THE ROLE OF BIOTIC AND ABIOTIC STRESSORS IN JEFFREY PINE SUSCEPTIBILITY TO JEFFREY PINE BEETLE

Nancy Grulke

USDA Forest Service

ngrulke@fs.fed.us

Assumptions

Bark beetle attacks are more common in dense stands or in marginal populations

Drought increases pine susceptibility to bark beetle

Approach

Quantify level of tree-tree competition Test for differences in physiological drought stress in:

different stand densities and between attacked and unattacked trees

Relate physiological drought stress to resin exudation rate Test for definitive spectral signature using high resolution remote sensing to assist management of east-side dry pine forests

Right: Pinus Jeffreyi (Grev. & Balf.) (right), attacked by Dendroctonus jeffreyi (Hopkins);

Site selection: core sites (east side)

Lassen NF

Tahoe NF

Inyo NF

Sequoia NF

San Bernardino NF

SOUTHERN CASCADES

SIERRA NEVADA

TRANSVERSE RANGE

Crater Lake NP

Lassen Volcanic NP, Lassen NF

Tahoe NF

Sequoia NP, Sequoia NF

San Bernardino NF

San Pedro Martir NP

Inyo NF

Also draw upon other studies of Pinus ponderosa (var. pacifica and scopulorum) to answer questions (all in ResearchGate/Grulke)

Fremont NF

Tree selection (core work)

Chose 6-7 stands:

3 thinned (10-30 yrs ago)

3 dense

prescribed or wildfire burns (not presented here)

In each stand, the first 8 mature trees (90 to 120 yr old) were chosen within a belt transect

~280 trees in the study

Competition: stand density vs. nearest neighbors

We use stand density, but it only takes one stressed tree to initiate a bark beetle outbreak

The neighboring trees drive biotic pressure, not stand density per se

Stand basal area vs. tree-tree competition

BASAL AREA: 30 m DIAMETER PLOT TOTAL AREA, ALL TREES BY SPECIES

NEAREST NEIGHBOR: 25 m RADIUS OUT FROM TARGET (CENTER) TREE, LIST BA AND SPECIES OF NEAREST TREE IN EACH QUADRAT, EXCLUDING TREES

Latitudinal gradient of stand basal area (BA): DENSE AND THIN STAND BA DIFFERED BY 2 FOLD

0

10

20

30

40

50

60

70

BA

SAL

AR

EA, m

2 H

A-1

BA/ha

PIJE

SOUTH TO NORTH

NEARLY PURE STANDS OF PIJE

PIJE, PIPO, ABCO, LIDE

ALL TREES PIJE

NO RELATIONSHIP between stand density (x) and distance to nearest neighbor (y)

0

5

10

15

20

25

30

0 20 40 60 80

Dis

tan

ce t

o N

ear

est

Tre

e, m

Total Basal Area/HA, all species

ANY SPECIES, SINGLE NN

NO RELATIONSHIP between stand density (x) and distance to nearest neighbor (y)

0

5

10

15

20

25

30

0 20 40 60 80

Dis

tan

ce t

o N

ear

est

Tre

e, m

Total Basal Area/HA, all species

0

5

10

15

20

25

30

0 20 40 60 80

Dis

tan

ce t

o N

ear

est

PIJ

E, m

Total Basal Area/HA, PIJE

0

5

10

15

20

25

30

0 20 40 60 80A

ve D

ista

nce

to

Su

rro

un

din

g P

IJE,

m

Total Basal Area/HA, PIJE

ANY SPECIES, SINGLE NN PIJE, SINGLE NN

PIJE, AVERAGE of 4 QUADRATS

Competition, summary

• Across 5 Forests, most PIJE is within 6 m of another PIJE, and averaged 4 m (bole center to bole center) • Many trees have canopy to canopy contact • Distribution the result of ‘clumpy/gappy’ management

• BB attacked trees were more often in thinned stands, but occurred in denser clumps with- in those stands

