RESPONSE OF VEGETATION AFTER WILDFIRE ON THE WARM SPRINGS NATURAL AREA IN MOAPA, NEVADA

Annual Meeting of the SER Southwest ChapterNovember 21, 2015

V on K. W in k el , P h .D.Dav id J . S y z d ekS outh er n N evad a W ater A uth or i ty

Warm Springs Natural Area

50 miles northeast of Las Vegas, Nevada

Warm Springs Natural Area

• 1220-acre nature preserve owned by the Southern Nevada Water Authority

• 28 sensitive species

• Annual rainfall 5.4 inches

• Elevation: 1689-1923 above sea level

• Five major spring complexes form the headwaters of the Muddy River

• Water emanates from 90⁰ F thermal springs

Wildfire at the Warm Springs Natural AreaWildfire at Warm Springs

History of Wildfires at Warm Springs

Pre-1987: Every ten years? More frequent in the last 100 years due to presence of man and palm trees.

1987: Several acres, several homes and other buildings destroyed.

1994: Several acres on the Moapa National Wildlife Refuge, Moapa dace impacted.

2004: Several acres, one home destroyed.

2008: 2.5 acres

2010: 601 acres, four homes, out buildings

2010 WildFire Facts

• Date of fire: July 1, 2010

• Source of fire: truck

• Acreage burned: 601

• Structures destroyed: Four homes and several outbuildings

By Land and By Air

2010 Wildfire601 Acres

Human Impacts

Biological Impacts

Apcar and Refuge Streams

Refuge Stream

Impacts to Sensitive Species

Moapa Dace – loss of habitat (stream-side vegetation). No noticeable reduction in population.

Southwestern willow flycatcher – loss of habitat (willow and ash), no reproduction 2010-2015.

Phainopepla – loss of habitat (mesquite).

Vermillion Flycatcher – loss of habitat (mesquite).

ObjectiveDetermine the response of native tree and shrub species to wildfire.

Methods

Sample Measurements and Analyses - Trees

• Photo of Von using hypsometer

• Randomly identified 100 burned trees each of Prosopis glandulosa var. torreyana, Fraxinus velutina, and Prosopis pubescens, and 29 burned Populus fremontii trees.

• Selection Criteria: (1) entire above-ground portion of tree killed by fire and (2) tree remains upright.

• Measured height (in feet) of burned tree and tallest re-sprout with Opti-Logic hypsometer. One foot was added to Prosopis glandulosaburned tree height due to reduction of tree height by fire.

• Significant differences between sample means were determined using 2-sample t-tests. Recovery time was determined with linear regression.

Sample Measurements and Analyses - Shrubs

• Randomly identified 100+ points in burned and unburned patches of Pluchea sericea and Lycium Andersonii.

• Measured plant height in inches at each point.

• Significant differences between sample means (burned vs. unburned) were determined using 2-sample t-tests.

Results

Trees

• Prosopis glandulosa var. torreyana

• Fraxinus velutina• Prosopis pubescens• Populus fremontii• Acacia greggii• Tamarix ramosissima• Washingtonia filifera

Pre-burn R

e-sprout

Mean15.3’(n=93)

Mean 12.4’(n=93)

Prosopis glandulosa var. torreyana

A

B

• Re-sprouting trees = 93%• Recovery time = 5.94 years (r2=0.94)

Pre-burn

Re-sprout

Mean23.0’(n=89)

Mean 12.6’(n=89)

A

B

Fraxinus velutina• Re-sprouting trees = 89%• Recovery time = 7.67 years (r2=0.78)

Fraxinus velutinaMultiple resprouts after fire

Ratio: resprouts to burned = 7.5:1 (n=25)

Prosopis pubescens

Pre-burn

Mean18.7’n=100

Re-sprouting trees = 2%

Mean20.5’n=2

Re-sprout

Pre-burn

A

Re-sprout

B

Mean49.8’(n=6)

Populus fremontii• Re-sprouting trees = 21.7%• Recovery time = 10.8 years (r2=0.82)

Mean19.7’(n=6)

Acacia greggii

Tamarix ramosisima

Washingtonia filifera

Shrubs

• Pluchea sericea

• Lycium andersonii

Lycium andersonii

Burned Unburned

Mean 42”

(n=100)

Mean 68.3”

(n=100)

B

A61% of unburned mean

Pluchea sericea

UnburnedBurned

AB

Mean 61.1”

(n=100

Mean 69.2”

(n=162)

Other Species

Sporobolis airoides Distichlis spicata

Wet Meadow Species

Anemopsis californica

Muhlenbergia asperifolia

Eleocharis spp.

Juncus spp.

2010

2015

2010

2015

2010

2015

Conclusions - Trees• Prosopis glandulosa var. torreyana: 93% of trees resprouted after fire and

could achieve pre-fire heights approximately 6 years after the fire.

• Fraxinus velutina: 89% of trees resprouted after fire and could achieve pre-fire heights approximately 8 years after the fire. New sprouts exceeded burned stems 7.5:1.

• Prosopis pubescens: This was the largest contiguous stand of this species in Nevada and hosted the largest breeding population of vermillion flycatchers in Nevada. Only 2% of these trees resprouted after fire, but resprouts grew quickly.

• Populus fremontii: 21% of trees resprouted after fire, resprouts grew quickly and could achieve pre-fire heights approximately 11 years after the fire.

Conclusions - Shrubs

• Lycium andersonii resprouts achieved 61% of non-burned plant height 5 years after the fire.

• Pluchea sericea resprouts had exceeded pre-fire heights after 5 years. Does fire enhance the growth of this species?

Tools• Be smart - Know how your plant species respond to fire.

• Be patient - Allow re-sprouting species time to recover after fire.

• Plant re-sprouting species in areas prone to fire (e.g., plant ash instead of cottonwood).

• Remove or maintain palm trees (i.e., remove dead fronds).

• Utilize firebreaks (maintain bare ground or low-growing grasses in fire break to prevent weed invasion and erosion without providing fuel). Warm Springs Natural Area maintains over 2 miles of fire breaks.

Acknowledgments

Marty Woods (USFS, photos)Crystal Shanley (SNWA, photos)

Questions?