disease and insect effects on ecosystem processes in the context of climate change christa mulder...
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Disease and Insect Effects on Ecosystem Processes
in the context of Climate Change
Christa MulderUAF
Conceptual Overview
Herbivores and
Pathogens
Plant populations (mortality, growth rates)
Community composition
Ecosystem Processes
Climate Change
Dominant or keystone
Δ competition or facilitation
Herbivores and
Pathogens
Plant populations (mortality, growth rates)
Community composition
Ecosystem Processes
OUTBREAK SPECIES
Dominant or keystone
Herbivores and
Pathogens
Plant populations (mortality, growth rates)
Community composition
Ecosystem Processes
NON-OUTBREAK SPECIES
Δ competitionor facilitation
Δ abundancedominant or keystone
Overview
Outbreak species:1) Alder (Alnus tenuifolia) and canker2) Spruce and spruce budworm3) Aspen and leafminer
Non-outbreak species: parasite communities on…1) Alder (Alnus viridis)2) Cranberry (Vaccinium vitis-idaea)3) Rose (Rosa acicularis)
0 1 2 3 4 5 6 7 8 9 10
DBH Diameter Class (cm)
0
500
1000
1500
Den
sity
(st
ems
ha-1
)
Quartz Creek - Kenai Region
Live without cankerLive with cankerDead from cankerOther dead
719 stems / 3 plots
0
20
40
60
80
100
Pro
port
ion
Infe
cted
or
Dea
d (%
)
0 1 2 3 4 5 6 7 8 9 10
DBH Diameter Class (cm)
0
1000
2000
3000
4000
Den
sity
(st
ems
ha-1
)
Alder Shrub - Tanana River
Live without cankerLive with cankerDead from cankerOther dead
1745 stems / 3, 18X18 m plot
0
20
40
60
80
100
Pro
port
ion
Infe
cte
d or
Dea
d (%
)
0 1 2 3 4 5 6 7 8 9 10
DBH Diameter Class (cm)
0
1000
2000
3000
Den
sity
(st
ems
ha-1
)
Alder Shrub - Eagle River Anchorage Basin
Live without cankerLive with cankerDead from cankerOther dead
719 stems / 3 plots
0
20
40
60
80
100
Pro
port
ion
Infe
cte
d or
Dea
d (%
)
2005 Canker (Valsa melanodiscus) Survey on A. tenuifolia
(Roger Ruess and colleagues)
10 30 50 70 90
Proportion of Canopy Dead from Canker (% tree-1)
0
20
40
60
80
100
Pro
po
rtio
n o
f T
ota
l N
od
ule
Bio
mas
s L
ive
(% t
ree
-1)
Eagle RiverQuartz CreekTanana
Y = 96.08 - 0.76 X
r2 = 0.63, P < 0.0001
0 20 40 60 80 100
Proportion of Basal Area Dead from Canker (%)
0
20
40
60
80
100
Pro
po
rtio
n o
f L
eaf
Are
a D
ead
fro
m C
anke
r (%
)
Eagle RiverQuartz CreekTanana
Y = 1.3897 + 0.7187*X
r2 = 0.67, P<0.0001
Effects of canker on whole-stand N inputs are driven by declines in nodule biomass associated with ramet mortality
5
7
9
11
13
N F
ixat
ion
Rat
e (
mo
l N g
no
du
leD
WT
-1 h
r-1)
Eagle River Quartz Creek Tanana
a
b
a
a
0
5
10
15
20
25
Pro
po
rtio
n B
asal
Are
a o
r L
eaf
Are
a D
ead
Fro
m C
anke
r (%
)
% Basal Area Dead% Leaf Area Dead
Eagle River Quartz Creek Tanana
A
b
a
a
A
B
Also appears to be an effect of canker infection on N fixation rate (at the nodule level)
1) Investigate the susceptibility of green alders (Alnus viridis ssp. fruticosa, synonym =A. crispa) to infection by Valsa melanodiscus under water stress.
2) Monitor the response of the water transport system to infection and colonization.
3) Determine if alders respond to disease by adjusting water use efficiency.
4) Measure the effect of disease development on photosynthesis (light saturation pt., quantum efficiency).