0

5

10

15

20

25

30

35

40

45

Total BA/ha Total BA/ha, PIJE

Bas

al A

rea

(m2

)/ h

a

unattacked attacked

Competition, summary

• Across 5 Forests, most PIJE is within 6 m of another PIJE, and averaged 4 m (bole center to bole center) • Many trees have canopy to canopy contact • Distribution the result of ‘clumpy/gappy’ management

• BB attacked trees were more often in thinned stands, but occurred in denser clumps with- in those stands • We may be thinning stands, but we are not reducing within- species competition… 0

5

10

15

20

25

30

35

40

45

Total BA/ha Total BA/ha, PIJE

Bas

al A

rea

(m2

)/ h

a

unattacked attacked

WHAT DO WE KNOW ABOUT PHOTOSYNTHETIC CAPACITY AND WATER USE EFFICIENCY OF JEFFREY PINE IN MARGINAL POPULATIONS?

MARGINAL POPULATIONS? ELEVATIONAL AND LATITUDINAL VARIATION IN

GROSS PHOTOSYNTHESIS OF JEFFREY PINE

0

2

4

6

8

10

12

30

32

34

3638

4042

44

1800

2000

2200

2400

Pg

LAT

ELEV

PIJE

Low-elevation populations had lower Pg than at mid or higher elevations. Northern-most, highest elevation population had the highest Pg, and most ‘flexibility.’

Grulke (2007)

MARGINAL POPULATIONS? ELEVATIONAL AND LATITUDINAL VARIATION IN

WATER USE EFFICIENCY OF JEFFREY PINE

LITTLE DIFFERENCE IN WATER USE EFFICIENCY (WUE) ACROSS A LARGE LATITUDINAL GRADIENT; LESS WUE AT LOWEST ELEVATION AND LATITUDE SITE

Grulke (2007)

0.00

0.05

0.10

0.15

0.20

0.25

30

32

34

3638

4042

44

1800

2000

2200

2400

WU

E

LAT

ELEV

PIJE

Attack and mortality observations over 3 years

9% of Jeffrey pine trees were attacked by Jeffrey pine beetle 7% attacks in thinned stands; 2% in dense stands

4% attacks in northern stands, 3% in southern stands

1% died of flat headed wood borer (Lassen NF) Mantgem & Stephenson (2007) report 3% mortality for west slope

mixed conifer Sierran stands; In this study, mortality averaged 1.6% in dense stands and 16.6% in thin stands Most mortality occurred 1 yr after attack

0

5

10

15

20

25

30

LNF TNF INF SNF SBNF

% P

IJE

ATT

AC

KED

BY

JP

B

DENSE THIN

summed over 3 years

Primary abiotic stressor: DROUGHT!

Primary abiotic stressor: DROUGHT!

Total annual precipitation (ppt)

Soil water availability

Evapotranspiration

Drought index

Annual % average precipitation

…but how is ‘drought’ related or correlated to physiological tree drought stress?

Attributes that DON’T define physiological drought stress

6 am 12 pm 6 pm Ψtotal

ΨP (turgor)

ΨPD total (PREDAWN)

ΨSN total (SOLAR NOON)

ΨS+M

TIS

SU

E W

AT

ER

PO

TE

NT

IAL

NE

GA

TIV

E

P

OS

ITIV

E

} = Δ ψtotal

6 am 12 pm 6 pm Ψtotal

ΨP

ΨPD total ΨSN total

ΨS+M

TIS

SU

E W

AT

ER

PO

TE

NT

IAL

NE

GA

TIV

E

P

OS

ITIV

E

CELL TURGOR MAINTAINED

OSMOREGULATION

NO

T P

HY

SIO

LOIG

CA

LLY

D

RO

UG

HT

STR

ESSE

D

6 am 12 pm 6 pm

ΨP (turgor)

