Mountain pine beetle ecology/dynamics research in the Canadian Forest Service

Allan L. CarrollResearch Scientist

Natural Resources Canada, Canadian Forest ServicePacific Forestry Centre, Victoria, BC

OverviewMPB research in the CFS – an overviewMPB ecology/dynamics – native habitato The epidemic phaseo The endemic phase

Knowledge gaps for novel habitatso Alberta north of Banff, FMF

Summary and conclusions

CFS MPB research (ongoing)Ecosystem response to outbreaks(Alfaro, Hawkes)Spread modelling(Aukema/Carroll, Shore/Riel)Effects of weather/climate, climate change(Carroll, Cooke, Régnière)Genomics(Aukema, Cooke)Remote sensing(Wulder)Reproduction in alternative hosts (spruce)(Aukema, Bleiker)Beetle/fungus/tree interactions(Carroll/Bleiker, Langor/Rice)Population ecology/dynamics(Carroll/Aukema, Langor)

Go to CFS bookstore http://bookstore.cfs.nrcan.gc.ca

MPB ecology/dynamics: native habitatsPopulations exist in two phases: epidemic & endemicEndemic phase is the most common state, necessary for persistent populations

Epidemic phase

Endemic phase

Stand resistance

Bee

tle p

opul

atio

n si

ze

Incip

ient e

pidem

ic

N0

Epidemic threshold

Adapted from: Berryman 1982

The epidemic phase (native habitats)The epidemic phase (native habitats)

Niche: mature pine treesConstraints:

o Host abundanceo climate favouring beetle survival

Niche: mature pine treesConstraints:

o Host abundanceo climate favouring beetle survival

The epidemic phase: host constraints (native habitats)

Beetles prefer large, mature trees:o higher quality food (thicker phloem)o protection from predators and

weather extremes (thicker bark)o escape from competitors (and

associated natural enemies)

42×

Tree diameter (cm)

Rel

ativ

e be

etle

pro

duct

ion

05

101520

2530354045

0 10 20 30 40

Adapted from Safranyik and Carroll 2006

1930

26%

1970

49%

1950

35%

40 80 120

160

200

240

Forest age (years

0

1

2

3

4

5

1

2

3

4

51910

17%

1990

53%

Are

a (h

a ×

106 )

Host constraints: native habitats (BC)

Reconstructed pine forests based on past disturbances (fire, harvesting, beetles)

Area of susceptible trees at outbreak start 3 times greater than 1910

Adapted from Taylor and Carroll 2004

40 80 120

160

200

240

40 80 120

160

200

240

Trees most susceptible between 80 and 160 years old(varies with site quality)

Current AB pine, similar age-class structure

The epidemic phase: host constraintsKnowledge gaps for novel habitats

Epidemic niche (outbreak potential) = distribution/abundance of mature pine?

LowSusceptibility

High

Shore & Safranyiksusceptibility rating system, spread modellingAssumption: equivalent beetle behaviour in novel habitats

The epidemic phase: host constraintsKnowledge gaps for novel habitats (FMF)

≈40% higher productivityLower optimal attack densityDue to:o less-evolved resistance?o unusually high attack rate?

Different for Pj, Pl/Pj hybrids?

Attack density (galleries/m2)

Bro

od a

dults

/atta

ck

0 50 100 150 200 2500

5

10

15

20y = a(-0.5(ln(x/x0)/b)2)

95% confidence band , R2 = 0.39, P<0.0001

From Raffa & Berryman 1983

Naïve lodgepole pine, Tumbler Ridge 2007

Low

Very low

Moderate

Extreme

High

Climatic suitability

Low

Very low

Moderate

Extreme

High

Low

Very low

Moderate

Extreme

High

Low

Very low

Moderate

Extreme

High % A

rea

% A

rea

0

10

20

30

40

1921

-5019

31-60

1941

-7019

51-80

1961

-9019

71-00

Very low

0

5

10

15

20

25

1921

-5019

31-60

1941

-7019

51-80

1961

-9019

71-00

Low

% A

rea

05

1015202530

1921

-5019

31-60

1941

-7019

51-80

1961

-9019

71-00

Moderate

05

1015202530

1921

-5019

31-60

1941

-7019

51-80

1961

-9019

71-00

High

02468

101214

1921

-5019

31-60

1941

-7019

51-80

1961

-9019

71-00

Extreme

% Area in climatic suitability class

From Carroll et al. 2004

The epidemic phase: climate constraints (native habitats)

1941 - 1970

1941 - 1970Climatic suitability

LowVery low

Moderate

ExtremeHigh

1941 - 1970

1970

1941 - 1970

1971

From Carroll et al. 2004

Historic suitability = “Very Low”

1950 1960 1970 1980 1990 20000

200

400

600

800

1000

1200

1400

1950 1960 1970 1980 1990 20000

500

1000

1500

2000

2500 Historic suitability = “Low”

No.