An inoculation experiment with Alnus viridis (green alder) and Valsa melanodiscus:Susceptibility to infection and the physiological effects of disease development
(Jenny Rohrs-Richey)
Greenhouse Experiment
June 1
Aug 23
Two Weeks After Inoculation
PycnidiaNecrotic lesion
Water Availability and Disease Incidence
Infected Alders
Well-watered plants are less likely to become infected than water-limited plants(early in the growth season)
Non-infected plants fix more carbon than infectedplants… but only if theyare well-watered.
Stomatal Regulation of Photosynthesis
Spruce bud-worm on white spruce (Picea glauca)
Glenn Juday and colleagues
Date of spruce budworm heat requirement at Fairbanks
158
163
168
173
178
183
188
193
198
1905 1915 1925 1935 1945 1955 1965 1975 1985 1995 2005
year
Juli
an
date
moth @437.4 Linear (moth @437.4)
20042004
199319931995199519881988
19901990
1953?1953? 1975?1975?
Deg. CThreshold = 8.0GDD = 243
BA
RK
BA
RK
20052005
2000
2000
2001
2001
2002
2002
2003
2003
2004
2004
2006
2006
1999
1999
1998
1998
1997
1997
1996
1996
1992
1992
1991
1991
1990
1990
1995199519931993
spruce budwormspruce budwormdamagedamage heat/droughtheat/drought
limitationlimitation
Fairbanks Summer Temperature and W. Spruce Growth (BNZ LTER - 2PLS; 1902:2007; n = 2 trees)
11.0
11.5
12.0
12.5
13.0
13.5
14.0
14.5
15.0
15.5
20071997198719771967195719471937192719171907
year
May:A
ug
T (
de
g.
C)
0.0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1.0
1.1
mean
rin
g-w
idth
(m
m)
3-yr weighted May:Aug Temperature mean tree 5&8
Summer temperature vs. w. spruce growth(Bonanza Creek LTER -2 Parks Loop South; 1906-2006; n = 12 trees)
r2 = 0.32
0.0
0.2
0.4
0.6
0.8
1.0
1.2
9.0 10.0 11.0 12.0 13.0 14.0 15.0 16.0 17.0 18.0 19.0 20.0
previous May:Aug T (deg C)
mean
sam
ple
rin
g w
idth
(m
m)
1912 volcanic 1912 volcanic ash?ash?
1993 & 95 spruce budworm defoliation1993 & 95 spruce budworm defoliation
KILL ZONEKILL ZONE2004 record hot2004 record hot
Aspen leaf miner moth(Phyllocnistis populiella)(Diane Wagner, Pat Doak, Linda DeFoliart, Jenny
Schneiderheinze)
Univoltine
Adults emerge in May
before leaf-out, mate
Lay eggs on both sides of
new leaves
Eggs digest cuticle, sink
into leaf
Aspen leaf miner moth (Phyllocnistis populiella)
Larvae restricted to one
side of leaf
cannot switch sides
cannot exit and reenter
Consume epidermal cells as
move during instars I – III
Separation of cuticle from
mesophyll causes white
appearance of mines
Aspen leaf miner infestation of Alaskan forests
R. Werner, US Forest Service flyovers
1974
1977
1980
1983
1986
1989
1992
1995
1998
2001
2004
2007
AK
are
a in
fest
ed (
ha*1
000)
