NEPA--Environmental Assessment

2008). It differs from the wetland willow type by its better-drained soils and its upland landscape
position. Sheep readily browse on both of the willows of this type (ID team observation 2008), but
Salix planifolia seems to be preferred. Most willow plants and plant communities are vigorous, but
some heavy browsing is occurring in some places as reflected in hedged plants. Some sheep trailing
is also evident in this vegetation type. Current species composition and distribution in this type are
likely similar to conditions found during the reference period.
Krummholz, which is an upland type dominated by dwarfed conifers (mostly Picea engelmannii)
and herbaceous species, is a transition type that occurs between spruce-fir forests of the subalpine
climate zone and the treeless alpine zone. Sheep foraging in this type is relatively minor. Current
species composition and distribution in this type are likely similar to conditions found during the
reference period.
The spruce-fir forest type is an upland type dominated by Engelmann spruce and subalpine fir trees
and generally displays high tree densities and closed canopy covers, which limit forage production.
Within the project area, this type has been mostly unaffected by sheep grazing.
Threatened, Endangered, or Proposed Plant Species
There are no plant species federally listed as threatened, endangered, or proposed under the
Endangered Species Act known to occur on the San Juan Public Lands or within this Project Area.
Sensitive Plant Species
There are nineteen R2 Regional Forester’s sensitive species that occur on the Forest Service lands
within the San Juan Public Lands and six others that have the potential to occur there; and eight
BLM sensitive species that occur on the BLM lands within the San Juan Public Lands and one other
that has the potential to occur there. Most of them were removed from further analysis because there
are no known occurrences of those species within or near the project area, because it is highly
unlikely that they would be in the project area, or because the project area did not contain potential
habitat for them. Five sensitive plant species (Eriophorum altaicum var. neogaeum, Parnassia
kotzebuei, Machaeranthera coloradoensis, Cryptogramma stelleri, and Carex viridula were
evaluated in detail because they are known to occur in this project area, and three others
(Eriophorum chamissonis, Eriophorum gracile, and Gilia sedifolia) were evaluated in detail because
the project area contains potential habitat for them. Detailed descriptions and analysis of these
species can be found in the Biological Evaluation for Plants in the project record.
Noxious Weeds
Noxious weeds are the invasive or non-native species that are generally considered the worst
because of their negative impacts on native ecosystems, and are defined by the State of Colorado
(C.R.S. 1990). The most common noxious weeds within the Silverton landscape area are Yellow
toadflax and Canada thistle. Since 2002, noxious weed treatment has been concentrated along the
main travel corridors, including BLM Roads, some abandoned mining roads and sites, some system
trails, and dispersed camping areas. Control of weed populations has been relatively successful in
areas where treatment has occurred in the past years. Much of the project area is remote and
inaccessible by vehicles. Noxious weeds, especially yellow toadflax are continuing to spread but
are largely confined to motorized travel corridors. Biological control insects could be the most
efficient way to treat remote areas. The following summaries describe challenges unique to
specified grazing allotments within the project area.
Engine Creek/Deer Creek Allotment
Noxious weeds are not an issue on this allotment. There is some Canada thistle in the Engine Creek
and Deer Creek drainages. There is occasionally some musk thistle in the US Hwy 550 right of way.
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