In a massive study of soil and water samples from across the US, researchers frequently found low levels of glyphosate and its byproduct aminomethylphosphonic acid (AMPA). The concentrations are below levels considered harmful to humans and wildlife, but little information is available on possible effects of chronic low level concentrations of herbicides or pesticides. In 2007, 180-185 million pounds of glyphosate were used in agriculture in the US .
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Don’t rush to plant following herbicide application according to a new article published in Restoration Ecology. In pots in a greenhouse experiment sprayed with aminopyralid or picloram at the recommended rate, native forb and grass seeds from a dry NW grassland had lower seedling emergence and biomass than pots sprayed with water. Even though the herbicides target broadleaf plants, grass seeds also suffered. Not just seeding post-spraying but also seed recruitment from the seedbank would likely be affected by spraying.
Wagner, V.
Bushkiller vine, Cayratia japonica, has been found at 2 sites in Maryland, one in Anne Arundel Co. and the other in Baltimore (K. Kyde, MD DNR, 11/21/13). These are the northernmost known occurrences of this plant. This vine looks a lot like Virginia creeper, but the leaflets are not all attached to a central point. The lowermost leaflets occur in pairs. As it name implies, bushkiller vine can overtop shrubs blocking light to the shrub’s leaves. It climbs using tendrils.
Photo: Robert J. Richardson, North Carolina State University, Bugwood.org – See more at: http://www.invasive.org/browse/detail.cfm?imgnum=2105066#sthash.16vC8cJ1.dpuf
In a survey of 285 land managers in the U.S., researchers found that they spent nearly $4 million dollars per year on control of non-native Phragmites australis on 89,000 ha but few were happy with the results of their control efforts. The goals of most managers were to restore native flora and fauna and improve ecosystem function, but less than half felt they had met those goals. Most organizations cited a lack of personnel and monetary constraints, along with re-invasion of Phragmites and difficulty in accessing populations. The researchers found no correlation between amount spent on control and success in achieving management goals.
So does that mean that Phragmites control is a waste of time and money? Or just that there needs to be more long-term funding of control and monitoring or new techniques developed for control? Research on effects of Phragmites on natural systems shows mixed results. Some studies show changes to benthic fauna and others show few changes. Phragmites is thought to alter nutrient cycling and some hydrological processes. Different populations under different salinity levels and hydrological regimes may vary in their ecological effects. Many control projects receive one-time funding and re-invasion can occur before any significant changes in flora, fauna or ecosystem processes have had time to take place. Biological control is being investigated as a potential option, but because there are native strains of Phragmites australis, it could be difficult to find a biological control agent that doesn’t damage native populations.
The article ends with a cautionary note to land managers to assess what damage they think is occurring before spending money on control and to attempt to increase post-control monitoring.
Martin, L. J. and B. Blossey. 2013.
The magazine “Wood Wise” from Great Britain has an issue on managing invasive species (mostly plants) in woodlands. They cover several species also considered invasive in North America, giant hogweed and Himalayan balsam, and several species native to North America that are invasive there such as western skunk cabbage and rhododendron. http://www.scribd.com/doc/129905693/Wood-Wise-Invasive-Species-Spring-2013
The Smithsonian Ecological Research Center’s Marine Invasions Research Lab tackles the interesting question of what the definition of an invasive species is, http://www.serc.si.edu/labs/marine_invasions/feature_story/April_2013.aspx.
Does it depend on how it was introduced, how long it has been here, or what effects it has on the environment?
Higher light availability, later spring leaf-out, and higher soil nitrate levels in intact forests all correlate with a greater abundance of invasive plants. The authors of this study looked at interior forest understories where different canopy species resulted in different resource levels. One of the trees studied was black locust, Robinia pseudoacacia. This tree is native to a small part of the United States, but was widely planted in the eastern and central U.S. It may facilitate plant invasions into forests because of it fixes nitrogen and has relatively high light levels under its canopy.
Dreiss, L.M. and J. C. Volin. 2013. Influence of leaf phenology and site nitrogen on invasive species establishment in temperate deciduous forest understories. Forest Ecology and Management 296:1-8.
The Illinois Invasive Species Awareness Week blog has just posted a new installment on invasive species humor! This one focuses on illustrations, http://illinoisisam.blogspot.com/2013/02/the-hunt-for-invasive-species-slogans.html.
