increasing native

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Society for Range Management

Increasing Native Diversity of Cheatgrass-Dominated Rangeland through Assisted SuccessionAuthor(s): Robert D. Cox and Val Jo AndersonSource: Journal of Range Management, Vol. 57, No. 2 (Mar., 2004), pp. 203-210Published by: Allen Press and Society for Range ManagementStable URL: http://www.jstor.org/stable/4003920 .Accessed: 12/11/2013 07:28

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Methods

Site descriptionThe areas used in this study were on and

adjacent to the U.S. Army DugwayProving Ground (DPG), Tooele County,Utah. Due to an earlier fire, the studyareas were without native vegetation.Some areas were within the boundaries f

DPG (400 15'35 N 112? 49' 20 W; ele-vation = 1,600 m and 40? 12' 40 N 112047' 45 W; elevation = 1,446 m) and weredominated y a host of exotic annuals, pri-marily cheatgrass. The other areas wereimmediately adjacent to DPG on landadministered by the U.S. Department ofInterior Bureau of Land Management(BLM) (400 18' 36 N 1120 51' 20W; ele-vation = 1,550m) and were seeded withcrested wheatgrass after the last fire. Thesoils in all areas are Medburn coarse-loamy, mixed (calcareous), mesic, XericTorriorthents. Native vegetation at the

sites is considered to be Wyoming bigsagebrush (Artemisia tridentata Var.wyomingensis [Beetle & A. Young]Welsh), Indian ricegrass (Stipahymenoides R. & S.), bottlebrush squir-reltail, and bluebunch wheatgrass Elymusspicatus [Pursh] Gould) (Trickler et al.2000). The 36-year average precipitationfor the general area s 174 mm, occurringmostly in winter and spring (NOAA1999).

The experimental design was a split-block, with treatments randomized instrips across he replications. Three, 40-by

40-m replicate blocks were created eachyear for 2 years in a crested wheatgrassmonoculture nd in a cheatgrass-dominat-ed annual community. Seedbed prepara-tion treatments were randomly applied n10-m strips across the blocks, and seedingmethod reatments were randomly appliedperpendicular o the seedbed treatments.As a result, each 40-by 40-m replicateblock contained 16, 10-by 10-m experi-mental units of different eedbed prepara-tion and seeding method combinations.

Species seededA mixture of 8 species (3 shrubs and 5

grasses) native to the local area was seed-ed. Species and their seeding rates areshown in Table 1. Seeds were purchasedfrom Granite Seed Co., Lehi, Utah.

Seedbed preparationSeedbed preparation echniques nclud-

ed: tilling, harrowing, praying a chemicalherbicide, glyphosate (Roundup? superconcentrate weed and grass killer, N-

[phosphonomethyl] lycine), and a controltreatment of no seedbed preparation.Seedbeds were prepared n early February1998 and 1999. Tilling with a 162-cmwide Rotovator completely removed allexisting vegetation, mixed the soil to adepth of about 18 cm, and provided asmooth soil surface. Harrowing with a

200-cm wide field harrow resulted in avery rough soil surface, with moderatevegetation emoval. Glyphosate pplied asa broadcast pray at 1.26 kg a.i. ha-' in atotal volume of 358 liters ha-' from a 1-mboom installed on the rear of a 4-wheelall-terrain ehicle resulted n little soil dis-turbance, nd left dead vegetation as litteron the soil surface.

Seeding methodThe seeding methods investigated

included: drilling, broadcasting, roadcast-ing followed by covering he seeds, plus acontrol (no seed). Seed was sown in lateafternoons in mid-March each year.Drilling was done in 1988 with a JohnDeere Flex Drill and n 1999 with a TruaxFLXII-812 rangeland drill. Both drillswere calibrated y raising he openers andmanually urning he wheels. Openers on40-cm centers were set to place the seedabout 1 cm deep. As neither agebrush orrabbitbrush seed would pass reliablythrough he seed drills, they were broad-cast instead of drilled nto the appropriateexperimental nits. Broadcasting was done

by hand, taking care to provide completeand even coverage of the experimentalplots. The broadcast-cover method wasaccomplished y broadcasting ll the seedas described above, then pulling a railroadtie across he plot with a tractor.

