Restoring wildfire to the Sierra Nevada: Impacts on water ... · Restoring wildfire to the Sierra...
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Restoring wildfire to the Sierra Nevada: Impacts on water resources and drought response
Gabrielle BoisramPostdoctoral Scholar, University of California, Berkeley
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OutlineFire in Western mountainsFire land cover water interactionsThe Illilouette Creek Basins unusual fire historyEffects of fire on the landscapeChanging streamflow and soil moistureMicroclimate effects of fireHydrological model resultsObserved forest health
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Fire in Western Mountain Watersheds Historically, fires were frequent, small, and mixed severity.
Suppression alters forests adapted to frequent fires and allows fuel build-up.
Adapted from S. L. Stephens, R. E. Martin, N. E. Clinton, Prehistoric fire area and emissions from California's forests, woodlands, shrublands, and grasslands. Forest Ecology Management 251, 205 (2007).
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100,000
200,000
300,000
400,000
500,000
pre 1800 1950-1999
hect
ares
bur
ned
per y
ear
Estimated Forested Area Burned
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Fire in Western Mountain Watersheds
Frequent, mixed severity fires, virtually no previous work.
Infrequent, large, severe fires, hydrology effects well studied.
Dense, homogeneous forest
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The Illilouette Basin Rare example of natural fire regime (suppression ended 1973).
Only one other similar site exists, and it lacks streamflow records.
Question: How have these fires affected streamflow, summer soil moisture, and response to drought?
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Fire + Plants + Water = ?
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Fire + Plants + Water = ?
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Fire + Plants + Water = ?
Precip.
TT
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Storage
Infil
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StorageP
P
Solar Rad.
Solar
Solar
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Jigsaw Puzzle of Fires
Map created by Kate Wilkin and Shane Fairchild
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Changes in Land Cover
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Changes in Land Cover
Conifer
Shrub
Sparse MeadowDense Meadow
1969 1987 1997 2005 2012
Year
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Are
a (k
m2
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Changes in Land Cover
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Seeing the Forest Without the Trees
Diverse post-fire vegetation and drought-resistant wetlands.
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Back to the hydrological questions
Precip.
TT
EE
Storage
Infil
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StorageP
P
Solar Rad.
Solar
Solar
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Runoff ratio (flow/precip.) changes before and after 1973:
Watershed Difference P-Value
Upper Merced
0.0% 0.65
MF Stanislaus
-6% 0.05
SF Stanislaus
-9% 0.06
ColeCreek
-12% 0.02
Source: Boisram et al. 2016. Managed wildfire effects on forest resilience and water in the Sierra Nevada. Ecosystems. DOI: 10.1007/s10021-016-0048-1
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Soil moisture measurements
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Soil Moisture and Land Cover
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Conifer ->SparseConifer ->Shrubs
Conifer ->Meadow Meadow
40%20%
5% 3%
Soil Water Content
5%Conifer
Veg. Map
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Modeled Soil Moisture
2015Change from 1970 to 2015
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Conifer to Conifer
Dense Meadow to Dense Meadow
Conifer to Dense Meadow
1970 VWC
2014
VW
C
Conifer to Conifer
Dense Meadow to
Dense Meadow
Conifer to Dense Meadow
1970 VWC
2014 VWC
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Microclimate Effects of Fire
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Microclimate Effects of Fire
Wat
er C
onte
nt
Date
Daily Mean 60cm Soil Moisture
Meadow
Shrub
Trees
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Microclimate Effects of Fire
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mm
of s
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Snow Depth from Time Lapse Cameras
Meadow
Shrub
Trees
Manual Surveys
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10/11/2015 11/30/2015 1/19/2016 3/9/2016 4/28/2016
Perc
ent S
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Microclimate Effects of Fire
MeadowShrub
Trees
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10/11/2015 11/30/2015 1/19/2016 3/9/2016 4/28/2016
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Temperature Difference Between Forest and Shrub Sites
Diff
eren
ce (
C)
Night (Warmer Under Trees) Day (Warmer in Burned Areas)
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RHESSys ModelRegional Hydro-Ecologic Simulation System
Tague and Band (2004)
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Mean Flow 890 mm/year
Mean Storage 1700 mm
Stre
am
flow
Cha
nge
(mm
/yea
r)
Soil W
ate
r Sto
rage
Cha
nge
(mm
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Differences in Water Balance When Fire Included in Model
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Differences in Water Balance When Fire Included in Model
Mean T 70 mm/year
Soil E
vap
ora
tion
Cha
nge
(mm
/yea
r)
Tra
nsp
iratio
n C
hang
e (m
m/y
ear)
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Differences in Water Balance
Mean CWD 170 mm/year
Water YearWater Year
Pea
k Sn
owp
ack
Cha
nge
(mm
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Clim
atic
Wat
er D
efic
it (C
WD
) Cha
nge
(mm
/yea
r)
Mean Peak SWE590 mm
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Spatially Variability Snow Changes
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Spatially Variability Snow Changes
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Spatially Variability Snow Changes
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Fire Impacts on Drought Mortality
USFS aerial surveys map tree mortality each summer.
