3.0 Affected Environment - Knik Arm Bridge and Toll Authority

Knik Arm Crossing DraftFinal EIS
Affected Environment
Table 3-28. Regulated noxious weed species found in
the Study Area, as ranked for invasiveness by the
Alaska Natural Heritage Program
Scientific name
Common name
Invasiveness
ranking
(0–100; low–
high)
Cirsium arvense Canada thistle 76
Vicia cracca bird vetch 75
Linaria vulgaris yellow toadflax 63
Taraxacum officinale a common dandelion 62
Sonchus arvensis perennial sowthistle 56
Lupinus polyphyllus a large-leaf lupine 55
Poa annua annual bluegrass 51
Polygonum convolvulus black bindweed 51
a According to 11 AAC 34.030, when occurring in agricultural and vegetable
seeds, seeds of these species are identified as weed seeds.
3.8.7.3.2 Anchorage
Several upland habitat types occur within the Anchorage portion of the direct effects Study
Area. These include upland broadleaf forest, upland tall shrub, upland herbaceous meadow,
and urban areas.
Upland broadleaf forest
Upland broadleaf forest is common throughout the Anchorage Bowl. This habitat type is
characterized by an upper canopy dominated by paper birch and an understory composed of
alder, devil’s club, highbush cranberry, prickly rose, mountain ash (Sorbus sitchensis), tall
fireweed, and bluejoint reedgrass.
An important feature of this habitat type is its multilayered forest canopy. The upper tree
canopy provides bird nesting habitat and perch locations for raptors and owls. The midcanopy
provides protective cover for wildlife and supports a variety of plants used for food.
The lower canopy provides cover for many small mammals and birds, den sites, and resting
locations for larger mammals. The annual quantity of biomass exported from this habitat type
is typically high, supplying nutrients to the overall food web. Export of leaf litter, berries,
and decomposed woody material to downstream habitats provides streams, wetlands, and
water bodies with important detritus used by a variety of plant and animal species.
Upland tall shrub
Upland tall shrub habitat is common along the coastal bluff, areas adjacent to developments,
and along stream corridors. Dominant plant species include alder, devil’s club, salmonberry,
red elderberry, cow parsnip (Heracleum lanatum), and tall fireweed.
This habitat type provides cover for both mammals and birds, generally supporting excellent
nesting opportunities for songbirds. Along the toe of the coastal bluff north of the POA, this
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