Great Basin Naturalist

Volume 52 Number 3 Article 6

12-18-1992

Ecology and management of medusahead (Taeniatherum caput- medusae ssp. asperum Melderis)

James A. Young Agricultural Research Service, U.S. Department of Agriculture, Reno, Nevada

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Recommended Citation Young, James A. (1992) "Ecology and management of medusahead (Taeniatherum caput-medusae ssp. asperum Melderis)," Great Basin Naturalist: Vol. 52 : No. 3 , Article 6. Available at: https://scholarsarchive.byu.edu/gbn/vol52/iss3/6

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ECOLOGY AND MANAGEMENT OF MEDUSAHEAD (TAENIATHERUM CAPUT-MEDUSAE SSP. ASPERUM [SIMK.] MELDERlS)

ABsn\Acr.-Medusahead is nnother in the extensive list of annual herbaceous S],X-"Cies to invade thl:: tempemte desert rangelands of the Great Basin. Mednsahead is not preferred by large herhin)res and apparently is not preferred by gmnivores. Herbage ofthis anlllial gl'ass enhances ignition and sprei.ld ofwildFIres. Mcdwmhcad is highly competitive with the se<..--dlings of IlJltive spedcs and is prohably the greate..<>t threat to the biodiver.plant phYSiology, and ecology may find this species to be an excellent model for colonization.

Key words: rnedflSahead, "r:lenintherum caput-medusae, armual grass, r,oltmizing species, Wild/ires, grtJZing.

In the management of natural resources cies, there has heen confusion about the correct there are certain problems that by their persis­ scientific taxon for mcdusahead. The first tence, magnitude of ecological disruption. and deSCription ofmedusahead in a North American economic impact refuse to dissipate as a result /lora used the taxon EllfrntlS caput-medusae L. of being ignored and neglected. Unfortunately (Howell 1903). There is apparent agreement for range management, medusuhead that medusahead is a member of the tribe (Taeniathemm caput-medusae [L.] Nevski) is Triticeae ofthe grass family There is also appar­ that type of problem. DUring the 1950s ent agreement among morphologists and cyto­ medusahead was considered among the most geneticists that medusahead does not fit in the pressing problems on the rangelands ofCalifor­ genus Ellfrrms. Various authors have placed rna, Idaho, and Oregon. A greatdeal ofresearch medusahead in Hm-dell1H or Hmuely-mus. effort was devoted to solving themedusahead evski (1934) proposed that medusahead was problem. Valuable information was learned truly a different genus and published the name about the ecophysiology and synecology of Taeniathemm Jack Major of the University of medusahead. Control methods were developed CaWarnia suggested in 1960 that material intro­ using herbicides. The fatal link in integrated duced to the United States was Taeniatherom programs for the suppression of medusahead asperom (Major et al. 1960). Based on the populations proved to be mtificial revegetation European and Russian literature, Major technologies after medusahead was controlled. reported that Taetliatherurn contained three The nature of the sites infested had more to do geographic and morphologically distinct taxa, T with this failure than the weed itself, especially caput-medusae, T asperum, and T. crinituUl. in the Intermountain are.:'1. The recent discovery These three species are found in the Mediterra­ of medusahead in northern Utah has renewed nean region and extend eastward into central interest in suppressing this nmgeland weed. Asia. After examining the European material, My purpose in this review is to refresh our collective memories about medusahead ecology gmwing in plac:e. Major decided the United and management. States introduction was 1: asperum. The Danish scientist Signe Frederiksen TAXO:-JOMY revised the genus in 1986. He kept the same three taxa, but reduced them to subspecies of As is often the case with an introduced spe- Taeniatherum caput-medusae. Positive identifi-

