Exotic annual grass invasion has been implicated in

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1 RESEARCH ARTICLE Site-Specific Effects of Exotic Annul Grss Control Integrted with Revegettion L. Noelle Orloff, Jne M. Mngold nd Fin D. Menlled ABSTRACT Invsion y exotic nnul grss species such s downy rome nd Jpnese rome hs een implicted in ecosystem degrdtion in much of the western United Sttes nd strtegies to restore lnds dominted y these species re needed. We evluted integrtion of hericide nd revegettion to restore old-field nd rngelnd sites dominted y nnul rome species. In split-plot field studies, we compred three imzpic hericide rtes nd eight seeding tretments t n old-field nd rngelnd site. We evluted rome, seeded species, nd existing vegettion response to our tretments. Hericide controlled nnul rome t oth sites, with > 95% decreses in rome iomss in plots treted with the high rte compred to non-spryed controls. Control of nnul rome persisted for two growing sesons t the old-field site nd one seson t the rngelnd site. Annul rome undnce in non-treted control plots t oth sites decresed y 80% etween the first nd second growing seson. No seeded individuls estlished t the old-field site, ut they persisted through two growing sesons t the rngelnd site. Seeded species estlishment t the rngelnd site ws impcted y oth hericide rte nd seed mix, ut no cler ptterns emerged. Finlly, while we controlled rome t oth sites, existing desired vegettion incresed only t the old-field site, where perennil grss iomss incresed y out 30% in plots spryed with oth rtes of hericide. The differing responses of the existing nd seeded plnt communities cross the two sites highlight the importnce of integrting site-specific knowledge into restortion plns. Keywords: Bromus rvensis, Bromus tectorum, Conservtion reserve progrm, downy rome, Jpnese rome, lnd use history Exotic nnul grss invsion hs een implicted in ecologicl dmge nd chnge round the gloe (D Antonio nd Vitousek 1992). In the western United Sttes, downy rome (Bromus tectorum) invsion in prticulr hs een ssocited with decresed recruitment of desired species, ltered fire regimes, nd degrdtion of wildlife hitt (Mck 2011, Blch et l. 2013). This species hs lso een identified s rrier to restortion efforts in degrded lnds (Allen 1995, Di Tomso 2000). Jpnese rome (Bromus rvensis) is nother exotic nnul grss closely relted to downy rome (Bskin nd Bskin 1981). Although Jpnese rome does not hve the invsive potentil of downy rome, these two species often grow together in the western United Sttes, prticulrly in the Northern Gret Plins, nd re concern in oth croplnd nd rngelnd settings (Ogle et l. 2003, Gsch et l. 2013). Simply controlling exotic nnul grsses does not necessrily restore desired perennil plnt community on given site. In some cses, desired perennil vegettion increses in undnce following removl of nnul grsses (Dvies nd Sheley 2011, Elserod nd Rudd 2011). In other Ecologicl Restortion Vol. 33, No. 2, 2015 ISSN E-ISSN y the Bord of Regents of the University of Wisconsin System. cses, long-term dominnce y exotic nnul grsses leds to the loss of desired perennil species from plnt communities through decresed recruitment nd seed nk impoverishment, hindering the long-term success of control progrms (Humphrey nd Schupp 2001, 2004). These differences in plnt community responses to mngement re driven y site-specific fctors such s perennil plnt community composition, lnd use history, nd iotic chrcteristics such s episodic events of episodic precipittion for given yer (Rdosevich et l. 2007). In some cses, weed control nd revegettion should e integrted s long-term strtegy to suppress exotic nnul grsses nd provide hitt for livestock nd wildlife (Elserod nd Rudd 2011, Hirsch-Shntz et l. 2014). However, re-estlishing desired species is often difficult on lnds dominted y invsive nnul grsses (Allen 1995, Di Tomso 2000). Though mny fctors cn influence estlishment of seeded perennil species, competition from exotic nnul grsses in prticulr cn decrese estlishment of perennil grsses nd contriute to filure of seeding efforts (Hull nd Stewrt 1948, Romo nd Eddlemn 1987, Dvies et l. 2010, ut see Jmes nd Svejcr 2010). Suppression of nnul grsses my help perennil species to estlish during revegettion (Morris et l 2009, Dvies nd Sheley 2011). June 2015 ECOLOGICAL RESTORATION 33:2 147