TIS

SU

E W

AT

ER

PO

TE

NT

IAL

NE

GA

TIV

E

P

OS

ITIV

E CELL TURGOR LOST

INSUFFICIENT CELL OSMOREGULATION

PH

YSI

OLO

GIC

ALL

Y

DR

OU

GH

T-ST

RES

SED

Ψtotal

ΨS+M

SAME NOON FOLIAR WATER POTENTIAL, ONE STRESSED, ONE NOT

Definition Of Drought Stress

Moderate drought stress • reduction in cell turgor (e.g., elongation growth) • reduction in stomatal conductance

Severe drought stress

• reduction or loss of cell turgor, • reduction in stomatal conductance or stomatal closure • concentration of cell osmoticum (changes enzymatic function) • cell death

Levitt, 1980

0

50

100

150

200

250

300

1883 1893 1903 1913 1923 1933 1943 1953 1963 1973 1983 1993 2003

TO

TA

L A

NN

UA

L P

PT

, C

MTo

tal a

nn

ual

pp

t, c

m

Physiological drought stress of ponderosa pine is related to the % of average precipitation within the same year.

Drought, and physiological drought stress, is common (Grulke et al. 2010).

120 yr regional precipitation record from Big Bear Dam

120 year average precipitation (ave ppt)

80% of ave ppt induces moderate drought stress (16% of time)

60% of ave ppt induces extreme drought stress (30% of time)

0

50

100

150

200

1987

1989

1991

1993

1995

1997

1999

2001

2003

2005

2007%

of lo

ng term

avera

ge p

pt

0

50

100

150

200

1987

1989

1991

1993

1995

1997

1999

2001

2003

2005

2007%

of lo

ng term

avera

ge p

pt

0

50

100

150

200

1987

1989

1991

1993

1995

1997

1999

2001

2003

2005

2007%

of lo

ng term

avera

ge p

pt

0

50

100

150

200

1987

1989

1991

1993

1995

1997

1999

2001

2003

2005

2007%

of lo

ng term

avera

ge p

pt

SBNF

SNF

INF

TNF

LNF

0

50

100

150

200

1987

1989

1991

1993

1995

1997

1999

2001

2003

2005

2007%

of lo

ng term

avera

ge p

pt

LONG TERM PRECIPITATION RECORDS FOR EACH SITE:

EXPRESSED CURRENT YEAR PPT AS % OF AVERAGE

SNF

S BERDO SEQUOIA INYO TAHOE LASSEN

1990 77 52 83 84 59

1991 106 90 88 82 65

1992 118 119 93 65 52

1993 236 151 122 134 141

1994 101 75 82 61 69

1995 182 197 149 183 188

1996 83 115 109 152 131

1997 110 132 120 159 151

1998 173 158 141 146 165

1999 53 75 80 133 106

2000 73 80 76 99 116

2001 63 60 104 60 61

2002 30 69 87 92 89

2003 94 92 122 102 117

2004 58 73 89 82 103

2005 181 148 165 99 107

2006 86 131 135 128 156

2007 31 58 45 51 47

2008 104 96 68 63 56

2009 41 29 44 24 23

MUSTARD: < 60%; GRAY GREEN: 61-80%; AQUA: >95%

WIDE RANGE OF PRECIPITATION OVER THE FIRST 3 YRS OF INTENSIVE STUDY

Needle and lateral branchlet elongation growth is a simple, integrated measure of the level of drought stress experi-enced by an individual tree within a stand. Needle elongation growth was expressed as % of maximum growth observed for all retained needle age classes. This relative measure corrects for canopy position and nearest neighbor effects.

2002

2003

2000

NEEDLE AND BRANCH ELONGATION GROWTH: simple proxy for physiological drought stress

2001

NORTHERN SITE: TREES IN DENSE STANDS WERE MORE DROUGHT-STRESSED THAN IN THINNED STANDS. RESPONSE WAS SUBTLE BUT PREDICTABLE

R² = 0.6628

R² = 0.7134

0

10

20

30

40

50

60

70

80

90

100

0 50 100 150 200

% o

f M

axim

um

Ne

ed

le L

en

gth

% Average Precipitation

NL, dense

NL, thin

Linear (NL, dense)

