the rotating slinger throwingthe heavy pellets caused the bucket to spin, whichultimately caused the connecting cable to unwind.Only one-third of the pellets were actually appliedbefore the cable was deemed unsafe.

Computer Modeling—Results andConclusionsThe results of the field testing on the VentanaWilderness prompted a more rigorous analysis ofthe dynamics involved in the seed flight. Visual

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information as well as the distribution datagathered proved that neither seed coated to doublethe weight nor uncoated seed formed equal swathswhen dropped in identical conditions. Computermodeling of these situations explained theseobservations. The only way to cause two particlesto travel through the air with the same pattern is togive them the same weight and cross section areain the direction of travel. Although doubling theweight of each seed did bring the densities slightlycloser together, the change was not large enough.Unifying densities requires consideration of thecurrent densities along with the density of thecoating. Seed with a relatively low-density coatingdemonstrated the potential drawback of thisrequirement; unifying the densities of 10 seedsresulted in increasing some of the seeds’ relativeweight up to 34 times their original weight.

General Native Seed IssuesThe initiative to use native seed mixtures for soilstabilization after wildfire includes more thanaerodynamic issues. Every step in the practice ofnative seed mix reseeding requires newimplementation practices. Interviews withhelicopter operators, supervisors, and native seedsuppliers generated considerable information onhow to improve the technique with or without seedtreatment.

The first, and in many ways, most critical aspect ofimproving native seed reseeding is to ensure thatthe proper mix is used in each situation. The issueis far more complex than picking species off a list.Chuck Cambra of Kamprath Seed Co. lists manyfactors critical to ensuring germination of thedesired species. First and most important is theunderstanding that not all native seed species willgrow in all areas of their native region. Oneparticularly common oversight is in neglecting tospecify the altitude of application for altitude-sensitive species. Kamprath Seed offers distinctvarieties of some seeds grown at specific altitudesto automatically select the correct variety. Whileone particular variety of specie may be more costlythan another, Cambra says the only way to ensurea healthy and long-lasting stand is to use theproper variety.

Paul Albright of Albright Seed Co. argues thepracticality of replicating the exact native seedmixtures formerly appearing on the wildfire-damaged land. He pointed out that the immediategoal of soil stabilization might be lost quickly if theparticular native seed mixtures are unavailablefrom seed suppliers, or if the particular variety of anative seed available from a seed supplier isunsuited to the area. He added that hybrid species,usually grown by seed companies, generallyincorporate greater genetic diversity into the plant,making the plant hardier in a wider range ofenvironments. Native species rapidly becomegenetically specialized to a particular microclimate,so that in as little as one growing season, thesame specie of native grass may have two differentand mutually exclusive strains growing within a fewhundred yards of each other. Albright refers tothese strains as ecotypes. He supports the intentof the native seed policy, but not the strict practiceof it.

Similar issues apply to varying soil content andtype. Wildfires can significantly alter soil chemistry,so proper seed selection necessitates knowledgeof each seed’s pH tolerance. Seeds that aresensitive to the acidity or basicity of soil maytotally fail where they were once the primaryground cover. Coatings and seed treatments canaid in this area as well. Stu Barclay of Seedbioticshas worked on mine reclamation sites where a thinseed coating created a sufficient buffer betweenthe pH-sensitive seed and the acidic soil that theplants established permanently with the samegermination rate as on neutral soil.

Sometimes several species share common namesand seed suppliers often disagree on the propercommon name for individual seed. Since individualareas often buy seed from various suppliers,mistakes involving seed names are relativelycommon. The seed suppliers contacted during thisresearch urged standardization of orderingaccording to proper Latin names to avoid suchconfusion.

Moisture availability is also a primary concern forreseeding. While species may be particularlydrought resistant as plants, seeds may be pushed

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into dormancy by lack of water. If a seed enters adormancy phase that can be broken only byfloodlike conditions, the seed is likely to beworthless for establishing early ground cover.Some seed coating companies also offertreatments to prime the seed, which breaksdormancy for rapid establishment.

