Final Environmental Impact Statement

Vestal Final Environmental Impact Statement Chapter 3
Noxious Weeds
Noxious weed infestations are expected to increase under this alternative, in the short
term. Commercial and non-commercial timber harvest activities and prescribed fire often
provide mechanisms for the introduction, establishment, and spread of noxious weeds.
Anywhere there has been some form of soil disturbance, the potential for the
establishment of noxious weeds exists. The potential for noxious weed establishment is
even greater in disturbed areas adjacent to existing weed populations. The movement of
equipment in and out of these areas also facilitates weed establishment. Roads and skid
trails create a network of corridors through which seed dispersal can occur.
There is a potential for up to 25,449 acres being disturbed from mechanical vegetation
treatments, fuels treatments, and prescribed fire. Skid trails, landings, burn piles and
areas where machinery is working could create conditions in favor of seedbeds for
noxious weeds. Design criteria is included to minimize bare ground and the potential for
spread of weeds. The actual amount of disturbance is dependent on the scope and
amount of acres infested with mountain pine beetle, type of equipment used, and the time
of year the disturbance occurs.
A ten-year review of timber sales estimated that between 2.0 and 3.5 percent of the acres
in a timber sale are likely to develop weed infestations (USDA Forest Service, 1996,
p.III-192). For the purpose of this analysis, 3.0 percent of all treatment activities with
the exception of acres of prescribed fire were used to estimate the acres of infestation that
are likely to result from harvest activities. New road construction and reconstruction
would result in approximately 0.12 acres of new weed infestation per mile of road
(USDA Forest Service, 1996 p. III-194). Based on this analysis, Alternative 2 may lead
to approximately 800 acres of new infestation, in the short term (1 year following
disturbance). However, treatment of noxious weeds would continue and the total acres
of infestation would be expected to decrease below current levels within 4-5 years, if
weed treatments are fully funded each year.
Additional acres may be infested by noxious weeds as a result of prescribed fire
activities. Dozer line, hand lines, staging areas, and areas burned so that mineral soil is
exposed are susceptible to weed infestation. At this time, there is no formula to estimate
how many acres of infestation might result from such activities. A number of variables
including soil temperature, fire intensity, and time of year can influence the effect that
prescribed fire can have on noxious weeds. While beneficial to forest health, fire can
also be conducive to the spread of noxious weeds. Broadcast burning is proposed to be
low-intensity, but there would probably be pockets of higher intensity fire that could
result in exposure of mineral soil and loss of understory herbaceous species. At highest
risk would be areas containing larger fuel loads and downed timber which create a place
for past seed accumulation and would burn with much higher intensities. The loss of
existing grasses and forbs provides an opportunity for weeds to become established.
Many noxious weed species are very competitive and may prevent re-establishment of
desirable grasses and forbs. Pre-treatment of weed infestations prior to prescribed fire
implementation is included as design criteria and would reduce the risk of spread. Again,
movement of equipment needed during fire operations can contribute to the spread of
weeds. There is a risk of new species being introduced to the area when equipment is
brought in from out of the local area. It should be noted that fire managers plan to use
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