Post on 14-Mar-2021
Phragmites australis invasion into disturbances in Chesapeake Bay tidal wetlands:
Dispersal, colonization, fitness, and restoration
Karin Kettenring1,4, Eric Hazelton1,4, Sally Gallagher2,4, Heather Baron3,4, Melissa McCormick4, Matt Sievers4,5, and Dennis Whigham4
1Utah State University, Logan, UT 2University of Wisconsin and Wisconsin Department of Natural Resources, Madison, WI
3 Oregon State University, Corvallis, OR 4Smithsonian Environmental Research Center, Edgewater, MD
5Case Western Reserve University, Cleveland, OH
The role of disturbances across different life stages of Phragmites invasion
Disturbance: Anthropogenic
or natural
Dispersal: Distances and
mode Colonization: Seedling
emergence and
establishment Fitness: Viable seed production
Restoration: A disturbance
Phragmites australis
Native to North America
Introduced European haplotype (Saltonstall 2002) = invasive Phragmites
One of the most problematic invasive plants in North American wetlands
How are disturbances related to its spread?
The role of disturbances across different life stages of Phragmites invasion
Disturbance: Anthropogenic
or natural
Dispersal: Distances and
mode Colonization: Seedling
emergence and
establishment Fitness: Viable seed production
Restoration: A disturbance
What are sources of new wetland habitat in the Chesapeake Bay?
% developed land in watershed
0 20 40 60 80
abu
nd
ance
est
imat
e
0
1
2
3
4
5
6
7
Developed Mixed - Dev Forested
0 20 40 60 80
Ph
rag
mit
es a
bu
nd
ance
est
imat
e
0
1
2
3
4
5
6
7
Developed Mixed - Developed Forested
Phragmites more abundant in developed watersheds. N levels higher in surface water and Phragmites leaves.
King et al. 2007
What are sources of new wetland habitat in the Chesapeake Bay? Human-derived disturbances
What are sources of new wetland habitat in the Chesapeake Bay? Human-derived disturbances
Photo: Brandon White
Shoreline structures = physical disturbances (vegetation removal and sedimentation)
What are sources of new wetland habitat in the Chesapeake Bay? Natural disturbances
Photo: Brandon White
What are sources of new wetland habitat in the Chesapeake Bay? Natural disturbances
Iva
Sch
oeno
plec
tus
Spa
rtina
/Distic
hlis
Typha
Flat
Hole
Mound
Iva
Sch
oeno
plec
tus
Spa
rtina
/ Distic
hlis
Typha
Count
0
10
20
30
40
50
60
Small 0-1m2
Med. >1-2m2
Large >2m2
Trail
Number, type, and size of disturbances varies by plant community. Summer intern: Sally Gallagher
• 5 transects / vegetation type / marsh • 4 m * 75 m transects
The role of disturbances across different life stages of Phragmites invasion
Disturbance: Anthropogenic
or natural
Dispersal: Distances and
mode Colonization: Seedling
emergence and
establishment Fitness: Viable seed production
Restoration: A disturbance
How does Phragmites get to these disturbances?
McCormick, Kettenring, Baron, and Whigham J. Ecology 2011
Evidence for sexual reproduction:
Substantial genetic variation within and among patches
91% of patches had >1 genotype
55% of patches had 4 genotypes
No pair of patches shared a genotype
Some clonal expansion within patches
How does Phragmites get to these disturbances? Sexual reproduction and spread
4 leaves collected
McCormick, Kettenring, Baron, and Whigham Wetlands 2010, J. Ecology 2011
The majority of dispersal is local and within subestuaries.
How does Phragmites get to these disturbances? Seed dispersal
Distance separating sample pairs (m)
0 500 1000 500000 1000 2000 3000 4000 5000
Mora
n's
I(m
ean +
SE
)
0.0
0.2
0.4
0.6
0.8
1.0 Rhode River Chesapeake Bay – 9 subestuaries
The role of disturbances across different life stages of Phragmites invasion
Disturbance: Anthropogenic
or natural
Dispersal: Distances and
mode Colonization: Seedling
emergence and
establishment Fitness: Viable seed production
Restoration: A disturbance
How does Phragmites emerge and establish in these wetlands?
