Post on 05-Oct-2020
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?