Data collection and analysisData were collected n July of each sam-

pling year (1998, 1999, and 2000), using a200-by 30-cm rectangular quadrat, ran-domly placed 12 times in each experimen-

tal unit. Within his quadrat, ercent overwas visually estimated using cover classesfor crested wheatgrass and cheatgrass.Species presence was noted, and for seed-ed species, the number of seedlings pre-sent within the quadrat was recorded.Emergence data were collected the sum-mer after seeding, in July of 1998 and

1999. Establishment data were collectedthe following years. For data analysis andinterpretation, the seeded species wereplaced into 3 groups: native grasses,Wyoming big sagebrush and rubber rab-bitbrush (Chrysothamnus nauseosus[Pallas] Britt.), and fourwing saltbush(Atriplex canescens [Pursh] Nutt.). TheMixed Models analysis in SAS (SASInstitute 1996) was used to determinetreatment effects and interactions. Theanalysis factors in the design were site(crested wheatgrass vs. cheatgrass),seedbed preparation echnique (till, har-row, glyphosate, no treatment), seedingtreatment drill, broadcast, broadcast pluscovering, no seed), and year of seeding(1998 vs. 1999). These factors and theirinteractions were considered ixed in themixed models analysis. Factors onsideredrandom were replications nd interactionsof replications with other factors.Significant differences were accepted atthe a = 0.05 level.

Results

PrecipitationPrecipitation was very different n the 2

seeding years of this study (Fig. 1). In1998, February nd March received aboveaverage precipitation, while April andMay received only average or below aver-age precipitation. n 1999, however, theopposite occurred: February and Marchprecipitation was below average, whileApril, May, and June precipitation wasabove average.

Table 1. Native plant species and rate seeded in kg ha pure live seed, Toole Co, Utah-1998 and1999.

Species Rate, Pure Live Seed

Wyoming big sagebrush Artemisia ridentata var wyomingensis (kg/ha)[Beetle & A. Young] Welsh) 0.3

Four-wing saltbush Atriplex anescens [Pursh] Nutt.) 2.5Rubber rabbitbrush Chrysothamnus auseosus [Pallas] Britt.) 0.2Bluebunch wheatgrass Elymus spicatus [Pursh] Gould) 1.7Galleta (Hilariajamesii [Torr.] Benth.) 1.2

Needle and thread grass (Stipa comata Trin.& Rupr.) 1.1Sandberg bluegrass Poa secunda Presl) 1.1Squirreltail Elymus elymoides [Raf.] Swezey) 1.1

