Evaluating strategies for facilitating native plant establishment in northern Nevada crested wheatgrass seedings

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1 RESEARCH ARTICLE Evluting strtegies for fcilitting ntive plnt estlishment in northern Nevd crested whetgrss seedings J. Kent McAdoo 1,2, John C. Swnson 3, Peter J. Murphy 3, Nncy L. Shw 4 Non-ntive crested whetgrsses (Agropyron cristtum nd A. desertorum) were used historiclly within the Gret Bsin for the purpose of competing with weed species nd incresing livestock forge. These species continue to e used in some res, especilly fter wildfires occurring in low elevtion/precipittion, formerly Wyoming ig sgerush (Artemisi tridentt ssp. wyomingensis)/herceous communities. Seeding ntive species in these sites is often unsuccessful, nd lck of estlishment results in invsion nd site dominnce y exotic nnuls. However, crested whetgrss often forms dense monocultures tht interfere competitively with the estlishment of desirle ntive vegettion nd do not provide the plnt structure nd hitt diversity for wildlife species equivlent to ntive-dominted sgerush plnt communities. During 5-yer study, we conducted trils to evlute chemicl nd mechnicl methods for reducing crested whetgrss nd the effectiveness of seeding ntive species into these sites fter crested whetgrss suppression. We determined tht discing tretments were ineffective in reducing crested whetgrss cover nd even incresed crested whetgrss density in some cses. Glyphoste tretments initilly reduced crested whetgrss cover, ut weeds incresed in mny treted plots nd seeded species diminished over time s crested whetgrss recovered. We concluded tht, lthough increses in ntive species could possily e otined y repeting crested whetgrss control tretments, reducing crested whetgrss opens window for invsion y exotic weed species. Key words: Agropyron cristtum nd A. desertorum, ssisted succession, exotic weeds, mechnicl nd chemicl tretments, monocultures, revegettion with ntive species Implictions for Prctice Glyphoste tretments cn e effective in reducing crested whetgrss cover, ut effectiveness diminishes within few yers s this competitive species recovers. Reducing crested whetgrss opens window for weed invsion if ntive seeding fils; successfully estlished ntive species my decline s crested whetgrss recovers. Converting crested whetgrss monocultures to ntive plnt communities my require multiple tretments over time to remove crested whetgrss plnts nd seed nk, weed reduction tretments, nd/or supplementl seeding or outplnting of ntive species. Introduction Non-ntive grsses hve ltered the composition, structure, nd function of vegettion over vst res in drylnd ecosystems cross the gloe (D Antonio & Vitousek 1992). Although mny non-ntive grsses hve een introduced indvertently, others were, nd some hve continued to e, selected intentionlly for seeding pstures or distured wildlnd lndscpes (Jouert & Cunninghm 22; Mrshll et l. 212). These include nnul nd perennil C3 nd C4 species (see Hull 1974; D Antonio & Vitousek 1992) selected for their ese of estlishment, forge production, soil stiliztion, nd resistnce to exotic invsives. Extensive monocultures of these species, nd in some cses their spred into ntive communities, hve resulted in reduced iodiversity, wildlife hitt, nd ecosystem services over lrge res. Incresing emphsis on conservtion nd restortion of ntive communities hs led to efforts to control, replce, or reduce the dominnce of these non-ntives y reestlishing ntive species. However, control nd replcement of such species, such s ulous luegrss (Po ulos L.) nd Lehmnn lovegrss (Ergrostis lehmnnin Nees), re difficult (Hull 1974; Biedenender et l. 1995). In the United Sttes, more thn 5 million hectres of semirid nd rid western rngelnds were seeded with non-ntive crested whetgrsses (Agropyron cristtum (L.) Gertn. nd A. desertorum) [Fisch. ex Link] Schult) nd Sierin whetgrss Author contriutions: JKM, NLS conceived the study; JKM, JCS collected the dt; PJM nlyzed the dt; JKM, JCS, PJM drfted the originl mnuscript; JKM, JCS, PJM, NLS edited the mnuscript. 1 Coopertive Extension, University of Nevd, 71 Wlnut Street, Elko, NV 8981, U.S.A. 2 Address correspondence to J. K. McAdoo, emil mcdook@unce.unr.edu 3 College of Agriculture, Biotechnology, nd Nturl Resources, University of Nevd, Reno, NV 89512, U.S.A. 4 USDA Forest Service Rocky Mountin Reserch Sttion, 322 E. Front Street, Suite 41, Boise, ID 8372, U.S.A. 216 Society for Ecologicl Restortion doi: /rec.1244 Supporting informtion t: Restortion Ecology 1

2 Ntive plnt estlishment in crested whetgrss (Agropyron frgile [Roth] P. Cndrgy) y the 199s (Mrylnd et l. 1992). From the 195s through the erly 197s, pproximtely 45,h of sgerush (Artemisi spp.) rngelnd in Nevd were converted to crested whetgrss, (Young et l. 1979) primrily for the purpose of incresing livestock forge nd reducing hlogeton (Hlogeton glomertus [M. Nie.] C. A. Mey), n exotic plnt tht is toxic to domestic sheep (Miller 1943). The use of crested whetgrss hs continued in recent yers for post-fire rehilittion (Knutson et l. 214). Crested whetgrss is often used for exotic nnul grss control (Nfus & Dvies 214) ecuse of its lower cost nd reltive ese of estlishment compred with ntive perennil grsses (Eiswerth et l. 29; Boyd & Dvies 21; Dvies et l. 213). Continued use of crested whetgrss is controversil (Dvies et l. 211; Fnsler & Mngold 211). Crested whetgrss often forms dense monocultures (Pyke 199) nd interferes competitively with the estlishment of desirle ntive vegettion (Gunnell et l. 21; Knutson et l. 214). Although recent reserch shows little evidence of sustntil chnges in ecologicl processes (such s C nd N cycling nd soil wter vilility) when ntive perennil unchgrsses re replced with crested whetgrss in former sgerush plnt communities (see Dvies et l. 211), crested whetgrss monocultures do not provide the plnt structure nd hitt diversity for wildlife species equivlent to sgerush plnt communities (McAdoo et l. 1989). Of considerle concern is tht crested whetgrss hs een plnted over lrge res of current nd historic rnge of the sge-grouse (Centrocercus urophsinus) nd hs negtively impcted this species (Connelly et l. 2). Becuse of these concerns, lnd mngers would prefer to use ntive plnt species when revegetting low elevtion/precipittion Wyoming ig sgerush (Artemisi tridentt Nutt. ssp. wyomingensis Beetle & Young) communities (Dvies et l. 215). However, competition from exotic nnuls often interferes with estlishment of ntive species nd results in the further spred of exotics nd incresed wildfire risk (Knutson et l. 214). Crested whetgrss hs een considered ridge species tht, once estlished, my fcilitte estlishment of more desirle nd diverse ntive vegettion (Cox & Anderson 24; Pellnt & Lysne 25). Cox nd Anderson (24) suggested tht crested whetgrss seeding could cpture distured, former sgerush-perennil grss communities from weedy species, with such communities susequently rehilitted/diversified through ssisted succession y mechniclly or chemiclly reducing competition from crested whetgrss nd then seeding ntive species. Recent reserch y Hulet et l. (21) in Uth nd Fnsler nd Mngold (211) in Oregon tested the ssisted succession hypothesis, with generlly unsuccessful results. To further evlute methods for estlishing ntive plnts in crested whetgrss seedings, we tested mechnicl nd chemicl methods designed to shift the successionl trjectory of crested whetgrss communities in northern Nevd. We used pproches similr to those of Hulet et l. (21) nd Fnsler nd Mngold (211), ut pplied dditionl hericide tretments in different ecologicl setting nd over longer (5-yer) study period. We conducted two trils treted 2 yers prt nd trcked precipittion, hoping to reduce response vriility nd enhnce the strength of our inferences. We ddressed three questions. First, does mechnicl tretment, lone or in comintion with glyphoste, fvor the estlishment of ntive seeded species in these communities? Second, do vrious pplictions of glyphoste suppress crested whetgrss in fvor of seeded ntive species? Third, do chemicl lterntives to glyphoste outperform this populr hericide in the suppression of crested whetgrss in fvor of seeded ntive species? We hypothesized tht (1) the selected tretments used would decrese crested whetgrss density nd cover; nd (2) tretments nd seeding would result in mesurle estlishment of ntive species within our 5-yer study window. Methods Study Are The study site ws locted in the South Fork Stte Recretion Are, 24 km southest of Elko, NV, within the Owyhee High Plteu Mjor Lnd Resource Are (MLRA) t n elevtion of 1,615 m. Soil is lom (Orovd Puett ssocition with sndy lom surfce texture). The re is in the Lomy 8 1 PZ ecologicl site (8 1 inch [ mm] precipittion zone), nd ws formerly dominted y Wyoming ig sgerush plnt communities (USDA-NRCS 215). Climte in this re is typicl of the northern Gret Bsin, with hot dry summers nd precipittion occurring primrily during the cool winter nd spring months. Crop-yer (Octoer June) precipittion rnged from 55 to 124% of norml for the study period (Tle S1, Supporting Informtion). The study re ws historiclly in privte ownership, nd specific sgerush reduction methodology is unknown. After sgerush ws controlled, the re ws seeded to crested whetgrss (Agropyron desertorum), most likely the Nordn cultivr (sed on historicl records of nery pulic lnd seedings). The re ws fenced to exclude livestock grzing in 1989, ut wildlife ccess to the study site ws unrestricted. Vegettion t the site ws essentilly monotypic crested whetgrss, with less thn 1% shru cover (McAdoo et l. 213), only occsionl occurrence of Indin ricegrss (Achntherum hymenoides [Roemer & J.A. Schultes] Brkworth) nd sin wildrye (Leymus cinereus [Scrin. & Merr.] Á. Löve), rre mnifesttions of ntive fors (primrily Astrglus spp. [L.] nd Descurin pinnt [Wlter] Britton), nd scttered ptches of hlogeton. Bsed on the USDA Nturl Resources Conservtion Service (NRCS) ecologicl site description nd oservtions of djcent unseeded plnt communities, pre-conversion vegettion in ddition to Wyoming ig sgerush, Indin ricegrss, nd sin wildrye would likely hve included the following species: needle-nd-thred grss (Heterostip comt [Trin. & Rupr.] Brkworth), Snderg luegrss (Po secund J. Presl), ottlerush squirreltil (Elymus elymoides [Rf.] Swezey), spiny hopsge (Gryi spinos [Hook.] Moq.), nd vrious ntive for species. No chetgrss (Bromus tectorum L.) ws oserved within the study res prior to tretment implementtion. 2 Restortion Ecology

3 Ntive plnt estlishment in crested whetgrss Experimentl Design, Tretment Implementtion, nd Plnt Mterils We conducted two 1-h study trils (Tril 1 nd Tril 2) locted pproximtely.9 km prt (center to center). Ech tril ws instlled s rndomized lock split-plot design with five 2-h locks. Ech lock ws divided into five.4-h min plots rndomly designted s untreted (U) or one of four crested whetgrss suppression tretments ssigned (see elow) to ech tril. Min plots were further divided into two.2 h split-plots tht were rndomly selected for either seeding or no seeding. Nonseeded split-plots were included to simulte the outcome of suppression tretments if the seeding tretment filed. For Tril 1, disced only (D) plots were 3-wy disced (t right ngles nd digonlly) during Novemer 27. In lte My 28, spring-pplied glyphoste (G) (Roundup Pro, post-emergent hericide tht includes surfctnt) nd comined discing + glyphoste (DG) plots were spryed with glyphoste. In erly Octoer 28, comined spring + fll-pplied glyphoste plots (GG) were spryed gin with glyphoste. All glyphoste tretments were pplied t the rte of 4.7 L/h. Tril 2 ws implemented in 21, llowing us to dptively modify tretments informed y Tril 1, which indicted tht discing ws ineffective t suppressing crested whetgrss (consistent with results reported y Fnsler & Mngold 211). Hence, we replced discing with dditionl hericide tretments. Crested whetgrss suppression tretments for Tril 2 consisted of full-rte glyphoste (G), hlf-rte glyphoste (G/2) t 2.35 L/h, imzpic (I) (Pnormic 2SL) t.73 L/h, nd chlorsulfuron + sulfometuron methyl (CS) (Lndmrk XP) t.15 L/h, ll pplied in My. The ltter two chemicls, pplied with.25% v/v nonionic surfctnt, cn function s oth pre- nd