Some seed can be coated and aerially distributedmuch more easily when “cleaned” or deawned, aprocess by which parts of the seed pod, notnecessary for germination, are removed. This canbe a problem when distributing uncoated seedbecause some awns orient the seed in flight,causing it to burrow into the ground on impact. Ifthe bare seed does not enter the ground,germination may suffer. In these situations coatingformulations designed to enhance germination maybe necessary.

General Seed DistributionConsiderationsMany factors could improve revegetation results,including more strict monitoring of helicopter dropperformance. Much like airtankers, helicopter seedbuckets were designed to apply seed or fertilizer ina consistent line, at a consistent coverage levelbased on the helicopter’s ground speed and heightabove ground level. Unlike airtankers, no formalguide exists for determining line width or coveragelevel with seed buckets. This information could begenerated, but the density dependence of linewidth would make such tables more complicated.

Drop performance could be improved in manycases by establishing more well-defined droplocations and perimeters. Topography can makethis difficult, but most reseeding projects begin withForest Service personnel flying with the pilots andestablishing global position system (GPS)coordinates for each site. The simplestimprovement would be to establish a northern,southern, eastern, and western border for eachsite. The helicopter pilot could then fly a gridpattern over the site, making even coverage easierto achieve. This grid should overlap the intendedreseeding area; using native seed should preventany harm from being incurred by dropping materialoutside the intended reseeding area.

Cost EvaluationsSeed coating could have become an acceptedpractice for all aerial seeding applicationsapproximately a decade ago when several seedcompanies demonstrated the technique’s benefits.Native seed can cost 10 to 100 times as much ascommonly used nonnative seed. Chuck Cambradescribed a demonstration at Camp Roberts MilitaryReservation using ryegrass. While the stands ofcoated seed established much faster and morevigorously than the stands of uncoated seed, theryegrass was so inexpensive that coating tripled theseed cost. Native seed mixtures often costapproximately $10 per pound uncoated, so theexpected cost of coating, around $1 per pound, is amuch lower price to pay for significant stand andgermination improvement.

The results of computer modeling suggest that anestimate of $1 per pound for uncoated seed will betoo low of a value to significantly improvehomogeneity of many dropped mixtures. Doublingoriginal seed weight will not normally be enough tounify density; care must be taken to apply morecoating to the less dense seed. A simple formulagives the necessary amount of coating when thecoating density and seed density are known. Coatingdensity is readily available from the coatingcompany and determining seed density requires onlya scale and a container with a known volume, suchas a soda bottle. SDTDC will provide instructions toany interested parties. Once a relationship with acoating company is established, this step wouldlogically become the coating company’sresponsibility.

Seed Dynamics, a company specializing invegetable seed pelletizing, returned samples of testspecies with satisfactorily uniform density. Thecoating material used to accomplish this sufferedone major drawback. Because the material was lessdense than many of the seeds in the test, the denseseeds required weight buildup as high as 34 timesthe original seed weight. Volume also became anissue. The uncoated seed samples used by thecompany were shipped in one small box, but thecoated samples were returned in nineteen 5-gallonbuckets, filling a shipping pallet. All the associatedcosts of such a process clearly discount it as a

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reasonable alternative for Forest Service emergencyrehabilitation use.

Another company, Harris Moran Seed Company,devised a method for effectively unifying seeddensities while minimizing the cost increase andvolume buildup. Keith Kubik, Salinas OperationsManager, directed the use of two different coatingmaterials in discrete blends to reduce two seeddensities while raising the rest. Weight buildupreached as much as 11:1 on a particuarly light andbulky seed, but seed volume remained much lowerthan that returned by Seed Dynamics. Kubik evenpacked the coated samples into a box about twicethe size of the one used to deliver the samples.Measured densities of the coated seeds varied byless than 20 percent. Uncoated seed densityvariance topped 400 percent. Depending ontype and size of the order, the technique used maybe available for roughly $3 per pound of raw seed.The distribution and potential germination benefitsavailable from seed coated in this manner couldeasily justify the expense in certain situations.

