Long-term experiments on invasive plants

Relatively few long-term experiments have been done surveying invasive plants in the same place, so we know relatively little about the long-term dynamics of invasive plants.  A study on Canada thistle, Cirsium arvense, on burned sites in Yellowstone reveal that over seven years thistle has disappeared from some sites as native vegetation has recovered  and at other sites its relative cover has declined.  Where it has remained or newly appeared, sites tend to have more fertile soils and areas with bare ground.

 

Wright, B. R. and D. B. Tinker.  2012. Canada thistle (Cirsium arvense (L.) Scop.) dynamics in young, postfire forests in Yellowstone National Park, northwestern Wyoming.  Plant Ecology DOI: 10.1007/s11258-012-0026-4.

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Demand for drought tolerant plants might bring in new invasives

A research paper in Frontiers in Ecology and the Environment demonstrates how new sources of plants and demand for new plants as climate changes may lead to new invasive plant introductions.  Emerging sources of nursery imports include parts of South America, Africa, and northern Europe.  Many new introductions are drought-tolerant plants as water restrictions and xeriscaping have increased demand.

The article encourages the use of weed risk assessments, but points out that with new suppliers, a history of invasion by a particular plant might be hard to come by and invasion history is an important factor in determining risk.    On a positive note, the authors point out that one nursery promoting drought tolerant plants has mostly increased the number of drought tolerant native plants it offers.

Bradley, B. A. et al. 2012. Global change, global trade, and the next wave of plant invasions.  Frontiers in Ecology and the Environment 10(1):20-28.

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Fungi helping cheatgrass (Bromus tectorum) invasions in North America

Researchers discovered that a new fungal-plant relationship developed between cheatgrass plants (Bromus tectorum) and a fire-dependent fungus (Morchella).  The fungus grows into the plant tissues and increases the biomass and seed production of the grass.  More biomass leads to more frequent fires and more seed production means more regeneration after a fire.  The fungus also increased the ability of seeds to survive heat from fires.  The fungal species (phylotypes) originated in western North America and do not occur in Europe.  This may be another explanation as to why cheatgrass invasion has been so successful in North America.

Melissa Baynes, George Newcombe, Linley Dixon, Lisa Castlebury, Kerry O’Donnell.  2012. A novel plant–fungal mutualism associated with fire. Fungal Biology 16(1): dx.doi.org/10.1016/j.funbio.2011.10.008)

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Using benthic barriers to stop Eurasian watermilfoil

Benthic barriers use geotextile fabric, plastic or other materials placed over the ground under water to stop the growth of unwanted rooted aquatic plants (for more information on benthic barriers see http://www.ecy.wa.gov/programs/wq/plants/management/aqua023.html).  A recent study looked at how long barriers needed to remain in place to kill Eurasian watermilfoil (Myriophyllum spicatum).  After 8 weeks 100% of the milfoil was dead.  Control was also improved by removing sediments that fell onto the barrier. 

Karen Laitala, Karen L Laitala, Timothy S Prather, Donn Thill, Brian Kennedy, and Chris Caudill. 2012. EFFICACY OF BENTHIC BARRIERS AS A CONTROL MEASURE FOR EURASIAN WATERMILFOIL. Invasive Plant Science and Management In-Press.

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Survey shows Maine nursery industry concern over invasive plants

A survey of Maine nursery and landscaping businesses showed that most respondents were concerned about invasive ornamental plants and tried to steer their customers towards buying non-invasive plants.  Most would also support labeling of invasive ornamental plants or would not carry invasive plants.  Interestingly, most were neutral about whether their customers were concerned about invasive plants.

Coats, V. C., L. B. Stack, and M. E. Rumpho.  2011. Maine nursery and landscape industry perspectives on invasive plant issues.  Invasive Plant Science and Management 4:378-389.

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Consumers willing to pay extra for non-invasive plants?

I was initially excited by the title of a new research article by Yue et al., “Do native and invasive labels affect consumer willingness to pay for plants? Evidence from experimental auctions” published in Agricultural Economics (2011) 42:195-205.  But after reading the definitions they used for native and invasive and seeing the plants they chose to test, I’m not sure whether this study does much to answer the title’s question.  Their plant pairings were:

  • Dianthus armeria with Dianthus repens
  • Daucus carota with Daucus pucillus
  • Oxalis vulcanicola with Oxalis crassipes
  • Gaura coccinea with Gaura lindheimeri
  • Epilobium angustifolium (MN genotype with E. angustifolium (AK genotype)

If the people chosen for the survey knew what these plants were it is unlikely that they would view them as a very invasive.  I’m not familiar with survey research using experimental auctions, but maybe it would have been better to make up a list of imaginary plants and label them as invasive or not invasive.  It it isn’t clear whether the participants were asked about their specific knowledge of the plants or not.  The question though is an important one as more states are contemplating labeling invasive plants in the horticulture industry, so I hope someone redoes this study.

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Management Guidelines for Florida Aquatic Plants now Online

The University of Florida Center for Aquatic and Invasive Plants has a new website for learning about aquatic invasive plant management, http://plants.ifas.ufl.edu/manage/.  The resources on the site will be helpful for land managers in many states.

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Field Guide for Pacific Coast Forest Invaders

Similar to its guide for Southern forests, the USDA Forest Service has published a guide to invasive plants in Pacific Coast forests.  Download it at http://www.fs.fed.us/pnw/pubs/pnw_gtr817.pdf or order a copy from http://www.fs.fed.us/pnw/publications/gtrs.shtml

Gray, A. N., K. Barndt and S. H. Reichard. 2011.  Nonnative invasive plants of Pacific coast forests: a field guide for identification.  Gen. Tech. Rep. PNW-GTR-817. Portland, OR.  USDA Forest Service, Pacific Northwest Research Station. 91 p.

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