post-emergent hericides. We pplied them during the ctive growth period of crested whetgrss to tke dvntge of post-emergent ction. For ech tril, personnel from the Aerdeen, Idho NRCS Plnt Mterils Center seeded rndomly selected split-plots with Trux Rough Rider minimum-till drill t NRCS-recommended rtes, in lte Octoer 28 for Tril 1 nd lte Octoer 21 for Tril 2. Press wheels nd drg chins instlled ehind disks on the minimum-till drill provided seed soil contct nd seed uril in drill rows for lrge seeds, wheres ptterned imprinter wheels enhnced seed soil contct in rodcst rows for smll seeds. The site-dpted seed mixture included Indin ricegrss, ottlerush squirreltil, needle-nd-thred grss, sin wildrye, Snke River whetgrss (Elymus wwwiensis J. Crlson & Brkworth), Snderg luegrss, Munro gloemllow (Spherlce munron [Dougls] Spch), lue flx (Linum perenne L.), western yrrow (Achille millefolium L.), Wyoming ig sgerush, nd spiny hopsge (see Tle S2 for seeding rtes nd cultivrs used). All species seeded were ntive with the exceptions of Snke River whetgrss, used ecuse of its dpttion to this low precipittion zone, nd lue flx, used s sustitute for Lewis flx (L. lewisii Pursh), which ws unville t the time. Vegettion Smpling During the summers of 29, 21, 211, nd 213 for Tril 1 nd 212 nd 213 for Tril 2, we used strtified rndom smpling design to mesure four vegettion prmeters: cover nd density of crested whetgrss, cover of exotic weeds, nd density of seeded species. We estlished five 18-m trnsects spced 1 m prt in ech split-plot. Along ech trnsect, we mesured density nd cnopy cover in 1 frmes of.25 m 2 plced t 2-m intervls long ech trnsect. Density of crested whetgrss nd seeded species ws determined y counting individul plnts within ech smpling frme. Cover ws estimted using Duenmire cover clsses (Duenmire 1959) for crested whetgrss. For exotic weeds, modified Duenmire method, including cover ctegory, ws used to more ccurtely reflect initil weed scrcity (see Htton et l. 1986). To determine percent cover for ech split-plot, we clculted midpoints of the cover clsses nd verged them cross trnsects. We pooled seeded perennil grss dt cross species for the first growing seson (29) of Tril 1 ecuse species were difficult to distinguish during the seedling stge. This difficulty, long with the high mortlity of seeded species oserved etween the first two growing sesons (similr to tht reported y Hulet et l. (21) nd Fnsler nd Mngold (211)), led us to dely initil dt collection for Tril 2 until the second growing seson fter seeding. Seeded for nd shru species were redily identified nd recorded y species for oth trils in ll yers. Sttisticl Anlyses We ssessed the effect of tretment, seeding, nd yer on cover nd density of crested whetgrss using the liner mixed model procedure (SAS version 9.2, SAS Institute Inc., Cry, NC, U.S.A.). Trils 1 nd 2 were initilly nlyzed seprtely ecuse they involved different tretments nd smpling yers. Fixed effects were tretment, seeding, nd yer nd ll two-wy interctions. The three-wy interction term (tretment seeding yer) ws dropped due to lck of significnce nd poorer model fit when it ws included, s indicted y higher Akike informtion criterion with correction for finite smple size (AIC C ). Becuse of the split-plot design, lock nd tretment-y-lock were treted s rndom effects. Yer ws repeted effect implemented with unstructured covrince, which produced etter fit (lower AIC C )thndid compound-symmetric or first-order utoregressive covrince models. For ech response, we compred tretment mens pirwise for oth Tril 1 nd Tril 2, using the Dunn Sidk method to control for multiple comprisons. Cover percentges were rcsine-squre root trnsformed nd densities log-trnsformed to meet ssumptions of ANOVA. Trils 1 nd 2 were not sttisticlly comprle cross ll tretments ecuse (1) some tretments were unique to ech tril; (2) stochstic events (especilly precipittion) were different for ech tril; nd (3) Tril 1 ws conducted over 5-yer period compred to only 3 yers for Tril 2. Nevertheless, the two trils were conceptully comprle, nd we mde sttisticl comprisons etween the two trils where pproprite. Restortion Ecology 3

4 Ntive plnt estlishment in crested whetgrss 3 A Tril 1 Tril 2 B Cover (%) Plnts / m C D D DG G GG U CS I G G/2 U Tretment Figure 1. Crested whetgrss cover nd density y tretment nd yer in two northern Nevd trils. Tretments re discing (D); discing plus glyphoste (DG); glyphoste (G); spring nd fll glyphoste (GG); undistured (U); chlorsulfuron + sulfometuron methyl (CS); imzpic (I); nd hlf-rte glyphoste (G/2). Brs represent ck-trnsformed mens (±95% CI) from nlyses sed on rcsine-squre root trnsformed percentges nd log-trnsformed densities. By vrile within ech tril, tretments (r groups cross yers) tht do not shre common letter differ significntly (p <.5, Dunn Sidk). Becuse Trils 1 nd 2 shred the glyphoste (G) nd control (U) tretments nd were smpled in 213, we tested for tretment-y-tril interction on crested whetgrss cover nd density in single-yer split-plot model. We used the sme methods to nlyze weed cover (totl nd y species). For seeded species, we ssessed the effect of tretment, yer, nd tretment-y-yer on log-trnsformed density using repeted-mesures nlysis of vrince. Ech species ws nlyzed seprtely, nd we rn nlyses for totl seeded species, perennils, nd fors. For ech response, we compred tretment mens pirwise for ech tril, gin using Dunn Sidk to control for multiple comprisons. As for crested whetgrss nd weed cover, we compred seeded species density in 213 y tril nd tretment for the glyphoste (G) nd untreted (U) plots. In the species-specific nlyses, lrge numer of zeroes in Tril 1 for seven species nd for ll seeded species in Tril 2 led to non-norml residuls nd suspect sttisticl conclusions. Results Crested Whetgrss Suppression All tretments tht included glyphoste reduced crested whetgrss cover compred to no tretment (U). Cover ws significntly lower in DG, G, nd GG thn in D nd U tretments in Tril 1 (F [4,16] = 2.4, p <.1; Fig. 1A) nd lower in G nd G/2 thn in other hericide tretments (CS nd I) nd U in Tril 2 (F [4,16] = 82.6, p <.1; Fig. 1B), verging out 