(1) Div. Biological Sciences, University of Montana, Missoula, MT 59812 USA Lincoln Smith, USDA-ARS, Northern Plains Agricultural Research Laboratory, Sidney, MT 59270
U.S.A.
(2) USDA-ARS, Northern Plains Agric. Res. Lab. 1500 N. Central Ave.
Sidney, MT 59270
U.S.A.
Phone: 406-482-9439; fax 406-482-5038
LSmith@sidney.ars.usda.gov

The INVADERS Database http://invader.dbs.umt.edu is an interactive web site that tracks the historic spread of approximately 900 exotic plants that have invaded the five Pacific Northwest states of United States since 1875. Core data include 80,000 distribution records from herbaria, weed identification laboratories, agency survey and other various sources. All distribution records have at least county level spatial resolution. Data can be verified as to source, and most have voucher specimens or originate from experienced weed taxonomists. Online outputs include county level distribution maps, time lapse spread maps, spread rate curve graphics, lists of exotics by user-specified state or county groupings, and a database engine with live links to other URL's with species specific descriptions. Point location records can be extracted and imported to GIS for climate matching, determination of habitats at risk to invasion, and other forms of spatial analyses. The site also includes examples of how regulatory agencies, weed program, and land managers have been using INVADERS data for risk assessment, environmental impact statements, selection of target weeds, legal noxious designations, and various on-the-ground projects. Taxonomically qualified users can submit new weed findings directly to the INVADERS web site. The new distribution records are immediately available for inclusion in output graphics and lists. Users can request automatic next morning e-mail notification of new reports of specific weeds. http://invader.dbs.umt.edu is a Java driven web site. It was designed to work best with the Microsoft Internet Explorer 4.01 browser, which allows full delivery of INVADERS web site graphics. The INVADERS team hopes to expand geographic coverage from the current 5 northwestern US states to at least the 50 US states or continental North America. if not the entire western hemisphere.

Keywords: database, web site, weed distribution, spread, mapping, GIS, risk assessment, invasions, exotics, strategy, climate matching

M. Richter

Institute of landscape - and plantecology, University of Hohenheim (320), D-70593 Stuttgart
Germany
richterm@Uni-Hohenheim.DE

Paulownia tomentosa is a tree species originating from East-Asia and has already been used as a solitary specimen in parks during the last century. The popularity of this species in Germany has risen especially in the last 10 years. This period covers the time during which most of the specimens in Stuttgart were planted. Paulownia tomentosa was chosen as a study object since this tree is found in cities lying at relatively northern latitudes with respect to the distribution in Europe: The spread and rejuvenation of tree growth in city-associated "warm islands" like in Stuttgart is, of course, in the initial stages. Spontaneous occurrences of Paulownia tomentosa have been observed in Germany, e.g. in Freiburg, Heidelberg and Stuttgart.  These natural and spontaneous occurrences can be observed to extend along the Upper Rhine Valley and Neckar River and up to the Stuttgart Basin, i.e. in climatically favourable areas (macroclimatic level). It is known that young buds of Paulownia, which comprise immature wood, die back under severe frost.
The areas in Stuttgart with planted and naturally occurring Paulownia were investigated and charted onto a distribution map. This allowed the occurrence of rejuvenation to be related to mesoclimatic factors. The warmest climatic areas in Stuttgart, indicated via infra-red photography, were shown to be favoured sites for rejuvenation (Bad Cannstatt, bottom of the valley in Stuttgart-City).
The scale of the infra-red photographs used (1:10 000) does not, however, allow an adequate resolution of local temperature differences between land utilisation units. Local land utilisation units such as gravel areas, building perimeters, turf, hedges, bushes, small forested areas etc., were climatically characterised by making over 1000 measurements during the warmest days of the year. The average maximum temperature of the soil surface was shown to be for example, only ca. 25 °C for small forested areas but ca. 45 °C for gravel areas or the perimeters of buildings. It was interesting to observe that the spontaneous rejuvenation of Paulownia tomentosa occurred exclusively in the warmest of the above mentioned land utilisation units (microclimatic level).
Apart from temperature dependency, the presence of a seed-bearing mother plant is also necessary.  A spatial relationship between the mother plant and spontaneous rejuvenation could be demonstrated in many cases. Certain examples are represented graphically, whereby the dependence on land utilisation types was especially obvious.  The morphological and germination biological relations are investigated.
The spontaneous occurrence of the investigated species was shown to be dependent on high temperatures at various spatial levels (micro-, meso- and macroclimatic levels).  In a few decades, it is likely that Paulownia tomentosa will, similar to Ailanthus altissima, become an integral part of the city identity where spontaneously occurring specimens may not be clearly differentiated from planted specimens.