204 JOURNAL OF RANGE MANAGEMENT 57(2) March 2004

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?70-E60r 50 T-:::11998

~~~40 ~ ~ ~ ~ ~ ~ ~ ~ ~ ~~1999|20 * 36-yr_mean

Month

Fig. 1. Precipitation n 1998 and 1999 and 36-year average precipitation by month for Dugway Proving Grounds, Tooele Co., Utah.

Native grass emergenceWhen the emergence of native grassseedlings was compared cross the 4 vari-ables of year, site, seedbed preparation,and seeding treatment, wo 3-way interac-tions occurred. A year by site by seedingmethod nteraction Fig. 2) indicated hatthe site effect was different n 1998 thanin 1999, and that within each year, emer-gence did not respond o seeding methodsin exactly the same way between sites. In1998, seeding into crested wheatgrassresulted in significantly greater nativegrass seedling densities than did seedinginto cheatgrass across all seeding tech-

niques. In 1999, the grass emergence wassimilar within all seeding treatments nde-pendent of seeding echnique.

The year by site by seedbed preparationinteraction showed a similar response(data not shown). In 1998, all seedbedpreparation reatments ielded nearly 100percent more seedlings m 2 in crestedwheatgrass than in cheatgrass. In 1999,however, the site effect was negligible. Inboth crested wheatgrass nd cheatgrass, lltreatments resulted in fewer than 4seedlings m2.

Artemisia ridentata andChrysothamnus auseosus emer-gence

Sagebrush and rabbitbrush mergencealso displayed two, 3-way interactionswhen year, site, seedbed preparation ndseeding method were considered. n a siteby seedbed preparation y seeding methodinteraction Fig. 3), emergence was greateron the crested wheatgrass site than thecheatgrass site except in site preparationcontrol plots. Seedling emergence variedby site preparation nd seeding techniquein crested wheatgrass, but neither had aneffect in cheatgrass. n crested wheatgrass,

87

E6 UDrill05-

T O~~~~~~~~~~UBroadcasta 4 --_ . . ...

EBroadcast + Cover

_Control

1 Si

01998 | 1999 | 1998 | 1999l

Crested wheatgrass Cheatgrass

Fig. 2. Means and standard errors for native grass emergence at Dugway Proving Grounds, Tooele Co., Utah, as affected by year, site, andseeding method (P = 0.04). Data collected July 1998 and 1999.

JOURNAL OF RANGE MANAGEMENT 57(2) March 2004 205



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E.5 iL Drill2- N~~~~~~~~~~~UBroadcast

.~1.5-T* Broadcast + Cover

00.5 0D A DControl

Crested wheatgrass Cheatgrass

Fig. 3. Means and standard errors for Artemisia ridentata nd Chrysothamnus auseosus emergence at Dugway Proving Grounds, Tooele Co.,Utah, as affected by seeding method, site, and seedbed preparation P = 0.04). Data collected July 1998 and 1999.

tilling the seedbed provided the greatestdensity of seedlings across all seedingtechniques. However, even a lower densi-ty of emergence 0.6 plants m-2with her-bicide application ollowed by broadcastand cover - would be an acceptable densi-ty if these shrubs established. Drill seed-ing in crested wheatgrass resulted in atleast 50% more emergence han any otherseeding technique. Broadcast nd cover incrested wheatgrass esulted n at least 46%more sagebrush nd rabbitbrush eedlingsthan simply broadcasting lone.

An interaction f year by site by seedingmethod not shown) exhibited a site effect

in 1998 and none in 1999. In 1998, thecheatgrass site showed little or no emer-gence across all seeding ypes. The crestedwheatgrass ite, however, had densities ofup to 2 seedlings m2. In 1999, no seedingmethod esulted n more than 0.2 seedlingsm-2 in either crested wheatgrass or cheat-grass.

Atriplex canescens emergenceAnalysis of the fourwing saltbush data

revealed a 2-way and a 3-way interaction.The 3-way interaction was of site, seedbedpreparation, nd seeding method (Fig. 4).

Seedling emergence was much greater on

the crested wheatgrass site, especiallywithin the tilling treatment, elative o thecheatgrass ite. In the crested wheatgrass,combinations hat included the till treat-ment provided at least 73% moreseedlings m-2 than combinations thatincluded other seedbed preparation ech-niques. In addition, the drill-seedingmethod provided greater han 30% moreseedlings m-2 han other seeding methodcombinations. In the cheatgrass site, allcombinations of seeding method andseedbed preparation produced less than0.4 seedlings m-2.The 2-way interaction(not shown) was year by seedbed prepara-

2 _E 1.5 I Drill

U Broadcast

X~ O Broadcast + CoverX.5 fJ1 ontrol C

l j ~Crested wheatgrass Cheatgrassl

Fig. 4. Means and standard errors for Atriplex canescens emergence at Dugway Proving Grounds, Tooele Co., Utah, as affected by seedingmethod, site, and seedbed preparation P = 0.01). Data collected July 1998 and 1999.




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1412 -

10,o*8Drill8- ~~~~~~~~~~~~~EBroadcast

| 68 1-

nEBroadcast CoverIL4 A- 1Control2TT0

|Till Harrow| pray |Control Till |Harrow| Spray |Controll1998 1999

Fig. 5. Means and standard errors for native grass establishment n crested wheatgrass at Dugway Proving Grounds, Tooele Co., Utah, asaffected by seeding method, year, and seedbed preparation P = 0.02). Data collected July 1998 and 1999.