5% less thn U. However, crested whetgrss density responded differently to glyphoste in the two trils. In Tril 1, ll glyphoste tretments reduced crested whetgrss density compred to D (y lmost hlf), ut no tretment significntly reduced density elow U (F [4,16] = 6.3, p =.3; Fig. 1C). Conversely, in Tril 2, glyphoste (G nd G/2) tretments nerly tripled density compred to U nd the other hericides (F [4,16] = 14.3, p <.1; Fig. 1D), which were ll similr. There ws tril (F [1,66] = 6.7, p =.12) nd tretment-y-tril interction for crested whetgrss density in 213 (F [1,66] = 34.7, p <.1; only G nd U included). Crested whetgrss cover incresed reltively consistently cross ll tretments over the yers in Tril 1 (yer, F [3,152] = 99.2, p <.1; yer-y-tretment, F [12,152] = 1.6, p =.12), while decresing slightly in nonglyphoste tretments in the second smpling yer of Tril 2 (yer, F [1,64] = 12.7, p =.1; yer-y-tretment, F [4,64] = 2., p =.12; Fig. 1A & B). Unlike cover, crested whetgrss density spiked in 211 in Tril 1 (F [3,152] = 22.8, p <.1; Fig. 1C) nd in 212 in Tril 2 (F [1,64] = 88.8, p <.1; Fig. 1D). The mgnitude of these spikes differed y tretment in oth trils, producing yer-y-tretment interctions (p <.1). By 213, G tretment hd reduced crested whetgrss cover compred to U more effectively in Tril 2 (y 58%) thn in Tril 1 (y 45%), driving tril effect (F [1,66] = 1.6, p =.2) nd tretment-y-tril interction (F [1,66] = 31.6, p <.1). This comprison is etween three growing sesons fter tretment for Tril 2 versus five for Tril 1. 4 Restortion Ecology

5 Ntive plnt estlishment in crested whetgrss Exotic Weed Cover (%) A Tril 1 Tril B D DG G GG U CS I G G/2 U Tretment c c Exotic Weed Cover (%) Figure 2. Totl exotic weed cover y tretment nd yer in two northern Nevd trils. Tretments re discing (D); discing plus glyphoste (DG); glyphoste (G); spring nd fll glyphoste (GG); undistured (U); chlorsulfuron + sulfometuron methyl (CS); imzpic (I); nd hlf-rte glyphoste (G/2). Brs represent ck-trnsformed mens (±95% CI) from nlyses sed on rcsine-squre root trnsformed percentges nd log-trnsformed densities. Within ech tril, tretments (r groups cross yers) tht do not shre common letter differ significntly (p <.5, Dunn Sidk). Note differences in scle etween left nd right verticl xes. Response of Exotic Weeds Exotic weed estlishment ws generlly fvored y glyphoste tretments tht suppressed crested whetgrss cover. We detected five weed species in Tril 1 nd four in Tril 2. Weed cover vlues rnged from 28% in Tril 1 nd.7% in Tril 2, with hlogeton nd tumle mustrd (Sisymrium ltissimum L.) gretest in cover. Chetgrss occurred t extremely low cover in oth trils (<.1% cross tretments). In Tril 1, we found significntly greter totl weed cover cross yers (y 1-fold) in DG nd GG tretments compred to D nd U, with G tretment flling etween these two groups (F [4,16] = 9.1, p <.1; Fig. 2A). Similrly, for Tril 2, exotic weed cover ws significntly greter (y n order of mgnitude) in G s compred to CS, I, nd U tretments, with G/2 flling etween these two groups (F [4,16] = 9.6, p <.1; Fig. 2B). However, with cover eing less thn 1% for ll tretments in Tril 2, the iologicl significnce of these differences is questionle. In Tril 1, weed cover incresed in 211 ( reltively wet yer, Tle S1), evidenced especilly in the glyphoste tretments (Fig. 2A) nd resulting in significnt effect of yer (F [3,152] = 39.74, p <.1) nd yer-y-tretment (F [12,152] = 6.1, p <.1). By the end of the study (213), 5-yer post-tretment, totl exotic weed cover in Tril 1 ws 8 to 12 times greter in two of the three glyphoste tretments, GG nd DG, thn in U (F [4,16] = 7.5, p =.1; Fig. 3A), two of the sme tretments tht lso reduced crested whetgrss cover (Fig. 1). Likewise, G tretment in Tril 2 (3-yer post-tretment) hd significntly more exotic weed cover thn CS, I, nd U, with G/2 flling etween the two groups (F [4,16] = 8., p =.1; Fig. 3C). By 213, hlogeton nd tumle mustrd were the primry exotic weeds in oth trils. Hlogeton cover ws numericlly greter in glyphoste tretments (Fig. 3B & D), ut vrile mong plots in oth trils, indicting no significnt differences y tretment (F [4,16] 2.7, p.68). Tumle mustrd cover ws consistently greter fter the DG tretment in Tril 1 nd fter oth the G nd G/2 tretments in Tril 2 (F [4,16] 5.8, p.5; Fig. 3B & D). Seeded Species Estlishment In Tril 1, the density of seeded species verged cross yers ws significntly higher (y pproximtely 7%) in DG, G, nd GG tretments thn in U, with D flling etween these groups (F [4,2] = 4.8, p =.7; Fig. 4A). Similrly, in Tril 2, though mesured vlues were n order of mgnitude lower thn in Tril 1, G tretment hd significntly (16 times) higher densities of seeded species thn CS, I, nd U tretments, with G/2 flling etween these groups (F [4,2] = 5.1, p =.5; Fig. 4B). In Tril 1, the surge of estlishment in 29 ws followed y shrp mortlity in 21 nd therefter, with lrger die-offs in D nd U plots (yer, F [3,2] = 151.7, p <.1; yer-y-tretment, F [12,2] = 3.8, p =.4; Fig. 4A). In Tril 2, mortlity from 212 to 213 ws lower ut significnt cross tretments (F [1,2] = 7., p =.15; Fig. 4B). Becuse of hevy mortlity, y 213 in Tril 1 (5-yer post-seeding) the effect of tretment ws mrginl on totl seeded density (F [4,2] = 2.7, p =.62) ut ws still significnt for seeded perennil grsses (F [4,2] = 3.1, p =.39), driven y the lmost 2-fold difference etween the DG tretment nd U (Fig. 5, top). By 213 in Tril 2 (3-yer post-seeding), totl seeded nd seeded perennil grss densities were significntly to mrginlly higher in G nd G/2 thn in the other tretments (F [4,2] 4.8, p.7; Fig. 5, ottom). When compring the effect of only G tretment versus U on seeded densities in 213 cross trils, no effect of tril (F [1,36].9, p.348), tretment (F [1,36].16, p.69), or tretment-y-tril (F [1,36] 1.2, p.275) ws found on seeded totl, perennil grss, or for species. Estlishment of seeded species ws more successful in Tril 1 thn in Tril 2. Across tretments 2 yers fter seeding, totl densities were roughly 6% higher in Tril 1 thn in Tril 2 (.88 vs..14 plnts/m 2 ; Fig. 4A & B, 21 vs. 212, respectively). However, y 213 (5-yer nd 3-yer post-tretment for Trils 1 nd 2, respectively), totl seeded densities were only out 4% higher in Tril 1 thn in Tril 2 (.14 vs..1 plnts/m 2 ). Across yers nd tretments, totl densities of seeded species rnged from to 15.7 plnts/m 2 in Tril 1 (grsses: 15.4, fors: 1.5) nd from 1.1 plnt/m 2 in Restortion Ecology 5

