Seeds, Stolons, and Rhizomes. Oh My! Pathways of Introduction and ...

Seeds, Stolons, and Rhizomes. Oh My! Pathways of Introduction and Spread of

Non-native Phragmites

Karin M. Kettenring

Department of Watershed Sciences and Ecology Center Utah State University

Who am I and who do I work with?

Where do I work?

Photo: Brandon White

Outline

• Reproductive system and how it spreads

• Factors that influence spread

• Implications for management

Outline

• Reproductive system and how it spreads

• Factors that influence spread

• Implications for management

How does Phragmites spread?

Asexual reproduction

Sexual reproduction

Environmental and biological factors

Asexual reproduction Rhizomes

Horizontal, underground stem

Spread, storage of carbohydrates

Stolons (“runners”)

Horizontal stem creeping along the ground and rooting at the nodes or at the tip and giving rise to a new plant

Spread, foraging for light

Harris and Harris 2007

Rhizomes

Rhizomes

Photo credit: science and plants for schools (flickr)

Rhizomes

Photo credit: Gwylan (flickr)

Rhizomes

Stolons

Stolons

Photo credit: Travis Henspeter (flickr)

Seeds - inflorescences

Seeds – immature and mature inflorescences

Photo credit: MI SeaGrant (flickr)

Seeds – immature inflorescence

Seeds – inflorescences and florets

Seeds – florets

Photo credit: MI SeaGrant (flickr)

Photo credit: Matt Levin

Seeds – florets on spikelet

Photo credit: ophis (flickr)

Seeds – florets

Photo credit: Harry Rose (flickr)

Seeds – florets on spikelet

Photo credit: ophis (flickr)

Seeds – florets and caryopses

Photo credit: D. Walters and C. Southwick

Seeds – caryopsis

Photo credit: MI SeaGrant (flickr)

But do seeds really matter?!

McCormick et al. 2010, 2011

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

Similar results found by Belzile et al. 2010, Kirk et al. 2011

Sexual reproduction is more important than previously thought.

Native Subspecies americanus

Introduced, Invasive

Salt

on

stal

l et

al. 2

00

4

Native vs. introduced Phragmites comparisons are important

Sexual reproduction is more important for introduced vs. native Phragmites. (Kettenring and Mock 2012)

Expansion of Phragmites patches at fine spatial scales Combination of asexual and sexual spread (samples every 0.5m)

Kettenring and Mock, unpubl. data

Kettenring et al. 2011

Phragmites seed viability varies tremendously among patches.

Site name and patch number

1 2 4 6 7 3 11 12 15 17 19 1 5 7 8 18 4 5 9 13 20 2 5 8 10 18 2 3 5 10 14 2 6 9 13 18 1 6 9 15 18 1 7 12 15 17

Pro

po

rtio

n v

iab

le s

ee

ds

(arc

sin

e s

qu

are

ro

ot

of

me

an

± 1

SE

)

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

Forested

Mixed-developed

Developed

Battle

Creeek

BackRiver

CurtisBay

ElizabethRiver

MillCreek

ParkersCreek

Saint MarysRiver

SouthRiver

SevernRiver

More viable seeds result in substantially larger seed banks.

Seed viability level

Num

ber

of

Phra

gm

ite

s s

eedlin

gs

(mean ±

1 S

E)

0

1

2

3

4

5Severn River

South River

High Low High Low

Baldwin et al. 2010

Outline

• Reproductive system and how it spreads

• Factors that influence spread

• Implications for management

Drivers of asexual reproduction

Factor Conditions that improve emergence from rhizomes

Size Larger (Bart and Hartman 2003)

Burial Burial by sediment (Bart and Hartman 2002)

Disturbance Removal of existing vegetation (Minchinton and Bertness 2003); No effect (Kettenring et al. unpubl. data)

Flood levels Unflooded, then spreads through clonal integration (Amsberry et al. 2000;

Bart and Hartman 2000, 2003; Hellings and Gallagher, 1992)

