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