6 Ntive plnt estlishment in crested whetgrss Totl Cover (%) A c C c c Tril 1 c Tril 2 D DG G GG U CS I G G/2 U B D Exotic Weed Cover y Species (%) 5 c c AGDE All Exotic BRTE HAGL SAKA SIAL2 Weeds Other.2 Figure 3. Crested whetgrss nd exotic weed cover in the finl growing seson (213) for Tril 1 (5 yers post-tretment) nd Tril 2 (3 yers post-tretment), northern Nevd. The right-side pnels ((B) nd (D)) show weed cover y species. Tretments re discing (D); discing plus glyphoste (DG); glyphoste (G); spring nd fll glyphoste (GG); undistured (U); chlorsulfuron + sulfometuron methyl (CS); imzpic (I); nd hlf-rte glyphoste (G/2). Brs represent ck-trnsformed mens (±95% CI) from nlyses sed on rcsine-squre root trnsformed percentges. By vegettion ctegory within ech tril, tretments tht do not shre common letter differ significntly (p <.5, Dunn Sidk). Species revitions re: AGDE, crested whetgrss; BRTE, chetgrss; HAGL, hlogeton; SAKA, Russin thistle; nd SIAL2, tumle mustrd. Note differences in scle etween left nd right verticl xes. Seeded Plnts / m A Tril 1 Tril B Seeded Plnts / m 2 D DG G GG U CS I G G/2 U Tretment Figure 4. Totl seeded species density y tretment nd yer in two northern Nevd trils. Tretments re discing (D); discing plus glyphoste (DG); glyphoste (G); spring nd fll glyphoste (GG); undistured (U); chlorsulfuron + sulfometuron methyl (CS); imzpic (I); nd hlf-rte glyphoste (G/2). Brs represent ck-trnsformed mens (±95% CI) from nlyses sed on rcsine-squre root trnsformed percentges nd log-trnsformed densities. Within ech tril, tretments (r groups cross yers) tht do not shre common letter differ significntly (p <.5, Dunn Sidk). Note differences in scle etween left nd right verticl xes. Tril 2 (grsses:.8, fors:.2). Of the 11 species seeded (Tle S2), we initilly found 1 in Tril 1: Wyoming ig sgerush, ll six perennil grsses, nd ll three fors. In Tril 2, we detected seven: Wyoming ig sgerush, four perennil grsses, nd two fors. Spiny hopsge did not estlish in either tril. Notwithstnding sttisticl limittions of the species-specific seeding nlyses, the most undnt seeded ntive grsses cross yers in Tril 1 were sin wildrye, ottlerush squirreltil, nd Indin ricegrss, nd the most undnt seeded for ws Munro s gloemllow. However, y 213, only six seeded herceous species remined in Tril 1, with Indin ricegrss sent, leving sin wildrye, squirreltil, nd Munro s gloemllow s the dominnt seeded ntive species (Fig. 5, top). In Tril 2, only four herceous seeded species remined y 213, with the sme three seeded ntive species eing most undnt (Fig. 5, ottom). These three were more consistently present in the DG nd G tretments. Mrginlly or significntly higher densities for sin wildrye in Tril 1 nd ottlerush squirreltil in Tril 2 were oserved in glyphoste-treted plots compred to other tretments (Fig. 5). We recorded no estlishment of ntive species within ny unseeded split-plots. 6 Restortion Ecology

7 Ntive plnt estlishment in crested whetgrss Seeded Plnts / m All By Type Perennil Grsses Fors Tril 1 South Tril 2 CS I G G/2 U D DG G GG U Totl PerGr For ARTRW8 ACHY ELEL5 HECO26 LECI4 POSE PSSP6 ACMI2 LILE3 SPMU2 Figure 5. Density of seeded ntive species in the finl growing seson (213) for Tril 1 nd Tril 2 (5 nd 3 yers post-tretment nd seeding, respectively), northern Nevd. Tretments re discing (D); discing plus glyphoste (DG); glyphoste (G); spring nd fll glyphoste (GG); undistured (U); chlorsulfuron + sulfometuron methyl (CS); imzpic (I); nd hlf-rte glyphoste (G/2). Brs represent ck-trnsformed mens (±95% CI) from nlyses sed on log-trnsformed densities. By vegettion ctegory within ech tril, tretments tht do not shre common letter differ significntly (p <.5, Dunn Sidk). Arevitions re: PerGr, ll perennil grsses; For, ll for species; ARTRW8, Wyoming ig sgerush; ACHY, Indin ricegrss; ELEL5, ottlerush squirreltil; HECO26, needle-nd-thred grss; LECI4, sin wildrye; POSE, Snderg s luegrss; ELWA2, Snke River whetgrss; ACMI2, western yrrow; LIPE2, lue flx; SPMU2, munro gloemllow. Spiny hopsge (not shown) did not estlish in either tril. Discussion Crested Whetgrss Reduction Tretment Effectiveness Our hypothesis tht the selected tretments would decrese crested whetgrss density nd cover ws only prtilly supported y our dt. Although the effects of glyphoste tretments were trnsient, they generlly produced the est control of crested whetgrss. A comprison of our results with similr studies in Uth (Hulet et l. 21) nd Oregon (Fnsler & Mngold 211) demonstrtes the vriility in tretment responses mong vrious sites within low elevtion Wyoming ig sgerush communities. Nevertheless, results of ll three studies indicted tht, no mtter how effective specific tretment might e for initilly reducing crested whetgrss, these effects diminish stedily over time, resulting in incresing competition from crested whetgrss tht my interfere with estlishment nd persistence of seeded ntive species. Interestingly, the Agropyron desertorum Nordn cultivr used in our study is considered more susceptile to control with glyphoste hericide thn the other commonly plnted Agropyron cristtum Firwy nd Hycrest cultivrs (Lym & Kiry 1991). Repeted pplictions my e necessry ecuse crested whetgrss my recover following tretment (Hnsen & Wilson 26). Crested whetgrss plnts recovering fter control tretments enefit from reduced competition nd produce numerous tillers nd seedheds (Amrose & Wilson 23; Wilson & Prtel 23). High seed production from crested whetgrss plnts remining fter glyphoste tretment nd cover reduction (still pprent in 211) nd incresed resource vilility could hve lso contriuted to incresed seedlings in wet yer (see Amrose & Wilson 23). Therefore, the increse in crested whetgrss density oserved in 211 my hve een the result of seedlings responding to reltively wet spring (11 mm precipittion), ut incresed seedlings would