Restoring wildfire to the Sierra Nevada: Impacts on water resources and drought response

Gabrielle BoisramPostdoctoral Scholar, University of California, Berkeley

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

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).

0

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

Fire in Western Mountain Watersheds

Frequent, mixed severity fires, virtually no previous work.

Infrequent, large, severe fires, hydrology effects well studied.

Dense, homogeneous forest

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?

Fire + Plants + Water = ?

6

Fire + Plants + Water = ?

Fire + Plants + Water = ?

Precip.

TT

EE

Storage

Infil

.

StorageP

P

Solar Rad.

Solar

Solar

Jigsaw Puzzle of Fires

Map created by Kate Wilkin and Shane Fairchild

Changes in Land Cover

Changes in Land Cover

Conifer

Shrub

Sparse MeadowDense Meadow

1969 1987 1997 2005 2012

Year

0

20

40

60

80

100

120

Are

a (k

m2

)

Changes in Land Cover

Seeing the Forest Without the Trees

Diverse post-fire vegetation and drought-resistant wetlands.

Back to the hydrological questions

Precip.

TT

EE

Storage

Infil

.

StorageP

P

Solar Rad.

Solar

Solar

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

Soil moisture measurements

Soil Moisture and Land Cover

18

Conifer ->SparseConifer ->Shrubs

Conifer ->Meadow Meadow

40%20%

5% 3%

Soil Water Content

5%Conifer

Veg. Map

Modeled Soil Moisture

2015Change from 1970 to 2015

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

Microclimate Effects of Fire

Microclimate Effects of Fire

Wat

er C

onte

nt

Date

Daily Mean 60cm Soil Moisture

Meadow

Shrub

Trees

Microclimate Effects of Fire

-500

0

500

1000

1500

2000

2500

3000

mm

of s

now

Snow Depth from Time Lapse Cameras

Meadow

Shrub

Trees

Manual Surveys

0

20

40

60

80

100

120

10/11/2015 11/30/2015 1/19/2016 3/9/2016 4/28/2016

Perc

ent S

now

Cov

erag

e

Microclimate Effects of Fire

MeadowShrub

Trees

0

20

40

60

80

100

120

10/11/2015 11/30/2015 1/19/2016 3/9/2016 4/28/20160

20

40

60

80

100

120

10/11/2015 11/30/2015 1/19/2016 3/9/2016 4/28/2016

Temperature Difference Between Forest and Shrub Sites

Diff

eren

ce (

C)

Night (Warmer Under Trees) Day (Warmer in Burned Areas)

RHESSys ModelRegional Hydro-Ecologic Simulation System

Tague and Band (2004)

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

)

Differences in Water Balance When Fire Included in Model

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)

Differences in Water Balance

Mean CWD 170 mm/year

Water YearWater Year

Pea

k Sn

owp

ack

Cha

nge

(mm

)

Clim

atic

Wat

er D

efic

it (C

WD

) Cha

nge

(mm

/yea

r)

Mean Peak SWE590 mm

Spatially Variability Snow Changes

Spatially Variability Snow Changes

Spatially Variability Snow Changes

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

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

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.

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

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

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.

Questions?

gboisrame@berkeley.edu

Extra slides with more details

Conifer(83 km2)

Shrub (10 km2)

Sparse (7 km2)

Dense Meadow (1 km2)

4

3

94

4

Conifer(62 km2)

Shrub (13 km2)

Sparse (23 km2)

Dense Meadow (2 km2)

.3

55

1.3.3

2

1969 2012

17

Soil Moisture Measurements

Soil Moisture Relation to Vegetation

Soil Moisture and Fire History

0 1 2 3 40

10

20

Times Burned

VWC

Dry Conifers, n=15,65,256,34,25

0 1 2 30

10

20

Times Burned

VWC

Shrub, n=16,44,164,46,0

0 1 2 30

20

40

60

Times Burned

VWC

Wetland, n=1,47,28,61,0

0 1 2 30

10

20

Severity

VWC

Dry Conifers, n=15,64,166,150,0

0 2 3 40

10

20

Severity

VWC

Shrub, n=16,0,30,72,152

0 2 3 40

20

40

60

SeverityVW

C

Wetland, n=1,0,7,40,89

Dry Conifers Dry Conifers

ShrubsShrubs

Wetlands Wetlands

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