Vetch, the vexing invader

Bird vetch off College Rd. in Fairbanks. Oct. 6, 2011.

The Station Fire joined a series of fires in 2009 that nipped at the densest population centers of Southern California. Two years later, invasive weeds sprouted up between the charred oak and pine trees, according to an Oct. 3 Los Angeles Times article. The article follows botanist Katie VinZant across the fire scar as she leads a weeding team. VinZant tries to coax a Californian ecosystem into recovery by removing stressful intruders like the flammable Spanish broom.

Human diseases aren’t the only invaders that travel with us from place to place. Invasive species can spread across the world to new territory, shredding apart defenseless ecosystems.

Several species of plants and animals have invaded Alaska, too. One plant, a climber with curling tendrils and bright stacks of purple flowers, covers the local vegetation in dense mats.

Bird vetch.

We brought it here. There have been plenty of efforts to remove it — Alaska versions of VanZint’s team.

Vetch comes from Europe and Asia, where it fits into a tight ecological niche. Agricultural researchers brought vetch to Alaska around 1909, and to Fairbanks in 1955, according to the National Park Service. Turns out, livestock love the stuff — hence its other name, cow vetch.

Eventually, vetch escaped its confines. Those same characteristics that made vetch a wonderful food and a weed reducer allowed it to bounce across Alaska’s road systems. Vetch comes at the competition from two angles: resourcefulness, and good old-fashioned bullying.

Nitrogen, the most abundant element in our atmosphere, also plays a major role in the soil. Plants are often limited by not having enough of the right forms of nitrogen in the soil. Vetch worked out a partnership with bacteria on its roots, so that the bacteria convert nitrogen into usable building blocks. It brings its own lunch box to a place where most plants forage for their meals. This allows vetch to thrive in places that aren’t welcoming to other plants.

Vetch also controls its competitors. It uses a strategy known as “allelopathy,” a type of biological chemical warfare. In an introductory ecology class at the University of Alaska Fairbanks, I learned that extract from ground-up vetch could keep seeds from sprouting. (For a scientist’s viewpoint, Onur Koloren performed a similar experiment). Like Herod, vetch makes sure the next generation can’t rise to usurp its power.

Vetch relies on road systems for dispersal, because the plants and their seeds get caught up in tire tread.

Bird vetch is known not only as an invasive species, but as a noxious weed – a plant that doesn’t belong here, and hurts native plants. Where there are roads in Alaska, there is vetch. Vetch is not the only invasive species in Alaska by far, but its suffocation of native plantlife makes it noticeable.

Bird vetch flowers, by Michael Rasy of the University of Alaska, via forestryimages.org.

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One thought on “Vetch, the vexing invader

  1. You are a really good blogger, Kelsey. This post was short, interesting, and well-written. You took an obscure scientific interest, made it hyper-local and worth reading. The photo was a nice touch. You should continue to maintain the blog after your class and, if your professor thinks it a good idea, try and get it attached to ScienceBlogs.

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