tion technique. In 1998, tilling provided69% more emerged eedlings m-2 han har-rowing and 34% more than glyphosateapplication. n 1999, tilling yielded greaterthan 80% more seedlings m-2 han eitherharrowing r spraying.

Establishment of native grassseedlings

Each plot was reexamined n July of thesecond growing season to investigate heestablishment of seeded species. Theestablishment f native grasses displayed

a 4-way interaction (site by year byseedbed preparation y seeding method)

in this analysis. The interaction ssociatedwith site was simply no response survivalof previous year's emerged seedlings) incheatgrass across all treatment ombina-tions and levels vs. a varied response incrested wheatgrass. In crested wheatgrass(Fig. 5), establishment was generallymuch greater rom the 1998 planting hanthat of 1999. The exception to that was asimilar response in both years to the tilland drill and harrow and drill combina-tions, which produced similar results forboth years. Establishment rom 1998 drillor broadcast and cover seeding methodswas relatively similar across all land

preparation echniques. However, estab-lishment from 1999 was significantlystronger with drilling.

Establishment of Artemisia tridenta-ta and Chrysothamnus auseosus

The establishment f sagebrush nd rab-bitbrush lso displayed a 4-way interactionof site by year by seedbed preparation yseeding method. Again, the interactionassociated with site was simply noresponse (survival of previous year'semerged seedlings) n any treatment om-

binations or levels in cheatgrass. In crest-ed wheatgrass (Fig. 6), establishment of

6

_______ _______ _______ _______ _______ _____ UDrillE UBroadcast$3- UBroadcast Cover

2 - o Control

0Till Harrow Spray Control Till Harrow Spray Control

1998 1999

Fig. 6. Means and standard errors for Artemisia tridentata and Chrysothamnus nauseosus establishment in crested wheatgrass at DugwayProving Grounds, Tooele Co., Utah, as affected by seeding method, year, and seedbed preparation (P < 0.01). Data collected July 1998 and1999.




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when crested wheatgrass was sprayed n1998, but low emergence with the sametreatment n 1999. Cheatgrass over (datanot shown) was not affected ignificantly yany seedbed reparation reatments.

Discussion

This study llustrates way in which the3 basic components of succession (siteavailability, species availability, andspecies performance) may be manipulatedto influence he outcome of succession. Byusing crested wheatgrass to capture asite from cheatgrass, iche availability ndspecies performance or native seedlingsmay be enhanced, as evidenced byincreased mergence and establishment nthese areas. Seedbed perturbations canalso increase niche availability nd speciesperformance. Species availability wasincreased by seeding desirable species.

Different eeding methods esulted n vari-ous levels of success.Difficulty in establishing native species

in areas dominated by weedy annuals,including cheatgrass, s well documented(Pellant 1990, Allen 1995, Tausch et al.1995). Cheatgrass nhibits the establish-ment of native species in 2 ways. First,because cheatgrass can germinate at lowtemperatures, t can germinate n autumnor spring, fully using winter and earlyspring moisture (Beckstead et al. 1995)and expanding root length and biomassfaster than native species can at low tem-

peratures Harris 1967, Harris and Goebel1976, Aguirre and Johnson 1991). In theseconditions, cheatgrass may deplete soilwater and competitively exclude nativespecies. Second, cheatgrass-facilitatedincreases n fire frequency Houston 1973,Whisenant 990) may eliminate any nativeseedlings that do emerge. Because of thedouble eopardy of competition nd fire, itis extremely difficult to establish nativespecies in cheatgrass-dominated reas.

Site captureCrested wheatgrass is established on

more than 4 million ha of rangeland inwestern North America (Caldwell et al.1981, Rogler and Lorenz 1983, Bakker etal. 1997). In the Great Basin t is relativelyresistant to wildfire, aggressive in theseedling stage and has been shown to beeffective at capturing ites from cheatgrassand other annual species (D'antonio andVitousek 1992). It has persisted n stablemonocultures or over 40 years (Trlica andBiondini 1990). In the Great Basin, cap-turing a site from cheatgrass domination

through stablishment f a perennial uchas crested wheatgrass hanges plant com-munity structure and function. Fire fre-quency s reduced and resource allocationpattems shift to resemble those of a pre-disturbance community. Niches formedby perturbations n a crested wheatgrassmonoculture may remain open and beeffective for establishing native species,whereas niches formed in cheatgrassstands are often rapidly reinvaded. Thisapproach of assisted succession showspromise in restoring native species todegraded reas of the shrub-steppe egionsof the Great Basin.

Effects of precipitation and use ofsoil water

Differing precipitation atterns betweenthe 2 years may help explain the differ-ence in emergence of native speciesbetween the 2 sites. More seedlingsemerged on the crested wheatgrass ite in1998 than n 1999, while more emerged n1999 than 1998 on the cheatgrass ite. In1998, above-average precipitation inFebruary nd March may have facilitatedgermination nd emergence of the nativeseedlings. After the period of above-aver-age precipitation, verage or below aver-age precipitation n April and May accen-tuated competition or water n the cheat-grass areas.

