Mountain pine beetle ecology/dynamics research in the Canadian Forest Service
Allan L. Carroll Research Scientist
Natural Resources Canada, Canadian Forest Service Pacific Forestry Centre, Victoria, BC
Overview Ù MPB research in the CFS – an overview Ù MPB ecology/dynamics – native habitat o The epidemic phase o The endemic phase Ù Knowledge gaps for novel habitats o Alberta north of Banff, FMF Ù Summary and conclusions
CFS MPB research (ongoing) Ù Ecosystem response to outbreaks (Alfaro, Hawkes) Ù Spread modelling (Aukema/Carroll, Shore/Riel) Ù Effects of weather/climate, climate change (Carroll, Cooke, Régnière) Ù Genomics (Aukema, Cooke) Ù Remote sensing (Wulder) Ù Reproduction in alternative hosts (spruce) (Aukema, Bleiker) Ù Beetle/fungus/tree interactions (Carroll/Bleiker, Langor/Rice) Ù Population ecology/dynamics (Carroll/Aukema, Langor) Go to CFS bookstore http://bookstore.cfs.nrcan.gc.ca
MPB ecology/dynamics: native habitats Ă™ Populations exist in two phases: epidemic & endemic Ă™ Endemic phase is the most common state, necessary for persistent populations
ep ide mi c
Epidemic phase
In cip ien t
Beetle population size
Epidemic threshold
Endemic phase N0
Stand resistance
Adapted from: Berryman 1982
The epidemic phase (native habitats)
Ă™ Niche: mature pine trees Ă™ Constraints: o Host abundance o climate favouring beetle survival
The epidemic phase: host constraints (native habitats) Ă™ 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) Relative beetle production
45 40 35
42Ă—
30 25 20 15 10 5 0 0
10
20
30
Tree diameter (cm) Adapted from Safranyik and Carroll 2006
40
Host constraints: native habitats (BC) 5 1910
1930
1950
4
Ù Reconstructed pine forests based on past disturbances 35% (fire, harvesting, beetles)
2
17%
26%
5 4
1970
1990
40 80 12 0 16 0 20 0 24 0
1
3 2
49%
53%
0
40 80 12 0 16 0 20 0 24 0
1 40 80 12 0 16 0 20 0 24 0
Area (ha × 106)
3
Forest age (years Adapted from Taylor and Carroll 2004
Ù Trees most susceptible between 80 and 160 years old (varies with site quality) Ù Area of susceptible trees at outbreak start 3 times greater than 1910 Ù Current AB pine, similar ageclass structure
The epidemic phase: host constraints Knowledge gaps for novel habitats Ù Epidemic niche (outbreak potential) = distribution/abundance of mature pine?
Susceptibility Low
High
Ù Shore & Safranyik susceptibility rating system, spread modelling Ù Assumption: equivalent beetle behaviour in novel habitats
The epidemic phase: host constraints Knowledge gaps for novel habitats (FMF) Naïve lodgepole pine, Tumbler Ridge 2007 20 y = a(-0.5(ln(x/x0)/b)2) , R2 = 0.39, P<0.0001 95% confidence band From Raffa & Berryman 1983
Ù ≈40% higher productivity Ù Lower optimal attack density Ù Due to: o less-evolved resistance? o unusually high attack rate? Ù Different for Pj, Pl/Pj hybrids?
