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Sudden Oak Death and
Fire in Big Sur
Kerri Frangioso
UC Davis
Causal agent:
Phytophthora ramorum
Bay laurel
Umbellularia californica
Weather
Both mating types
and a separate
lineage of
Phytophthora
ramorum have
been found in
stream water in the
high elevation
(5000’+) mountains
of Vietnam
R.Cobb
Big Sur
Humboldt
www.suddenoakdeath.org
M. Kelly, UC-Berkeley
Big Sur
Ecological Monitoring
Plot Network
•153 of the 280 plots tested culture positive for P. ramorum
•Numerous plots with 100% infection of tanoak and a few of coast live oak
•Variable levels of mortality in different size classes
•3 times the amount of tanoak coarse woody debris and 1.4 times for host oak species
•Stands with more sporulating hosts were more likely to have the disease.
•Larger tanoaks are dying faster
Basin Complex Fire 2008
Basin Fire 2008
~95,000 ha
Interacting disturbances
Fire Phytophthora
ramorum
Fuel loads
Community structure
Pathogen survival
Inoculum pressure
Post-Burn Survey
2006
2008
Sudden Oak Death
progression
Burn severity was related to the stage of disease
progression and differences in fuels associated
with each stage.
Redwood mortality is size-dependent, with
unexpected increases due to SOD
Synergistic effects of both disturbances on redwood
were unexpected, and were not observed in other
SOD-resistant species, like bay laurel. Metz et al, 2013
N %
N %
BurnedUnburned
0.0
0.2
0.4
0.6
0.8
1.0
1.2
Invaded Uninvaded
C %
C %
05
10
15
20
Invaded Uninvaded
Ols
en P
O4-P
mg/g
Ols
en P
O4-P
mg/g
010
20
30
40
50
60
70
80
Invaded Uninvaded
pH
pH
5.5
6.0
6.5
7.0
7.5
Invaded Uninvaded
Wildfire and Disease
Interact Leading to
Greater Loss of Soil
Nutrients and Carbon
• Both Nitrogen and
Carbon were
reduced in the
burned area.
• Burn severity was
positively
correlated with
nutrient loss
Cobb et al, 2016
Interacting disturbances
Fire Phytophthora
ramorum
Fuel loads
Community structure
Pathogen survival
Inoculum pressure
Pathogen survival
post fire
.
• In 2009, P. ramorum survived in burned watersheds,
• But could not be found in 80% of previously positive plots in the burn area
• Pathogen survival more likely with -Greater bay and tanoak abundance
-Lower fire severity
• 2010 greater recovery of the pathogen
-More time-Wetter winter in 2009
• Other species of Phytophthora(P.nemorosa and P.pseudosyringae) in burn plots where we had never found them before
• Suggests other species of Phytophthora enjoy a competitive niche over P. ramorum
M.Beh 2012
• Both fire and SOD
individually are
significant factors
influencing bark
beetle attraction to
tanoak trees in the
Big Sur region.
Beetle Trapping Results
2009 and 2010
• Fire and SOD do not interact to result
in a multiplicative or synergistic
attraction to bark beetles; the effects
of the two disturbances combined are
strictly additive.
M.Beh 2014
Resprouting trees play an important role in regeneration if they
can survive disease related fuels.
• Larger trees are more likely to
survive post-fire to resprout
• But as more fuels accumulate,
fewer trees survive due to
damage to belowground buds.
• Fewer surviving trees = less
competition for resources.
increased SOD impacts leads to
more vigorously resprouting.
• When the pathogen is present
post-fire, SOD appears to not
hinder resprouting.
• Too narrow a fire interval and
they won’t have enough time to
recover resources between fires.
Soberanes Fire 2016
• 1/3 of the long-term
plots burned
• 11 plots burned for
the first time on
record
• 22 plots burned in
both 2008 & 2016
• 34 long-term plots
have not burned
since plot
establishment
90 Long–term plots
Big Creek Reserve 2017
Increased potential for mortality of resprouting
trees both above and below ground
• How much disease
combined with repeat
high severity fires
can resprouting trees
take?
• Resprouters may be
susceptible to narrow
fire intervals because
there is less time for
trees to recover the
belowground
resources
What happens when you have a
“short” (8 yr) fire return interval?
2006
2017
Preliminary data collected in 2017 shows fewer
seedlings recruited in plots that burned in both
2008 & 2016
• Plots that burned
in both 2008 &
2016 had fewer
seedlings recruit.
• Could be due
to erosion
• Could be due
to depleted
seed bank
• More plot
surveys
necessary
0
100
200
300
400
500
600
700
800
Unburned 1 yr post-fire
Unburn 1 yr post-fire
Burned in2008 &2017
Average number of Seedlings/Plot
1 year post-Basin Fire 1 year post-Soberanes Fire
• How do nutrients get
back into the system
post fire? Ceanothus,
Lupine, Vicia, etc..
• How long does it take
to replenish nutrients
lost during the fire?
The role of nitrogen
fixing plants
Acknowledgments• Rizzo lab- Margaret Metz, Richard Cobb, Shannon Murphy, Allison
Wickland, Kamyar Aram, Heather Mehl, Clay DeLong, Allison
Simler, Tyler Bourret
• Big Sur Field Help- Lulu Waks, Josh Vieregge, Kevin Pietrzak and
Emily Paddock, Whalen Dillion, Lawrence Miracle,
Ashley Hawkins
• Ross Meentemeyer lab, NCSU
• Matteo Garbelotto Lab, UC Berkeley
• Everett Hansen and Jennifer Parke, OSU
• Susan Frankel and Ellen Goheen, USDA
• Ted Swiecki, Phytosphere