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The Global Invasive Species Team | |
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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 --------------------------------------- 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://tncweeds.ucdavis.edu I'll leave the light on for you. --------------------------------------- 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. --------------------------------------- 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. --------------------------------------- 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) --------------------------------------- 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. |
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