245 246 GREAT BASIN NATURALIST [Volume 52 cation to the lowest level possible is absolutely south of Steptoe Butte (Sharp and Tisdale essential for any proposed biological control 1952). Fred Renner told Jack Major hehad seen program for medusahead. According to medusahead near Mountain I-lome, Idaho, as FredeIiksen's revision, subspecies cnnitum has early as 1930, and Lee Sharp bad reports from a very strict spike. Subspecies caput-medusae ranchers that the species occurred in Idaho as has a large open spike with straight awns. The early as J942. The medusahead infestation in spike of subspecies asperl11n is intermediate Idaho increased to 30,000 acres by 1952. Min with angled awns. Subspecies asperurn is the Hironaka estimated that 150,000 acres were only one of the three with pronounced barbs infested by 1955, and the Bureau ofLand Man­ coated with silica on the awns. Apparently, the agement estimated 700,000 acres were infested correct taxon fiJf the medusahead of western by 1959. At that rate of spread it appeared that North America is Taeniatherurn capui-medt.&wJ.e all of Idaho would be infested by the end ofthe ssp. asperum (Simk) Melderis (Frederiksen next decade. The spread ofmedusahead slowed 1986). and nearly continuous infestations remained TaeniatllRrurn caput-medusae ssp. caput­ confined to Gem, Payette, and \iVashington medusae is mostly restricted to Portugal, Spain, counties in southwestern Idaho. There were southern France, Morocco, and Algeria. It has several spot infestations in surroundingcounties been collected outside this area in Europe and (llironaka and Tisdale 1958). Asia, but FredeJiksen considers it adventitious Medusahead spread south in California to in these areas. Subspecies crinitum is found Santa Barbara on the southern coast and Fresno from Greece and Yugoslavia eastward into Asia. County in the intelior valleys. The rapid spread Subspecies asperurn completely overlaps the from southwestern Oregon through northern distribution of the other two subspecies. All and central California occurred in annual-dom­ three subspecies integrate with each other. inated grassland, oak (QuemlS) woodland. and Apparently only the one subspecies occurs in chaparral communities. These areas have a North AmeJica. Does this indicate one or very Mediterranean type climate with hot, dry sum­ limited introductions? mers and cool, moist f~llls, winters, and springs. Medusahead is predominantly self-polli­ Germination occurs in the fall and flowering nated. Genetically the genus appears to stand and seed set in the spring. alone in genomic relations within the Triticeae In northeastern California, east ofthe Sierra (Schooler 1966, Sakamoto 197:3). Apparently Nevada-Cascade rim, mcdusahead invasion T'aeniathenl1n has a genome that is distinct, but occurred at a much slower rate. In the Pitt River hrintly related to those of Psathyrostachys, drainage, vegetation is an intergrade ofOregon Dasypyn.tm, Ercrnopyntm, or HordEUm. white oak (Quercus garryana) woodlands, (Frederiksen and Bothner 1989). cismontane California species, western juniper (juniperus occidentalis), ponderosa pine (Pi.nus HISTOHY IN NOHTH AMERICA ponderosa) woodlands, and sagebrush (Artemi­ sia)/bunchgrass communities rnore typical of Medusahead was first collected in the the Intermountain area. United States near Roseburg, Oregon, on 24 Medusahead was discovered in the Great June 1887 by Thomas Jefferson Howell (1903). Basin at Verdi, Nevada, in the early 1960s. Iso­ It was next collected near Steptoe Butte in east­ lated infestations were subsequently found ern Washington in 1901 by George Vasey (Piper along the eastern front of the Sierra Nevada in and Beattie 1914), followed by a collection near areas where range sheep bands used to concen­ Los Gatos, California, in 1908byCharles Hitch­ trate while waiting for mountain summer pas­ mck (Jepson 1923). Medusahead certainly tures to be free ofsnow. attracted the noted agrologist. McKell, Rohin­ Innortheastern California in the Great Basin son, and Major (1962) commented on this during the early 1960s, there were two small strange initial distribution reaching 390 miles infest;:ltions in city lots in Susanville and a small north and 450 miles south from the point of infestation at the old sheep-shearing site of initial collection. Early herbarium specimens Viewland along the railroad above Wendel, Cal­ show a rapid spread to the south into California. ifornia. Another isolated infestation occurred at J. F. Peehanec made the first collection in the mouth of Fandango Pass in Surprise VaIley. Idaho in 1944 near Payette or about 180 miles By the early 1970s, medusahead was nearly 1992] ECOLOGY AND MANAGEMENT OF MEDUSAHEAD 247

