Phragmites australis, in Chesapeake Bay tidal wetlands · Subestuaries of Chesapeake Bay studied as...

A landscape-scale approach to

management of a major invasive species,

Phragmites australis, in Chesapeake

Bay tidal wetlands

Dennis Whigham1, Eric Hazelton1,2, Melissa McCormick1, and Karin Kettenring1,2

1Smithsonian Environmental Research Center

2Utah State University

Saltonstall. 2002. PNAS 99: 2445-2449

Rhode River 1970

Rhode River 2009

A fundamental question in ecology

What drives the (rapid) spread of invasive species?

Characteristics of environment

Characteristics of invader

0 25 50 75 10012.5Kilometers

.

LANDUSEAgricultural

Developed

Forested

Mixed-Ag

Mixed-DevElizabeth

Chesapeake Bay

Warwick

Piankatank

Totuskey

St. Clements

St. Mary'sBreton

Wicomico

Tred Avon

Wye

Southeast

Langford

BirdBack

Patapsco

Curtis

Severn

Rhode

Battle

Miles

Corsica

Gwynns Falls

Jones Falls

Magothy

South

Manokin

MillSt. Leonards

Nomini

Ware

Pagan

Subestuaries of Chesapeake Bay studied as part of EPA-funded Atlantic Slope Consortium project

King, R.S., W.V. Deluca, D.F. Whigham, and P.P. Marra. 2007. Threshold effects of coastal urbanization on Phragmites australis (Common Reed) abundance and foliar nitrogen in Chesapeake Bay. Estuaries and Coasts 30: 469-481.

Have environmental factors driven the spread of Phragmites in recent years?

Phragmites seedling emergence higher in disturbances (p<0.001) in some plant communities (p<0.001). Rhizome emergence was low and not related to disturbances

% s

eedl

ing

emer

genc

e(m

ean

± 1

SE

)

0

10

20

30

40 controlaboveground disturbancebelowground disturbance

Iva Schoenoplectus Spartina/Distichlis Typha

a

b

ab

a

b b

a

b

b

a a

a

Phragmites seedlings (but not rhizomes) growth higher under elevated nitrogen (p=0.003) and plants were taller and produced more stems

Tota

l bio

mas

s (m

ean

± 1

SE

)

0.0

0.5

1.0

1.5

2.0

2.5

0 g m-2 yr-19 g m-2 yr-118 g m-2 yr-135 g m-2 yr-170 g m-2 yr-1

a

ab

c bc

bc

More florets (p=0.006) and inflorescences (p<0.001) are produced per plant with elevated nutrients

Num

ber o

f flo

rets

(mea

n ±

1 S

E)

0

1000

2000

3000

4000 ambient nutrientselevated nutrients

Num

ber o

f inf

lore

scen

ces

(mea

n ±

1 S

E)

0

2

4

6

8

10

12

14ambient nutrientselevated nutrients

Kettenring, McCormick, Baron, and Whigham, J. Appl. Ecol. 2011

CO2 + N experiment at the SERC Global Change Research Wetland

Mozdzer TJ, Megonigal JP (2012) Jack-and-Master trait responses to elevated CO2 and N: A comparison of native and Introduced Phragmites australis. PLoS ONE 7(10): e42794. doi:10.1371

Have biological factors driven the spread of Phragmites in recent years?

How does Phragmites reproduce and spread?

Rhizomes - Clonal (asexual) propagation

Seeds - Sexual reproduction (outcrossing)

Shoots - Clonal (Rooting at nodes)

Substantial genetic variation within and among patches: 91% of patches had >1 genotype

McCormick, Kettenring, Baron, and Whigham. 2010. Wetlands

# of genotypes per patch increased with watershed development

Kettenring, McCormick, Baron, and Whigham, J. Applied Ecology

Watershed Class

Forested Mixed- Developed

Developed

# of

gen

otyp

es p

er p

atch

(o

f 4 p

ossi

ble;

mea

n +

1SE

)

0

1

2

3

4 p=0.035 r2=0.145

McCormick, Kettenring, Baron, and Whigham J. Ecology 2011

Bruvo genetic diversity (natural log transformed)

-6 -5 -4 -3 -2

Prop

ortio

n vi

able

see

ds (l

ogit

of 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

Increased local genetic diversity positively related to viable seed production

McCormick, Kettenring, Baron, and Whigham Wetlands 2010, J. Ecology 2011

The majority of dispersal is local and within subestuaries

Where do the seeds establishing patches on hardened shoreline come from?