0
50
100
150
200
250
300
Aspen leaf miner infestation of Bonanza Creek LTER
R. Werner, www.lter.uaf.edu and pers. comm.
0
50
100
150
200
250
300
1975
1977
1979
1981
1983
1985
1987
1989
1991
1993
1995
1997
1999
2001
2003
2005
2007
Year
Asp
en l
eaf
min
ers
(N p
er m
2 fo
liag
e) Aspen leaf miner
Tortrix
Bottom mining reduces photosynthesis
L. Defoliart, Wagner et al. in review
% Mining on leaf bottom
0 20 40 60 80 100
Net
pho
tosy
nthe
sis
(µm
ol C
O2
m-2
s-1
)
0
5
10
15
20
25
Surface mined
Neither Top Bottom
Net
Pho
tosy
nthe
sis
(µm
ol C
O2
m-2
s-1)
0
2
4
6
8
10
Bottom mining reduces photosynthesis
J. Schneiderheinze, Wagner et al. in review
a
a
b
Bottom mining disrupts stomatal function
Wagner, Defoliart, Doak, Schneiderheinze in review
Surface mined
Neither Top Bottom0.00
0.02
0.04
0.06
0.08
0.10
b
aa
Con
duct
ance
(mol
m-2
s-1)
% Bottom mining
0 20 40 60 80 100Le
af
13C
-33
-32
-31
-30
-29
-28
-27
-26
Top mining affects water balance
% Leaf top mined
0 20 40 60 80 100
% L
eaf H
2O
40
45
50
55
60
65
Leaf mining leads to early leaf abscission
Percent leaf mining damage
0 1-25 26-50 51-75 76-100
Dat
e of
leaf
abs
ciss
ion 15
30 5
5
45
16-Aug
1-Sep
16-Sep
1-Oct
16-Oct
Data: L. Defoliart
Mining reduces aspen growth
2005 2006 2007
Dia
met
er
ch
an
ge
(mm
)
0.0
0.2
0.4
0.6
0.8
1.0
Year
2005 2006 2007
BNZ ED
ControlSprayed
Wagner, Defoliart, Doak, Schneiderheinze in review.
Summary
1) Outbreak pathogen (canker) on a keystone shrub species (alder):
• reduces fixation rates of nodules on infected trees• reduces carbon fixation rates via reduced stomatal
conductance• climate change: reduced water availability may increase
susceptibility to this disease
2) Outbreak herbivore on a dominant tree white spruce greatly reduces growth (C fixation)
• Combined with increased temperature could result in massive die-offs
3) Outbreak herbivore reduces photosynthetic rates (C fixation) and stomatal conductance in a dominant tree species (trembling aspen)
Non-outbreak species on leaves(Christa Mulder & Bitty Roy)
Alnus viridis (alder):13 herbivores9 pathogens
Rosa acicularis (rose):11 herbivores13 pathogens
Vaccinium vitis-idaea(cranberry):5 herbivores7 pathogens
Summer temperature and precipitation, 2002-2006
-3
-2
-1
0
1
2
3
4
5
6
may jun
ejul
yau
gm
ay june
july
aug
may jun
ejul
yau
gm
ay june
july
aug
may jun
ejul
yau
g
dif
fere
nce
fro
m l
on
g-t
erm
mea
n t
emp
(C
)
-60
-40
-20
0
20
40
60
80
100
120
dif
fere
nce
fro
m l
on
gte
rm m
ean
p
reci
pit
atio
n (
mm
)
temperature precipitation
2002 2003 2004 2005
A
2006
Winter temperature and snow depths, 2002-2006
-8
-6
-4
-2
0
2
4
6
8
10
oct
dec
feb
apr
oct
dec
feb
apr
oct
dec
feb
apr
oct
dec
feb
apr
oct
dec
feb
dif
fere
nc
e f
rom
lo
ng
term
me
an
te
mp
in
de
gre
es
C
-300
-250
-200
-150
-100
-50
0
50
100
150 dif
fere
nc
e f
rom
lo
ng
term
me
an
sn
ow
de
pth
in
mmtemperature snow depth
2001-2002 2002-2003 2003-2004 2004-2005 2005-2006
B
Total damage patterns 2002-2006
0
5
10
15
20
25
2002 2003 2004 2005 2006
% o
f le
af a
rea
dam
aged
other
pathogen
herbivore
a a bd c d
a a b
a
a
A ALNUS
0
1
2
3
4
5
6
7
8
9
10
2002 2003 2004 2005 2006
% o
f le
af a
rea
dam
age
other
pathogen
herbivore
ab a
c
bc
ab ab
a
ab
bc
b
E VACCINIUM
0
2
4
6
8
10
12
14
16
2002 2003 2004 2005 2006
% o
f le
af a
rea
dam
age
other
pathogen
herbivore
a b b a
ab
bab
a
C ROSA •Fairly constant total biological damage•Relative contribution of herbivores vs. pathogens varies
Herbivory patterns by feeding mode
0
2
4
6
8
10
12
14
16
2002 2003 2004 2005 2006
Per
cen
t o
f le
af a
rea
dam
aged
leafroll
mining
sucking
chewing
a a ab a
a b
a
a
a
a
a
a
b
a
a
a
b
b
a
ALNUSB
0
0.5
1
1.5
2
2.5
3
2002 2003 2004 2005 2006
Per
cen
t o
f le
af a
rea
dam
aged
mining
sucking
chewing
ab a cbc bc
VACCINIUMF
0
1
2
3
4
5
6
7
8
2002 2003 2004 2005 2006
Per
cen
t o
f le
af a
rea
dam
aged
mining
sucking
chewing
ba b b
b
a
a
a
ROSAD