Linear (NL, thin)

SOUTHERN 4 SITES: LOWER PPT SIGNIFICANTLY INCREASED PHYSIOLOGICAL DROUGHT STRESS. DROUGHT STRESS DID NOT DIFFER BETWEEN DENSE AND THINNED STANDS

NORTHERN SITE: TREES IN DENSE STANDS WERE MORE DROUGHT-STRESSED THAN IN THINNED STANDS. RESPONSE WAS SUBTLE BUT PREDICTABLE

R² = 0.6628

R² = 0.7134

0

10

20

30

40

50

60

70

80

90

100

0 50 100 150 200

% o

f M

axim

um

Ne

ed

le L

en

gth

% Average Precipitation

NL, dense

NL, thin

Linear (NL, dense)

Linear (NL, thin)

R² = 0.6203

R² = 0.4117

0

10

20

30

40

50

60

70

80

90

100

0 50 100 150 200

% o

f M

axim

um

Ne

ed

le L

en

gth

% Average Precipitation

NL, dense

NL, thin

Log. (NL, dense)

Log. (NL, thin)

Physiological response attribute: % needle length

This physiological attribute wasn’t refined enough to test for the difference between attacked and unattacked trees

0

10

20

30

40

50

60

70

80

90

100

% NL 06 % NL 07 % NL 08 % NL 09

% o

f M

axim

um

Ne

ed

le L

en

gth

unattacked attacked

Definition Of Drought Stress

Moderate drought stress • reduction in cell turgor • reduction in stomatal conductance

Severe drought stress

• reduction or loss of cell turgor, • reduction in stomatal conductance or stomatal closure • concentration of cell osmoticum (changes enzymatic function) • cell death

PHYSIOLOGICAL DROUGHT STRESS

Attacked Unattacked Delta, Mpa: Significant?

Needle Ψtotal PD Low Higher 0.10 NS

Needle Ψtotal SN Low Higher

Key Results – RESIN EXUDATION IS BEST CORRELATED TO BOLE WATER POTENTIAL

-2

0

2

4

6

8

10

12

ATTACKED CLEAN

1.2

1.0

.8

.6

.4

.2

0

-.2

Ψtu

rgo

r Cam

biu

m (

MPa

)

Cambial turgor potential is lower in attacked trees

Attacked Unattacked Delta, Mpa:

Significant?

Bole Cambium Ψtotal

Low Higher 0.10 NS

Bole Cambium Ψturgor

Low Higher 0.87 ***

Key Results – RESIN EXUDATION IS BEST CORRELATED TO BOLE WATER POTENTIAL

-2

0

2

4

6

8

10

12

ATTACKED CLEAN0.0

0.2

0.4

0.6

0.8

1.0

1.2

0 10 20 30 40 50

RE

SIN

EX

UD

AT

ION

, g

/h

Bole Cambium Ψ total (MPa)

Less Resin

0 -1 -2 -3 -4 -5

Lower total water potential

Threshold? 1.2

1.0

.8

.6

.4

.2

0

-.2

Ψtu

rgo

r Cam

biu

m (

MPa

)

Cambial turgor potential is lower in attacked trees Trees with lower Ψtotal express less resin

Attacked Unattacked Delta, Mpa:

Significant?

Bole Cambium Ψtotal

Low Higher 0.10 NS

Bole Cambium Ψturgor

Low Higher 0.87 ***

CAN TREE DROUGHT STRESS BE IDENTIFIED USING REMOTE SENSING?

