Assessing plants for invasiveness

I’ve been steeped in the nuances of assessments of plant invasiveness the last few months as the Maryland Invasive Plant Advisory Committee develops an assessment for non-native terrestrial plants that grow or could grow in Maryland.  Most assessments look at a plant’s ability to establish and spread and the impact the plant can have at the population, community and ecosystem levels.  Some also include economic impacts including impacts to trade, agriculture, and built environments.  When it comes to establishment, geography and climate play an important role in determining where a species can survive.  A new paper published in Biological Invasions models how climate and human influences affect the distribution of Japanese honeysuckle, Lonicera japonica.  It finds that human influences extend the predicted range based solely on climate.  So if you want to figure how much risk a plant might have of invading your region, consider both climate change and distribution by people.

Carolyn M.Beans, Francis F. Kilkenny and Laura F. Galloway (2012). Climate suitability and human influences combined explain the range expansion of an invasive horticultural plant. Biological Invasions, online 10 Apr 2012, DOI: 10.1007/s10530-012-0214-0

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Controlling Para grass without herbicides

Para grass, Urochloa mutica, grows in the southeastern United States in fields, marshes and swamps.  It spreads by runners to form dense stands. It can be controlled with herbicides, but managers often wish to avoid using herbicides in sensitive wetland areas.  Research on non-chemical control methods in Florida show that Para grass can be controlled using a combination of flame weeding or mowing and flooding.   Particularly in areas where water levels can be manipulated, burning or cutting plants prior to flooding proved can be an effective means of killing Para grass.

Sushila Chaudhari, Brent A. Sellers, Stephen V. Rockwood, Jason A. Ferrell, Gregory E. MacDonald, Kevin E. Kenworthy. 2012. Nonchemical Methods for Paragrass (Urochloa mutica) Control. Invasive Plant Science and Management: January-March 2012, Vol. 5, No. 1, pp. 20-26.

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Tadpole morphology changed by Roundup

Researchers discovered that tadpoles of three frog and toad species (wood frogs, leopard frogs and American toads)  developed the same tail shape that they do when exposed to predators such as dragonfly larvae or newts.   The different tail shape helps them to escape predators.  The study also showed that although tadpoles had the same mortality risk when exposed to Roundup as has been found in other studies, that the risk of mortality decreased if the tadpoles were also exposed to predator cues.  The investigators hypothesize that the herbicide stratifies in the water and that tadpoles dive to the bottom where the herbicide is less concentrated when they think predators are around.

Relyea, Rick A. 2012. New effects of Roundup on amphibians: Predators reduce herbicide mortality; herbicides induce antipredator morphology. Ecological Applications, 22:634–647. dx.doi.org/10.1890/11-0189.1]

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