Brood adults/attack
15
10
5
0 0
50
100
150
200
Attack density (galleries/m2)
250
Extreme 14 12 10 8 6 4 2 0
25
Extreme
30 25 20 15 10 5 0
Low
20
15
10
19 21 19 - 50 31 19 - 60 41 19 - 70 51 19 80 61 19 - 90 71 -0 0
Climatic suitability
19 21 19 - 50 31 19 - 60 41 19 - 70 51 19 80 61 19 - 90 71 -0 0
19 21 19 - 50 31 19 - 60 41 19 - 70 51 19 80 61 19 - 90 71 -0 0
% Area
High
19 21 19 - 50 31 19 - 60 41 19 - 70 51 19 80 61 19 - 90 71 -0 0
Very low
19 21 19 - 50 31 19 - 60 41 19 - 70 51 19 80 61 19 - 90 71 -0 0
Moderate
% Area
Low
% Area
The epidemic phase: climate constraints (native habitats) % Area in climatic suitability class 30 25 20 15 10 5 0
40
5 10
0 0
High
Moderate
Very low
30
20
From Carroll et al. 2004
1941 - 1970
Climate change-induced range expansion
Climatic suitability Very low Low Moderate High Extreme
1400
Historic suitability = “Very Low”
1200 1000 800 600 400
No. infestations
1970 1971
200 0 1950 2500
1960
1970
1980
1990
2000
Historic suitability = “Low”
2000 1500 1000 500 1941 - 1970
0 1950
1960
1970
1980
1990
2000
From Carroll et al. 2004
MPB climatic suitability Very low Low Moderate High Extreme
2041 - 2070
From Carroll et al. 2007a
The epidemic phase: climate constraints Knowledge gaps for novel habitats (FMF) 1971-2000
2001-2030
Ù Finer temporal resolution (<30-year normals) Ù Finer spatial resolution (<1km DEM) Ù RCM versus GCM (regional vs global model) Ù Mesoscale effects of synoptic climate patterns (PDO, ENSO, AO) Ù Improved MPB phenology module Ù etc…
MPB ecology/dynamics: native habitats Ă&#x2122; Populations exist in two phases: epidemic & endemic Ă&#x2122; Endemic phase is the most common state, necessary for persistent populations
ep ide mi c
Epidemic phase
In cip ien t
Beetle population size
Epidemic threshold
Endemic phase N0
Stand resistance
Adapted from: Berryman 1982
The endemic phase (native habitats)
Ù Ù
Niche: suppressed/damaged pine trees Constraints…
The endemic phase: primary constraints (native habitats)
Natural enemies Host resistance
Host quality
Competitors (secondary bark beetles)
The endemic phase: competitors (BC)
Pseudips mexicanus
Photo WM Ciesla
Ips latidens
Hylurgops spp.
Ù Expoitation and interference competition Ù Geographically consistent assemblage Ù Predictable attack sequence/succession
Dendroctonus murrayanae
Ips pini
The endemic phase (native habitats)
Trophic interactions, mediated by interspecific competition, constrain MPB populations to the endemic phase (long-term persistence)
Escape from the endemic phase: interspecific competition
Proportion of MPB-colonized trees with prior 2º beetle attacks
1.0 Stand A Stand B Stand D Stand F Stand G
0.8
Ù Requirement for “predisposition” declines as MPB population increases
0.6
Ù Escape from competition with 2º bark beetle assemblage
0.4
Ù Escape from natural enemies?
0.2
0 0
1000
2000
3000
4000
No. attacking MPB ha-1 From Carroll et al. 2007b
5000
Escape from the endemic phase: host shift
Relative tree diameter (cm)
8
Ù Shift to large-diameter trees as MPB population increases
6 4 Stand A Stand B Stand D Stand F Stand G
2 0
Ù Access to high-quality resources Ù Further separation from 2º bark beetle assemblage
-2 -4 0
1000
2000
3000
4000
No. attacking MPB ha-1 From Carroll et al. 2007b
5000
Escape from the endemic phase: mass attack success
Proportion of trees resisted
0.6 Stand A Stand B Stand D Stand F Stand G
0.5 0.4
Ù Mass attack success increases as MPB population increases
0.3
Ù Stand resistance no longer restricts population Ù Positive feedback initiates
0.2 0.1 0.0 0
1000 2000 3000 4000 No. attacking MPB ha-1 From Carroll et al. 2007b
5000
Escape from the endemic phase: the outbreak
Mean nearest neighbour distance (m)
60 Stand A Stand B Stand D Stand F Stand G
50
Ù Attacks cluster as population builds Ù Mass attack success increases
40
Ù Spot infestations develop, spread, coalesce
30 20 10 0 0
1000
2000
3000
4000
No. attacking MPB ha-1 From Carroll et al. 2007b
5000
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
-
+ Brood
Food availability
-
+
+
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
-
+ Brood
Food availability
-
+
+
Brood
The endemic phase: trophic interactions Knowledge gaps for novel habitats
?
?
Natural enemies
?
Host resistance
?
?
? ? ? Host quality
Competitors (secondary bark beetles)
Summary/Conclusions Ù Epidemic 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
Ù Endemic phase (persistent) o Native habitats:
Niche/constraints - quantification emerging
o Novel habitats:
Trophic interactions largely unknown
Ù Ramifications – knowledge gaps in novel habitats o Limited predictive capacity
Population ecology/dynamics/spread, impacts, management
Thank you