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