- Our project goal is to promote the abundance of the endangered Fender’s blue butterfly
(Icaricia icarioides fenderi) by recreating upland prairie habitat in former agricultural land at
Finley National Wildlife Refuge, Corvallis, Oregon. To achieve this goal we initiated the
following three studies.
Study One: Experimental Investigation on the Effectiveness of Restoration Treatments
Our approach was to set up experimental field plots in a former agricultural field into
which we sowed seeds of native grasses and dicots in the fall for two years, 2003 and 2004.
Objective one: Investigate the effect of carbon banding on abundance of sowed native
species and non-native species. Carbon banding is a treatment used by Willamette
Valley grass seed farmers to promote seedling establishment of agricultural grasses and
inhibit seedling establishment of weeds.
Objective two: Investigate the effect of the sowing sequence of native dicot and grass
species on the abundance and species richness of the sowed species. Our experiments
were designed to test the hypothesis that our native grasses are more aggressive than
the target native dicots in the initial stages of restoration.
Objective three: Investigate the effect of the sowing sequence of the native dicot and
grass species on the abundance of non-native species.
Study Two: Monoculture Sowing of Native Species Compare the cover of non-native
species and the cover of native species one and two years after sowing native species in
Study Three: Buffer Sowing of Native Grasses Monitor the abundance of the native
grasses sowed in the buffer areas outside the experimental plots.
Carbon banding had no significant effect on cover of non-native species or on cover and
species richness of sowed native dicots or grasses after both the first and second growing
seasons. However, carbon banding tended to reduce the cover of the annual Clarkia
rhomboidea after the first growing season.
Our results supported the hypothesis that our native grasses are more aggressive than the target
native dicots in the initial stages of restoration. The sowing sequences tested did not affect
cover and species richness of grasses but did affect cover and species richness of dicot species.
Both dicot cover and dicot species richness were greater when sowed a year ahead of the
grasses. Eriophyllum lanatum had significantly greater cover when sowed a year before the
grasses. Average cover of sowed dicots was significantly greater when dicots were sowed with
grasses compared to when dicots were sowed into a year-old stand of grasses. In particular,
Madia gracilis and Prunella vulgaris var. lanceolata had less cover when sowed into the
existing stand of grass.
Species richness of all native species (grasses + dicots) was significantly less when dicots were
sowed into a year-old stand of grasses. However, total cover and species richness of sowed
native species (grasses + dicots) were not significantly different whether dicots were sowed a
year ahead of the grasses or whether dicots and grasses were sowed together. Average cover of
sowed native dicots after two years was always greater than the cover of sowed native grasses
except when dicots were sowed a year after the grasses. After two growing seasons, non-native cover did not significantly vary among the three sowing
sequences of sowing grasses and dicots at the same time, sowing grasses into existing dicot
vegetation, and sowing grasses into existing dicot vegetation.
The first year after sowing the monocultures (Study two), Collinsia grandiflora had the highest
cover, greatly surpassing the next top performers, Sanguisorba occidentalis and Madia
gracilis, all of which are annual species. In general, the cover of individual species sowed in
monocultures decreased the second year after sowing. Only seven species, all of which were
perennials, out of the 26 sowed species increased in cover. Two of these species Eriophyllum
lanatum and Prunella vulgaris var. lanceolata were the top performers for 2005, but their
cover did not reach the levels of the top performers in 2004.