Precipitation n February nd March of1999 was approximately 0% of average.This lack of precipitation could haveseverely reduced both germination andemergence of grasses. After this low-moisture period, 3 consecutive monthswith above-average recipitation rovideda flush of moisture hat may have amelio-rated the competition for water in thecheatgrass area, allowing a greater per-centage of germinated seedlings toemerge.

Although quite variable, greater emer-gence and establishment of nativeseedlings occurred on crested wheatgrassareas compared with areas dominated bycheatgrass nd other annuals. By capturingthe site with an aggressive perennial uchas crested wheatgrass, he effects of envi-ronmental variations, such as the timingand amounts f precipitation, may be ame-liorated or smoothed, so that nativespecies have a greater hance of survivingto establishment.

Seedbed preparation and seedingmethod

Once the site is captured by crestedwheatgrass, niche-opening disturbancesmust be used to open niches and allow

establishment of native species. In thisstudy, almost no seedlings emerged orestablished n experimental units withoutdisruption of the monoculture, whethercrested wheatgrass r cheatgrass. When adisruption, uch as tilling, harrowing, orspraying of glyphosate, occurred, nativespecies generally established in crestedwheatgrass but not in cheatgrass. It wasimportant hat seedbed perturbations othremove existing vegetation and prepare nadequate eedbed for the seeded species.In this study, glyphosate was less effectivein the second year likely as a result ofunfavorable growing conditions duringapplication, which did not allow fulltranslocation f the herbicide.

Although recovery of crested wheat-grass cover must be expected, openingscaused by disruptions persisted longenough for the native species to establish.Even the most severe disruptions wereinsufficient o allow a window of opportu-nity for establishment f native species inthe annual-dominated reas.

Certain ombinations f seedbed prepa-ration techniques and seeding methodsmay be particularly ffective in openingniches and allowing native seedlings toestablish in crested wheatgrass. Tillingwas especially effective, because it com-pletely removed all existing plant competi-tion and prepared very uniform eedbedinto which the seeds were placed.Application of an herbicide proved effec-tive at reducing competition, as it has inprevious studies (Nelson et al. 1970), animportant ind, given the scale and sitecharacteristics here restoration s needed.Tilling may often be limited by terrain orarea size; in that case glyphosate may beapplied from the ground or from the air,which would be less costly than tillage,especially for large areas in need ofrestoration.

Seeding methods ollowed a similar pat-tem. Drilling s generally ecognized as aneffective way to seed rangelands Nelsonet al. 1970, Haferkamp t al. 1987, Winkelet al. 1991) and was most consistently uc-cessful in this study. Drilling, however,can be impractical ver rough terrain andis limited by area. With this in mind,broadcasting may be as effective asdrilling in certain conditions, especiallywhen the seed is covered (Winkel et al.1991, Roundy t al. 1993).

Recommendations

The long-term performance nd persis-tence of seeded species, as well as the




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recovery of cheatgrass nd crested wheat-grass populations, hould be evaluated nthe future. This study suggests a 2-stepapproach to restoring native diversitythrough using a model of assisted ucces-sion, in sagebrush teppe areas currentlydominated by cheatgrass. The first step isto convert a site from annual- o perennial-domination. Former sagebrush-steppeareas, now dominated by cheatgrass orother weedy annuals, xperience a shift infire frequency rom 30-70 years to a fre-quency of every few years. Any nativespecies that survive competitively n suchareas are likely to be bumed out within afew years. An overall effect of invasiveannual species is to arrest econdary uc-cession of these sites at an annual stage;succession does not continue o the long-lived, fire-intolerant native species.Crested wheatgrass or other aggressiveperennial plants may be used to replacecheatgrass, hereby assisting succession oa perennial-dominated ystem. Many areasof the Great Basin have already been seed-ed to crested wheatgrass or other stablemonocultures nd are primed or the sec-ond step.

The second step in this process is toinsert native species nto the stable perenni-al matrix. Combinations of selectedseedbed preparation echniques nd seedingmethods may be used to insert the nativespecies into the stable matrix. Crestedwheatgrass s not expected o be eliminatedwith such a strategy, but the diversity,structure nd function of the resulting om-munity will be more similar o those of theoriginal, native community. n many cases,application f glyphosate may be as effec-tive as more abor and cash-intensive illingor harrowing. Broadcasting he seed, thencovering t by dragging, was intermediateto drilling; and simple broadcasting mayprove a worthy compromise n manage-ment applications.

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