2 Figure 1. Annul nd long term precipittion dt for the closest wether sttion to ech study site (Ft. Assinioine, Montn, US for the old-field site [~30 km from site]; Mlt 7 E, Montn, US for the rngelnd site [~ 8 km from site]). All yers in the period of record were used to clculte mens (94 nd 39 yers for Ft. Assinioine nd Mlt 7 E, respectively) (WRCC 2014). Imzpic is n hericide tht cn e used to control winter nnul grsses in rngelnds nd old-field sites (Morris et l. 2009, Mngold et l. 2013) nd help revegettion efforts. Integrting imzpic with seeding cn fvor seeded species, ut it could lso result in non-trget effects. For exmple, reserch suggests tht high rtes of imzpic reduce seeded species estlishment nd dmge eneficil plnts, though these effects re species-specific nd depend on timing of hericide ppliction reltive to seeding (Shinn nd Thill 2004, Sheley et l. 2007, Stell et l. 2011). Thus, evlution of perennil species tht re competitive with nnul grsses nd tolernt of imzpic rtes recommended for nnul grss control is needed to improve revegettion prctices. To chieve this gol, we evluted the integrtion of hericide (imzpic) nd seeding to restore sites in the Northern Gret Plins tht re dominted y nnul rome species. At two contrsting sites, we compred two hericide ppliction rtes tht would fcilitte the emergence nd survivl of seeded species y decresing nnul rome species undnce. Further, we tested the performnce of three species in monoculture nd mixes commonly used in revegettion settings. We hypothesized tht controlling nnul rome species would increse seeded species emergence nd estlishment nd increse existing perennil plnt undnce. Second, we hypothesized tht the responses of rome nd the existing perennil plnt community to our tretments would e site-specific. Methods We conducted this study over three yers ( ) t n old-field nd rngelnd site in north-centrl Montn, U.S.A. Sites differed in lnd use history, existing plnt community composition, nd nnul rome species composition. During the course of this study, oth sites experienced norml to ove verge nnul precipittion compred to historicl mens (old-field, ; rngelnd, ) (Western Regionl Climte Center 2014; Figure 1). 148 June 2015 ECOLOGICAL RESTORATION 33:2

3 Old-field Study Site The old-field site (48 26'55.40" N, '57.45" W) ws locted t n elevtion of 800 m, with fine lom soils nd men nnul precipittion of 307 mm (Soil Survey Stff 2013, Western Regionl Climte Center 2014). The site ws locted in former griculturl field which ws plowed nd seeded to perennil grss mix in 2003 s prt of the Conservtion Reserve Progrm (CRP). We initited our study in 2009 nd y then mix of downy rome nd Jpnese rome, herefter referred to s rome, dominted the site, with n ssocited sustntil litter lyer. When we strted our study, the existing non-rome plnt community ws comprised of remnnt perennil grsses seeded y the privte lndowner in 2003 (western whetgrss [Pscopyrum smithii], green needlegrss [Stip viridul], nd crested whetgrss [Agropyron cristtum]) nd weedy perennil nd nnul fors (dndelion [Trxcum officinle], field indweed [Clystegi hederce], yellow sweetclover [Melilotus officinlis], prickly lettuce [Lctuc serriol], nd kochi [Bssi scopri]). Rngelnd Study Site The rngelnd site (48 08'23.59" N, '15.58" W) ws locted t n elevtion of 725 m, with cly lom soils nd men nnul precipittion of 329 mm (Soil Survey Stff 2013, Western Regionl Climte Center 2014). This site ws on privte lnd used primrily for cttle production nd hd no history of plowing or cultivtion. Jpnese rome dominted the site, with n ssocited sprse litter lyer. The remining plnt community ws comprised lrgely of ntive species including perennil grsses (Snderg luegrss [Po secund], lue grm [Boutelou grcilis] nd western whetgrss), perennil fors ( pririe coneflower [Rtiid columnifer], scrlet gloemllow [Spherlce coccine], nd common yrrow [Achille millefolium]), nd shrus ( plins pricklyper [Opunti polycnth] nd yellow ritrush [Chrysothmnus vicidifloris]). Clumoss (Selginell dens) ws lso prevlent t this site. Experimentl Design At ech site, we implemented rndomized split-plot design with four replictions rrnged s locks. Eight seeding tretments were rndomly ssigned to 11.0 m 2.4 m min plots, nd three hericide rtes were rndomly ssigned to 3.0 m 2.4 m suplots. There were 1.2 m uffers etween min plots, nd 1 m uffers etween suplots. Hericide tretments were pplied efore rome species emergence in fll 2009 with CO2 pressurized ckpck spryer (August 31, 2009 t rngelnd site; Septemer 1, 2009 t old-field site). Hericide (Plteu ; BASF Corportion, Reserch Tringle Prk, NC, U.S.A) ppliction rtes were control (no hericide), low (66 g i imzpic/ h; 296 ml Plteu /h), nd high (105 g i imzpic/h; 473 ml Plteu /h). Seeding tretments were pplied the spring following the hericide ppliction (April 19, 2010 t the rngelnd site; April 20, 2010 t the old-field sites). We used 120 cm wide hoe seeder to sow eight rows in ech min plot t 30 cm spcing nd two cm depth. We chose three species for ech loction sed on site chrcteristics (e.g., precipittion nd soil type), fll-pplied imzpic tolernce ccording to the product lel, nd oservtions of locl plnt communities (Anonymous 2008, Sheley et l. 2008). Species consisted of two grsses nd for t ech site, nd seeding rtes for single species plots followed Sheley et l. (2008). Seeded species nd rtes t the old-field site were thickspike whetgrss (Elymus lnceoltus Bnnock ) t 12 kg pure live seed (PLS)/h, puescent whetgrss (Thinopyrum intermedium Lun ) t 16 kg PLS/h, nd purple pririeclover (Dle purpure Bismrk ) t 9 kg PLS/h. At the rngelnd site, we sowed western whetgrss ( Rosn ) t 18 kg PLS/h, nd puescent whetgrss nd purple pririeclover t the sme rtes s ove. Ech species ws sown singly, nd in ll comintions of two nd three species for totl of eight seeding tretments including non-seeded control. For mixtures, we djusted seeding rtes so the totl numer of seeds/m2 remined constnt nd species were seeded in equl proportions. Smpling ws conducted in 2010 nd 2011 to quntify rome nd plnt community response to hericide tretments, nd seeded species emergence (2010) nd estlishment (2011). For ll mesurements, three 20 cm 50 cm (0.1 m2) smpling frmes were rndomly plced in ech suplot, ech centered lengthwise on seeded row. Frme loctions were permnently mrked for repeted smpling. For ll smpling dtes listed elow, oveground iomss smples were collected fter cnopy cover nd density were recorded. At the old-field site, we mesured nnul rome cnopy cover nd seeded species density on June 22, 2010; nnul rome iomss ws smpled on June 30, We mesured nnul rome cnopy cover nd iomss gin on June 29, 2011, s well s perennil grss cover nd iomss, seeded species density, nd cover of fors, litter, nd re ground. At the rngelnd site, we smpled Jpnese rome cnopy cover nd iomss nd seeded species density on July 7, On June 27, 2011 we mesured Jpnese rome cnopy cover nd iomss, seeded species density, nd cnopy cover of perennil grsses, fors, clu moss, nd re ground. All iomss ws dried to constnt mss nd weighed. We smpled rome iomss slightly differently in In tht yer, we did not destructively smple rome iomss within permnently mrked frmes, nd we did not smple ll seeding tretments ecuse we ssumed the effect of seeded species on rome iomss would e negligile two months fter seeding. Thus, we rndomly selected four suplots per repliction of ech spry tretment nd smpled iomss from two rndomly locted frmes in ech. June 2015 ECOLOGICAL RESTORATION 33:2 149

