November 28, 2007
Wednesday AM

The USDA Forest Service is acting to counter the threats posed by invasive species to our natural ecosystems. Invasive plants can upset the balance of nature in a variety of ways. We have surveyed much of the Tongass National Forest for invasive plants and are in the early stages of managing invasive plant populations on the Forest.

Japanese knotweed and related species are indeed a serious concern for Southeast Alaskans. In Oregon and Washington many miles of salmon spawning habitat have been degraded by this invasive plant. Japanese knotweed forms thick impenetrable stands that literally smother other plant species in their way, increase stream erosion and alter nutrient cycling in streams. What isn t apparent is that most of the plant is underground. The soil under a knotweed patch is full of a network of underground stems that contain most of the biomass of the plant. Knotweed roots (technically rhizomes) extend horizontally beyond the edges of the plant and vertically up to three feet deep, so it can be difficult to remove: Only the smallest clumps can be killed by digging, pulling, or covering up with tarps. Cutting down the plants is completely ineffective.

Now some good news: It is possible to control knotweed by judicious application of relatively safe herbicides with minimal risk to the environment. Japanese knotweed only rarely produces seed and has not been observed producing seed in Ketchikan, so it only moves from one site to another when we move plant parts or contaminated soil. Please do not move knotweed plant parts or infested soil, especially to sensitive areas such as stream banks!

Many people in the community might be concerned about the potential harmful effects of herbicides on the environment. The Tongass National Forest has no plans at this time to use herbicides to control invasive plants, but may consider doing so in the near future. In such a case, this would only proceed after examining a range of alternatives in consultation with members of the community and other federal, tribal, state and local authorities.

Integrated Vegetation Management principles advocate a well thought out approach to invasive plant control, using all of the tools at our disposal for the most effective outcome, considering alternatives such as hand pulling or use of mechanized equipment, shading by native species and other non-chemical means before using herbicides, and using herbicides in a manner that minimizes the risk to desirable species, ecosystems, and human health.

Knotweed is just one of a dozen or so invasive plant species that threaten our native plant communities. I strongly encourage people in Ketchikan who are concerned about Japanese Knotweed and other invasive species to form a community group to work together to educate the public and to try to manage invasive species populations wherever feasible. The Forest Service can facilitate this getting off the ground but cannot lead the effort because this needs to be led by the community of Ketchikan. Please contact me at theutte@fs.fed.us or 228-4132 for more information about invasive plants, forming an invasive plant working group, or to report an invasive species problem you know about.

Tom Heutte
Invasive Species Coordinator, Ketchikan-Misty Fiords Ranger Distric
theutte@fs.fed.us
Ketchikan, AK

About: " Botanist and Invasive Species Coordinator for the Ketchikan Ranger District, Tongass National Forest who has studied, surveyed and managed invasive plants in Southeast Alaska for the past five years."

Received November 27, 2007 - Published November 28, 2007

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