Segura Burciaga S. (1) and Jorge Meave (2)

(1) Programa de Control Ecològico del Campus, UNAM. Av. Revoluciòn No. 2045, Ciudad Universitaria. C. P. 04510, Coyoacan
Mèxico D.F.
Tel.: 56 22 48 35; Fax: 56 22 34 94
sagseb@servidor.unam.mx,
(2) Laboratorio de Ecologia, Facultad de Ciencias, UNAM. Ciudad Universitaria. C. P. 04510, Coyoacan
Mèxico D.F.
Tel.: 56 22 48 35; Fax: 56 22 48 28
jamdc@hp.fciencias.unam.mx,

In 1951 a few juvenile individuals of the exotic species Eucalyptus aff. resinifera were introduced in a successional xerophytic community developing on a lava field of approximately 2,200 years of age. Individual trees were planted as a single row bordering the two largest remaining fragments of natural vegetation along road edges. These two areas were declared as ecological reserve in 1983. This initially linear and peripheral distribution facilitated the spreading of the eucalypts further into the fragments interior through the natural establishment of consecutive rows of eucalypts; by 1990 the eucalypt-dominated strip reached a maximum width of 225 m. The high rate of this spreading makes it possible to regard this phenomenon as an invasion. Eucalypts alter the natural conditions and the resource availability at the sites because of their fast growth rate and efficient water and nutrient uptake. These attributes make this species a successful competitor in this low-stature (< 7m), heliophyte dominated community. Considering the light interception of the eucalypts' canopies and the litter layer interference on the seeds, we designed an experiment to test if any, or both factors acting synergically have an effect in the natural composition. We defined four treatments with eight 20-m2 circular replicates, each centred in an individual eucalypt: 1) with tree (shade) and with litter, 2) with tree and without litter (removed), 3) without tree (cut) and with litter, 4) without tree and without litter. Four reference samples in the native vegetation were also located 50 m beyond the last eucalypt line. All these sites were censused in 1996 (rainy season, prior to treatments), 1997 (dry and rainy seasons) and 1998 (dry and rainy seasons). The initial results on diversity showed that the natural community samples were richer than the sites with eucalypts in terms of species number, except in one case before the treatments were applied. The Shannon diversity index for individuals produced a similar result, except in one case. Both variables presented more seasonality-related variations in the sites with eucalypts than in those without them. Analysis in progress are considering other factors of the plants analysed, like biogeographical affinity (native vs non native) and crown cover changes through time.

Indra Kumar Sharma

Commission on Ecological Management WCU/IUCN, Bhagwati Bhavan, Ratanada Road - Jodhpur 342020
India

Some hardy vigorous growth wide adaptive flora escape from cultivation in nearby wilderness areas, come over less hardy and vigorous growing flora there. Then that useful flora groove invasive weed if not properly controlled. Prosopis juliflora was introduced in arid barren tanks of western Rajasthan and in northern Guyrat for afforestation. In these decades it has became over dominated flora around villages and towns outskirts.
Eichhomia crassipes was introduced in some tanks of towns but it spread wide to cover most of tanks suppressing native flora and fauna and caused many other lizards. I studied various ecological and human aspects of rise and control of invasive vigorous flora, often growing noxious weeds. How the vigorous weeds may be utilised as useful crop was also studied. I continued my study for last 25 years in Rajasthan and other neighbour states of India. My inferences and recommendations topics wise are as follows.