not necessrily increse cover. Fll ppliction of glyphoste (Tril 1) might hve een more effective with greter soil moisture, ut July Septemer precipittion (29 mm) prior to Octoer sprying ws not enough to produce green-up. Looking t oth trils, ll three of the hericides were leled for post-emergent ction, ut only glyphoste hd ny impct. Also, mny of the crested whetgrss frgments cused y discing my hve survived (see Fnsler & Mngold 211), keeping oth cover nd density mesurements high. Response of Exotic Weeds Exotic weeds were more responsive to tretments in Tril 1 thn Tril 2. This my hve een cused y ny one or comintion of the following fctors: (1) level of weed infesttion efore tretment; (2) proximity of off-site weed source to tril loction; (3) timing of tretments s relted to precipittion ptterns; (4) effectiveness of crested whetgrss control tretment, which could hve reduced competition nd llowed more weed cover; nd/or (5) pre-emergent weed control potentil of CS nd I hericides used in Tril 2. Bsed on mesurements in untreted (U) plots nd pre-experiment reconnissnce, exotic weed cover ws miniml in oth tril res efore tretment implementtion, ut smll ptch of tumle mustrd ws oserved within.2-km west of the Tril 1 re nd ws Restortion Ecology 7

8 Ntive plnt estlishment in crested whetgrss likely introduced into the re y previling westerly winds. Regrding precipittion ptterns, oth trils were seeded during yers of ove norml crop-yer precipittion. However, precipittion for Tril 1 in 29 ws 32% higher in spring (April June) nd 93% higher in summer (July Septemer) s compred to tht for Tril 2 in 211 (see Tle S1). High spring precipittion results in high germintion nd vigorous growth of exotic winter nnul weeds, including tumle mustrd (Eckert et l. 1974; Allen & Meyer 214). Regrding tretment effectiveness, three of the four crested whetgrss control tretments used in Tril 1 (ll including glyphoste) initilly reduced crested whetgrss cover significntly, nd two of the four tretments in Tril 2 (oth involving glyphoste) were similrly effective on crested whetgrss cover s compred to untreted res. Finlly, the I hericide (Tril 2) with its 12-dy hlf-life, though pplied in My s post-emergent tretment 5 months efore seeding, could hve hd some residul pre-emergent control potentil nd my hve reduced weed emergence, especilly during the first growing seson fter seeding. Higher weed cover in G tretment compred to CS nd I tretments lends some vlidity to this possiility. However, the issue is complicted y the significnt reduction of crested whetgrss y G tretment, s compred to CS nd I tretments, resulting in less competition for invding weeds. The CS hericide, with hlf-life less thn tht of G hericide, would hve hd negligile effect. Other studies hve shown tht ntive species estlishment nd survivl cn e seriously compromised if persistent seed nks of crested whetgrss or weeds re not dequtely reduced prior to seeding (Henderson & Neth 25; Hulet et l. 21). More specificlly, reserchers hve issued cution regrding the risk of chetgrss invsion fter crested whetgrss reduction (Hulet et l. 21; Dvies et l. 213), prticulrly if the seeded ntive species re not successfully estlished. Chetgrss invsion ws not the gretest exotic weed thret during our study. However, even though this species ws undetected efore tretment implementtion, y study s end (213) there ws minor expression of chetgrss cross tretments. Tumle mustrd ecme the dominnt exotic weed in ll three glyphoste tretments during 211 (for Tril 1), the third growing seson fter crested whetgrss reduction nd concurrent with 124% of norml crop-yer precipittion (Tle S1). Tumle mustrd declined precipitously fter 211 ut ws the co-dominnt exotic species with hlogeton y study s end. Seeded Species Estlishment Our hypothesis tht crested whetgrss reduction tretments nd seeding would result in successful estlishment of ntive plnt species ws prtilly supported y our dt. By reducing crested whetgrss (in the short term), ll glyphoste tretments except G/2 initilly resulted in higher densities of ll seeded species comined in oth Tril 1 nd Tril 2 s compred to untreted plots. However, the grdul ut significnt nnul increse in crested whetgrss cover over 5 yers in Tril 1 nd the corresponding decline in seeded ntive species over time underscores findings of other studies indicting competition from introduced species like crested whetgrss cn e reduced ut not eliminted (Bkker et l. 23), nd tht non-ntive perennil grsses re more competitive thn ntive species (Chmers et l. 1994). The competitive trits of crested whetgrss, including high seed production nd seed nk domintion (Pyke 199), s well s rpid soil wter extrction nd rpid nutrient cquisition (Gunnell et l. 21), re mechnisms tht interfere with the growth nd estlishment of ntive perennil grsses. According to Knutson et l. (214), seedings t lower, reltively drier loctions re less likely to result in estlishment of perennil grsses. The literture is replete with sttements nd conclusions indicting tht introduced unchgrsses generlly hve higher estlishment rtes thn ntive unchgrsses in sgerush-dominted nd formerly sgerush-dominted plnt communities (e.g. Roertson et l. 1966; Hull 1974; Boyd & Dvies 21). If persistent seed nks of crested whetgrss re not sufficiently reduced efore seeding, ntive species estlishment nd persistence my e seriously jeoprdized (Henderson & Neth 25; Hulet et l. 21), with crested whetgrss potentilly out-recruiting ntive grsses y mny orders of mgnitude (Nfus et l. 215). During our study, we routinely oserved numerous crested whetgrss seedlings from seed germintion s well s tillers from estlished plnts. Previous reserch hs shown the difficulty of successfully seeding ntive fors in crested whetgrss stnds (Hulet et l. 21; Fnsler & Mngold 211). Competition from crested whetgrss s well s poor for estlishment nd persistence cn ll e influencing fctors. Estlishing fors even in res without crested whetgrss is often difficult (Pyke 199; Leger et l. 214; Ott et l. 216). Persistence of I hericide tretment, with its hlf-life of 12 dys, could hve somewht negtively impcted ntive seeded