4 Tle 1. Mens ± stndrd errors for plnt community ttriutes of n old-field nd rngelnd site in north-centrl Montn, US. Ech site ws smpled in 2010 nd Cover is the percent cover for ech group. Seeded species were sown in April Hericide rtes were control (no hericide), low (66 g i imzpic/h), nd high (105 g i imzpic/h). Brome refers to mix of nnul rome species (downy nd Jpnese rome), nd BRJA refers to Jpnese rome. Vlues in ech row within yer which do not shre the sme letter re different (α = 0.05, ANOVA followed y Wld post hoc test). NA (not pplicle) mens we did not smple vrile in the yer indicted. Yer Smpled Hericide Rte Control Low High Control Low High Old-field site Seeded species plnts m 2 31 ± 6 56 ± ± Brome g/m ± ± 3 7 ± 2 c 38 ± 9 8 ± 2 4 ± 1 c Brome cover 48 ± 6 19 ± 3 11 ± 2 c 5 ± 2 1 ± ± 0.2 c Perennil grss g/m 2 N/A N/A N/A 252 ± ± ± 19 Perennil grss cover N/A N/A N/A 18 ± 2 24 ± 2 25 ± 2 Litter cover N/A N/A N/A 75 ± 2 72 ± 2 72 ± 2 Rngelnd site Seeded species plnts/ m 2 48 ± 7 38 ± 8 61 ± ± 4 15 ± 3 18 ± 4 BRJA g/m 2 31 ± 3 4 ± 3 1 ± 0.3 c 6 ± 1 7 ± 1 5 ± 1 BRJA cover 4 ± 1 1 ± ± 0.1 c 2 ± ± ± 0.2 Perennil grss cover N/A N/A N/A 32 ± 3 34 ± 3 32 ± 3 For cover N/A N/A N/A 17 ± 1 12 ± 1 14 ± 1 Clu moss cover N/A N/A N/A 25 ± 3 27 ± 3 28 ± 3 Litter cover N/A N/A N/A 13 ± 2 13 ± 3 12 ± 3 Bre ground cover N/A N/A N/A 11 ± 1 11 ± 2 11 ± 1 Dt Anlysis Sites were nlyzed seprtely due to differences in plnt community composition nd lnd use history. Split-plot nlysis of vrince (ANOVA) with repeted mesures through time ws used to determine the effects of hericide rte nd seeding tretment on nnul rome cover nd iomss. Additionlly, split-plot ANOVA ws used to investigte the effects of hericide rte nd seeding tretment on existing plnt community functionl group cover t oth sites, nd perennil grss iomss t the old-field site. For the rngelnd site, split-plot ANOVA with repeted mesures through time ws used to determine the effects of hericide rte nd seeding tretment on seeded species emergence nd estlishment (density two months nd 14 months fter plnting, respectively). Seeded species did not persist through the first growing seson t the old-field site, so only seeded species emergence ws considered for nlysis for tht site. There were few existing fors nd very little re ground (men cover of 1 ± 0.2% nd 1 ± 0.4%, respectively) t the old-field site, so these vriles were lso excluded from further nlysis. Response vriles were nturl log trnsformed s needed to chieve norml distriutions nd homogeneity of vrince. Men seprtions were ccomplished using post hoc Wld tests, nd differences were considered significnt t p Non-trnsformed mens for ll vriles re presented in the results. Anlyses were conducted using R softwre including the nlme, lme4, gmodels, nd LMERConvenienceFunction pckges (Pinheiro et l. 2013, Tremly nd Rnsijn 2013, Wrnes et l. 2013). Results Old-field Site The effect of hericide on the rome popultion persisted over two growing sesons s shown y lck of hericide rte y yer interction for oth rome cover (ANOVA; F2,112 = 0.97, p = ) nd iomss (F2,65 = 1.22, p = 0.303) estimtes. Annul rome iomss nd cover decresed with incresing hericide rte in oth yers (Tle 1). For exmple, in 2010, untreted rome iomss ws 180 ± 34 g/m2 (men ± stndrd error), while plots treted with low nd high hericide rtes hd rome iomss vlues of 17 ± 3 g/m2 nd 7 ± 2 g/m2, respectively (Tle 1). The pttern of decresing rome undnce with incresing hericide rte persisted in 2011, when control iomss ws 38 ± 9 g/m2 nd low nd high plots hd iomss of 8 ± 2 g/m2 nd 4 ± 1 g/m2, respectively (Tle 1). It is importnt to note tht rome iomss in non-spryed control plots ws 180 ± 34 g/m2 in 2010, nd decresed to 38 ± 9 g/m2 in 2011, decrese of out 79%. Hericide rte positively impcted existing perennil grss cover nd iomss (ANOVA; F2,62 = 6.83 nd 4.27, p = nd 0.018, respectively). In 2011, non-spryed control plots hd the lowest existing perennil grss iomss with 252 ± 20 g/m2 (Tle 1). We filed to detect difference etween plots treted with low (339 ± 27 g/m2) nd high (322 ± 19 g/m2) rtes of hericide, where perennil grss iomss incresed y 35% nd 28%, respectively compred to the non-spryed control. We filed to detect response of litter cover to our hericide tretments 150 June 2015 ECOLOGICAL RESTORATION 33:2