How particular flora groove invasive weed: it was observed that hardy, adaptive, vigorous growth profuse seedling flora often escape wide from the cultivation area, grow vigorously and empowers less vigorous and hardy flora thereby, soon from thicket, than may prove noxious weed to local men.

Adverse ecological and economic effects and their control: when particular flora grows excessive vigorous, suppresses nearby plants, then it proves noxious weed. This may be properly controlled with proper pruning and screting unwanted growths and plants. Proper regular management is required for satisfactory results. It was observed that regular vigilant supervision to check unwanted growth of flora in an area need not much labour, effort and expenses. On considerable growing negligence to control weed's growth, the weed may cause mortality to delicate flora nearby.

Control management: as weeds plants are very hardy and adaptive can grow vigorously anywhere, alternative change in the cultivations are may not prove much useful. Pruning, harvesting and weeding are necessary to control flora proving weed. Early routing of weed flora definitely check nuisance of weeds in the area. Considerable delay to route the weed flora, may avail weed to flower and disperse seeds widens, then it becomes difficult to control wide spread weed.

Prominent invasive flora proving noxious weeds if not properly managed for control and utilisation.
Prosopis juliflora: it is very hardy and vigorous growing flora, grows vigorously even in saline, lime alkaline, rocky barren areas and water-logged areas, hence now dominating flora around towns and villages, get widely distributed with droppings of cattle, particularly the goat. Cattle relishes its legumes. Parsanty dwellers cut it indiscriminately for firewood, hence the flora remains as compact bush, by constant indiscriminate cuttings, where properly pruned, it grows well as shade thick tree. Where it is not wanted, it may be easily uprooted at early stage but people neglect so then the flora establishes firmly then very difficult to uproot it as its roots grow very deep and wide. With proper pruning the tree grows as fine shade tree, provide nectar to honey-bees and edible palatable legumes to herbivores, they relish that. Its tickets raises forest areas, increases rainfall and forest cover to wide range of wild fauna. There is anti juliflora lobby largely comprises of charlatan naturalists and some charlatan foresters. They condemn juliflora as noxious weed, plead to destroy it. (abstract)
 

M. Shevera

Institute of Botany, National Academy of Sciences of Ukraine, Tereshchenkivska str., 2, Kyiv-1, 252601
Ukraine
botan.kiev.ua!smos@botanua.uucp

Different types of parks existed in the territory of the town of Uzhgorod (Transcarpathia, Ukraina): in the XVII-XVIII c.c. there were forest parks, in the XIX-XX c.c. - arboreta, in the second half of the XX c. - recreation parks. In the present-day Uzhgorod, there are several parks differing in their age, size, location, principles of formation, mode of use etc. Synanthropization of the plant cover of urban parks is mostly neglectable.
In arboreta, the herbaceous plant cover is poorly developed, and consists of anthropophilous plants (Dactylis glomerata, Aegopodium podagraria L., Glechoma hederaceae L., Stellaria media (L.) Vill., Ranunculus repens L., Lamium album L. etc). In the forest parks the aboriginal species prevail; synanthropization is considerably higher, especially on ruderal plots (roads, alleys and riversides). Abundance of synanthropic species, especially adventive ones (Impatiens parviflora DC., Reynoutria japonica Houtt., Helianthus tuberosus L.), depends on the age of the park (it is much higher in modern parks), management and use.