Sulfide Lower sulfide (Bart and Hartman 2000)

Salinity Lower salinity (Bart and Hartman 2002, 2003; Hellings and Gallagher 1992); wider salinity tolerance that native Phragmites (Vasquez et al. 2005)

Nutrients Elevated nitrogen (field study: Minchinton and Bertness 2003); No effect (greenhouse

study: Kettenring and Whigham unpubl. data)

Drivers of sexual reproduction

Factor Conditions that improve seed production, viability, dormancy, germination, and seedling emergence and survival

Herbivory Reduces flowering potential (Tscharntke 1999; Lambert et al. 2007; Tewksbury et al. 2002)

Clonal diversity More genotypes (Kettenring et al. 2010, 2011)

Disturbance Small disturbances benefit emergence (Kettenring et al. unpubl. data);

Light Germinates in light and dark (Ekstam et al. 1999); higher seedling emergence in disturbances with higher light (Kettenring et al. unpubl. data)

Nutrients More florets, inflorescences produced (Kettenring et al. 2011); more robust seedlings (Kettenring and Whigham, unpubl. data; Saltonstall and Stevenson 2007)

Drivers of sexual reproduction

Factor Conditions that improve seed production, viability, dormancy, germination, and seedling emergence and survival

Herbivory Reduces flowering potential (Tscharntke 1999; Lambert et al. 2007; Tewksbury et al. 2002)

Clonal diversity More genotypes (Kettenring et al. 2010, 2011)

Disturbance Small disturbances benefit emergence (Kettenring et al. unpubl. data);

Light Germinates in light and dark (Ekstam et al. 1999); higher seedling emergence in disturbances with higher light (Kettenring et al. unpubl. data)

Nutrients More florets, inflorescences produced (Kettenring et al. 2011); more robust seedlings (Kettenring and Whigham, unpubl. data; Saltonstall and Stevenson 2007)

Number of genotypes per patch(of 4 possible)

2111 42 331 222 3 42 33333 42 44431 43 432 42 3 42 44444444

Pro

port

ion v

iable

seeds

(arc

sin

e s

quare

root

of

mean ±

1 S

E)

0.0

0.1

0.2

0.3

0.4

0.5

0.6

a

b b

b

Kettenring et al. 2010, 2011

Increased local genetic diversity positively related to viable seed production.

Seeds and leaves collected

Cross pollination benefits viable seed production, elevated nutrients do not.

Pro

port

ion

via

ble

seed

s (

mean

± 1

SE

)

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

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

Kettenring et al. 2011

Drivers of sexual reproduction

Factor Conditions that improve seed production, viability, dormancy, germination ,and seedling emergence and survival

Herbivory Reduces flowering potential (Tscharntke 1999; Lambert et al. 2007; Tewksbury et al. 2002)

Clonal diversity More genotypes (Kettenring et al. 2010, 2011)

Disturbance Small disturbances benefit emergence (Kettenring et al. unpubl. data);

Light Germinates in light and dark (Ekstam et al. 1999); higher seedling emergence in disturbances with higher light (Kettenring et al. unpubl. data)

Nutrients More florets, inflorescences produced (Kettenring et al. 2011); more robust seedlings (Kettenring and Whigham, unpubl. data; Saltonstall and Stevenson 2007)

Seedling emergence significantly higher in disturbances.

% s

ee

dlin

g e

me

rge

nce

(me

an

± 1

SE

)

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

Kettenring et al. unpubl. data

Drivers of sexual reproduction

Factor Conditions that improve seed production, viability, dormancy, germination ,and seedling emergence and survival

Herbivory Reduces flowering potential (Tscharntke 1999; Lambert et al. 2007; Tewksbury et al. 2002)

Clonal diversity More genotypes (Kettenring et al. 2010, 2011)

Stand age No effect on seed production (Hazelton et al. in review)

Disturbance Small disturbances benefit emergence (Kettenring et al. unpubl. data);

Light Germinates in light and dark (Ekstam et al. 1999); higher seedling emergence in disturbances with higher light (Kettenring et al. unpubl. data)

Nutrients More florets, inflorescences produced (Kettenring et al. 2011); more robust seedlings (Kettenring and Whigham, unpubl. data; Saltonstall and Stevenson 2007)

More florets and inflorescences are produced per plant with elevated nutrients.

