facilitated stewardship permits on the Green Line to
normalize the relationship between the utility and
its partners and allow for longer term planning.
Biodiversity as a Tool
City-mandated pesticide reduction policies limit SCL's
ability to heavily utilize chemical vegetation control
methods—policies appreciated by many within the
Seattle-area's abundant progressive-minded popula-
tion. Mechanical methods—mowing and mechanized
cutting—are used where possible because they help
reduce labor and do not have the toxicity concerns
associated with herbicides. However, mowing also
results in compacted and disturbed soils and higher
light penetration at the soil surface—conditions
that favor pioneer plant species establishment.
Pioneer species that come in after mowing are
often non-native and invasive plants or native
tree species that are incompatible in ROWs. While
the invasive species are often low-growing, their
relative dominance makes it difficult for compat-
ible native plant communities to ever reestablish
(Parker et al. 1999). ROWs dominated by non-na-
tive species generally provide poor quality wildlife
habitat (McNeely 2001) and may be more prone
to fire (Brooks & Matchett 2004) and/or erosion
that can threaten transmission infrastructure. Of
the native pioneer species that come in after a dis-
turbance, several ROW-incompatible tree species
including black cottonwood (Populus trichocarpa),
big leaf maple (Acer macrophyllum), red alder
(Alnus rubra), black locust (Robinia pseudoacacia),
and silver poplar (Populus alba) are reliably suc-
cessful/dominant. SCL had to find a way to promote
diverse, ROW-compatible plant communities
while suppressing non-desirable monocultures.
Habitat Pilot Study
The purpose of the pilot study was to evaluate a novel
mixed prairie-scrub and shrub pollinator habitat to
suppress tree and invasive plant regeneration. SCL >>
urban-forestry.com 25
Pictured above is the Creston-Duwamish Transmission
Line and Green Line Project Sites.