continuous over about 60,000 acres of the seeds touching a mOisture-supplying substrate. Willow Creek-Tablelands northeast of Susan~ In this situation, germination of medusahead ville. Currently, after four years of extreme seeds is controlled by the relative humidity drought, medusahead spot infestations occur within the litter and the incubation tempera­ over perhaps an additional million acres on the ture, which of course influences the relative western margin ofthe Great Basin. humidity. The needlelike, vitreous caryopses of medusahead appear hydrophobic rather than BIOLOGY OF MEDUSAHEAD hygroscopic. Not only can medusahead seeds germinate under these conditions, but they can be dried until the primary root is dead; then, Medusahead, in some ways, is a rerun of following remoistening, a new adventitious root cheatgrass (Bromus tectorum) invasion. will develop. Cheatgrass dominates secondary succession in a majority of sagebrushlbunchgrass communi­ Raymond Evans and I demonstrated what a great modifYing influence litter cover can be to ties in the Great Basin and proVides a significant portion of the forage base for livestock grazing. the surface of seedbeds on temperate desert However, there are highly significant differ­ rangelands in terms of redUcing extremes in ences in the ecology of the two grass species temperature and conserving moisture (Evans (Harris and Wilson 1970, Al-DakheeI1986). and Young 1970, 1972). Caryopses of GERMINATION.-The caryopsis of medusa­ squirreltail (Elymus hystrix) are very similar in head is less than a millimeter wide with a very morphological appearance to those of sharp callus and an elongated, non-geniculated medusahead. As I will discuss later, squirreltail awn. The medusabeadcaryopsis is covered with seedlings are one of the few native species that small barbs ofsilica. Vicious is the best descrip­ can become established in undisturbed tion for this grass caryopsis. Bovey et aJ. (1961) medusahead stands. Both Taeniatherum and determined that medusahead had a much Elymus are members ofthe tribe Triticeae, but higher ash content (over 10%) than other grass they do not share the sarne genome. species and tbe ash was about 75% silica. Heavy Medusahead populations easily exceed lOOO deposition ofsilica occurs on the barbs of awns plants per square foot, and they are phenotypi­ and the epidermis ofleaves. cally plastic enough that a population of1 plant For the vast majority of collections of per square foot can exceed the seed production cheatgrass from the Intermountain area, seeds of lOOO plants per square foot (unpublished are ready to germinate when they are mature. research, ARS, Reno, Nevada). Huge seed No pregermination treatments are necessary banks develop in medusahead communities in (Young and Evans 1982). For collections from the litter and soil. Medusahead seed acquires a the Great Plains and perhaps the Columbia dormancy in the field similar to that of Basin, seeds may have a briefafterripening dor­ cheatgrass (see Young et at. 1969). These dor­ mancy. In contrast, seeds ofmedusaheadhave a mant seeds respond to enrichment ofthe seed­ temperature-related afterripening, and germi­ bed with nitrate and gibberellin (Evans and nation will not occur except at cold incubation Young 1975). temperatures for about 90-120 days after matu­ LiFE CycLE.-Medusahead seeds can ger­ rity (Young et al. 1968). Nelson and Wilson minate in the fall, winter, or spring; and seed­ (1969) found this dormancy was controlled by lings from all seasons can produce flowers and materials located in the awn. seeds early in the summer. The striking thing The high silica content on the herbage of about the medusahead life cycle is that it medusahead makes the litter very slow to matures from 2 to 4 weeks later than other decompose. Harris (1965) described the chok­ annual grasses. All those famous botanists and ing accumulations of medusahead litter that range scientists who were Qut on the range dis­ built up for several years. We evaluated the covering new infestations of medusahead were germination of seeds of various annual grass led to tbe populations by the bright green color species in medusallead litter (Young et at. I971a). when all other annuals in either cismontane Allelopathy was not suspected, but rather the California or the Great Basin were brown. physical holding ofseeds out ofcontact with the R. L. Piemeisel recognized the dominance surface ofthe seedbed. Medusahead seeds ger­ of alien plant species in the secondary succes­ minate very well without the callus end of the sion ofdisturbed sagebrush communities in the 248 GREAT BASIN NATURAUST [Volume 52

