RE: Invasive Plant Species
By Tom Heutte
November 28, 2007
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
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 email@example.com 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.
Invasive Species Coordinator, Ketchikan-Misty Fiords Ranger Distric
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
Invasive plant species By Victoria McDonald
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