TEST TO REMOTELY DISTINGUISH TREE DROUGHT STRESS:

APPROACH

Image credit: Saint Mary’s College, CA

WEST-SIDE SIERRA NEVADA SITE, SEQUOIA NATIONAL PARK 132 JEFFREY PINE IN MESIC AND XERIC MICROSITES PHYSIOLOGICAL DROUGHT STRESS OF EACH TREE DOCUMENTED (Grulke et al., 2002a; b) MEASURED AND TESTED ADEQUACY OF 14 ATTRIBUTES OF CANOPY HEALTH AND 3 BANDS OF SPECTRAL DATA (+ ASSOC INDICES) PARTIALLY VALIDATED PREDICTIVE CAPABILITY ON A SITE 30 km N

Thermal Images

PATTERNS OF WITHIN-CANOPY MORTALITY

TOP-DOWN BRANCH DRYING/ MORTALITY: PESTS & PATHS

BOTTOM-UP BRANCH DRYING/ MORTALITY: DROUGHT

TEST FOR ABILITY TO DISTINGUISH TREE DROUGHT STRESS AND HEALTH

Image credit: Saint Mary’s College, CA

SEPARATED SPECTRAL DATA INTO TOP AND UPPER MID-CANOPY SECTIONS OF THE TREE MASKED SHADED PORTION OF THE CANOPY RANDOMLY SAMPLED SPECTRAL SIGNATURE OF 30 POINTS IN EACH SHAPE FILE

‘UNSEEN’

Correlation of remotely sensed and canopy health attributes

Spectral Canopy Health

Top

Canopy

Red Whorl #

NIR Chlorotic mottle 1

R:NIR Chlorotic mottle 2

NIR Scalar Chlorotic mottle 4

NDVI Chlorotic mottle 6

Thermal % Needle length

Upper Mid

Canopy

Red % branchlet foliation

NIR Branchlet Diameter 2

R:NIR Cone frequency

NIR Scalar Leaf scale

NDVI Leaf cutter

Thermal Mistletoe

Δ’s (top-mid)

Red ∆ Elytroderma

NIR ∆ Early senescence

R:NIR ∆

NIR scl. ∆

NDVI ∆

Therm. ∆

Red (650 nm), NIR (860 nm), thermal (8.1-12.4 nm) bands

Canonical Correlation Analysis: Significance of squares Adj. R: Pillai’s trace = .023 X | Y = .07 Y | X = .04

Classification tree model

Grulke, et al. Remote detection and attribution of Jeffrey pine canopy health and drought stress in the south central Sierra Nevada. (in prep)

Initial classification tree model:

• THE Δ THERMAL WAVELENGTH BETWEEN UPPER AND MID CANOPY ALONE COULD DEFINITIVELY DISTINGUISH TREES WITH DIFFERING LEVELS OF PHYSIOLOGICAL DROUGHT STRESS

• ADDING Δ NDVI IMPROVED PREDICTIVE CAPACITY

Classification tree model

Grulke, et al. Remote detection and attribution of Jeffrey pine canopy health and drought stress in the south central Sierra Nevada. (in prep)

Initial classification tree model: 2nd site for partial validation:

• THE Δ THERMAL WAVELENGTH BETWEEN UPPER AND MID CANOPY ALONE COULD DEFINITIVELY DISTINGUISH TREES WITH DIFFERING LEVELS OF PHYSIOLOGICAL DROUGHT STRESS

• ADDING Δ NDVI IMPROVED PREDICTIVE CAPACITY

Conclusions - I

STAND DENSITY EFFECTS ON DROUGHT STRESS, BARK BEETLE ATTACK AND TREE MORTALITY

At the northern-most site, trees in dense stands were more drought-stressed

than in thinned stands, but south of Lassen NF, this didn’t hold true No apparent difference in attack or mortality rates between northern and

southern latitudes Attacked Jeffrey pine was 8x more frequent in thinned stands, but mortality

occurred in dense clumps within those stands implications for ICO, clumpy/gappy management

Thinned stand mortality was 5x greater, and dense stand mortality was 2x greater In east-side PIJE-dominated stands than in mixed conifer stands in west-side Sierra Nevada stands (van Mantgem & Stephens 2007)

Conclusions - II

PHYSIOLOGICAL DROUGHT STRESS EFFECTS ON TREE SUSCEPTIBLITY TO BARK BEETLE ATTACK AND ITS (REMOTE) DETECTION Physiological drought stress decreased the tree’s capacity to physically repel

beetles: attacked trees were more drought-stressed than unattacked trees (lower cell turgor), and lower cambial water potential was correlated with lower resin flow

