Invasive Plant Guide Blog

Assessing plants for invasiveness

admin — Thu, 26 Apr 2012 17:58:55 +0000

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

Controlling Para grass without herbicides

admin — Thu, 12 Apr 2012 13:36:52 +0000

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.

Tadpole morphology changed by Roundup

admin — Thu, 05 Apr 2012 13:43:27 +0000

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]

Adaptations of native plants to invasive plants

admin — Thu, 29 Mar 2012 19:26:33 +0000

I often get questions about what the long-term outlook is like for native plants, so it was great to see a study that looks at genetic adaptations of native species in invaded grasslands. The authors have been studying adapations of native grasses in grasslands invaded by Russian knapweed, Acroptilon repens. They found that native grass species taken from invaded areas were better able to grow compared to the same grass species taken from uninvaded areas when planted with a novel invader, Canada thistle, Cirsium arvense. The authors recommend conserving populations of native species growing with invasive species to encourage new adaptations that could be used in restoration projects. Let’s hope lots of native species harbor the potential to adapt to invasions.

Ferrero-Serrano, Á., Hild, A. L. and Mealor, B. A. 2011. Can invasive species enhance competitive ability and restoration potential in native grass populations? Restoration Ecology, 19: 545–551. doi: 10.1111/j.1526-100X.2009.00611.x

How wide to stream buffers need to be to reduce plant invasions?

admin — Thu, 29 Mar 2012 19:16:18 +0000

Most riparian buffer regulations are set to reduce nutrient inputs to waterways, but riparian buffers also serve as habitat for native plants and animals. Plant invasions can significantly alter riparian habitats. A new paper by Ferris et al. looks at plant invasions along riparian corridors of different widths within the White Clay Creek Watershed in Pennsylvania and Delaware. They find that wider areas (15 – 25 m wide and wider) had significantly lower rates of invasion by garlic mustard (Alliaria petiolata) and Oriental bittersweet (Celastrus orbiculatus). However, even the widest areas were still invaded by Japanese honeysuckle (Lonicera japonica) and multiflora rose (Rosa multiflora).

Ferris, G., V. D’Amico, and C. K. Williams. 2012. Determining effective riparian buffer width for nonnative plant exclusion and habitat enhancement. International Journal of Ecology 2012. Available online: http://www.hindawi.com/journals/ijeco/2012/170931/

Invasive Plant Legacies

admin — Mon, 26 Mar 2012 17:50:53 +0000

Invasive plants can leave legacies after they have been removed, just as politicians do. Rather than a legacy of public works or corruption, invasive plants may leave a legacy of altered soils, hydrology or new genes. A recent paper by Corbin and D’Antonio summarizes biotic and soil chemistry and physical changes left behind after invasive plant removal. Examples include local extinctions of native species, hybridization with closely related species, and changes to soil communities, soil nitrogen and salinity levels, and soil accumulation rates. These legacies must be considered in planning restorations.

Corbin, J. D. and C. M. D’Antonio. 2012. Gone but not forgotten? Invasive plants’ legacies on community and ecosystem properties. Invasive Plant Science and Management 5(1): 117-124.

Herbicide resistant creeping bentgrass

admin — Sun, 11 Mar 2012 21:24:30 +0000

Another study on the potential effects of escaped transgenic creeping bentgrass, Agrostis stolonifera, is out. This study shows that in Central Oregon wetland communities are at particular risk of invasion by creeping bentgrass and by redtop, Agrostis gigantea. Redtop can cross-pollinate with creeping bentgrass potentially picking up the glyphosate herbicide resistance gene. Currently control of these invasive grasses principally relies on herbicides containing glyphosate.

Bollman, M. A. et al. 2012. Wetland and riparian plant communities at risk of invasion by transgenic herbicide-resistant Agrostis spp. in central Oregon. Plant Ecology 213(3):355-370.

Long-term experiments on invasive plants

admin — Sun, 11 Mar 2012 20:57:58 +0000

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.

Demand for drought tolerant plants might bring in new invasives

admin — Tue, 14 Feb 2012 18:52:38 +0000

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.

Fungi helping cheatgrass (Bromus tectorum) invasions in North America

admin — Fri, 10 Feb 2012 14:15:08 +0000

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)