Drought and Bark Beetles: Status Report and Plan for Research

By

Michael R. Wagner [1], Monica Gaylord [1], Thomas E. Kolb [1], and Joel D. McMillin [2]

[1] Northern Arizona University School of Forestry, Flagstaff, AZ [2] US Forest Service, Forest Health Protection, Flagstaff, AZ

Outline

• Current Drought • Bark Beetles (BB) • Drought/BB Impacts • Drought or BB? • Current Research • Future Research Needs

-3

-2

-1

0

1

2

3

BC

Bel

ow-a

vera

ge

Abo

ve-a

vera

ge

prec

ipita

tion

pre

cipi

tatio

n

AD

500 1000 1500 2000

Y ear

(Grissno-Mayer et al. 1997; Wagner et al. 2000)

0

Annual Precipitation in Flagstaff, AZ (1976-2003)

0 5

10 15 20 25 30 35 40

)

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

Ann

ual p

reci

pita

tion

(inch

es 50 yr (1951-2000) AVE ANN PRECIP = 21.7 inches

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

0 5

10 15 20 25 30 35

li i i l i

Pi

Ponderosa mber pinyon Apache Ch huahua Br st econe Mex can pinyon

Host tree

No.

of b

ark

beet

le

spec

ies ne feeding Scolytidae in AZ

Juniper feeding Scolytidae in AZ5

4

3

2

1

0

Alligator Utah Rocky One-Mount. seeded

Hos tree

No.

of b

ark

beet

le s

peci

es

Ponderosa Pine Bark BeetlesAvailable life history

information Genus No. of species, % Yes No Partial Ips 12 41.4% 3 6 3 Dendroctonus 6 20.7% 6 0 0 Pityophthorus 4 13.8% 0 4 0 Pityogenes 2 6.9% 0 1 1 Carphoborus 1 3.4% 0 1 0 Hylastes 1 3.4% 0 0 1 Hylurgops 1 3.4% 1 0 0 Pityoborus 1 3.4% 0 1 0 Pityokteines 1 3.4% 0 1 0

9 29* 100.0% 10 14 5 (* potentially 5 additional species to be verified)

Feeding Guild for Ponderosa Pine Bark Beetles

Small Trunks and Genus Species Twigs branches Large branches Roots Ips Dendroctonus Pityophthorus Pityogenes Carphoborus Hylastes Hylurgops Pityoborus Pityokteines

9

12 6 4 2 1 1 1 1 1

29*

0 0 4 0 x 0 0 x 0 6

0 0 0 0 x 0 0 x 0 2

12 6 0 2 0 1 1 0 1

23

0 0 0 0 0 x x 0 0 2

X: feeding on both tissue types; * Potentially 5 additional species to be verified

Ponderosa pine mortality caused by Dendroctonus and Ips spp. complex

in AZ and NM, 1995-2003

0 1995 1997 1998 1999 2000 2001 2002 2003

AZ NM

50,000 100,000 150,000 200,000 250,000 300,000 350,000 400,000 450,000 500,000

Acr

es

1996

Year

(Sources: Forest Insect and Disease Conditions in the SW Region, 1995-2003)

Ponderosa pine mortality caused by Ips beetles in AZ and NM, 1995-2003

0 1995 1996 1997 1998 1999 2000 2001 2002 2003

AZ NM

50,000 100,000 150,000 200,000 250,000 300,000 350,000 400,000 450,000 500,000

Acr

es

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

0 1995 1996 1998 2001 2002 2003

AZ NM

10,000

20,000

30,000

40,000

50,000

60,000 A

cres

1997 1999 2000

Year

(Sources: Forest Insect and Disease Conditions in the SW Region, 1995-2003)

Ponderosa pine mortality caused by Mountain pine beetles in AZ and NM, 1995-2003

0 1995 1996 1997 1998 1999 2000 2001 2002 2003

AZ NM

2,000

4,000

6,000

8,000

10,000

12,000 A

cres

Year

(Sources: Forest Insect and Disease Conditions in the SW Region, 1995-2003)

Ponderosa pine mortality caused by Roundheaded pine beetles in AZ and NM, 1995-2003

0 1995 1996 1997 1998 1999 2000 2001 2002 2003

AZ NM

5,000

10,000

15,000

20,000

25,000

30,000 A

cres

Year

(Sources: Forest Insect and Disease Conditions in the SW Region, 1995-2003)

The meaning of acres of bark beetle mortality

• 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

Prec

ipita

tion

(inch

es)

Pinyon-Juniper, Spruce-firOak woodland,And/Or Chaparral

40

35

30

25

20

15 Ponderosa pine

10Grass Land

5

4,000 5,000 6,000 7,000 8,000 9,000 10,000 11,000

Elevation (feet)

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?

Relationship between bark beetle infested acres and winter precipitation (January to April)

R2 P

0 0 150 250

)

2000 1994 2001

2003

2002 y = -3588.8x + 703791

= 0.826, = 0.033

100,000 200,000

300,000

400,000

500,000 600,000

700,000

50 100 200

Winter precipitation (mm

Infe

sted

acr

es in

AZ

stat

ewid

e

(Bark beetle species included the complex of Dendroctonus brevicomis, D. ponderosae, D. adjunctus, and Ips spp. on ponderosa pine)

Y X

Z

N1

N2

Critic

al T

hres

hold

Beetle #’s

Epidemic Domain

Endemic Domain

R2 R1

Host Resistance

Does It Matter?

• 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

• ≈ 40 Studies (manuscript) • 80% in Progress • 80% Flagstaff Based (NAU, RMRS, FHP)• ≈ 95% Federal Funds

Ponderosa Pine Bark Beetle Research Topics

• 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 communitystructure, life history strategy, and naturalenemies are most important to populationdynamics?

• Long-term economic, social, and ecologicaleffects 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

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