5 Figure 2. Effects of seeding tretment on seeded species density two months fter seeding n old-field site locted in Montn, US. Seedlings did not persist to the second seson fter sowing t this site. NG is ntive grss thickspike whetgrss, IG is introduced grss puescent whetgrss, nd NF is ntive for purple pririe clover. Letters seprte mens tht differed ccording to post hoc Wld tests (α = 0.05). (ANOVA; F2,62 = 1.33, p = 0.272), nd it hd n overll men vlue of 73 ± 2%. Seeded species emergence t the old-field site ws positively ffected y oth hericide rte (ANOVA; F2,42 = 3.42, p = 0.042) nd seeding tretment (ANOVA; F6,18 = 9.34, p < 0.001). According to post hoc tests, only the high hericide rte incresed seeded species emergence compred to control plots (Tle 1). Control plots hd seeded species emergence of 31 ± 6 seedlings/m2, while those treted with the low nd high hericide rte hd emergence of 56 ± 13 nd 53 ± 8 seedlings/m2, respectively. Plots sown with only the ntive for hd the lowest men emergence t 6 ± 8 seedlings/m2, nd we filed to detect difference in emergence etween the other six seed mix tretments, which hd overll men emergence of 53 ± 46 seedlings/ m2 (Figure 2). Rngelnd Site At the rngelnd site, the effect of hericide on Jpnese rome iomss nd cover differed y yer s shown y the rte y yer interctions for oth vriles (ANOVA; F2,68 = nd F2,112 = 32.91, p < for oth vriles). Incresing hericide rte led to decresed Jpnese rome iomss nd cover one yer fter tretment, ut the effect of hericide did not persist to the second yer fter tretment (Tle 1). For exmple, Jpnese rome iomss in control plots one yer fter tretment ws 31 ± 3 g/m2, nd it decresed to 4 ± 3 g/m2 nd 1 ± 0.3 g/m2 in the low nd high hericide rte plots, respectively (Tle 1). However, there ws no difference in Jpnese rome iomss etween hericide rtes two yers fter tretment (Tle 1). Interestingly, Jpnese rome iomss in non-spryed control plots ws 31.2 ± 3 g/m2 in 2010, nd decresed to 6 ± 1 g/ m2 in 2011, decrese of out 82%. At the rngelnd site, we found no evidence to support our hypothesis tht controlling nnul Jpnese rome would increse undnce of the remnnt plnt community. Only existing for cover responded to hericide tretments (ANOVA; F2,62 = 5.02, p = 0.010). For cover ws highest in control plots t 17 ± 1%, nd we filed to detect difference etween the low nd high rtes, which hd for cover vlues of 12 ± 1% nd 14 ± 1%, respectively (Tle 1). Overll men existing perennil grss cover ws 33 ± 17%, nd did not chnge with hericide ppliction (ANOVA; F2, 62 = 1.71, p = 0.190). Similrly, cover of clu moss, litter, nd re ground were not impcted y hericide rte (ANOVA; F2,62 = 0.791, nd 0.092, p = 0.458, nd 0.912, respectively) with overll men vlues of 27 ± 15%, 13 ± 14%, nd 11 ± 8%, respectively (Tle 1). Seeded species density t the rngelnd site differed y yer (ANOVA; F1,80 = 9.52, p = 0.002). Men seeded species density ws 49 ± 5 plnts/m2 in 2010 nd 17 ± 2 plnts/m2 in Seeded species were lso impcted y n interction etween hericide rte nd seed mix (ANOVA, F12,80 = 2.88, p = 0.001). Hericide rte ffected seeded species density in four of the seven seeding tretments, ut we did not oserve cler pttern in this reltionship (Figure 3). For exmple, the ntive grss lone hd the June 2015 ECOLOGICAL RESTORATION 33:2 151

6 80 Hericide rte Control Low High 2011 seeded species plnts/ m NG NF IG NG+NF NG+IG NF+IG NG+IG+NF Seeding tretment Figure 3. Effects of seeding tretment nd hericide rte on seeded species density 14 months fter sowing t rngelnd site locted in Montn, US. Hericide tretments were control (no hericide), low (66 g i imzpic/ h), nd high (105 g i imzpic/h). NG is ntive grss western whetgrss, IG is introduced grss puescent whetgrss, nd NF is ntive for purple pririe clover. Letters seprte mens for hericide rtes tht differed within seeding tretments ccording to post hoc Wld tests (α = 0.05). lowest estlishment in non-spryed control plots, while the introduced grss sown lone hd the highest estlishment in non-spryed control plots (Figure 3). In contrst, we filed to detect difference in estlishment etween the control nd high rtes of hericide in the ntive grss + ntive for nd ntive grss + introduced grss + ntive for seed mixes, while the low rte of hericide yielded the lowest density of estlished seedlings (Figure 3). For the remining three seed mixes, we filed to detect n effect of hericide rte on seedling estlishment. Discussion Overll, this study highlights the concept tht efficcy of restortion prctices depends on site-specific fctors (Sheley et l. 2010). We investigted the utility of restoring n old-field nd rngelnd site y