Luis Silva

Department of Biology, University of the Azores, 9500 Ponta Delgada
Portugal
Phone: +351-96-652602; Fax: +351-96-653455
silva@alf.uac.pt

Clethra arborea Aiton (Clethraceae), a tree endemic to Madeira Island, is naturalised in São Miguel Island (Azores). In Madeira this tree is found in the Clethro-Laurion, and in São Miguel in the Juniperion brevifolii, two similar communities. The shrub and tree species associated with C. arborea in Madeira are: Vaccinium maderense, Laurus azorica, Erica scoparia ssp. platycodon, Erica arborea and Myrica faya. In São Miguel the more frequent species are: L. azorica, C. arborea, Erica scoparia ssp. azorica, Ilex perado ssp. azorica, Viburnum tinus ssp. subcordatum, Vaccinium cylindraceum, Myrsine africana and Juniperus brevifolia. Three other important alien species are also found associated with C. arborea in São Miguel: Leycesteria formosa, Gunnera tinctoria and Hedychium gardneranum. Vegetation higher and lower canopy limits and basal diameter are higher in Madeira than in São Miguel. Those parameters are also higher for C. arborea and L. azorica in Madeira than in São Miguel. In São Miguel C. arborea is more often the tallest tree. Flowers are visited by several insect species and, contrary to native shrubs, C. arborea presents a copious production of small, readily germinating seeds. Germination is light dependent and seeds survive for more than one year in the forest soil. Seedlings are mainly found in vertical surfaces covered by bryophytes, but not in the litter covered forest soil. Saplings present a high survival rate. While in Madeira two species of insects feeding on leaves were found, in São Miguel an endemic bird and a native insect feed on the seeds. A phypathogenic fungus, causing a foliar disease might be specific and present in both islands. C. arborea may be controlled with low herbicide rates, namely with tryclopir, which stimulates the development of fungi and wood decay. Young plants might be controlled by uprooting.

E.Sobrino Vesperinas and M. Sanz Elorza

Departamento Producciòn Vegetal Botanica y Protecciòn Vegetal. Escuela Tècnica Superior Ingenieros Agronomos. 28040 Madrid
Spain.
esobrino@pvb.etsia.upm.es

Actually, both the soil and vegetation of the Mediterranean coast of the Iberian Peninsula are degraded strongly from the effects of many centuries of agricultural activity and the more recent problems of excessive tourism and construction. As a consequence, many allocthonous plants have invaded the different ecological niches of the area in a process that has accelerated over the last two decades.

Using as a model a 60 km long by 10 km wide coastal strip in the Baix Camp (Tarragona, Spain) (UTM quadrants 31TCF45, 31TCF46, 32TCF45, 32TCF46, 32TCF47, 33TCF46, 33TCF47, 34TCF46, 34TCF47, 35TCF47, 35TCF48, 36TCF47, 36TCF48, 37TCF47, 37TCF48, 38TCF47 and 38TCF48), an area under maritime influence, a study was made of the reception capacity of  allocthonous species  and the ecological factors that facilitate their invasion. A detailed inventory of the area showed that 20% of the plant species were allocthonous, and that 40% of these were from tropical areas.  A large number of these species were recent arrivals, with some showing strong invasive behaviour (Araujia sericifera Brot., Gomphocarpus fruticosus (L.) Ait. f. in Ait., Chloris gayana Kunth, Ipomoea purpurea Roth, Bidens subalternus DC., Bidens pilosa L., Bidens frondosa L., Arctotheca calendula (L.) Levyns). For all the allocthonous species found, the relationship between origin and new ecological niche colonized is discussed, so as the cause of their introduction and effects on the environment. Finally, a comparison is made of the reception capacity of this coastal land more strongly affected by man with areas of more continental climate and with a largely unaltered maritime area. In all the cases a greater ratio of xenophytes was found in the altered coastal area.
 