species estlishment during the first yer. However, the significnt reduction of crested whetgrss y G tretment s compred to CS nd I tretments, resulting in less competition for emerging seeded species, ws more likely the primry reson for disprity in seeded species estlishment mong hericide tretments. Although sgerush estlishment during this study ws very wek (<.1 shru/m 2 ) nd there were no significnt differences mong tretments y the end of the study, the few sgerush tht survived in res where crested whetgrss hd een initilly reduced y the vrious tretments my e ecologiclly importnt nevertheless (Brec et l. 215). Similrly, Dvies et l. (213) reported surviving densities of sgerush seeded into crested whetgrss stnds controlled with glyphoste to e.7/m 2. Most mortlity of seeded sgerush occurs during the first yer fter seeding (Young & Evns 1989; Boyd & Ordovich 214; Schlepfer et l. 214), presenting one of the most difficult restortion chllenges (Brec et l. 215). Our study re lso experienced high popultions of lck-tiled jckrits (Lepus clifornicus) from t lest , during which time numerous sgerush trnsplnts were hrvested (cut t ground level) y jckrits in n djcent study site (McAdoo et l. 213). Becuse of the ffinity tht jckrits hve for oth succulent herceous vegettion (McAdoo et l. 1987) nd shrus (Fgerstone et l. 198), we ssume 8 Restortion Ecology

9 Ntive plnt estlishment in crested whetgrss tht jckrits impcted the survivl of our seeded species, including sgerush. Herceous species re notoriously competitive with sgerush during the first seson of estlishment (Young & Evns 1989; Boyd & Ordovich 214), nd therefore sgerush restortion in res dominted y perennil grsses my require trgeted reduction of grss competition (Boyd & Svejcr 21). However, fter sgerush hs estlished it hs high persistence in crested whetgrss communities due to niche differentition etween these species (Gunnell et l. 21). The importnce of this shru for sgerush-dependent wildlife species is well-documented, nd the ddition of sgerush into crested whetgrss seedings leds to greter diversity of hitt structure importnt to vriety of wildlife species (McAdoo et l. 1989; Kennedy et l. 29). Although lterntive strtegies for sgerush estlishment (e.g. from plnting stock) re eing implemented successfully in some res (Dvies et l. 213; McAdoo et l. 213), these techniques hve prcticl nd economic limittions, so the need for improving sgerush survivl from seed remins prmount. Mngement Implictions Our study underscores the chllenges of diversifying crested whetgrss monocultures in semirid Wyoming ig sgerush sites so tht they my provide wider rnge of ecologicl services including hitt more suitle for sgerush-oligte wildlife species. Our reserch nd tht of others indicte tht reduction of crested whetgrss is possile ut will e trnsient over time. Leverging our finding out initil crested whetgrss reduction with glyphoste, we would recommend future reserch such s following glyphoste tretment with pre-emergent imzpic tretment to control exotic nnuls nd crested whetgrss seed germintion, then seeding nd outplnting sgerush fter residul effects of imzpic hve susided. Other dptive mngement pproches, including the use of livestock grzing to reduce crested whetgrss nd enhnce ntive species estlishment (Nfus et l. 216), should lso e evluted. Becuse seeding ntive species is often less thn successful in rid sites (Knutson et l. 214), the more redily estlished crested whetgrss (Roertson et l. 1966; Boyd & Dvies 21) my often e the likely cndidte for seeding (Dvies 21), especilly since this species cn limit exotic nnul grsses t low elevtions (Dvies et l. 215). However, reserchers re grdully mking strides in the relm of ntive seed dpttion (Johnson et l. 21; Bower et l. 214) nd seeding technology (Boyd & Lemos 215; Mdsen et l. 216). Therefore, seeding site-dpted ntive species following plnt community disturnce still holds promise for restoring ntive plnts in Wyoming ig sgerush plnt communities. Acknowledgments The uthors grtefully cknowledge the ssistnce of C. Poulsen during the first field seson, the NRCS seeding crew from Aerdeen, ID nd J. Trux for their invlule input with the seeding component, technicins with Slter Seeding, Inc. for ssistnce with discing nd hericide ppliction components of this study, nd J. Wilkinson for ccommodting this reserch on Stte lnds. We lso pprecite the thoughtful reviews y nonymous reviewers nd the coordinting editors. This reserch ws funded y the USDA Forest Service Gret Bsin Ntive Selection nd Increse Plnt Selection nd Increse Project. Authors hve no conflict of interest regrding this reserch. LITERATURE CITED Allen PS, Meyer SE (214) Community structure ffects nnul grss weed invsion during restortion of sgerush steppe ecosystem. Invsive Plnt Science nd Mngement 214:1 13 Amrose LG, Wilson D (23) Emergence of the introduced grss Agropyron cristtum nd the ntive grss Boutelou grcilis in mixed-grss pririe restortion. Restortion Ecology 11: Bkker JD, Wilson SD, Christin JM, Li X, Amrose LG, Wddington J (23) Contingency of grsslnd restortion on yer, site, nd competition from n introduced grss. Ecologicl Applictions 13: Biedenender SH, Roundy BA, Aott L (1995) Replcing Lehmnn lovegrss with ntive grsses. Pges In: Roundy BA, McArthur ED, Hley JS, Mnn DK (eds) Wildlnd shru nd rid lnd restortion Symposium Proceedings. Generl Technicl Report INT-GTR-315, USDA Forest Service, Ogden, Uth Bower AD, St. Clir JB, Erickson V (214) Generlized provisionl seed zones for ntive plnts. Ecologicl Applictions 24: Boyd CS, Dvies KW (21) Shru microsite influences post-fire perennil grss estlishment. Rngelnd Ecology & Mngement 63: Boyd CS, Lemos JA (215) Evluting winter/spring seeding of ntive perennil unchgrss in the sgerush steppe. Rngelnd Ecology & Mngement 68:494 5 Boyd CS, Ordovich M (214) Is pile seeding Wyoming ig sgerush (Artemisi tridentt susp. wyomingensis) n effective lterntive to rodcst seeding? Rngelnd Ecology & Mngement 67: Boyd CS, Svejcr TJ (21) The influence of plnt removl on succession in Wyoming ig sgerush. Journl of Arid Environments 75: Brec MM, Germino MJ, Shinnemn DJ, Pilliod DS, McIlroy SK, Arkle RS (215) Chllenges of estlishing ig sgerush (Artemisi tridentte) in rngelnd restortion: effects of hericide, mowing, whole-community seeding, nd sgerush seed sources. Rngelnd Ecology & Mngement 68: Chmers JC, Brown RW, Willims BD (1994) An evlution of reclmtion success on Idho s phosphte mines. Restortion Ecology 2:4 16 Connelly JW, Schroeder MA, Snds AR, Brun CE (2) Guidelines to mnge sge-grouse popultions nd their hitts. Wildlife Society Bulletin 28: Cox RD, Anderson VJ (24) Incresing ntive diversity of chetgrss dominted rngelnd through ssisted succession. Journl of Rnge Mngement 57:23 21 D Antonio CM, Vitousek PM (1992) Biologicl invsions y exotic grsses, the grss/fire cycle, nd glol chnge. Annul Review of Ecology nd Systemtics 23:63 87 Duenmire RF (1959) Cnopy coverge method of vegettion nlysis. Northwest Science 33:43 64 Dvies KW (21) Revegettion of medushed-invded sgerush steppe. 