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 HistoryExploitable for Long-Term Management

Annual

Herbaceous Perennial

Evergreen Perennial

Woody Perennial

Plant Demography

PropaguleSeedling/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. 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

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

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.

Plant Synecology

DiversityCompetitionCommunity 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 watermilfoil: Madsen et al.

1991.

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

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. 2004

• 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. 2004 Shallow Lake Alternate Stable State Hypothesis

(Scheffer 1998) We do not have a current working conceptual

model of aquatic plant community dynamics

Environmental Sievevan der Valk 1981

Marsh Cyclevan der Valk and Davis 1978

Shallow Lake Alternate Stable States

Turbid State Clear State

Benthivorous omnivorous fishHigh TSS loadingHigh nutrient loadingCatastrophic events

Reduced resuspension

Macrophyte growth

Increased sedimentation

Reduced TSS loading

Abundant plant growthLow turbidityHigh transparency

High turbidityLow transparencyLittle 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. 2005

• Physical predictors – Hawes et al. 2003 – 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. 2003

• 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