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Global Invasive Species Team listserve digest #050
Mon, 20 Dec 1999 16:56:41 -0800 (PST)
--CONTENTS--
1. Additions to Weeds Web Site
2. Polygonum cuspidatum in riparian areas
3. Mapping weeds yields clues to dispersal in a NY prairie
4. Japanese knotweed spread into healthy riparian areas
5. Japanese Honeysuckle on flatrock
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1. Additions to Weeds Web Site
From: Barry Rice (bamrice(at)ucdavis.edu)
If you have not visited the TNC Weeds website lately, a trip is overdue.
We are extending the site's coverage to include weeds for which we do not
have Species Management Summaries, and have already added information like the following:
---Photographs of 80 new weeds
---More than a dozen short papers on different new weeds and their control
---Additions to the "Weed News" area, including a report on giant Salvinia
---News from Betsy Lyman's Pennsylvania weed symposium
---A new weed alert---the dread Ononis alopecuroides!
We are at http://tncinvasives.ucdavis.edu
I'll leave the light on for you.
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2. Polygonum cuspidatum in riparian areas
From: Peter Dunwiddie (pdunwiddie(at)tnc.org)
Polygonum cuspidatum can definitely invade established riparian
vegetation. It readily invades established vegetation of many sorts
through vegetative reproduction (i.e., expansion of established stands).
However, I have also seen it in numerous locations where the only presumed
mode of invasion was either by seeds or fragments (often carried by
flooding). Heavily shaded areas are probably the least likely to be
invaded, but I would consider almost any reasonably sunny location,
vegetated or not, as potentially invadable.
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3. Mapping weeds yields clues to dispersal in a NY prairie
From: Marilyn Jordan (mjordan(at)tnc.org)
Two undergraduate students (Christine Kutzman and Brie-Anne McKernan)
working with Dr. Russell Burke at Hofstra University have completed a weed
mapping project at the Hempstead Plains, a remnant tall grass prairie on
Long Island. They mapped five cover classes for Sericea lespedeza
(Lespedeza cuneata) and Artemisia vulgaris (mugwort) in 2 m x 2 m "pixels"
across a 4 acre portion of the Plains. Color maps prepared for each weed
graphically display weed distributions. Results were compared with
similar maps generated by undergraduate biology classes in 1995.
Mugwort is concentrated in discrete, presumably disturbed areas around the
perimeter of the Plains, and appears to be spreading inward gradually via
adventitious runners. In contrast, lespedeza spreads by seeds and is more
widely distributed and scattered across the Plains. The lespedeza is
especially abundant along an old gravel road, and along a loop trail that
TNC mows annually. Lespedeza seems to be spreading into the Plains along
the trail. Mowing may distribute lespedeza seeds into new areas, or
create favorable habitat into which seeds can later spread, or both.
Maybe regular mowing of trails is a bad idea, at least when weed seeds are
ripe and ready for dispersal. After mowing weedy areas that are in seed,
it would be a good idea to clean the mower before moving to an uninvaded
site. Yes, common sense, but we don't always pay enough attention to
"weed hygiene."
The students also found a correlation between weed presence and a soil pH
increase of 0.8 in the field, and possibly also in pots in which weeds
were grown. Increased soil pH is associated with other weedy invaders,
such as Japanese stilt grass and Japanese barberry (P. Kourtev, W. Huang,
J. Ehrenfeld, Rutgers Univ.). Cause is as yet unknown.
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4. Japanese knotweed spread into healthy riparian areas
From: Clare Billett (clare-nlt(at)wildmail.com)
Since Japanese knotweed (Polygonum cuspidatum) is seed-germinating in our
area, I suspect that it could invade established riparian area where there
is enough light, even if it first gets in along just an eroded stream bank
and then spreads from there. The only prerequisite would be a
seed-source.
PLEASE post your responses to Jonathan's question about whether knotweed
can successfully invade established riparian vegetation...I'd love to see
other people's opinions on this topic!
(Note: Karen Budd TNC-PA noted on her weed survey that P. cuspidatum can
invade new, downstream areas by detached vegetative propagules. Seed is
not necessary---Barry Rice)
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5. Japanese Honeysuckle on flatrock
From: Paul J. Harmon (pharmon(at)dnr.state.wv.us)
Does anyone have any experience or thoughts regarding how feasible it is
to control such invasive plant species as Japanese Honeysuckle (Lonicera
japonica) that is invading a 'flatrock' community along a high energy
river? John Perez of the National Park Service's New River Gorge, asked
me regarding how feasible it is to use fire to control invasives in such a
community. Of course, my immediate question is whether there is enough
fuel in the open, sandstone outcrop adjacent to the river. At one time,
before the river was damed, periodic, scouring floods keep not only woody
vegetation at bay, but kept species not adapted to such flood events from
getting a stronghold in these communities.
I can imagine one being able to find enough fuel to burn the wooded edge
of the community, but I wonder if the deciduous tree leaf litter would be
adequate to produce a fire that could kill the viny honeysuckle. Any
thoughts on this would be appreciated.