Intermounllrin area (Piemeisel 1951). Working In the Intermountain area, Maynard on the Snake River plains of Idaho during the Fosbergofthe UniversityofTdaho reported that 19305, Piemeisel enumerated dominance from the medusahead infestations along the Colum­ Russian thistle (Salsala australis) to tumble bia River in Washington, Idaho, and Oregon mustard (Sisymbrium altissimum) to cheat­ were restricted to clay-textured soils (Fosberg grass. Continued disturbance tended to per­ 1965). He suggested that the greater soil mois­ petuate cheatgra.'is dominance. According to tnre-holding capacity of these soils allowed Piemeisel, the annual species that germinates medusahead to complete its life cycle. fIrst, reaches maximum growth and maturity Building on the work of Fosberg and first, has the capacity to withstand crowding. Hironaka, I sampled the plant communities in and has high seed production is the one that will the medusahead invasio'n area along the western occupy and persist in seralsagebrush plantcom­ edge of the Great Basin (Young and Evans munities. Piemeisel always noted that no one 1970). Medusahead was found on the margins species had a clear dominance on all these char~ of many degraded meadows where moisture acteristics, but on balan<.-e cheatgrass was the relationships probably favored it over dear winner. cheatgrass. A much larger area of infestation Medusahead cuntradicts several of Wlli; sagebrush/grass communities. The sage­ Piemeisel's criteria. Medusahead seeds are ini­ brush communities consisted of mountain big tially dormant with temperature-related sagebrush (Artemisia tridelltata ssp. vaseyarul) afterripening requirements, while cheatbrrass on soils with sandy loam to loam-textured sur­ seeds have no such restraints. This works only face horizons and often well-developed argillic for initial establishment because once seed horizons. Asecond series ofsagebrush commu­ banks are established with seeds with acquired nities consisted oflow sagebrush (A. arbuscnla) dormancy, our research indicates that growing on soils with clay-textured surface hori­ cheatgrass and medusahead seeds have equal zons. Harry Summerfield (retired soil scientist, chances ofgermination with the initial moisture Soil ConselVation Service and Forest Servil:e, event in the fall. Medusahead does take much USDA) snggests the low sagebrusb soils share longer to mature than cheatgrass and perhaps the same development as the big sagebrush tum hie mustard. Min Hironaka and his students soils, but the surface horizons 'have been have conducted a series of excellent experi­ removed by erosion (personal communication). ments comparing the cumulative growth curves On the Modoc Plateau ofnortheastern Califor­ for roots and aerial structures of medusahead nia these two series ofplant communities divide and othergrasses (Hironaka 1961, Hironakaand tile land,cape about equally(Young et aI. 1977). Sindelar 1973, 1975). Dr. Hironaka concluded In the northern Great Basin low sagebrush con­ from these shIdies that the comparative growth stitntes only about 10% of the total sagebrush phenology restricts medusahead to areas with vegetation. surplus soil moisture after cheatgrass normally On the western edge of the Great Basin, matures. medusahead, in nonmeadow situations, is largel), restricted to low sagebrush potential plant communities. Would this restriction to SOILS clay soils change over time as appears to have happened in cismontane California? Remem­ Raymond Evans noted in the 1950s when ber the stndies of Raymond Evans that showed medusahead fIrst invaded Glenn and Colusa competition in the cismontane portion of the counties in the nurthern Sacramento Valley of California annual grasslands is initially for light, California that medusahead appeared to he while in cheatgra.~s communities of the Inter· restrieted to clay-textured soils (personal com­ mountain a.rea, competition is overwhelmingly munication). Mallor)' (1960) reported on this for soil moisture (Evans et aI. 1970, 1975). relationship at the 1960 meeting ofthe Califomi.a section of the Society for Range Management. Burgess Ka)' made the chilling obselV'dtion tI,at WILDFIRES aftera conple ofdecades this relationship disap­ peared and mednsahead occapied many sites Accumulation.'