integrting hericide nd revegettion. These two sites differed in lnd-use history, soil type, nd nnul rome species composition nd undnce, which precluded forml comprison etween sites. However, we speculte tht these differences led to the dissimilr responses to our tretments. While rome species were controlled with hericide t oth sites, durtion of control differed etween sites. Furthermore, sites differed in whether control ctully trnslted into greter seeded species estlishment nd incresed undnce of the existing plnt community. Annul rome undnce differed etween our two sites nd this difference ws most likely driven y lnd use history. Downy rome ws much more undnt t our old-field site compred to Jpnese rome t the rngelnd site; where men pre-tretment cover in the non-spryed control plots ws ~ 48% nd ~ 4%, respectively. Similrly, in survey of CRP fields versus undistured rngelnd sites in Colordo, Munson nd Luenroth (2012) found tht nnul grsses hd n verge cnopy cover of 37% which peked in seven-yer-old CRP stnds, while undistured rngelnd hd nnul grss cnopy cover of 1%. It is likely tht the higher undnce nd productivity of nnul rome t the old-field site ws result of the history of cultivtion disturnce inherent to CRP lnds, nd the resulting erly- to mid-successionl sttus of the plnt community (Munson nd Lurenroth 2012). At oth the old-field nd rngelnd sites, nnul rome undnce declined y pproximtely 80% in non-treted control plots etween 2010 nd 2011, mening tht they declined due to fctors other thn the tretments we imposed. Becuse comprle decline occurred in these two sites tht hd different lnd use history, different nnul grss species composition, nd were reltively fr prt (160 km), we speculte tht it ws cused y climtic fctors. Annul plnt undnce cn vry sustntilly with yer to yer vritions in precipittion mount nd sesonlity, nd the pttern often oserved is tht nnul grsses increse in undnce in yers with more spring or fll moisture thn verge (Mck nd Pyke 1983, Hferkmp et l. 1993, Concilio et l. 2013). We oserved n opposite pttern, with mrked decrese in nnul grss undnce in the summer of 2011 fter verge to ove verge precipittion during fll nd spring of 2009 through June 2015 ECOLOGICAL RESTORATION 33:2

7 The timing of precipittion nd tempertures during key periods of nnul grss growth re prole explntory fctors. For exmple, in Novemer of 2010 the wether sttions ssocited with oth sites experienced 18 dys of reltively wrm tempertures rnging etween 4 nd 24 C followed y seven dys with lows rnging from 22 to 28 C (NOAA 2014). It is possile tht cohort of nnul rome emerged during the wrm weeks nd ws killed off y the cold snp, leding to the nnul grss reduction we oserved in the 2011 growing seson. Annul rome undnce decresed s result of pplying hericide efore nnul rome emerged in the fll, with higher rte (105 g i imzpic) cusing greter reduction thn lower rte (66 g i imzpic). However, control durtion differed etween sites; we detected n effect of hericide throughout the two-yer smpling period t the old-field site nd for only one yer t the rngelnd site. It is possile tht the previously discussed nnul grss decline my hve ffected our results. However, our results correspond to previous studies tht oserved tht durtion of nnul rome control with imzpic is site-specific, with reductions in undnce lsting etween one nd four yers (i.e., Morris et l. 2009, Elserod nd Rudd 2011). Despite controlling nnul rome, hericide rte hd wek effects on seeded species emergence t the old-field site, nd there ws no cler pttern in the effect of hericide rte on seeded species emergence or estlishment t the rngelnd site. Previous reserch hs shown tht pplying 105 g i/h imzpic t lest 120 dys efore seeding perennil grsses cused little or no injury to seeded species (Stell et l 2011), nd tht imzpic rtes up to 105 g i/h cn increse estlishment of seeded perennil species in nnul grss dominted sites (Morris et l. 2009). For these resons, it is unlikely tht hericide injury confounded the effects of hericide on estlishment in our study. Insted, we suspect tht the reltively low undnce of nnul grsses t the rngelnd site mde it difficult to detect response from