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

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

Plant Life History Exploitable for Long-Term Management Annual Herbaceous Perennial Evergreen Perennial Woody Perennial

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

Invasion Process of Eurasian watermilfoil Dispersal Establishment Colony Formation

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

Carbohydrate Storage and Allocation  Purple loosestrife – Katovich et al  Waterhyacinth – Madsen et al  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

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

Plant Synecology Diversity Competition Community Dynamics “Succession” Ecosystem response

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

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

Invasive Plants reduce Native plant diversity and abundance Eurasian watermil foil: Madsen et al

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

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)

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

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  Shallow Lake Alternate Stable State Hypothesis (Scheffer 1998)  We do not have a current working conceptual model of aquatic plant community dynamics

Environmental Sieve van der Valk 1981

Marsh Cycle van der Valk and Davis 1978

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

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 Physical predictors – Hawes et al –Water level fluctuation, wave exposure, etc.

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

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

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

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.

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

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

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

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