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10 Ntive plnt estlishment in crested whetgrss Dvies KW, Boyd CS, Johnson DD, Nfus AM, Mdsen MD (215) Success of seeding ntive compred with introduced perennil vegettion for revegetting medushed-invded sgerush rngelnd. Journl of Rnge Mngement 68: Eckert RE, Asher JE, Christensen MD, Evns RA (1974) Evlution of the trzine-fllow technique for weed control nd seedling estlishment. Journl of Rnge Mngement 27: Eiswerth ME, Kruter K, Swnson SR, Zielinski M (29) Post-fire seeding on Wyoming ig sgerush ecologicl sites: regression nlyses of seeded nonntive nd ntive species densities. Journl of Environmentl Mngement 9: Fgerstone KA, Lvoie GK, Griffith RE Jr (198) Blck-tiled jckrit diet nd density on rngelnd nd ner griculturl crops. Journl of Rnge Mngement 33: Fnsler VA, Mngold JM (211) Restoring ntive plnts to crested whetgrss stnds. 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Ntive Plnts Journl 11: Jouert DF, Cunninghm PL (22) The distriution nd invsive potentil of fountin grss Pennisetum setceum in Nmii. Dinteri 27:37 47 Kennedy PL, Deno SJ, Brtuszevige AM, Lueders AS (29) Effects of ntive nd nonntive grsslnd plnt communities on reeding psserine irds: implictions for restortion of northwest unchgrss pririe. Restortion Ecology 17: Knutson KC, Pyke DA, Wirth TA, Arkle RS, Pilliod DS, Brooks ML, Chmers JC, Grce JB (214) Long-term effects of seeding fter wildfire on vegettion in Gret Bsin shrulnd ecosystems. Journl of Applied Ecology 51: Leger EA, Goergen EM, Foris de Queiroz T (214) Cn ntive nnul fors reduce Bromus tectorum iomssndindirectlyfcilitteestlishmentof ntive perennil grss? Journl of Arid Environments 12:9 16 Lym RG, Kiry DR (1991) Effect of glyphoste on introduced nd ntive grsses. Weed Technology 5: Mdsen MD, Dvies KW, Boyd CS, Kery JD, Svejcr TJ (216) Emerging seed enhncement technologies for overcoming rriers to restortion. Restortion Ecology doi:1.1111/rec Mrshll VM, Lewis MM, Ostendorf B (212) Buffel grss (Cenchrus ciliris)s n invder nd thret to iodiversity in rid environments: review. Journl of Arid Environments 78:1 12 Mrylnd HF, Asy KH, Clrk DH (1992) Sesonl trends in herge yield nd qulity of Agropyrons. Journl of Rnge Mngement 45: McAdoo JK, Longlnd WS, Cluff GJ, Kleenow DA (1987) Use of new rngelnd seedings y lck-tiled jckrits. Journl of Rnge Mngement 4: McAdoo JK, Longlnd WS, Evns RA (1989) Nongme ird community responses to sgerush invsion of crested whetgrss seedings. Journl of Wildlife Mngement 53: McAdoo JK, Boyd CS, Sheley RL (213) Site, competition, nd plnt stock influence trnsplnt success of Wyoming ig sgerush. Rngelnd Ecology & Mngement 66: Miller MR (1943) Hlogeton glomertus, poisonous to sheep. Science 97:262 Nfus AM, Dvies KW (214) Medushed ecology nd mngement: Cliforni nnul grsslnds to the Intermountin West. Invsive Plnt Science nd Mngement 7: Nfus AM, Svejcr TJ, Gnskopp DC, Dvies KW (215) Aundnces of coplnted ntive unchgrsses nd crested whetgrss fter 13 yers. Rngelnd Ecology & Mngement 68: Nfus AM, Svejcr TJ, Dvies KW (216) Disturnce history, mngement, nd seeding yer precipittion influence vegettion chrcteristics of crested whetgrss stnds. Rngelnd Ecology & Mngement doi:1.116/j.rm Ott J, Cox RD, Shw NL, Newinghm BA, Gnguli AC, Pellnt M, Roundy BA, Eggett DL (216) Post-fire drill-seeding of Gret Bsin plnts: effects of contrsting drills on seeded nd non-seeded species. Rngelnd Ecology & Mngement doi:1.116/j.rm Pellnt M, Lysne CR (25) Strtegies to enhnce plnt structure nd diversity in crested whetgrss seedings. Pges In: Shw NL, Pellnt M, Monsen SB (eds) Sge-grouse hitt restortion Symposium Proceedings. RMRS-P-38. USDA Forest Service, Fort Collins, Colordo Pyke D (199) Comprtive demogrphy of co-occurring introduced nd ntive tussock grsses: persistence nd potentil expnsion. Oecologi 82: Roertson JH, Eckert RE, Blek AT (1966) Response of grsses seeded in n Artemisi tridentt hitt in Nevd. Ecology 47: Schlepfer DR, Luenroth WK, Brdford JB (214) Nturl regenertion processes in ig sgerush (Artemisi tridentt). Rngelnd Ecology & Mngement 67: USDA-NRCS (Nturl Resources Conservtion Service) (215) Ntionl we soil survey. ccessed 15 Decemer 215 Wilson SD, Prtel M (23) Extirption or coexistence? Mngement of persistent introduced grss in pririe restortion. Restortion Ecology 11: Young JA, Eckert RE, Jr, Evns RA (1979) Historicl perspectives regrding the sgerush ecosystem. Pges 1 13 In: Johnson K (ed) The sgerush ecosystem: symposium. Uth Stte University, Logn, Uth Young JA, Evns RA (1989) Dispersl nd germintion of ig sgerush (Artemisi tridentt) seeds. Weed Science 37:21 26 Supporting Informtion The following informtion my e found in the online version of this rticle: Tle S1. Precipittion (mm) y qurter for wter yer nd crop yer, , for two seeding trils* t South Fork Stte Recretion Are, Nevd (from South Fork Stte Recretion Are Wether Sttion nd Dtse). Tle S2. Seeded species nd pure live seed (PLS) seeding rtes for tretments t South Fork Stte Recretion Are, Nevd, plnted in lte Octoer 28 for Tril 1 nd lte Octoer 21 for Tril 2. Coordinting Editor: Stephen Murphy Received: 21 Octoer, 215; First decision: 6 Jnury, 216; Revised: 25 My, 216; Accepted: 3 My, Restortion Ecology