The hydroseeding industry is especially tailored tothe sod market. While hydroseeding typicallyunderprices sod, the market for which hydroseedingis suited is the small application market. Manydepartments of transportation use hydroseeding forroadcut stabilization, but again this represents asmall application market. Because aerial reseedingof fire-damaged lands covers vast tracts with acomparatively low seed density, hydroseed to seedratios are necessarily great. This alone is enough tomultiply the cost of the application by large factorseven before considering resource cost. Typical seeddensity specifications call for less than 20 pounds ofseed per acre, while hydroseed wood fiber is rarelyapplied at rates lower than 1,500 pounds per acre.Creating the hydroseed slurry requires an amount ofwater weighing approximately 20 times as much asthe wood fiber. Applying even 1 acre of seedsuspended in hydroseed slurry would require a largehelicopter or fixed-wing aircraft, while the sameaircraft may be able to seed 100 acres with regularseed. Hydroseeding companies show great interestin the project but offered no insight into costmediation.

Organic mulch pellets are a conceptually attractiveoption, but the technique suffers from far too manyquestions to be immediately viable. The currentmarket for the technique is too small to determine anaccurate cost estimate for the size associated with atypical reseeding project. The actual distributionvehicle, the mulch pellet, may be envisioned ashydroseed without the water or difficulties inapplication. In this sense, the pellet contains highlydesirable qualities, but the mulch pellet still suffersfrom the large carrier weight to seed weightdiscrepancy that afflicts hydroseeding. If thetechnology associated with the technique advances,the option may become viable in the future.

The organic mulch pellets applied to the Kirk firerehabilitation areas illustrate the need for costmitigation before the technique experiences anygeneral use. Of the 306 acres covered in thereseeding test, organic mulch pellets were applied to33 acres. The total seed weight, after coating, forthe other 273 acres was 2,173.2 pounds; the totalweight of the pellets provided for the 33 acre testwas 7,200 pounds. The cost of coating for the seedsupplied to CelPril was approximately $715, whichcovered 242 acres. The cost of the organic mulchpellets to cover 33 acres was close to $7,000.Perhaps the most costly increase caused by theextra weight of the pellets was in the expected flighttime of the helicopter. While only two to three flightswere expected to apply the coated seed,approximately seven trips were necessary to drop allthe pellets.

Figure 4–Helicopter distributing coated seed after the Kirk Fire,Ventana Wilderness, Los Padres NF.

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The adoption of mixing seed bucket standards woulddefinitely be the most cost-effective, long-termsolution if even ground distribution could beguaranteed. Some companies offer buckets withsuch mixing features while others have showninterest in designing buckets to meet requirements.Should a mixing system prove necessary for coatedseed mixtures, development of a new type of mixingbucket may be desirable. Coatings suffer no damagefrom cement mixer-type mixing designs, but auger orpaddle mixers can shear off coatings.

Suspension materials offer one clear advantage ofeffectively suspending the mixture at minimal cost.Unless the suspension can somehow ensureuniform aerodynamic characteristics, the solutiondoes not address the identified problem.

General RecommendationsConsiderable disagreement between the partiesinvolved has slowed the evolution of a standardpractice for aerial reseeding using native species.Native specie mandates have no bearing on aerialseed application practices, and several individualsinterviewed during this market search told storiesof early native seed debacles when old reseedingtechniques were employed. Those areas wherereseeding is most common show the mostprogress when adopting experience-basedmethods to achieve the desired distribution. TheBoise National Forest provided many of the tipsfor improving distribution contained in this report.At one time the office experimented with coatedseed and saw too little improvement to warrant achange in policy. Those involved with aerialreseeding in the Boise National Forest felttreatments, such as coating, would probably be awaste of money, since they were confident theirapplication method accomplished the goals soughtby this market search.

Much of the Boise National Forest’s experiencewith aerial reseeding comes from projects that areimplemented over a timescale greater than thatavailable to other projects; for instance, reseedingin the Boise National Forest is sometimesscheduled just after a significant snowfall so seedis sure to remain stationary relative to the grounduntil snowmelt can ensure rapid germination.

Under these circumstances a coating would probablybe a waste of money, but snowfall is not available tomany of the most vulnerable burn areas in the country.This example highlights the need to evaluate everyproject on an individual basis.