\ of litter, on areas where with coarser-textured soils (personal communi- medusahead is established, will bnrn. McKell, cations). . Wilson, and Kay (1962) had initial result, that 1992] ECOLOGY AND MANAGEMENT OF MEDUSAHEAD 249 seemed to indicate that burning was the answer not know what the influence of medusahead to the control of medllsahead. The idea was to invasion would be on other granivores. Seeds of burn stands while competing annual grasses other recently introduced weeds in temperate were fully mature and medusahead seeds were desert communities, such as those of barbwire still in the inflorescences. This study showed Russian thistle (Salsola paulsenii), are heavily hurned seeds would not germinate. However, preyed upon by granivores. Ifcheatgrass popu­ the burned seeds were apllUrently incubated at lations crash because of replacement by 20 C, and unburned fresh seed would not have medusahead, what happens to cheatgrass seed germinated at that temperature. We tried a predators? series ofburning experiments on the Pitt River A studyconducted at Washin6'!on State Uni­ Indian reservation and found burning favored versity illustrates that granivore preference medusahead (Young et al. 1972). We helped works both ways in plant succession. Bi.rd pop­ Forest SelVice range conservationists evaluate ulations prefer the seeds of native perennial burning treatment on low sagebrush communi­ grass species over those of cheatgrass and ties on the Silver Lake district of Fremont medusahead (Goebel and Berry 1976). National Forest in Oregon; the off-season burns Utilization of medusahead by large herbi­ appeared to favor remnant perennial grasses vores of infested ranges results in increased over medusahead. incidence ofinjury from the seeds. Data on the Low sagebrush communities, because of level of injury are not available for domestic lack ofherbaceous cover, are relatively resistant livestock and certainly not available for wildlife. to the spread of wildfires. Big sagebrush com­ munities, especially those with cheatgrass CONTROL OF MEDUSAIIEAD understories, are very subject to the spread of wildfires. Invasion of medusahead into low sagebrush communities introduces wildfires to Kay developed highly technical and verysuc­ these communities, perhaps for the first time cessfiJI control and revegetation techniques for since they were in pristine condition. Perennial the annual-dominated rangelands of cismon­ grass, forb, and shrub cover are all negatively tane California using the herbicide paraquat correlated with medllsahead cover in the west­ (1,l'-dimethyl-4,4' bipyridinium ion) and spe­ ern Great Basin (Young and Evans 1970). cialized seeding equipment (Kay 1963, 1966. Kay and McKell 1963). This technique was not successful in the GHAZING PHEFERENCE Intermountain area hecause meelusahead plants were not susceptible to paraquat in the It is obvious from the above discussion that temperate desert environment and the annual preference by grazing animals plays an impor­ legumes that proved so adapted to cismontane tant part in the successional dynamics of California were not adapted to the sagebrush medusahead communities. One ofthe few stud­ environment (Young et aL 1971b). Herbicidal ies of medusahead palatability was conducted fallow techniques using atrazine (6-chloro-N­ on the nOlthern coast of California using sheep ethyl-N'-[I-methylethyl]-1,3,5,-triazine-2,4-di in small hurdle plots (Lusk et al. 1961). Under amine) or dalapon (2,2-clichloropropanoic the confined conditions ofthe study, sheep uti­ acid), and mechanical fallow techniques were lized medusahead when it was green. When developed for use in the Great Basin. Hilken faced with no choice, they used some herbage and Miller (1980) provide a summary ofherbi­ after the medusahead matured. How much uti­ cidal control measures applied experimentally lization ofmedusahead would occur in temper­ for the control of medusahead. A large part of ate desert situations is unknown. the area infested with medusallead in the west­ Cheatgrass stands put a tremendous produc­ ern Great Basin was never adapted to these tion of grass caryopses into a local ecosystem. treatments because of surface rock cover that Veltebrate granivores have adapted to this food prohibited tillage or seed-drilling techniques. source. Savage et aL (1969) showed in feeding The current mass cancellation of federal regis­ trials that Chukar Partridges (Alectoris gracea) tration for uses ofherbicides on rangelands and could not utilize the caryopses of medusahead the failure offederalIand management agencies as a food source. These birds are dependent on to adopt the use ofherbicidal revegetation tech­ cheatgrass seeds in the fall and winter. We do niques have made the use of these techniques 250 GREAT BASI ATl1RALlST [Volume 52

