Drought and Bark Beetles:
Status Report and Plan for Research
By
Michael R. Wagner [1], Monica Gaylord [1],
[1]
[2]
Thomas E. Kolb , and Joel D. McMillin
[1] Northern Arizona University School of Forestry, Flagstaff, AZ
[2] US Forest Service, Forest Health Protection, Flagstaff, AZ
Outline
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•
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•
•
•
Current Drought
Bark Beetles (BB)
Drought/BB Impacts
Drought or BB?
Current Research
Future Research Needs
Above-average
precipitation
3
2
1
Below-average
precipitation
0
-1
-2
-3
BC AD
0
500
1000
1500
2000
Year
(Grissno-Mayer et al. 1997; Wagner et al. 2000)
Annual precipitation (inches)
Annual Precipitation in Flagstaff, AZ (1976-2003)
40
35
30
25
20
15
10
5
0
50 yr (1951-2000) AVE
ANN PRECIP = 21.7 inches
76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 00 01 02 03
Year
Pine Bark Beetles in Arizona
Most important
• Pine engraver beetles (Ips)
-11 species in AZ
• Western pine beetle
• Roundheaded pine beetle
• Mountain pine beetle
• Southern and Mexican pine
beetle (Chiricahua Mts.)
• Larger Mexican pine beetle
• Red turpentine beetle
Least important
No. of bark beetle
species
35
30
25
20
15
10
5
0
Pine feeding Scolytidae in AZ
Ponderosa
limber
pinyon
Apache
Host tree
Chihuahua Bristlecone
Mex ican
pinyon
No. of bark beetle species
5
Juniper feeding Scolytidae in AZ
4
3
2
1
0
Alligator
Utah
Rocky
Mount.
Hos tree
Oneseeded
Ponderosa Pine Bark Beetles
Genus
Ips
Dendroctonus
Pityophthorus
Pityogenes
Carphoborus
Hylastes
Hylurgops
Pityoborus
Pityokteines
9
No. of species, %
12
41.4%
6
20.7%
4
13.8%
2
6.9%
1
3.4%
1
3.4%
1
3.4%
1
3.4%
1
3.4%
29*
100.0%
Available life history
information
Yes
No
Partial
3
6
3
6
0
0
0
4
0
0
1
1
0
1
0
0
0
1
1
0
0
0
1
0
0
1
0
10
14
5
(* potentially 5 additional species to be verified)
Feeding Guild for Ponderosa Pine Bark Beetles
Genus
Species
Small
Trunks and
Twigs branches Large branches
Roots
Ips
12
0
0
12
0
Dendroctonus
6
0
0
6
0
Pityophthorus
4
4
0
0
0
Pityogenes
2
0
0
2
0
Carphoborus
1
x
x
0
0
Hylastes
1
0
0
1
x
Hylurgops
1
0
0
1
x
Pityoborus
1
x
x
0
0
Pityokteines
1
0
0
1
0
29*
6
2
23
2
9
X: feeding on both tissue types; * Potentially 5 additional species to be verified
Acres
Ponderosa pine mortality caused by
Dendroctonus and Ips spp. complex
in AZ and NM, 1995-2003
500,000
450,000
400,000
350,000
300,000
250,000
200,000
150,000
100,000
50,000
0
AZ
NM
1995 1996 1997 1998 1999 2000 2001 2002 2003
Year
(Sources: Forest Insect and Disease Conditions in the SW Region, 1995-2003)
Acres
Ponderosa pine mortality caused by
Ips beetles in AZ and NM, 1995-2003
500,000
450,000
400,000
350,000
300,000
250,000
200,000
150,000
100,000
50,000
0
AZ
NM
1995 1996 1997 1998 1999 2000 2001 2002 2003
Year
(Sources: Forest Insect and Disease Conditions in the SW Region, 1995-2003)
Ponderosa pine mortality caused by
Western pine beetles in AZ and NM, 1995-2003
60,000
AZ
50,000
NM
Acres
40,000
30,000
20,000
10,000
0
1995 1996 1997 1998 1999 2000 2001 2002 2003
Year
(Sources: Forest Insect and Disease Conditions in the SW Region, 1995-2003)
Acres
Ponderosa pine mortality caused by
Mountain pine beetles in AZ and NM, 1995-2003
12,000
AZ
10,000
NM
8,000
6,000
4,000
2,000
0
1995 1996 1997 1998 1999 2000 2001 2002 2003
Year
(Sources: Forest Insect and Disease Conditions in the SW Region, 1995-2003)
Acres
Ponderosa pine mortality caused by
Roundheaded pine beetles in AZ and NM, 1995-2003