The exorbitant cost of many native seeds, as comparedto that of previously utilized species, calls for specialinvestigation into ways to protect the investment. Theavailable options with coatings should be carefullyconsidered when ordering native seed. If a seedtreatment promises 30 to 50 percent strongergermination at a cost of 10 percent seed cost, thenmoney and seed can be saved by using the coating.

Those techniques that improve aerial reseeding withuncoated native seed mixtures, such as those listed inthis report, should be immediately shared with allconcerned parties. Sharing experience drives progress.When ordering seed, the customer should askquestions. Many species have developed varietiessuited for disparate environments. Informed seedcompanies have this information and are eager toshare it. Some seed suppliers, such as Kamprath Seed,regularly work with seed coating companies and canmake informed suggestions concerning all types ofseed treatments. All factors should be considered andno options ignored.

This report offers recommendations that, whencombined with practice and dialogue, couldeconomically solve the observed problems with aerialnative seed distribution. Recognizing that each step inthe process has the potential to cause poor distribution,each reseeding operation should be handled on anindividual basis. Some techniques listed here may beimpractical for certain situations but perfect for others.Hydroseeding, for instance, has proved to be aninvaluable asset on several mine reclamation projectswhere many other techniques have failed. The chancesthat hydroseeding will be economically attractive to apost-wildfire reseeding operation are slim, but theoption exists. Similarly, some locations may have a verylow native plant diversity and will not encounterdifficulties with seed segregation. Each case should beevaluated on an individual basis with priority given tothe most effective native plant regeneration at the mostreasonable cost.

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Suggestions for Further StudyThe conclusions reached by this market searchshould not be interpreted as standard-settingmaterial. The actual research done to verify thevarious manufacturers’ claims is far too incompleteto warrant trust in the methods described. Thecharacteristics of reseeding projects conducted bythe Forest Service are unique and will necessitatespecial consideration by any company thatbecomes involved in a project. Implementation ofany of the options mentioned will require planningbefore any other reseeding preparations begin.Forest Service personnel will need to learn therequirements of each method for achieving thedesired results. While careful implementation canprovide the desired benefits, any mistakes or evenmiscommunications during the planning can bedisastrous.

None of the companies offering the techniquesdescribed have regularly worked on the shorttimescales typically demanded by burned areaemergency rehabilitation. For this reason, thesecompanies will typically need more advancenotice. The seed provider will likewise need tounderstand the necessity of delivering the seed ina timely manner. Introducing another element intothe process demands very careful planning.

Other concerns that should be studied before anyformal change in technique is adopted include(a) whether treatments of interest affect animalbehavior towards seeds, (b) how coating buildupsgreater than what is standard affect germination,(c) the claims by companies that certaintreatments enhance germination, and (d) whethertreatments that claim to offer hydrophilicenhancement actually do.

The preliminary cost analysis presented hererepresents the greatest shortcoming of this report.All cost estimates are accurate only in magnitudeand will fluctuate from project to project. Thebiggest limiting factor in accurately estimating costfor the proposed methods is the unpredictability ofthe material requirements from project to project.Effectiveness will likewise hinge on each particularsituation. As is the case with current practices ofaerial reseeding, the effectiveness of reseedingwith seed treated to improve ballistics will dependon effective implementation. The greater numberof parties involved with any reseeding effort usingtreated seed creates more chances for error. TheForest Service could benefit from applying thetechnology available to treat seeds, butimplementation on any level is guaranteed to be acomplex task.

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ReferencesBureau of Land Management. (No date). Second draft: policy on the use of native plant materials in California.

California Native Plant Society. 1995. Statement of policy—seeding after wildfire. December.

Knapp, E.E.; Rice, K.J. 1994. Starting from seed: genetic issues in using native grasses for restoration.Restoration and Management Notes. 12: a40-45.

Lesica, P.; Steele, B.M. 1994. Prolonged dormancy in vascular plants and implications for monitoring studies.Natural Areas Journal. 14: 209-212.

Owen, W.R., Forest Botanist, Boise National Forest. (No date). Restlessness among the natives: an essay on theappropriate uses of native plants.

