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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