Num

ber

of

flore

ts(m

ean ±

1 S

E)

0

1000

2000

3000

4000 ambient nutrients

elevated nutrients

Num

ber

of

inflore

scences

(mean ±

1 S

E)

0

2

4

6

8

10

12

14ambient nutrients

elevated nutrients

Kettenring et al. 2011

Drivers of sexual reproduction

Factor Conditions that improve seed production, viability, dormancy, germination, and seedling emergence and survival

Temperature Greater amplitude and summer temperatures → germination (Ekstam and

Foresby 1999; Ekstam et al. 1999); cold, moist conditions → breaks dormancy (Kettenring and Whigham 1999)

Flood levels Lower flooding levels better for seed/lings; tolerance increases with age (Armstrong et al. 1999; Baldwin et al. 2010; Mauchamp et al. 2001; reviewed in Chambers et al. 2003)

Oxygen Hypoxia increased germination but seedlings inhibited by low O2 levels (Wijte and Gallagher 1996a, b)

Sulfide Lower sulfide; tolerance increases with age (reviewed in Chambers et al. 2003)

Salinity Lower salinity; tolerance increases with age (Wijte and Gallagher 1996a; Mauchamp

and Mesleard 2001; reviewed in Chambers et al. 2003)

Drivers of sexual reproduction

Factor Conditions that improve seed production, viability, dormancy, germination, and seedling emergence and survival

Temperature Greater amplitude and summer temperatures → germination (Ekstam and

Foresby 1999; Ekstam et al. 1999); cold, moist conditions → breaks dormancy (Kettenring and Whigham 1999)

Flood levels Lower flooding levels better for seed/lings; tolerance increases with age (Armstrong et al. 1999; Baldwin et al. 2010; Mauchamp et al. 2001; reviewed in Chambers et al. 2003)

Oxygen Hypoxia increased germination but seedlings inhibited by low O2 levels (Wijte and Gallagher 1996a, b)

Sulfide Lower sulfide; tolerance increases with age (reviewed in Chambers et al. 2003)

Salinity Lower salinity; tolerance increases with age (Wijte and Gallagher 1996a; Mauchamp

and Mesleard 2001; reviewed in Chambers et al. 2003)

Environmental drivers of emergence, establishment, and survival

Chambers et al. Estuaries 2003

X=plant death

Mechanisms for Phragmites spread

Rhizomes/stolons

• Larger

• Burial

• Disturbances

• Elevated nutrients

• Unflooded, lower sulfide

• Lower salinity

Seeds

• No herbivores

• More genotypes

• Disturbances, higher light

• Elevated nutrients

• Unflooded, lower sulfide

• Lower salinity

• Greater amplitude and summer temperatures

Outline

• Reproductive system and how it spreads

• Factors that influence spread

• Implications for management

How can we best control Phragmites?

Understanding characteristics of the environment and the plant that contribute to its spread

Management implications

Environment

• Nutrient management

• Causes of disturbances

• Minimize drawdowns

• Reductions in salinity

Biology

• Seed production and dispersal (timing of spraying)

• Seed banks (follow up)

• Small patches before accumulate genetic diversity

Evaluating the effects of: • Summer vs. fall glyphosate • Summer vs. fall imazapyr • Summer mow followed by fall

glyphosate • Spring mow, cover with black plastic

Tracking Phragmites cover, seed banks, inflorescence production, and native plants

Phragmites control experiments

Rohal, Cranney, Hazelton, and Kettenring

Questions?

Karin Kettenring [email protected]

https://www.cnr.usu.edu/htm/facstaff/Kettenring/