USDA Forest Service. 1994. Policy on the use of native plant material in restoration (and) other revegetationprojects. From Ronald E. Stewart, Regional Forester, to Forest Supervisors, Staff Directors and StationDirectors, PSW. June.

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Appendix ASeed Coaters/PelletizersCelPril Industrial251 Oak StreetManteca, CA 95337(209) 823-1738Contact: Chuck Loach or John Walsh

Harris Moran1155A Harkins RoadSalinas, CA 93901(831) 757-3652Contact: Gil Markle

Seed Dynamics, Inc.1081-B Harkins RoadSalinas, CA 93912(831) 424-1177Contact: Mel Bachman, Seed Technology Manager

Seedbiotics818 Paynter AvenueCaldwell, ID 83605(800) 764–6639Contact: Stu Barclay or Bill Talley, Owners

Incotec, Inc.1293 Harkins RoadSalinas, CA 93901-4495(831) 757-4367Contact: Dave Pickenpaugh or Suzanne Emery

Unique Forest Products, Inc.1535 East Orangewood Avenue, Suite 117Anaheim, CA 92805Contact: Stan Raddon, President

Elk Grove Milling8320 Eschinger RoadElk Grove, CA 95758-9739(916) 684-2056Contact: Robert Lent, Owner

Seed Technologies, Inc.1315-B Dayton StreetSalinas, CA 93901(831) 753-2344

Synergene Seed & Technology, Inc.1147 Madison LaneSalinas, CA 93907(800) 352-9987Contact: Merv Selvidge

Hydroseeding CompaniesTri-State HydroseedingP.O. Box 147Kingston, ID 83839(208) 784-4202 or (208) 682-3565Contact: Shane Waechter

Conwed Fibers1002 Bucks Industrial ParkStatesville, NC 28625(800) 366-1180Contact: Ambe Lewis

Quality Hydroseeding and Restoration2017 Orange AvenueRamona, CA 92065(760) 789-8040

Canfor R&D Center#101–1750 West 75th AvenueVancouver, BC Canada V6P 6G2(800) 426-6002

Erickson Air Crane Co.3100 Willow Springs RoadP.O. Box 3247Central Point, OR 97502(541) 664-7615Contact: Jeff Stein

Native Seed SourcesS&S Seed Co.5690 Casitas Pass RoadCarpenteria, CA 93014-1275(805) 684-0436

Truax Native Seed Drill Co. (612) 537-6639Product: pelletized seed, belly grinders (Drill Seeders)Contact: Jim Truax

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Kamprath Seed Co. LLC205 Stockton Street.Manteca, CA 95337(209) 823-6242 or (800) 466-9959Contact: Chuck Cambra

Albright Seed Co.487 Dawson DriveBay 5SCamarillo, CA 93012Contact: Paul Albright

Granite Seed Co.1697 West 2100 NorthLehi, UT 84043

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Appendix BResourcesCalifornia Department of ConservationDivision of Mines and GeologyP.O. Box 670Santa Rosa, CA 95402(707) 576-2275Contact: Tom Spittler

California Department of ConservationDivision of Mines and Geology801 K StreetSacramento, CA 95814(916) 327-6977Contact: Trinda Bedrossian

California Fish, Wildlife, and ParksRegion Vegetative Management—Santa Rosa(707) 576-2275Contact: Brad Valentine, Kevin ShafferCalifornia Fish, Wildlife, and Parks(916) 327-0713

California Native Plant Society1722 J Street, Suite 17Sacramento, CA 95814(510) 649-0460Contact: Emily Roberson

Civil Engineering Resource LabContact: Dr. Steve Warren(800) 872-2375, ext. 5455

Franklin, Scott, Consultant25059 Highspring AvenueSanta Clarita, CA 92321(805) 254-2376

Iowa Department of TransportationProduct: helicoptersContact: Steve Holland(515) 239-1768

U.S. Department of AgricultureNatural Resources Conservation ServiceLockeford Plant Materials Center—Pelletized SeedP.O. Box 68Lockeford, CA 95237(209) 727-5319

USDA Forest ServiceCoordinator of Burned Area EmergencyRehabilitative Program630 Sansome StreetSan Francisco, CA 94111(415) 705-2876Contact: Robert Griffith