Restoring Native Plants to Crested

Wheatgrass Stands in Eastern Oregon

Jane Mangold and Valerie FanslerMontana State University, Bozeman, MT

Pike San Isabel National Forest, Colorado Springs, CO

Crested Wheatgrass

• Introduced to North America in 1898

– Used to

• Stabilize soils

• Livestock forage

• Prevent weed invasion

• Reduce wildfire hazard

• Occupies more than 5 million

hectares in western U.S.

(Pellant and Lysne 2005)

Crested Wheatgrass Legacy

• Dominates seed bank and limits growth of native

species

• Native species recruitment unlikely

• To re-establish diversity:

– Suppression of crested wheatgrass plants and

propagules

– Deliberate introduction of desired species

(Marlette and Anderson 1986, Bakker et al. 1997, Cox

and Anderson 2004, Henderson and Naeth 2005)

Benefits of Restoring Natives

• Improves resource capture and cycling

• Increases resilience and resistance to

disturbance

• Improves wildlife habitat (esp. sagebrush

obligate species)

(USDI USFWS 2001, Kinzig et al. 2002,

USDI BLM 2005, USDA USFS 2008)

Objective

• Test various strategies for restoring native

plant species to crested wheatgrass-

dominated rangeland

Hypotheses

• Suppression treatments would decrease

crested wheatgrass density and cover

• Suppression treatment and revegetation

would interact to increase native species

density

Study Site

• 80 km south of Burns, OR

• Malheur National Wildlife Refuge

Burns

X

6/29/06

6/23/05

• Seeded to crested

wheatgrass in 1981 following wildfire

Crested Wheatgrass

Suppression Treatments

• Mechanical

– One pass with disk (1M)

– Two passes with disk (2M)

• Herbicide (glyphosate)

– Low rate (LH)

• 0.25X recommended rate

– High rate (HH)

• 1.0X recommended rate

• Undisturbed (UD)

• Mechanical

-17 Oct. 2005 (Trial 1)-15 May 2006 (Trial 2)

• Herbicide -12 July 2005 (Trial 1)

- 5 May 2006 (Trial 2)

Revegetation Treatments

• Seeded

• Non-seeded

• Truax™ Rough Rider no-till drill

• Cool season and fluffy seed boxes • 31 Oct. – 1 Nov. 2005 (Trial 1)

• 30-31 Oct. 2006 (Trial 2)

Native Seed Mix

• 4 grasses– bluebunch wheatgrass (L)

– Sandberg’s bluegrass (S)

– Indian ricegrass (L)

– Squirreltail (L)

• 3 forbs– western yarrow (S)

– Lewis flax (L)

– Munro globemallow (L)

• 3 shrubs– Wyoming big sagebrush (S)

– four-wing saltbush (L)

– white-stemmed rabbitbrush (S)

Experimental Design

• Randomized block, split-split-plot

• Whole-plot = suppression treatment (30m

x 140m)

• Split-plot = seeding treatment (30m x 70m)

• Split-split-plot = year (2 trials)

• 5 replications

Sampling

• Density and canopy cover

– Crested wheatgrass

– Other perennial species

– Cheatgrass

• Density

– Seeded species

• 50, 0.25m2 frames/plot

• Trial 1

– 2006-2008

• Trial 2

– 2007-2008

Data Analysis

• Mixed effect split-split plot analysis

– Fixed effects = suppression treatment,

seeding treatment, year

– Random effects = block

• Means separated using Tukey’s Honestly

Significant Difference (HSD)

(Ramsey and Schafer 2002)

Treatment

HH 2M LH 1M UD

cre

ste

d w

he

atg

ras

s d

en

sit

y (

pla

nts

/m2)

0

2

4

6

8

10

12

14

16

18

2006

2007

2008

a

bb a

b

c

a

a aa

bb

a aa

X

Y

X X XX

Z

XY

Y

X

XY

Z

XY

Y

X

Treatment x Year Effect on

Crested Wheatgrass Density -Trial 1

HH = high rate herbicide

2M = mechanical, 2 passes LH = low rate herbicide

1M = mechanical,1 pass UD = undisturbed

HSDa = 1.1

HSDb = 1.5p < 0.01

Treatment

cre

ste

d w

heatg

rass d

en

sit

y (

pla

nts

/m2)

0

2

4

6

8

10

12

14

HH 2M LH 1M UD

a

bc

ab

d

cd

Treatment Effect on

Crested Wheatgrass Density -Trial 2

HSD = 1.7

p = 0.01

HH = high rate herbicide

2M = mechanical, 2 passes LH = low rate herbicide

1M = mechanical,1 pass UD = undisturbed

Treatment

HH 2M LH 1M UD

cre

ste

d w

heatg

rass c

over

(%)

0

5

10

15

20

25 2006

2007

2008

b

a

a

a

b

c

b

a

ab

a a

b

a

a

Y

X

XY

X

XY

Y

Z

YZ

XY Y

X X

Z

Z

Y

Treatment x Year Effect on

Crested Wheatgrass Cover-Trial 1

HSDa = 2.1

HSDb = 2.8p < 0.01

HH = high rate herbicide

2M = mechanical, 2 passes LH = low rate herbicide

1M = mechanical,1 pass UD = undisturbed

Treatment

HH 2M LH 1M UD

seed

ed

sp

ecie

s d

en

sit

y (

pla

nts

/m2)

0

10

20

30

40

50

2006

2007

2008

c

b

a

c

b

a

c

b

a

c

b

a

b b

a

X

X

X

Z

X

X

X

X

X

Y

X

X

X X

X

Treatment x Year Effect on

Seeded Species Density – Trial 1

HSDa = 4.9

HSDb = 5.0p < 0.01

HH = high rate herbicide

2M = mechanical, 2 passes LH = low rate herbicide

1M = mechanical,1 pass UD = undisturbed

Year

seed

ed

sp

ecie

s d

en

sit

y (

pla

nts

/m2)

0

5

10

15

20

25

30

2007 2008

a

b

Year Effect on Seeded Species Density

– Trial 2

HSD = 1.7p < 0.01

Conclusions—Eastern Oregon

• Suppression treatments not effective

• Mechanical suppression treatments increased

crested wheatgrass

• Seeded species

– High initial establishment in spite of poor

suppression

– Decreased over time

Implications

• Successive suppression treatments prior to

seeding natives

• Subsequent management to favor persistence of

native species

Acknowledgements

• USDA-Agricultural Research Service/EOARC

• USDA-FS-Rocky Mountain Research Station

• USFWS-Malheur National Wildlife Refuge

• USDA-NRCS

• Jim Truax

• GBNPSIP

• Colleagues in Idaho, Nevada, and Utah

Questions