•Fairly low damage in record hot year for all three species•Lowest sucking damage in record hot year for all three species•Highly variable relative contributions by different guilds
Impacts of herbivores and pathogens on reproduction in alder
0
0.5
1
1.5
2
2.5
0 5 10 15 20 25 30 35 40
Herbivore damage (mean % leaf area per tree)
Lo
g10
(m
ean
# c
atki
ns
pe
r b
ran
ch
) female catkinsmale catkins
A
0
0.5
1
1.5
2
2.5
-1 5 10 15 20
Pathogen damage (mean % leaf area per tree)
Lo
g1
0 (
mea
n #
cat
kin
s p
er b
ran
ch)
female catkinsmale catkins
C
Herbivore damage is negatively related to catkin production
Pathogen damage is positively related to catkin production
Woolly alder sawfly, Eriocampa
ovata
Ruess, R. W., M. D. Anderson, J. S. Mitchell, and J. W. McFarland. 2006. Effects of defoliation on growth and N2-fixation in Alnus tenuifolia: Consequences for changing disturbance regimes at high latitudes. Ecoscience 13:402-412.
Mortality in cranberry
• Cranberry ramet mortality rates are high (15-75% over the course of 4-5 years, or 3-15% per year)
• Winter-warm sites had higher rates of mortality and high rates of “red-brown dieback”
• Cause and effect are unclear– Could be physical damage– Could be a disease attacking
already dying leaves– Could be caused by a disease
Climate change and herbivores / pathogens: Alder
Warmer, drier summer conditions may favour pathogens… • Higher pathogen levels in warmer years, and at warmer sites
in 2004 (record hot dry year)• BUT: sucking insects were lower at warm sites or in warm
years
• Cold winters may favour herbivores:higher damage following winters with higher minimum temperatures
Climate change and herbivores / pathogens: cranberry and rose
Cranberry:• Sucking and mining damage were
greater at sites with warmer winter temperatures (in 2004) and in warmer years
Rose:• Between years, total herbivore
damage and sucking damage were lower when summer temperatures were higher
Summary
• TOTAL damage levels are fairly constant across years for all three species
• COMPOSITION of the parasite communities varies greatly between years
• Relationships with environmental characteristics depend on the feeding mode
• For alder, these damage levels may be high enough to substantially reduce N fixation rates
• Cranberry ramet mortality rates are high… but cause is unclear.
Herbivores and
Pathogens
Plant populations (mortality, growth rates)
Community composition
Ecosystem Processes
OUTBREAK SPECIES
Dominant or keystone
Herbivores and
Pathogens
Plant populations (mortality, growth rates)
Community composition
Ecosystem Processes
NON-OUTBREAK SPECIES
Δ competitionor facilitation
Δ abundancedominant or keystone
N fixation, C fixation, transpiration
??
Gaps
• Are the outbreak species fundamentally different from non-outbreak species, or can many of the numerous non-outbreak species become outbreak species with major impacts?
• Loss of dominant species will change species composition… how will that affect ecosystem processes?
• Non-outbreak species: – How does low-level (<20%) damage affect photosynthesis,
water balance, N fixation?– how do they affect community dynamics (composition)? How in
turn does this affect ecosystem processes?
Links to thresholds and regime changes
• Spruce bud-worm: may reduce the temperatures at which massive tree die-offs occur
• Alder and canker: could hot, dry conditions (have) increase(d) susceptibility to the point where outbreaks are possible?
• Could warm winters increase overwintering survival of herbivore species on alder to the point where they become outbreak species?
Links to Invasive Plants• Future research (Mulder lab): how do
biotic factors, including herbivores and pathogens, accelerate or retard the advance of invasives in burned habitat?– Potential for acceleration:
• “Enemy release” from soil pathogens• Introduction of new plant pathogens to natives
– Potential for deceleration:• Herbivory• Pathogens on invasives