30,000
AZ
25,000
NM
20,000
15,000
10,000
5,000
0
1995 1996 1997 1998 1999 2000 2001 2002 2003
Year
(Sources: Forest Insect and Disease Conditions in the SW Region, 1995-2003)
The meaning of acres of bark beetle mortality
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•
•
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Area of bark beetle activity
Intensity of mortality varies with activity polygon
Qualitative decision made during aerial survey
Same acre can have mortality over several years
Number of dead trees estimated
Pinon and ponderosa pine mortality detected
from aerial survey in Arizona, 2001-2003
2001
2002
2003
40
Precipitation (inches)
35
Pinyon-Juniper,
Oak woodland,
And/Or Chaparral
Spruce-fir
30
25
20
15
Ponderosa pine
10
Grass Land
5
4,000
5,000
6,000
7,000
8,000
Elevation (feet)
9,000
10,000
11,000
Drought or Bark Beetles?
Correlation of bark beetles and drought
Anecdotal reports of death w/o bark beetles
Little evidence from skilled necropsy
Rigorous experimental test is lacking
Drought as inciting agent
Conceptual understanding of inciting factors versus
sustaining factors
• Does it matter?
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Infested acres in AZ statewide
Relationship between bark beetle infested acres
and winter precipitation (January to April)
700,000
y = -3588.8x + 703791
R2 = 0.826, P = 0.033
2002
600,000
500,000
2003
400,000
300,000
200,000
2001
100,000
1994
2000
0
0
50
100
150
200
250
Winter precipitation (mm )
(Bark beetle species included the complex of Dendroctonus brevicomis, D. ponderosae,
D. adjunctus, and Ips spp. on ponderosa pine)
d
Cri
tic
al T
N2
hre
sho
l
Z
Epidemic
Domain
Beetle #’s
N1
Endemic
X Domain
Y
R2
Host Resistance
R1
Does It Matter?
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Drought can cause direct mortality
Bark beetles can cause direct mortality
Bark beetles require suitable host
Outbreaks can persist after drought ends
Active management (thinning) can reduce the
risk of both drought and bark beetle mortality
Southwest (AZ/NM) Ponderosa
Pine Bark Beetle Research
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≈ 40 Studies (manuscript)
80% in Progress
80% Flagstaff Based (NAU, RMRS, FHP)
≈ 95% Federal Funds
Ponderosa Pine Bark Beetle
Research Topics
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Stand structure, density, restoration effects
Tree physiology, resistance
Life history, seasonal and elevational patterns
Ecological effects (mistletoe, birds, CWD)
Prevention and tree protection
Important Research Questions
• Can stand/landscape scale treatments mitigate
bark beetle outbreak?
• Are current fuel risk reduction treatments well
suited for reducing bark beetle risk?
• What will be the combined effect of thinning
from below and bark beetles on future forest?
Important Research Questions
(Continued)
• Which aspects of bark beetle community
structure, life history strategy, and natural
enemies are most important to population
dynamics?
• Long-term economic, social, and ecological
effects of widespread loss of Arizona forests?
• Are current monitoring tools (pheromone,
aerial detection) adequate?
Summary
9 Unprecedented tree mortality in SW
9 Probably drought induced
9 Likely related to overstocked forest condition
9 Outbreak will continue for several years
9 Paucity of basic understanding of all aspects of
bark beetles
9 Coordinated SW research program needed
<< FHM Working Group Agenda