the pplied mngement prctices. In similr study, Jmes nd Svejcr (2010) found tht hnd-weeding low density of nnul grsses hd no detectle effect on sown seedling estlishment. These results suggest tht t low levels of invsion, removing invsive nnul grsses my not increse seeded species estlishment. However, our result should e interpreted cutiously: we implemented our restortion project during time of nnul grss decline, ut popultions of these nnul species cn re-expnd firly rpidly (Smith et l. 2008). Seeded species persisted through two growing sesons t the rngelnd site, ut no seeded individuls estlished t the old-field site, despite comprle emergence rtes two months fter sowing. Among the mny possile fctors tht my hve contriuted to the old-field seeding filure re site history nd the more resilient existing vegettion t tht site. This site hd history of griculturl production nd cultivtion which my hve hd residul effects on soil fertility, leding to productive remnnt plnt community. It ws lso sown with reltively competitive perennil grss mix in 2003, nd these species mrkedly incresed fter rome mngement. Compred to non-spryed control plots, existing perennil grss productivity ws ~ 30% greter when nnul rome ws removed with hericide, incresing from 2,520 kg/h to 3,220 kg/h two yers fter hericide tretment. This reltively vigorous perennil plnt community my hve een too competitive for sown seedlings to persist in treted plots, while the dense nnul rome species stnds in the non-spryed control plots my hve hd similr effect. These plnt communities were likely limited in the numer of sfe sites ville for sown seedling estlishment. Jmes nd Svejcr (2010) reported similr findings in post-fire sgerush steppe revegettion, where they concluded tht roust remnnt ntive plnt community cused sown seedling density to decrese over time. Tken together, these results re consistent with review of seed ddition experiments conducted y Turnull et l. (2000), who illustrted tht sfe sites tend to e more limited in plnt communities with high vegettion cover. These responses highlight the importnce of ssessing plnt community efore undertking n extensive restortion effort tht includes seeding, nd perhps implementing n invsive species control progrm efore seeding to ssess the existing plnt community s resilience. While we controlled nnul rome species t oth sites, existing desired vegettion incresed only t the old-field site nd only in the perennil grss functionl group. These results mirror recent literture where, in some cses, removing nnul grsses cused incresed existing perennil grss nd for growth (Dvies nd Sheley 2011, Kyser et l. 2013), nd in others it did not (Elserod nd Rudd 2011). In our study, the discrepncy in existing plnt community response my e explined y differing rome species undnce. Controlling nnul rome t the oldfield site mde reltively more spce ville for existing plnts to spred into compred to the rngelnd site. This process ws recognized y Orteg nd Person (2010) in spotted knpweed (Centure stoee) invded rngelnd, where the effects of hericide on plnt community relese depended on initil spotted knpweed undnce. Differences in existing perennil grss community composition my hve lso impcted their responses to rome control. The old field site ws dominted y western whetgrss (Pscopyrum smithii), colonizing rhizomtous grss, while the rngelnd site ws dominted y Snderg luegrss (Po secund) nd lue grm (Boutelou grcilis), two reltively smll-sttured unchgrsses. In previous studies, western whetgrss hs een shown to increse in undnce following nnul grss control. For exmple, Hferkmp nd Heitschmidt (1999) found tht hnd-pulling Jpnese rome led to ~ 23% increse in western whetgrss iomss production. In the sme plnt June 2015 ECOLOGICAL RESTORATION 33:2 153