Tree drought stress can be detected and attributed using high resolution remote sensing tools: the Δ thermal wavelength alone can be used to identify trees in mesic vs. xeric microsites

Remotely detected tree drought stress could be used to: identify stands at risk (bark beetle, wildfire) and to select the most at-risk individual trees to be removed in thinning operations

TOOLS FOR ID’ing DROUGHT STRESS

Significant signs of severe drought stress: Lower canopy primary branch excision; growing point dieback

Whole tree desiccation

Within whorl needle excision

Fremont National Forest, south-central Oregon, 2014-2015 ~25% of ave ppt Interior ponderosa pine

Significant signs of severe drought stress: Lower canopy primary branch excision; growing point dieback

Whole tree desiccation

Within whorl needle excision

NEEDLE AGE CLASSES OLDER THAN CURRENT YEAR WERE AFFECTED

Typically there is a steady increase in needle chlorosis or chlorotic mottle as needles age (Sequoia National Park, P. Jeffreyi; San Bernardino NF, P. ponderosa var. pacifica)

% c

hlo

roti

c m

ott

le

Typically there is a steady increase in needle chlorosis or chlorotic mottle as needles age (Sequoia National Park, P. Jeffreyi; San Bernardino NF, P. ponderosa var. pacifica)

Extreme drought stress in P. ponderosa var. scopulorum (Fremont NF) has significantly increased chlorosis in needles older than current year

% c

hlo

roti

c m

ott

le

0

25

50

75

100

125

150

175

1987

1989

1991

1993

1995

1997

1999

2001

2003

2005

2007%

of lo

ng term

avera

ge p

pt

4.2

4.4

4.6

4.8

5.0

5.2

5.4

5.6

MC MF XC XF

# o

f w

horls

06 w horls 08 w horls

Sequoia National Park, Jeffrey pine

Jeffrey pine experienced 57% of average precipitation (based on 60 yr record) in 2007

• SIGNIFICANT WHORL LOSS FROM 2007 DROUGHT, ~0.5 WHORLS LOST IN ONE YEAR IN XERIC SITES

• NO SIGNIFICANT WHORL LOSS IN MESIC SITES

• In interior ponderosa pine, we expect 2 to 4 needle age classes to be lost this year in south central OR

In excising branches, there is a high incidence of: • scale • sap-sucking insects • leaf cutters (caterpillars) • needle tip dieback • whole needle dieback • loss of needle age classes • loss of needles within a whorl

0.00

0.05

0.10

0.15

0.20

0.25

0.30

MC MF XC XF

NE

ED

LE

SC

ALE

Sequoia National Park, Jeffrey pine mortality 1998-2008

CAUSE OF MORTALITY: BARK BEETLE

5 in the last 10 yrs was < 60% of avg ppt

The physiological drought stress was translated to morphological indicators in the canopy: • whorl loss • within whorl needle loss • reduced needle elongation • reduced branch and bole growth • high incidence of foliar insects • • • • And high mortality

Since 2008, only a few more trees have died, all in the xeric (unfertilized) microsites

Assessing tree drought stress without toys

Track site % of average precipitation

Measure % of maximum needle elongation

Look for LOTS of foliar insects and pathogens

Look at whole tree foliar discoloration and location in canopy

Use remote sensing tools to identify and eliminate drought stressed trees in thinning prescriptions

Acknowledgments

• Steve Seybold PSWRS USFS

• Andy Graves UC Davis > R3 FHP

• Mary Kay Herzenach U Colorado

• Jason Maxfield Portland State University

• Miles Daly U of Colorado

• Flavio Peggion U of Florence

• Danielle Cibecchini U of Florence

• Danielle Olivero U of Florence

• Jessica Drodz U of Colorado

• Lassen, Tahoe, Inyo, Sequoia, and San Bernardino National Forests

• Sequoia National Park

• USDA NRI CREES SUPPORT