impossible. Landfnnns and soils of the sites limits establishment of perennial grass seed­ where medusahead is spreading into temperate lings, desert rangelands are criHcal factors in the eeo­ The area of medusahead invasion in the logical suppression ofthis species. western Great Basin is a microcosm where events in soil and plant ecology that influence NATUHE Of MEDUSAHEAD-INfESTED millions of acres in the Intermountain area are LANDSCAPES brought, by fortuitous combinations ofphysical and biological parameters, into sha'1' focus. In the medusahead invasion area, Jake-depOSIted The landscape of the western Great Basin red clay is in obvious discontinnitywith the thin, where medusahead has invaded is composed of grayish surface soil. In undisturbed profiles of a series of fairly recent basalt flows that com­ this situation the influence ofalleVIation ofsub­ prise the Modoc Plateau and theextreme south­ aelial deposited material is apparent on the ern extension 01 the Columbia RIver Basalts. structure of the day subsoil, indicating the Superimposed on the flows are clays from a antiquity of this process (personal communica­ Tertimy-a~e lake. This lake was much olderthan tion, Robert Blank. soil scientist, ARS, USDA). pluvial L,;];e Lahontan, which lapped at the Accumulations ofmedusahead litter change lower margins of the flows, The old lake .Ieft wildfire dlaracteristics, and the shruh compo­ thick beds ofclay-textured sediments occaSIon­ nent ofthe plant co~munityis eliminated: Con­ ally interbedded with diatomaceous earth. The tinued grazing of medusahead-dommated clay minerals are predommantly double lattice o~ remn~nt forms that expand and contract v.rith moisture graSShlllds is extremely delete,nolis perennial !,'TIlSses because ofdifferential grazmg content. This expansion and shrinkage has preference. In contrast to medusahead sorted basalt rock from the bu.ied flows into cheatgrass is seasonally preferred forage spe­ giant polygons and pressure ridges until por­ cies, and even the dry herbage of cheatgrass is, tions ofthe landscape resemble arctlc ICe packs utilized by livestock. This dilutes the effect of that are black instead ofwhite, grazing as far as the native perennials are con­ There are a host of topoedaphic situations cerned, Lack of preference for rnedusahead within this wilderness that support specific concentrates the effects of herbivory. Suhaeri­ assemblages ofplants; however, the landscape.is ally deposited surface soil is extremely erodible characteJized by upland areas of reSidual SOIls once protection of tile shrub canopy m,d Its with loam-texturedsurface soils thatsupport big dependent microphytic crust is lost. Loss ofthe sagebrush and clay-textured surface soils that surface leads to exposure of the clay sediments support low saaebrush. Vast, nearly level b that then function as Vertisols, shrinking, crack­ henches of lake sediments support swirling ing, and swallowing the surface and reexpand­ mosaics of basin big sagebrush (Artemisia ing with moisture. Medusaheadis one ofthe few tridentata ssp, tridentata) and a recently discov­ plant species adapted to these VertIsols. Perhaps ered type of sagebrush, a subspecies of low some of the soils of these landscapes were sagebrush known as Lahontan sagebrush. The wh~re always Vertisols where, in wet years, annual basin big sagebrush occurs in depression.s sunflowers (Heliat1thus annuus) and turkey erosional products a{.'cumulate on SOlis 'wlth mullein (Ererrwcarpn. setigerus) formed the clay-textured surface horizons, a very unusual only native vegetation. Perhaps excessive grdZ­ occurrence for the Great Basin, The La.hontan ing converted some of these soils to Vertisols sagebrush c-ommunities occur on the lake bed ~fore medusahead arrived. The important clay sediments that are veneered With thm point is that medusahead is actively attack~g layers ofsubaerially deposited, coarser-textured assemblages of native vegetation and changmg soil. the physical and biological potential ofthe SItes. "Vind erosion products accumulate under the shruh canopies and, coupled with organic matter hom leaffall, build mounds under the MANAGEMENT O~' MEDUSAHEAD shruhs while miniplaya., develop in the inter­ INFESTATIONS spaces. Eckert et al. (1989) have described and experimented with the seedbed, of these It is difficult to revegetate Vertisols in desert mound interspace situations, particularly the environments with both seedlings ofwoody and vesil:ular crust that forms in the interspaces and herbaceous ~pecies, native and exotic. ot only 1992J ECOLOGY AND MANACEMENT OF MEDUSAHEAD 251

