Seeds, Stolons, and Rhizomes. Oh My! Pathways of Introduction and Spread of Non-native Phragmites

Transcription

1 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

2 Who am I and who do I work with?

3 Where do I work? Photo: Brandon White

4 Outline Reproductive system and how it spreads Factors that influence spread Implications for management

5 Outline Reproductive system and how it spreads Factors that influence spread Implications for management

6 How does Phragmites spread? Asexual reproduction Sexual reproduction Environmental and biological factors

7 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

8 Rhizomes

9 Rhizomes

10 Rhizomes Photo credit: science and plants for schools (flickr)

11 Rhizomes Photo credit: Gwylan (flickr)

12 Stolons

13 Stolons Photo credit: Travis Henspeter (flickr)

14 Seeds - inflorescences

15 Seeds immature and mature inflorescences

16 Seeds immature inflorescence Photo credit: MI SeaGrant (flickr)

17 Seeds inflorescences and florets

18 Seeds florets Photo credit: MI SeaGrant (flickr)

19 Seeds florets on spikelet Photo credit: Matt Levin

20 Seeds florets Photo credit: ophis (flickr)

21 Seeds florets on spikelet Photo credit: Harry Rose (flickr)

22 Seeds florets and caryopses Photo credit: ophis (flickr)

23 Seeds caryopsis Photo credit: D. Walters and C. Southwick

24 But do seeds really matter?! Photo credit: MI SeaGrant (flickr)

25 Sexual reproduction is more important than previously thought. 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 McCormick et al. 2010, 2011 Similar results found by Belzile et al. 2010, Kirk et al. 2011

26 Saltonstall et al Native vs. introduced Phragmites comparisons are important Native Subspecies americanus Introduced, Invasive Sexual reproduction is more important for introduced vs. native Phragmites. (Kettenring and Mock 2012)

27 Expansion of Phragmites patches at fine spatial scales Combination of asexual and sexual spread (samples every 0.5m) Kettenring and Mock, unpubl. data

28 Phragmites seed viability varies tremendously among patches. 1.0 Proportion viable seeds (arcsine square root of mean ± 1 SE) Forested Mixed-developed Developed Battle Creeek Parkers Creek Saint Marys River Mill Creek South River Severn River Site name and patch number Back River Curtis Bay Elizabeth River Kettenring et al. 2011

29 More viable seeds result in substantially larger seed banks. 5 Severn River Number of Phragmites seedlings (mean ± 1 SE) South River 0 High Low High Low Seed viability level Baldwin et al. 2010

30 Outline Reproductive system and how it spreads Factors that influence spread Implications for management

31 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 Nutrients Lower salinity (Bart and Hartman 2002, 2003; Hellings and Gallagher 1992); wider salinity tolerance that native Phragmites (Vasquez et al. 2005) Elevated nitrogen (field study: Minchinton and Bertness 2003); No effect (greenhouse study: Kettenring and Whigham unpubl. data)

32 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)

33 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)

34 Increased local genetic diversity positively related to viable seed production. Seeds and leaves collected Proportion viable seeds (arcsine square root of mean ± 1 SE) a b b b Number of genotypes per patch (of 4 possible) Kettenring et al. 2010, 2011

35 Cross pollination benefits viable seed production, elevated nutrients do not. Nutrients Ambient 4g N m -2 year g P m -2 year -1 Elevated 8g N m -2 year g P m -2 year -1 Pollination Self Cross Proportion viable seeds (mean ± 1 SE) Out-crossed, ambient nutrients Selfed, ambient nutrients Out-crossed, elevated nutrients Selfed, elevated nutrients Kettenring et al. 2011

36 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)

37 Seedling emergence significantly higher in disturbances. % seedling emergence (mean ± 1 SE) a b control aboveground disturbance belowground disturbance ab a b b a b b a a a 0 Iva Schoenoplectus Spartina/Distichlis Typha Kettenring et al. unpubl. data

38 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)

39 More florets and inflorescences are produced per plant with elevated nutrients ambient nutrients elevated nutrients Number of florets (mean ± 1 SE) Number of inflorescences (mean ± 1 SE) ambient nutrients elevated nutrients 2 0 Kettenring et al. 2011

40 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)

41 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)

42 Environmental drivers of emergence, establishment, and survival X=plant death Chambers et al. Estuaries 2003

43 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

44 Outline Reproductive system and how it spreads Factors that influence spread Implications for management

45 How can we best control Phragmites? Understanding characteristics of the environment and the plant that contribute to its spread

46 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

47 Phragmites control experiments 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 Rohal, Cranney, Hazelton, and Kettenring

48 Questions? Karin Kettenring