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The Global Invasive Species Team | |
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Global Invasive Species Team listserve digest #092 Wed Sep 05 2001 - 16:52:27 PDT --CONTENTS-- 1. Clarification on weed-free topsoil (Maine) 2. Weed pamphlet from WIST (Global) 3. Upcoming workshops/meetings (Nationwide, USA) 4. NFWF reminder (Nationwide, USA) 5. Literature reviews (Global) --------------------------------------- 1. Clarification on weed-free topsoil (Maine, USA) From: Nancy Sferra (nsferra(at)tnc.org) I just wanted to clarify an item sent in by Ross Geredien in Invasive Species digest #91. Our restoration project in Maine did not rely on imported topsoil. We stockpiled topsoil from an intact sandplain grassland where a pipeline was going through and used that stockpiled topsoil for the restoration of the construction site. The seed bank in the stockpiled topsoil was a major contributor to the success of the revegetation of that site. --------------------------------------- 2. Weed pamphlet from WIST (Global) From: TunyaLee Martin/WIST (tamorisawa(at)ucdavis.edu) Do you need to explain to your community why that "pretty flower" should be removed from a natural area, or are you having trouble explaining what a "weed" is? The Wildland Invasive Species Team is ready to help! We are pleased to announce the internet publication of a pamphlet, "Weeds in the Wild: Weed Management in Natural Areas". The pamphlet is chock full of information on invasive plants and animals. It is one page, double-sided, and can easily be printed on a black/white or color printer, and then folded for site visitors, partners, and neighboring landowners. If it is well received, we may follow it up with similar pamphlets on other topics. Check it out! We have it on line at: http://tncweeds.ucdavis.edu/outreach.html --------------------------------------- 3. Upcoming workshops/meetings (Nationwide, USA) From: Barry Rice (bamrice(at)ucdavis.edu) In case you have not noticed, we maintain on our web site a list of approaching meetings that may be of particular interest to weed bashers. Right now, at http://tncweeds.ucdavis.edu/meetings.html you can see notes, information, and links on two meetings. First, the 28th Annual Natural Areas Conference (3-6 October, Florida) will include an Invasive Species Symposium hosted by the National Association of Exotic Pest Plant Councils and the Florida Department of Environmental Protection, Bureau of Invasive Plant Management. The plenary guest is Dr. Dan Simberloff. (Thanks for Ruark Cleary for news of this meeting.) The second is "Phragmites australis: A Sheep in Wolf's Clothing?" (6-9 January 2002, New Jersey), is dedicated to the complex issues surrounding Phragmites australis. Is it native? Is it really the villain it is often claimed to be? --------------------------------------- 4. NFWF reminder (Nationwide, USA) From: Barry Rice (bamrice(at)ucdavis.edu) Do not forget that the due date for NFWF (National Fish and Wildlife Foundation) grant proposals for the "Pulling Together Initiative" is November 6. NFWF funds projects which "...benefit multiple species, achieve a variety of resource management objectives, and/or lead to revised management practices that reduce the causes of habitat degradation. A special emphasis is placed on larger projects that demonstrate a landscape-level approach and produce lasting, broad-based results on the ground." Pulling Together Initiative proposals are particularly likely to be successful if they involve Cooperative Weed Management Areas, or some analogous consortia of multiple partners. These grants average about $50,000, but assume that 1/2 the funds are raised by the grantee via matching funds. For more information, look to the web site at: http://www.nps.gov/plants/nfwf/02rfp.htm --------------------------------------- 5. Literature reviews (Global) From: John Randall/WIST (jarandall(at)ucdavis.edu) D'Antonio, C.M., R.F. Hughes and P.M. Vitousek. 2001. Factors influencing dynamics of two invasive C4 grasses in seasonally dry Hawaiian woodlands. Ecology 82(1): 89-104. This work examines a case in which a previously established invasive species is pushed out by a more recent arrival and reveals the conditions and physiological mechanisms that allow this to occur. The perennial C4 bunchgrass Schizachryum condensatum from the American tropics and subtropics is now an abundant invader in Hawaii's seasonally dry woodlands. Following fires, however, this species is often replaced by another invasive C4 grass native to Africa, Melinus minutiflora (molasses grass). The authors' experiments indicated that molasses grass establishment is suppressed by the dense shade cast by established S. condensatum stands. Molasses grass establishment was promoted by removal of S. condensatum but not by nutrient addition alone. When seeds of both species were started at the same time the molasses grass seedlings consistently outcompeted S. condensatum, regardless of light or nutrient conditions. The authors concluded that where S. condensatum is already established molasses grass can invade only following fires which eliminate or sharply reduce the former species above-ground biomass. Molasses grass seed is generally abundant in these areas and it quickly becomes established and eventually replaces S. condensatum through resource competition. The authors also concluded that molasses grass could readily invade unburned woodland if it was not already dominated by other invasive bunchgrasses. Leslie, A.J., and J.R. Spotila. 2001. Alien plant threatens Nile crocodile (Crocodylus niloticus) breeding in Lake St. Lucia, South Africa. Biological Conservation 98: 347-355. Chromolaena odorata is an herbaceous perennial in the Asteraceae which is native to the American tropics (including south Florida) but invasive in parts of Africa, Asia and on many tropical and subtropical islands. It is now abundant around Lake St. Lucia and adjacent wetlands which lie near the Indian Ocean in South Africa's Kwazulu-Natal province and are the southernmost extent of the Nile crocodile's breeding range. The authors found that dense C. odorata root mats sharply reduced availability of crocodile nest sites at one study location. The heavy shade cast by C. odorata at every site examined also reduced soil temperatures so that they fell below a threshold at which the eggs yield roughly equal numbers of female and male offspring and perhaps even below the threshold which allows embryonic development to occur at all. The authors concluded that where C. odorata is not controlled, the highly female-biased sex ratio of nestlings will result in sharp decline and eventual extirpation of the Nile crocodile population. Larson, D.L., P.J. Anderson, and W. Newton. 2001. Alien plant invasion in mixed-grass prairie: effects of vegetation type and anthropogenic disturbance. Ecological Applications 11(1): 128-141. The researchers assessed frequency of non-native invasive species on more than 1300 transects in the two units of Theodore Roosevelt National Park in western North Dakota to determine whether anthropogenic disturbance or biotic and physical factors better explain variations in abundance of invaders there. Each transect was classified beforehand by park unit, vegetation type and as disturbed (here defined as within 100 mm of roads, trails, buildings, etc.) or undisturbed. Invasive species were present in all vegetation types but mesic communities had more species of invaders and higher frequencies of most species than did drier community types. Surprisingly, frequencies of six of the seven most abundant invaders in the Park (Melilotus officinalis, Poa pratensis, Tragopogon dubius, Taraxacum officinale, Bromus japonicus, Euphorbia esula) were best explained by vegetation or vegetation and unit. Frequencies of Bromus inermis (smooth brome) and several less abundant species were best explained by vegetation type and disturbance or disturbance alone. The authors note that there was a strong element of stochasticity in frequency differences between the two units of the Park for many invasive species which suggests that chance may play an important role in many invasions. Because vegetation type was the best predictor of frequency of non-native plants in aggregate and for 10 of the 17 species detected the authors suggest that it be explicitly taken into account in the design of invasive plant monitoring and management plans. |
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