establishment but also subsequent growth are and micmphytic crust that covers the mounds problems on these soils despite both tremen­ to extend down to minglewith vesicular crust in dous cation exchange capacity and moisture­ the interspaces. The thallophytic crust of holding capacity. The tremendous matIic mosses, lichens, and liverworts is obviously potentialofthesefine claysoils is always surpris­ gone, and we can only speculate on the fate of ing. Moisture is not available for nornlal plant the microsoopic crust ofalgae, fungi, and bacte­ growth when soils still stick to your boots. ria. Prolonged medusahead dominance may decrease populations of mycorrhizae spores in NATURAL SUCCESSIO the soil and thus influence growth ofartificially established perennial seedlings (personal com­ munication, Jim Trent, soil microbiologist, ARS, Dr. Min Hironaka suggests that over pre}­ USDA, Reno, Nevada). longed periods perennial seedlings might estab­ Specific plant pathogens, developed and lish in medusahead-infested sites, especially the marketed by biotechnological companies, may short-lived perennial grass squirreltail (Him­ have a role in range weed control. Perhaps a naka 1963). Dr. Hironaka and his students fol­ Fusarium species exists that would be higWy lowed this aspect of medusabead succession in specific for medusabead (personal communica­ several studies. He demonstrated that squirrel­ tion, Joe Antognini, National Program scientist, tail can establish in medusabead communities, Weed Science, ARS, USDA). but he found the perennial grass populations to Taxonomists and geneticists who have be cycliC. When the squirreltail plants die, they worked with medusahead have commented on are replaced by medusahead, not longer-lived how variable individual collections may be. perennial grasses (personal communication). Common garden studies have shown this to be In the western Great Basin, Dr. Hironaka's true for collections from the American West work is borne out hy gradual increases in (McKell, Robinson, and Major 1962, Young et squirreltail plant density as grazing manage­ al. 1911b). We found, in common garden stud­ ment systems have been implemented. This has ies, a collection from northern California that been especially noticeable during the past four matured 4 weeks earlier tban the average for years of extreme drought. Densities of one othercollections oron orbefore the maturity for squirreltail plant per 10 square feet began to cheatgrass. As medusaheadevolves, we have yet change the aspect of medusahead-dominated to see the limits of its potential on the western sites, but the fragile nature ofthis improvement range. The recent discovery of medusahead in is apparent when bioassay of seed banks shows Utah illustrates that portions of the eastern 250-500 viable medusabead seeds per square Great Basin have the potential to be invaded by foot (down from 1000 persquarefoot before the this weed (Horton 1991). drought) and fails to detect any viable squirrel­ tail seeds (unpublished research ARS, USDA, Reno, Nevada). LITERATU RE CITE0 As you look at medusahead-infested areas on the Vertisols of the western Great Basin, you AL-DAKUEEL, A J. 1986. lnterferenre, growth and physi~ have a nagging thought that something is miss­ logical response of downy brome and medusabead. Unpublished doctoral dissertation, University of Cali­ ing. The Lahontan and big sagebrush commu­ fornia, Davis, and San Diego State University. San nities ofthe ancient lake sediments have as their Diego, California. most frequent perennial grass Sandberg blue­ Bevn. R. w., D. LF.TOURNF.AU. and L. C. EHICKSON. 1961. grass. This species is completely absent from the The chemical composition of medusahead and downy brome. Weeds 9: 307-311. rnedusabead stands and is missing from the EcKERT. R. E., JR. F. F. PRTERSON. M. K. WOOD. W. H. stands where squirreltail has begun to return. BUCKBURN. and J. A. STEPHENS. 1989. The role of What factors of seedbed quality exclude the soil surface morphology in the function of semiarid native invader Sandberg bluegrass and are the rangelands. TB-B9-01 Nevada Agricultural Experi­ ment Station, University of Nevada. Reno. samefactors related tothefailure ofhigher-level EvANS. R. A., and J. A. YOUNG. 1970. Plant litterandestab­ perennial grasses to become established in Iishment of alien annual species in rangeland commu­ squirreltaillmedusabead communities? nities. Weed Science 18: 697-703. The striking difference between native and __. 1972. Microsite requirements for establishment of annual rangeland weeds. Weed Science 20: 350-356. medusabead communities, other than loss of _--,' 1975. Enhancing germination ofdormant seeds of shrub canopies, is loss of subcanopy mounds downy brome. Weed Science 23: 354--357. 252 GREAT BASIN NATURALIST [Volume 52