Mean distance separating sample pairs (m)

Rhode River

0 1000 2000 3000 4000 5000

Sim

ilarit

y (m

ean

Mor

an's

I +S

E)

0.0

0.2

0.4

0.6

0.8

1.0 Chesapeake Bay – 9 subestuaries

0 500 1000 50,000

100m 500m

Conceptual Model Based on Recent Findings

Feedback

Shoreline Structures • Genetic diversity • Dispersal

Phragmites Removal Experiment • Water quality • Fish and invertebrates transects • Transects • Each quadrat (n = 405):

– Plant Community – Nutrients – Salinity – Phragmites vigor – Phragmites clonal diversity – Phragmites flowering density – Phragmites herbivore density – Seed bank

Current Project (Focus: three types of subestuaries)

Shoreline disturbances

Shoreline TypeNatural Riprap Bulkhead

Gen

otyp

es(m

ean

+se)

0

1

2

3

4

5

6Forested Agriculture Developed

Shoreline hardening promotes more genetically diverse Phragmites patches

shoreline P=0.005 watershed P<0.001 shore x w-shed P=0.335

*

Why are patches associated with hardened shorelines more diverse? •Wave action deferred by bulkheads may cause repeated disturbances or may concentrate dispersing seeds at the edges. •Riprap may provide places for seeds to lodge. •Areas targeted for hardening may be those with the greatest fetch and/or disturbance and so might have the most (and most diverse) Phragmites anyway.

Herbicide application (glyphosate) over three years

At each site • Native • Phragmites removed • Phragmites control

Patapsco River (Developed)

Native outlier likely Iva

Native Control

Removal

St. Leonard River (Forested)

Outlier is open water

Native Control

Removal

Wye River (Agricultural)

Native Control

Removal

Is there any hope that effective management can happen?

Hazelton, E.L.G., Mozdzer, T.J., Burdick, D. Kettenring, K.M. and Whigham, D.F. 2014. Phragmites australis management in the United States: 40 years of methods and outcomes. AoB Plants, doi:10.1093/aobpla/plu001

Implications For Management • Without an effective management strategy, the non-native genotype potentially could occupy all brackish wetlands and, potentially, the majority of tidal freshwater wetlands •Effective long-term management can only be done at the scale of entire subestuaries (removal of primary sources of seeds)

•Following removal, management can focus on periodic inspections and removal of any new invasions.

•Efforts should be made to identify important subestuaries where most of the uplands are forested and few or relatively few patches of the non- native genotype occur. Complete removal and periodic inspections and follow-up are required.

•Some areas (e.g., around Baltimore and Norfolk) are so heavily invaded that removal and management are too expensive.

Rock Hall

Patapsco

Patch History

1970 – 1 patch Mid-1990s – 1 shoreline patch (VIMS) 2013 – 12 patches

St. Leonard Creek

Parkers Creek

Battle Creek

Fairhaven: Community action

Jay O’Neill – Head Technician, Plant Ecology lab, SERC Matt Sievers – SERC intern Heather Baron – SERC intern. MS - Oregon State Jared Staap – SERC intern. MS University of Maine Liza McFarland – SERC intern. MS – U. Maryland Hope Brooks – SERC intern. Senior at Penn State Funding sources: EPA – STAR program NOAA – Chesapeake Bay office Smithsonian Institution NOAA Smithsonian Institution

Matt

Heather

Melissa

Jared

Karin and Jay

Liza

Hope