Carey Suehs, Laurence Affre and Frederic Medail

Universite d'Aix-Marseille III, Faculte des Sciences et Techniques de Saint-Jerome, Institut Mediterraneen d'Ecologie et de Paleoecologie (IMEP, CNRS), case 461, 13397 Marseille cedex 20
France
Tel : 33.4.91.28.85.35; Fax : 33.4.91.28.80.51
csuehs@mail.utexas.edu
laurence.affre@botmed.u-3mrs.fr
f.medail@botmed.u-3mrs.fr

Invasion by the introduced and invasive succulent Carpobrotus (Aizoaceae) constitutes one of the most severe threats to numerous terrestrial plant communities in coastal and island habitats of the Mediterranean Basin. Two South African taxa, C. edulis and C. aff. acinaciformis, have been introduced in Mediterranean France during the middle of the XIXth century. They have invaded the backdunes, coastal rocky slopes and cliffs, and even coastal scrubs, mainly in siliceous continental parts of Provence and on the island of Corsica. These alien taxa may induce severe local extinctions of native plants with a high patrimonial value (endemic, rare and/or protected plant species).
After a historical and biogeographical background about the invasion in the Mediterranean Basin, the present study is focused on the islands of Hyeres (Provence), mainly in the Port-Cros National Park. The two taxa show a combination of sexual and asexual strategies for reproduction. Asexual reproduction occurs both by vegetative propagation and facultative agamospermy (i.e. the formation of unreduced seeds by asexual processes). The relative frequencies of sexual versus asexual reproduction has a significant impact on the spatial genetic structure of natural populations. The purpose of this paper is (i) to determine the reproductive ecology and genetics of natural populations of the two invasive taxa (and their potential hybrids) in island habitats, and (ii) to examine how the dynamics of the two invasive taxa can influence the integrity of the local natural environment and native plant communities. First, we have quantified (i) the ability to autonomously self-fertilise, (ii) the relative performance of selfing and outcrossing, (iii) the level of agamospermy, (iv) the variation of floral traits related to the mating system, and (v) the rate of pollinator visitation. The level of genetic variability allows us to assess the clonal mosaic of genotypes. We could then compare between the two invasive taxa the reproductive success and the capacities of competition in these island habitats. Second, we have examined edaphic and floristic consequences of the presence of these two Carpobrotus taxa, particularly when important dense mats occur.
Finally, the clonal genetic structure is discussed in relation to the patterns of introduction of the two exotic taxa.

Leonardo Sulas

CNR, Centro di Studio sui Pascoli Mediterranei, Via E. De Nicola - 07100 Sassari
Italy.
Tel. 0039 079229332; fax 0039 079229354
sulas@hpj.ss.cnr.it

Arctotheca calendula (L.) Levyns, herbaceous annual, (Asteraceae) is a native species of South Africa and it has become naturalised in other countries. In Western Australia A. calendula has become a pest, the major weed of crops and pastures in all habitats. The content of Capeweed was estimated from 37% of pasture dry matter in high-rainfall grazing areas to 50% in lower-rainfall wheat belt areas. Due to the wide diffusion, it is investigated by Australian researchers as a potential forage source.
After its accidental introduction this species has been also recognised in Sardinia where it has shown a strong competition against sowed and native pasture species and invasive capacity. Some biological and agronomic traits of A. calendula in relation to the management of local forage farming systems are discussed in this paper. The very high seed production per plant, the easy seed dispersion by wind and animal, the high level of seed dormancy, the rapid growth of seedling after late summer rain, the extension of the root system,  the vigour and prostrate habit of the plant are the key factors in the  success of Capeweed.  Moreover its earliness of flowering, low palatability for sheep and the undirect effect of agronomic techniques (e.g. ploughing, hay harvest) in maintaining the seed bank in the soil contribute to increase its persistence. On the basis of the available data and observations a prudential and integrated control of this exotic species is recommended for Sardinia.