EVANS, H. A., B. L. KAY, and J. A. YOUNG, 1975. Microenvi­ McKELL 1961. Medusahead palatability. Journal of ronment of a dynamic annual community in relation to R,mge Management 14: 248-251. range improvement. Hilgardia 43: 79-102. MAlon. J., C. M. McKELL. and L. J. B£lu\)'. 1960. Improve­ EVM\S. R. A., H. R. BOLBO, R. K ECKEHT, JB .. and J. A, ment of medusahead infested rangela.nd. California YOUNG, 1970. Functional environment of downy Agricultural Experiment Station Extension Service brame communities in relation to weed control and Leaflet 123. revegetation. Weed Science 18: 154-162. MALLOHY, J. 1960. Soil relations ,vith medusahead, Pages FOSBEHG, M. A. 1965. Relationship of cheatgrass and 39--41 in Proceedings of the California Section of the medusahead to soils in the Columbia River Basin. Society for Range Management. Fresno, California. Proceedings of the Cheatgrass Symposium, Vale, McKELL, C. M., J. P. ROBISON, and J. MAloH. 1962. Eco­ Oregon. U.S, Department of the Interior, Bureau of typic variation in medusahead, an introduced annual Land Management, Washington, D.C. grass. Ecology 43: 686-698. FlumEHIKsE"J, S. 1986. Revision of Taeniatherum McKELL, C. M., A. :\1, WILSON, mdE. L.IGw.1962. Effec­ (Poaceae). Nordic Journal of Botany 6: 389-397. tive burning of rangeland infested with medusahead. FlllmEHIKsEN, S" and R. \'OK BOTII~EH. 1989, lnter­ Weeds 10: 125-131. generic hybridization between Taeniatherom and dif­ NELSON, J. R., and A. M, WILSON, 1969. Influence of age ferent generae of Triticeana Poaceae. Nordic Journal and awn removal on dormancy of medusahead seeds. of Botany 15: 229-240. Journal of Range Management 22: 289-290. (',OEllEL, C. J., and G. BEHHY. 1976. Selectivity of range NEVSKI. S. A. 1934. Schedae ad Herbarium Florae Asiae grass seeds by local birds, Journal of Range :Manage­ Mediae. Acta Umu Asiae Med VlIIb. Botanica 17: ment 29: 393-395. 1~94. HAHllJS. G, A.1965. Medusahead competition. Pages 66--69 PIE MEISEL, R. L. 1951. Causes affecting change and role of in Proceedings of the Cheatgrass Symposium, Vale, change in a vegetation ofannuals in Idaho. Ecology 32: Oregon. Bureau of Land Management, Portland, 53-72. Oregon. PIPEH, C. V., and R. K. BEATTIE. 1914. Flora of southwest­ HAHHlS, G. A., and A. M, WILSON, 1970. Competition for ern \Vashington and adjacent Idaho. The New Era moisture Hmong seedlings of annual and perennial Printing Co., Lancaster, Pennsylvania, grasses as influenced by root elongation at low temper­ SAKAMOTO, S. 1973. Patterns of phylogenetic differentia­ atures. Ecology 51: 530-534. tion in the tribeTriticeae. Seik Ziho 24: 11---.31. I-IILKI':N. T. 0., and H. F. MILLEH, 1980. ~'ledusahead SAVAGE, D. E., J. A. YOUNG, and R A. EVANS, 1969. Utili­ (Taeni,(Ithemm asperom NevskO: a review and anno­ zation of medusahead and downy brome caryopses by tated bibliography. Station Bulletin 664. Agricultural Chukar Partridges. Journal of \Vildlife Management Experiment Station, Oregon State University, 33: 975-978. COl'va.\lis, SCIIOOLEH, A. B. 1966. Elymus caput-medusae L. crosses H1noNAKA. M. 1961. The relative rate of root development \vith Aegilops cylindrica host. Crop Science 6: 79-82. ofcheatgrass and medusahead. Journal ofRange Man­ SUAIU', L. A. and E. W. TI~DALE, 1952. Medusahead, a agement 14: 263-267. problem on some Idaho ranges, Research Note 3. HIHOI\!\KA, M., and B. W SINDELAH, 1973. Reproduction Forest, Wildlife and Range Experiment Station, Uni­ sllccess of squirreltail in medusahead infested ranges. versity ofIdaho, Moscow. Journal of Range Management 26: 219-221, YOL'NG, T. A" and R A. EVANS. 1970, Invasion of --c-' 1975. Grovvth characteristics of squirreltail seed­ medusahead into the Great Basin. V,.'eed Science 18: lings vs. competition with medusahead. Journal of 89~97. Range Management 28: 283-285. ___. 1982. Temperature profiles for germination ofcool HIHONAKA. M" and E. W. TISDALE. 1958, Relative role of season range grasses. ARR-W-27. Agricultural root development ofmedusaheadandcheatgrass. Page Research Service, USDA, Oakland, California. 28 in Progress Report, Western Weed Control Confer­ YOUNG, J. A" R A. EVANS, and R. E. ECKEHT JH. 1968. ence' Germination of medusahead in response to tempera­ ___ ' 1963. Secondary succession in annual vegetation in ture and afterripening. \Veed Science 16: 92-95. southern Idaho. Ecology 44: 810-812. ___. 1969. Population dynamics ofdowny brame. ,",Veed HOHTON, W H. 1991. Medusaheud: importance, distribu­ Science 17: 20-26. tion, and control. Pages 387---.394 in L. F. James, J. O. YOUNG, T. A., R A. EVANS, and B. L. KAy. 1971a. Germina­ Evans, M. H. Ralphs, and R. D, Childs, eds., Noxious tion' of caryopses of annual grasses in simulated litter. range weeds. \Vestview Press, Boulder, Colorado. Agronomy Journal 63: 551-.555. I-Io\VELL, T. 1903. A flom of northwest America. Vol. 1. ___. 1971b. Response ofmedusahead to paraquat. Jour­ Phanorogamue. Binford and Mort, Portland, Oregon. nal ofRange Management 24: 41-43. JEPSON, W. L. 1923. Annals offloweringplants ofCalifornia. YOUNG, J. A., R A. EVANS, and J. MAIO\{. 1977. Sagebrush Sather Gate Bookshop, Berkeley, California. steppe. Pages 763-797 in M. G. Barbour and J. Major, eds., Terrestrial vegetation ofCalifornia. John Wiley & KAY. B. L. 1963, Effects of dalapon on a medusahead com­ munity. Weeds 3: 207-209. Sons, Nev.' York. YOUNG, J, A., R. A. EVANS, andJ. ROllISON. 1972, Influence --c,,' 1966. Pamquat for seeding \vithout cultivation. California Apiculture 20: 2-4. of repeated annual burning on a medusahead commu­ nity. Journal of Range Management 24: 451-454. Kw, B, L., and C. M. MCKELL, 1963. Pre-emergence her­ bicides as an aid on seedling annual rangeland. \Veeds lL 260~264. Receivecl23 'May 1991 UJSK. W. G, M. B. JONES, D. T. TOHELL, and C. M. Accepted 22 June 1992