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Global Invasive Species Team listserve digest #057
Wed Mar 22 2000 - 17:30:01 PST
--CONTENTS--
1. Purple loosestrife in bogs (New York)
2. More on the purple loosestrife tug-of-war (Washington)
3. Phalaris and Euonymus added to TNC Invasives web site (Nationwide)
4. Recent weed articles (Nationwide)
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1. Purple loosestrife in bogs (New York)
From: Sandy Bonanno (sbonanno(at)tnc.org)
Regarding the question of whether purple loosestrife (Lythrum salicaria)
can invade bogs, I have not yet seen it in a bog site...
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2. More on the purple loosestrife tug-of-war (Washington)
From: Marcy Summers (msummers(at)tnc.org)
We have found it most effective to pull purple loosestrife (Lythrum
salicaria) in the winter at one privately-owned island site in Puget
Sound, WA. For the last two years, we have been cutting seed heads in
summer and pulling in the winter. During the winter, the soils are much
wetter and looser, and plants have come up easily and completely by hand.
So far, with this technique, they do not seem to be resprouting.
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3. Phalaris and Euonymus added to TNC Invasives web site (Nationwide)
From: Barry Rice (bamrice(at)ucdavis.edu)
Phalaris arundinacea (reed canarygrass) got you down? We have posted a
brand new Species Management Summary on this pest for you on our web site. To retrieve it, visit
our web site (http://tncinvasives.ucdavis.edu/esadocs.html).
Euonymus alatus (winged wahoo, burning bush) has been spotted escaping in
Connecticut, Virginia, Pennsylvania, and Illinois. This is a common
horticultural tree, so watch out for it! We have a weed alert on the plant
on our site (http://tncinvasives.ucdavis.edu/alert/alrteuon.html). Read,
learn, be alert!
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4. Recent weed articles (Nationwide)
From: John Randall (jarandall(at)ucdavis.edu)
IMPACTS OF INVASIVE PLANTS:
Schmidt, K.A. and C.J. Whelan. 1999. Effects of exotic Lonicera and
Rhamnus on songbird nest predation. Conservation Biology 13(6):
1502-1506.
The authors followed nest predation on American robins and wood thrushes
for 6 years in a 200 ha woodland fragment near Chicago. They found that
robin nests in Lonicera maackii and Rhamnus cathartica experienced higher
predation rates than nests in similar native shrubs (Crataegus, Viburnum)
and in native trees. Part of this difference was due to nests in the
Lonicera being built closer to the ground. The authors speculate that
absence of thorns on the exotics and a branch structure that facilitates
movement of predators like raccoons may also help explain the difference.
Robin use of Lonicera increased sharply during the 6-year study and the
authors suggest this may be due to the exotic shrub's early leaf-out. If
so, higher predation rates early in the season may also help explain the
difference between nest success in exotic and native plants. Predation on
wood thrush nests in native and exotic plants was not significantly
different. High proportions of thrush nests were in Lonicera and as use of
Lonicera by robins increased, predation rates on thrushes increased. The
authors caution that these results are specific to a single site and to
the two bird species followed and that it is not known whether they will
be applicable to other sites or species. But they note that if higher nest
predation rates are found in exotic shrubs elsewhere, restoring native
shrubs would serve several conservation goals simultaneously.
de Winton, M.D. and J.S. Clayton. 1996. The impact of invasive submerged
weed species on seed banks in lake sediments. Aquatic Botany 53:31-45.
The authors sampled seed banks in sediments from a total of 102 sites in
21 shallows lakes in New Zealand. They classified vegetation status at each
site in one of three categories: native vegetation; invaded by
non-natives; or de-vegetated. The invaders were Egeria densa, Hydrilla
verticillata, both of which are also severe pests in North America, and
Elodea canadensis. Numbers of seeds and other reproductive structures
(turions, oospores) were significantly higher under native vegetation than
under invasive plants or de-vegetated areas. Seed numbers beneath invaders
were less than 5% of those beneath natives. Numbers of species in seed
banks below natives were also significantly higher. Where sites with
native vegetation and sites with invaders coexisted in the same lake, seed
bank differences were still significant but not as pronounced. Seed banks
beneath invaders were not statistically different from those in
de-vegetated areas. Examination of seed banks within 10 cm sections of
deep cores showed that numbers of seeds under invaders are sharply lower
in the upper 20 cm which were deposited in recent years, since the
invasion, but about the same as under native vegetation at greater depths.
The authors point out that the invaders continue to spread in New
Zealand's lakes and suggest sharp reductions in seed banks beneath invaded
sites will hinder recovery of vegetation following disturbances or other
devegetation events like those that have been observed in New Zealand
lakes.
USING FIRE TO CONTROL INVASIVE PLANTS
Willson, G.D. and J. Stubbendieck. 2000. A provisional model for smooth
brome management in degraded Tallgrass prairie. Ecological Restoration.
18(1): 34-38.
Prescribed burns may be effective for reducing smooth brome (Bromus
inermis) abundance in tallgrass prairie if carried out at the right time
of year AND if warm season tallgrasses are abundant enough (>20% cover) to
take over and keep smooth brome from reclaiming the area.
Meyer, M.D. and P.M. Schiffman. 1999. Fire season and mulch reduction in
a California Grassland: a comparison of restoration strategies. Madrono
46(1): 25-37.
Results indicate that the season during which burning occurred was a vital
factor in determining impacts on native and non-native plant species in a
California grassland (Carrizo Plain natural area), and that this was due
to seasonal differences in plant phenology, fire intensity and consequent
reduction of litter by fire. Late-spring and early-fall burning increased
the cover and diversity of native vegetation and decreased the cover and
seed viability of alien grasses relative to untreated areas. Winter
burning and reducing mulch by raking did not increase cover of natives and
was only moderately effective at reducing alien plant species cover. The
authors conclude that late-spring or early-fall burning is the most
effective strategy for restoring native annual vegetation to California
grasslands and that winter burning or grazing are not effective.