Modeling Ecological and Economic Benefits of Post-Fire Revegetation

in the Great Basin

Becky Niell

Brief Ecological History of Sagebrush-Steppe

• Historically co-dominated by native bunchgrasses and sagebrush

• Cattle grazing (1850’s) decline of native bunchgrasses & increase in sagebrush

• Cheatgrass invasion (early 1900’s) increased fire frequency & changed successional patterns

• invasion of nonnative plant species• loss of native shrublands• increased fire frequency

• loss of native biodiversity• reduced forage for livestock• increased management costs• decreased water quality• reduced recreation values

Ramifications of Ecological Change

Aggressive management is needed ….

•Revegetation•Crested wheatgrass•Native seed

What to do……

Constrained by lack of information & high costs.

Need:“predictive models to forecast the potential effects of various management actions on resources”

“economic models that can put restoration costs and benefits into a framework that will support choosing among restoration alternatives as well as explaining benefits to the public and other constituents (BLM 2000).”

Markov chain model (quantitative, dynamic model)

State-and-transition model (conceptual model)

1. Predict long term vegetation change

2. Predict costs and benefits of revegetation strategies

2. Native Perennial Bunchgrass - Sagebrush

1. Native Perennial Bunchgrass Dominant

3. Sagebrush- Native Perennial Bunchgrass

4. Dense Sagebrush- Sparse Bunchgrass

Cheatgrass Understory

5. Dense Sagebrush w/ Cheatgrass Understory

6. Cheatgrass Dominant w/ Sagebrush

7. Cheatgrass w/ Sagebrush seedlings & rootsprouting shrubs

8. Cheatgrass Monoculture

10. Introduced Perennial Bunchgrass - Sagebrush

9. Introduced Perennial Bunchgrass Dominant

11. Sagebrush - Introduced Perennial Bunchgrass

Natural SuccessionFire EventFire Event with RevegetationState TransitionWyoming Big Sagebrush Vegetation in the Great Basin with

grazing and cheatgrass present. (8-10 inch precipitation zone)

Ranges are the highest and lowest estimates obtained from literature and expert opinion. Fire Frequency Average Fire Vegetation Type (i ) Vegetation Type

Parameter Frequency (years) of Fire Occurrence Following Fire ffire 1 25 - 100 1. Native perennial

bunchgrass dominant 1. Native perennial bunchgrass dominant

ffire 2 25 - 100 2. Native perennial bunchgrass - Sagebrush

1. Native perennial bunchgrass dominant

ffire 3 25 - 100 3. Sagebrush - Native perennial bunchgrass

1. Native perennial bunchgrass dominant

ffire 4 10 - 100 4. Dense sagebrush, sparse bunchgrasses, cheatgrass understory

7. Cheatgrass with shrub potential

ffire 5 2 - 15 5. Sagebrush dominant with cheatgrass understory

7. Cheatgrass with shrub potential

ffire 6 2 - 15 6. Cheatgrass dominant with sagebrush

7. Cheatgrass with shrub potential

ffire 7 2-15 7. Cheatgrass with shrub potential

8. Cheatgrass monoculture

ffire 8 2 - 15 8. Cheatgrass monoculture

8. Cheatgrass monoculture

ffire 9 40 - 100 9. Introduced perennial bunchgrass dominant

9. Introduced perennial bunchgrass dominant

ffire 10 40 - 100 10. Introduced perennial bunchgrass - sagebrush

9. Introduced perennial bunchgrass dominant

ffire 11 40 - 100 11. Sagebrush-introduced perennial bunchgrass

9. Introduced perennial bunchgrass dominant

represent the highest and lowest estimates obtained from literature and expert opinion. Average

Transition Transition pathwayParameter Time (years) from: to:

m 1,2 20 - 50 1. Native perennial bunchgrass dominant

2. Native perennial bunchgrass - Sagebrush

m 2,3 5 - 50 2. Native perennial bunchgrass - Sagebrush

3. Sagebrush - Native perennial bunchgrass

m 3,4 10 - 100 3. Sagebrush - Native perennial bunchgrass

4. Dense sagebrush, sparse bunchgrasses, cheatgrass understory

m 4,5 10 - 40 4. Dense sagebrush, sparse bunchgrasses, cheatgrass understory

5. Sagebrush dominant with cheatgrass understory

m 6,5 40 - 60 6. Cheatgrass dominant with sagebrush

5. Sagebrush dominant with cheatgrass understory

m 7,6 10 - 25 7. Cheatgrass with shrub potential

6. Cheatgrass dominant with sagebrush

m 9,10 20 - 30 9. Introduced perennial bunchgrass dominant

10. Introduced perennial bunchgrass - sagebrush

m 10,11 20 - 40 10. Introduced perennial bunchgrass - sagebrush

11. Sagebrush-introduced perennial bunchgrass

Average Transition Times Between Vegetation Types

Average Fire Frequencies

Markov Chain Model

K Successional states (chain states)Probability of moving from state i to state j in a given time period

(K x K) Transition matrix

(1xK) is allocation of the landscape across K successional states

Simulate vegetation change by:

150 year simulation of Cheatgrass Monoculture:

31 - 41%25%

35 - 51%

40 - 69% 78 - 89%

w/ revegetation

no revegetation

t = 0 t = 20 t = 150

No reveg.

Reveg.

Immediate Action Needed!!

Without revegetation:

Revegetation is not cheap: $25-100+ /acre (1.7 million acres burned in 1999)

40 – 69% of the landscape cheatgrass monoculture or worse in 20 years.

1/20 to 1/3 of landscape burning every year…

Costs….

So… What are economic and ecological

trade-offs of different post-fire revegetation strategies?

• Reducing cheatgrass monoculture• Maintaining native vegetation• Minimizing management costs

50 YEAR RESULTS:

0

10

20

30

40

50

60

70

80

NoRevegetation

Native SeedMix

CrestedWheatgrass

% o

f la

ndsc

ape

in y

ear

50

Area of Cheatgrass Monoculture (% of landscape)

Goal 1. Reduce Area of Cheatgrass Monoculture:

•No revegetation (71%)•Native seed (42%) *•CWG (42%) *

0

5

10

15

20

25

30

35

40

45

NoRevegetation

Native SeedMix

CrestedWheatgrass

% o

f La

ndsc

ape

in y

ear

50

Area of Native Vegetation (% of landscape)

Goal 2. Increase Area of Native Vegetation:

•No revegetation (10%)•Native seed (42%) *•CWG (10%)

Goal 3. MinimizeManagement Costs:

•No revegetation ($7.83/ac)•Native seed ($6.64/ac)•CWG ($6.00/ac) *

0

100

200

300

400

500

600

700

800

900

NoRevegetation

Native SeedMix

CrestedWheatgrass

Ave

rage

Ann

ual C

ost

($ /

100

acr

es)

Average Management Costs ($ / 100 ac.)

•Management costs = fire suppression costs + reveg. costs

Revegetation can cost 1.9 times more per acre than fire suppression and still cost less than no

revegetation in the long run!!

1) No revegetation Ecological and economic disaster

2) Post-fire revegetation was more effective than no revegetation for:

• achieving ecosystem objectives• reducing costs

3) The appropriate choice of seed mix depends on the prioritization of management objectives

• native seed costs more than crested wheatgrass seed• native seed was equally or more effective for achieving each ecosystem goal

4) Post-fire revegetation is not sufficient!

Conclusions:

Questions??