infe

stat

ions

Climate change-inducedrange expansion

2041 - 2070

MPB climaticsuitability

Very lowLow

Extreme

ModerateHigh

From Carroll et al. 2007a

The epidemic phase: climate constraintsKnowledge gaps for novel habitats (FMF)

Finer temporal resolution(<30-year normals)Finer spatial resolution(<1km DEM)RCM versus GCM(regional vs global model)Mesoscale effects of synoptic climate patterns(PDO, ENSO, AO)Improved MPB phenologymoduleetc…

1971-2000

2001-2030

MPB ecology/dynamics: native habitatsPopulations exist in two phases: epidemic & endemicEndemic phase is the most common state, necessary for persistent populations

Epidemic phase

Endemic phase

Stand resistance

Bee

tle p

opul

atio

n si

ze

Incip

ient e

pidem

ic

N0

Epidemic threshold

Adapted from: Berryman 1982

The endemic phase (native habitats)The endemic phase (native habitats)

Niche: suppressed/damaged pine treesConstraints…Niche: suppressed/damaged pine treesConstraints…

The endemic phase: primary constraints (native habitats)

Host resistance

Host quality Competitors(secondary bark beetles)

Natural enemies

The endemic phase: competitors (BC)

Expoitation andinterference competitionGeographically consistent assemblagePredictable attack sequence/succession

Pseudips mexicanus Hylurgops spp.

Ips latidensPhoto WM Ciesla

Ips piniDendroctonus murrayanae

The endemic phase (native habitats)The endemic phase (native habitats)

Trophic interactions, mediated by interspecificcompetition, constrain MPB populations to the endemic phase (long-term persistence)

Trophic interactions, mediated by interspecificcompetition, constrain MPB populations to the endemic phase (long-term persistence)

Escape from the endemic phase: interspecific competition

Requirement for “predisposition”declines as MPB population increasesEscape from competition with 2º bark beetle assemblageEscape from natural enemies?

Pro

porti

on o

f MP

B-c

olon

ized

tree

sw

ith p

rior 2

ºbee

tle a

ttack

s

0.2

0.4

0.6

0.8

No. attacking MPB ha-1

0 1000 2000 3000 4000 50000

1.0Stand AStand BStand DStand FStand G

From Carroll et al. 2007b

Escape from the endemic phase: host shift

Shift to large-diameter trees as MPB population increases

Access to high-quality resources

Further separation from 2ºbark beetle assemblage

Rel

ativ

e tre

e di

amet

er (c

m)

-4

No. attacking MPB ha-1

0 1000 2000 3000 4000 5000

-2

0

2

4

6

8

Stand AStand BStand DStand FStand G

From Carroll et al. 2007b

Pro

porti

on o

f tre

es re

sist

edEscape from the endemic phase: mass attack success

Mass attack success increases as MPB population increases

Stand resistance no longer restricts population

Positive feedback initiates

No. attacking MPB ha-10 1000 2000 3000 4000 5000

0.0

0.1

0.2

0.3

0.4

0.5

0.6Stand AStand BStand DStand FStand G

From Carroll et al. 2007b

Mea

n ne

ares

t nei

ghbo

urdi

stan

ce (m

)Escape from the endemic phase: the outbreak

Attacks cluster as population builds

Mass attack success increases

Spot infestations develop, spread, coalesce

No. attacking MPB ha-1

Stand AStand BStand DStand FStand G

0 1000 2000 3000 4000 50000

10

20

30

40

50

60

From Carroll et al. 2007b

MPB dynamics: conceptual framework (native habitats)

Stress events

-

• Drought• Windthrow• Age/suppression• Root disease

Susceptible trees:secondary beetles

+ Susceptible trees:mountain pine beetle

+

Food availability

+

Food availability

+

Brood

-+

Brood

-+

+

+

MPB dynamics: conceptual framework (native habitats)

Stress events

-

• Drought• Windthrow• Age/suppression• Root disease

Susceptible trees:secondary beetles

+ Susceptible trees:mountain pine beetle

+

Food availability

+

Food availability

+

Brood

-+

Brood

-+

+

+

The endemic phase: trophic interactionsKnowledge gaps for novel habitats

Host resistance

Host quality Competitors(secondary bark beetles)

Natural enemies

?

?

?

?

?

?

? ?

Summary/ConclusionsEpidemic phase (ephemeral)o Native habitats:

Niche well known (mature, thick-phloem trees)Constraints understood (host abundance, climate)

o Novel habitats:Niche requires quantification (beetles/unit phloem)Constraints understood, but form of interaction with niche unknown; scale issues hamper applicability to FMF

Endemic phase (persistent)o Native habitats:

Niche/constraints - quantification emergingo Novel habitats:

Trophic interactions largely unknownRamifications – knowledge gaps in novel habitatso Limited predictive capacity

Population ecology/dynamics/spread, impacts, management

Thank youThank you