Unusually high mortality in 2015 throughout Sierra Nevada.
http://www.sacbee.com/opinion/op-ed/soapbox/article75645627.html
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2014 mortality. Figure from: Boisram et al. 2016. Managed wildfire effects on forest resilience and water in the Sierra Nevada. Ecosystems. DOI: 10.1007/s10021-016-0048-1
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Impacts on Drought Mortality
2015 mortality. Figure from: Boisram et al. 2016. Managed wildfire effects on forest resilience and water in the Sierra Nevada. Ecosystems
A B
Control watersheds had up to 50 times more dead trees per forested acre in 2015.
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Conclusions
Landscape still in transition
Fire history and topography determine local response to fire
Overall, fire appears to be increasing discharge and soil moisture, and increasing drought resilience
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Conclusions
limited individual fire extent increased streamflow and
soil moisture a diverse landscape deeper, more persistent
snow low disease-related tree
mortality
This areas resistance to drought is demonstrated by
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Thank You
Thank you to Yosemite National Park for creating the amazing place that is the Illilouette Creek Basin, and allowing us to conduct research there.
This project was supported by the Philomathia Foundation and Joint Fire Sciences Program. Field and research assistants: Kate Wilkin, Miguel Naranjo, Andy Wong, Perth Silvers, Jeremy Balch, Seth
Bergeson, Amanda Atkinson, Tom Bruton, Diane Taylor, Madeleine Jensen, Isabel Schroeter, Katy Abbott, Bryce King, Zubair Dar, Katherine Eve, Sally McConchie, Karen Klonsky, Yves Boisrame, James Hart, Caroline Delaire, Louis Alexandre-Couston, Catherine Fong, Melissa Thaw, Anthony Everhart, Skye Niles, Lena Nitsan, Chris Phillips, Anthony Ambrose, Wendy Baxter, Chris Phillips, Lena Nitsan, Julia Cavalli, Melissa Ferriter, Ian McGregor, Kelly Archer, Shahad Jawad, Jingxuan Xiao, and Frank He.
Valuable guidance provided by Sally Thompson, Scott Stephens, Brandon Collins, Naomi Tague, and Maggi Kelly.
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Questions?
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Extra slides with more details
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Conifer(83 km2)
Shrub (10 km2)
Sparse (7 km2)
Dense Meadow (1 km2)
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3
94
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Conifer(62 km2)
Shrub (13 km2)
Sparse (23 km2)
Dense Meadow (2 km2)
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55
1.3.3
2
1969 2012
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Soil Moisture Measurements
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Soil Moisture Relation to Vegetation
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Soil Moisture and Fire History
0 1 2 3 40
10
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Times Burned
VWC
Dry Conifers, n=15,65,256,34,25
0 1 2 30
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Times Burned
VWC
Shrub, n=16,44,164,46,0
0 1 2 30
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Times Burned
VWC
Wetland, n=1,47,28,61,0
0 1 2 30
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Severity
VWC
Dry Conifers, n=15,64,166,150,0
0 2 3 40
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Severity
VWC
Shrub, n=16,0,30,72,152
0 2 3 40
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SeverityVW
C
Wetland, n=1,0,7,40,89
Dry Conifers Dry Conifers
ShrubsShrubs
Wetlands Wetlands
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Impacts on Drought Mortality: More DetailsWatershed Conifer
Area (km2)
Dead Trees 2014
Dead/km2 2014
Dead Trees 2015
Dead/km2 2015
Ratio 2014 Ratio 2015
ICB 80.6 325 4.0 1040 12.9 1 1MF Stanislaus
39.3 351 8.9 540 13.8 2.2 1.1
SF Stanislaus
71.7 11024 153.8 23352 325.8 38.1 25.2
Cole Creek
36.0 544 15.1 6294 174.6 3.7 13.5
Bridalveil 49.5 6094 123.0 33505 676.9 30.5 52.4Chilnualna 34.7 306 8.8 10579 304.8 2.2 23.6USF Merced
87.6 1787 20.4 5348 61.0 5.1 4.7
Restoring wildfire to the Sierra Nevada: Impacts on water resources and drought responseOutlineFire in Western Mountain WatershedsFire in Western Mountain WatershedsThe Illilouette BasinSlide Number 6Fire + Plants + Water = ?Fire + Plants + Water = ?Jigsaw Puzzle of FiresChanges in Land CoverSlide Number 11Changes in Land CoverChanges in Land CoverSeeing the Forest Without the TreesBack to the hydrological questionsSlide Number 16Soil moisture measurementsSlide Number 18Modeled Soil MoistureSlide Number 20Microclimate Effects of FireMicroclimate Effects of FireMicroclimate Effects of FireMicroclimate Effects of FireTemperature Difference Between Forest and Shrub SitesRHESSys ModelSlide Number 27Differences in Water Balance When Fire Included in ModelDifferences in Water BalanceSpatially Variability Snow ChangesSpatially Variability Snow ChangesSpatially Variability Snow ChangesFire Impacts on Drought MortalitySlide Number 34Impacts on Drought MortalityConclusionsConclusionsThank YouSlide Number 39Extra slides with more detailsSlide Number 41Soil Moisture MeasurementsSoil Moisture Relation to Vegetation Soil Moisture and Fire HistoryImpacts on Drought Mortality: More Details