8 community, the remining vegettion dominted, in prt, y Snderg luegrss nd lue grm, ws not ffected y removl of Jpnese rome. These results support the ide tht simply controlling nnul grsses my or my not e sufficient to restore desired perennil plnt communities (Elserod nd Rudd 2011), nd tht the composition of these communities is n importnt fctor to consider when plnning restortion efforts. The differing responses of the existing nd seeded plnt communities to our hericide nd seeding tretments cross the two sites highlight the importnce of integrting site-specific knowledge into restortion plns. Conducting reserch such s wht is presented here cn help us etter understnd how mjor fctors such s lnd use history, remnnt plnt community composition nd invsive species undnce might help us refine ppliction of tretments nd predict susequent outcomes of tht mngement on site-specific sis. Acknowledgements The uthors would like to thnk Mrko Mnoukin nd Joe Broesder from Montn Stte University Extension for technicl expertise nd field ssistnce, nd three nonymous reviewers who hd helpful suggestions for improving the mnuscript. Two privte lndowners provided ccess to study sites, nd the Montn Noxious Weed Trust Fund funded this reserch. References Allen, E.B Restortion ecology: Limits nd possiilities in rid nd semirid lnds. Pges 7 15 in Proceedings of the Wildlnd Shru nd Arid Lnd Restortion Symposium. Ls Vegs, NV: Intermountin Reserch Sttion. Anonymous Plteu hericide product lel. BASF Puliction No. NVA Reserch Tringle Prk, NC: BASF. Blch, J.K., B.A. Brdley, C.M. D Antonio nd J. Gómez-Dns Introduced nnul grss increses regionl fire ctivity cross the rid western USA ( ). Glol Chnge Biology 19: Bskin, J.M. nd C.C. Bskin Ecology of germintion nd flowering in the weedy winter nnul grss Bromus rvensis. Journl of Rnge Mngement 34: Concilio, A.L., M.E. Loik nd J. 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9 knpweed (Centure stoee) invsion. Invsive Plnt Science nd Mngement 3: Pinheiro, J., D. Btes, S. DeRoy, D. Srkr nd R Development Core Tem nlme: Liner nd Nonliner Mixed Effects Models. R pckge version Vienn, Austri: R development Core Tem. Rdosevich, S.R., J.S. Holt nd C.M. Ghers Weed Ecology. Implictions for Mngement. 2nd ed. New York, NY: John Wiley nd Sons, Inc. Romo, J.T. nd L.E. Eddlemn Effects of Jpnese rome on growth of lueunch whetgrss, junegrss, nd squirreltil seedlings. Reclmtion Revegettion Reserch 6: Stell, G.M., R.G. Wilson, S.F. Enloe nd C. Hicks Propoxycrzone-sodium nd imzpic effects of downy rome (Bromus tectorum) nd newly seeded perennil grsses. Invsive Plnt Science nd Mngement 4: Sheley, R.L., M.F. Crpinelli nd K.J. Morghn Effects of imzpic on trget nd nontrget vegettion during revegettion. Weed Technology 21: Sheley, R.L., J. Jmes, B. Smith nd E. Vsquez Applying ecologiclly sed invsive plnt mngement. Rngelnd Ecology nd Mngement 63: Sheley, R.L., J. Mngold, K. Goodwin nd G. Mrks Revegettion guidelines for the Gret Bsin: Considering invsive weeds. Wshington, DC: US Deprtment of Agriculture, Agriculturl Reserch Service. Shinn, S.L. nd D.C. Thill Tolernce of severl perennil grsses to imzpic. Weed Technology 18: Smith, D.C., S.E. Meyer nd V.J. Anderson Fctors ffecting Bromus tectorum seed nk crryover in Western Uth. Rngelnd Ecology nd Mngement 61: Soil Survey Stff United Sttes Deprtment of Agriculture. Nturl Resouce Conservtion Service. We Soil Survey. wesoilsurvey.nrcs.usd.gov/ Tremly, A. nd J. Rnsijn LMERConvenienceFunctions: A suite of functions to ck-fit fixed effects nd forwrd-fit rndom effects, s well s other miscellneous functions. R pckge version 2.5. Vienn, Austri: R development Core Tem. Turnull, L., Crwley, M. nd M. Rees Are plnt popultions seed-limited? A review of seed sowing experiments. Oikos 88: Wrnes, G.R., B. Bolker, T. Lumley nd R.C. Johnson gmodels: Vrious R progrmming tools for model fitting. R pckge version Vienn, Austri: R development Core Tem. Western Regionl Climte Center Western U.S. Climte Historicl Summries. L. Noelle Orloff (corresponding uthor) Deprtment of Lnd Resources nd Environmentl Sciences, Montn Stte University, Bozemn, MT 59715, noelleorloff@gmil.com. Jne M. Mngold, Deprtment of Lnd Resources nd Environmentl Sciences, Montn Stte University, Bozemn, MT Fin D. Menlled, Deprtment of Lnd Resources nd Environmentl Sciences, Montn Stte University, Bozemn, MT Boutelou grcilis. USDA-NRCS PLANTS Dtse. Hitchcock, A.S Mnul of the grsses of the United Sttes. Wshington, DC: USDA Miscellneous Puliction No June 2015 ECOLOGICAL RESTORATION 33:2 155