Invasive Plant Ecology and Interaction with Native Plant Communities

1. Invasive Plant Ecology and Interaction with Native Plant Communities John Madsen, Chair Mississippi State University Toni Pennington, Portland State University John Titus, SUNY-Binghamton

2. Plant demography • Population Dynamics • Life History • Reproduction • Growth • Nutrition • Light Requirements • Temperature Requirements • Habitat Requirements • Response to disturbance • Herbivory Plant Autecology

3. Plant Life HistoryExploitable for Long-Term Management Annual Evergreen Perennial Herbaceous Perennial Woody Perennial

4. Plant Demography Survival/Establishment Germination/Sprouting Plant Density Seedling/Sproutling Propagule Production Dispersal Clonal Growth Mature Plant

5. Invasion Process of Eurasian watermilfoil Dispersal Colony Formation Establishment

6. Phenological Studies • Purple loosestrife – Katovich et al. 1998 • Waterhyacinth – Madsen et al. 1993 • Eurasian watermilfoil – Madsen 1997 • Hydrilla – Madsen and Owens 1998 • Curlyleaf pondweed – Woolf and Madsen 2003 • Application to management: Poovey et al. 2002

7. Carbohydrate Storage and Allocation • Purple loosestrife – Katovich et al. 1998 • Waterhyacinth – Madsen et al. 1993 • Eurasian watermilfoil – Madsen 1997 • Hydrilla – Madsen and Owens 1998 • Curlyleaf pondweed – Woolf and Madsen 2003 • Management implications – Kimbel and Carpenter 1981, Painter 1988, Owens and Madsen 1998

8. Modeling of plants • Biomass models – Best et al. 2001 • Individual-based models – Uchmanski and Grimm 1996. • Spatial and GIS models: Vis et al. 2003, Lehmann 1998.

9. Plant Synecology Diversity Competition Community Dynamics “Succession” Ecosystem response

10. Plant Competition • Wetland ecology: Typha latifolia versus Typha domingensis • Grace and Wetzel 1981, Grace 1987, 1988, 1989 • Najas v. Myriophyllum • Agami and Waisel 2002 Grace and Wetzel 1981

11. Shoot versus Root Competition • Shoot versus root competition (Wetland) • Twolan-Strutt and Keddy 1996 • Submersed plants • Spencer and Ksander 2005

12. Invasive Plants reduce Native plant diversity and abundance Eurasian watermilfoil: Madsen et al. 1991.

13. Management can reverse competition • Chemical control: Getsinger et al. 1997, Madsen et al. 2002 • Biological control: Gross et al. 2001, Newman and Biesboer 2000. • Mechanical control: Eichler et al. 1993 • Physical control: Eichler et al. 1995

14. Community Dynamics • Few “working theories” of aquatic plant community dynamics • Need for understanding of system to explain what invasive species do to system • In contrast to terrestrial plant ecosystems • Increase in fire frequency • Reduction in colonization rates (Yurkonis et al. 2005)

15. Long-term Aquatic Plant Community Studies • Few long term studies are available • Field sampling, Chenango Lake – Titus et al. 2004 • Paleoecological studies – Davidson et al. 2005

16. Aquatic Plant Community Dynamics • Succession – no real aquatic model • Hydrarch succession not a community dynamic model • Environmental sieve model van der Valk 1981 • Wetland cycle – van der Valk and Davis 1978 • Wetland Continuum - Euliss et al. 2004 • Shallow Lake Alternate Stable State Hypothesis (Scheffer 1998) • We do not have a current working conceptual model of aquatic plant community dynamics

17. Environmental Sievevan der Valk 1981

18. Marsh Cyclevan der Valk and Davis 1978

19. Shallow Lake Alternate Stable States Reduced resuspension Macrophyte growth Increased sedimentation Reduced TSS loading Benthivorous omnivorous fish High TSS loading High nutrient loading Catastrophic events Turbid State Clear State High turbidity Low transparency Little or no plant growth Abundant plant growth Low turbidity High transparency

20. Community Response to Stability and Disturbance • Drawdown • Hydrology – Englehardt and Ritchie 2002, van Geest 2005 • Nitrogen or nutrient loading – Tracy et al. 2003, James et al. 2005, Anderson et al. 2005 • Physical predictors – Hawes et al. 2003 • Water level fluctuation, wave exposure, etc.

21. What makes a Species Invasive? • Theories for plant invasiveness (Galatowitsch et al. 1999) • Growth is more favorable under new environmental conditions • Herbivores [and pathogens] may be absent from new locale • Interspecific hybridization may occur, resulting in novel phenotypes

22. Invasion Concepts at Opposition • Species traits drive invasion • Mechanistic; Invasives as a “Superplant” • “Hydrilla is the Perfect Weed” • Habitat invasibility (niche) allows invasion • Ecosystem as a “sick” superorganism • ‘Invasives are a symptom of poor ecosystem health” • Open habitat for species • Convergence of both – Milbau and Nijs 2004, Lonsdale 1999

23. Species Traits • Invasiveness • Propagule pressure • Climatic compatibility • Superior performance • Canopy structure • Superior resource competition

24. Invasibility • The poor get richer – poor sites are more susceptible to invasion – Espinosa-Garcia 2004 • The rich get richer – species-rich sites are more invasible (Stohlgren et al. 2003, Stohlgren 2002 • Disturbed Resource-Flux Invasion Matrix Sher and Hyatt 1999.

25. Invasive Plant Models – Peters 2004 • Nonspatial models – exponential and logistic models • Spatially Implicit Models – nonspatial models run using spatially-structured data • Spatially Explicit models – Model considers neighbor effects and contagious phenomena

26. Examples of Range Models • GARP model including hydrilla – Peterson et al. 2003 • Egeria najas and Egeria densa – Bini and Thomasz 2005 • Spatial model of purple loosestrife – Welk 2004

27. What We Lack • Complete plant demographic / life history analysis • Seasonal life histories of invasive species • Coherent theory of community dynamics • Spatially-relevant models of invasion • Predictive tools for invasion probability • Predictive tools for management

28. Possible Research Topics • Life history and management • Vectors of spread and prevention • Co-dispersal and positive feedback between invasive aquatic species • Competition and preemption of invasive plants • Prediction of potential invasion sites • Spread pathway analysis and prevention • Prevention, early detection, and rapid response • Alteration of community dynamics by invasive species