How does Phragmites emerge and establish in these wetlands? Disturbance: seedlings, not rhizomes
% s
eed
ling e
me
rge
nce
(me
an ±
1 S
E)
0
10
20
30
40control
aboveground disturbance
belowground disturbance
Iva Schoenoplectus Spartina/Distichlis Typha
a
b
ab
a
b b
a
b
b
a a
a
Sum
mer
inte
rn:
Sally
Gal
lagh
er
Seedling emergence significantly higher in disturbances.
How does Phragmites emerge and establish in these wetlands? Disturbance size and frequency
Undisturbed control Small, single clip Small, frequent clip Large, single clip Large, frequent clip
Transplant survivorship 64%. No treatment effect.
Ph.D. student: Eric Hazelton
The role of disturbances across different life stages of Phragmites invasion
Disturbance: Anthropogenic
or natural
Dispersal: Distances and
mode Colonization: Seedling
emergence and
establishment Fitness: Viable seed production
Restoration: A disturbance
How does Phragmites reproduce once established?
Bruvo genetic diversity (natural log transformed)
-6 -5 -4 -3 -2
Pro
port
ion v
iable
seeds (
log
it o
f m
ean)
-8
-6
-4
-2
0
2R2=0.26, P=0.0003
Kettenring, McCormick, Baron, and Whigham J. Applied Ecology 2011
Seeds and leaves collected
How does Phragmites reproduce once established? Cross pollination
Viable seed production positively related to patch-level genetic diversity.
Kettenring, McCormick, Baron, and Whigham J. Applied Ecology 2011
How does Phragmites reproduce once established? Cross pollination
Nutrients Ambient
4g N m-2 year-1 0.4g P m-2 year-1
Elevated 8g N m-2 year-1
0.8g P m-2 year-1
Pollination Self
Cross
Pro
port
ion v
iable
seeds (
mean ±
1 S
E)
0.00
0.05
0.10
0.15
0.20
0.25
0.30Out-crossed, ambient nutrients
Selfed, ambient nutrients
Out-crossed, elevated nutrients
Selfed, elevated nutrients
Viable seed production positively related to cross pollination. Disturbance / diversity feedback: seed production
How does Phragmites reproduce once established?
New Old
Perc
ent
of
sam
ple
s d
istinct
(mean +
SE
)
0
10
20
30
40
50
60
New Old
Bru
vo d
ivers
ity
(mean +
SE
)0.0
0.1
0.2
0.3
0.4
0.5
P<0.001 P=0.004
Summer intern: Matt Sievers
Diversity within patches declines with age (1970 vs. 2011). Leads to decline in seed production?
Patch age
Genet diversity and stand age
The role of disturbances across different life stages of Phragmites invasion
Disturbance: Anthropogenic
or natural
Dispersal: Distances and
mode Colonization: Seedling
emergence and
establishment Fitness: Viable seed production
Restoration: A disturbance
Does restoration create a disturbance that favors Phragmites invasion?
Does restoration create a disturbance that favors Phragmites invasion? Disturbance / diversity feedback
9 marshes, 3 treatments per marsh
– Phragmites removed; Phragmites intact (control); Native vegetation (reference)
Fall 2011: Herbicide Phragmites
Monitoring: genet diversity, reproduction for 4 years
Ph.D. student: Eric Hazelton
The role of disturbances across different life stages of Phragmites invasion
Disturbance: Anthropogenic
or natural
Dispersal: Distances and
mode Colonization: Seedling
emergence and
establishment Fitness: Viable seed production
Restoration: A disturbance
Short circuit disturbance pathway?
Invasion tightly coupled to disturbances
Questions?
Funding: NOAA, EPA Field and lab assistance: Jay O’Neill