P.S. Swamy, SM. Sundarapandian and R. Pandiselvi

Department of Plant Sciences, School of Biological Sciences, Madurai Kamaraj University, Madurai - 625021
India
Fax: ++91-452-859139; Tel: ++91-452-858928
smspandian@hotmail.com

Invasion by exotic species can alter the population and community structure of a native ecosystem is well documented, but information from the tropics is limited. Parthenium hysterophorus L. a ruderal exotic perennial weed has become a menace to agriculture, forestry plantations and disturbance regimes and wastelands. Growth, resource allocation, nutrient uptake and use efficiencies and reproductive effort of P. hysterophorus a ruderal weed current year seedlings and populations various in (1, 3, 5 and 8 mm basal diameter class) were evaluated under open and shade habitat in the semi-arid environment of Madurai, India. It was found that the variability in the environment altered growth, resource allocation patterns and reproductive efforts. More resources were allocated to growth and reproduction under open habitat. Increased leaf area and slower growth rates under shade may be due to reduced light availability (Chapin, 1980).  Decline of growth rate in older and previous year (2, 5 and 8 mm basal diameter class) populations caused by the reduction of leaf area due to high irradiance under open habitat. Older or previous year populations showed little or no variation in growth, resource allocation patterns and reproductive efforts in shade habitat.  This was attributed to physiological adjustment or phenological plasticity of the populations adapted to survive under shade (Grime, 1974).  Intraspecific variations could be related to differences in microhabitat and other intrinsic factors.  Thus, it is concluded that the species has an exploitative growth strategy characteristic of a ruderal species and it may be controlled by light curtailment under a canopy cover. (abstract)

References
Chapin, F.S., III. (1980) The mineral nutrition of wild plants. Annual Review of Ecology and Systematics, 11: 233-260.
Grime, J.P. (1974) Vegetation classification by reference to strategies. Nature, 250:26-31.

S. Chandrasekaran, SM. Sundarapandian and P.S. Swamy

Department of Plant Sciences, School of Biological Sciences, Madurai Kamaraj University, Madurai - 625021
India
Fax: ++91-452-859139; Tel: ++91-452-858928
smspandian@hotmail.com

In the recent past the Western Ghats of Tamil Nadu has undergone heavy environmental transformation for various reasons, such as changes in land use pattern, monoculture, forestry operation and developmental activities. The intentional and unintentional use of fire result in both arrival of new species to the site and also death of existing plant species, besides a change in edaphic environment for better plant growth. These and other associated perturbations to different ecosystems have resulted in the invasion of exotic noxious weeds and unpalatable grasses like Imperata cylindrica causing profound structural changes in the plant communities. Lantana camara and Chromolaena odorata, natives of Latin America, have rapidly invaded deforested hill slopes, wastelands and abandoned croplands in the region. In this context, an understanding of their distribution in different ecosystems becomes important. Exotic plants contributed about 17 and 35% of the total importance value indices to the plant community structure in natural and man-modified ecosystems respectively. L. camara and C. odorata were found to be the dominant exotic perennial weeds in both kinds of ecosystems studied. The high IVI of exotics in the man-modified ecosystems could be attributed to frequent disturbance and resource rich transient open environment here. The disturbance regime and the type of exotic plant invasions were analysed and found that frequent fires to the ecosystem resulted in monotypic savannah grasslands. C. odorata and L. camara invaded the sites where mechanical disturbance and occasional fires occurred. The density and weed composition varied considerably in different agroecosystems and agroforestry systems practised by "Kani" tribes in the region. This may be due to variation in the number of weedings and light availability to the ground floor through the crop canopy cover (Ramakrishnan, 1991; Chandrasekaran and Swamy, 1995).  During the secondary succession suppression of exotic weeds in 8 and 20 year old fallow could be attributed to decreased light availability by the larger shrubs and trees. (abstract)

References
Chandrasekaran, S. and Swamy, P.S. (1995) Changes in herbaceous vegetation following disturbance due to biotic interference in natural and man-made ecosystems in Western Ghats. Tropical Ecology 36:213-20.
Ramakrishnan, P.S. (1991) Ecology of biological invasions: an overview. Ecology of Biological Invasion in the Tropics. International Scientific Publications, New Delhi. pp. 1-19.
 

Anne-Marie Planty-Tabacchi and Eric Tabacchi

Centre d'Ecologie des Systemes aquatiques Continentaux, UMR C5576, 29 rue Jeanne Marvig, 31055 Toulouse Cedex 04
France
Tel.: (33) 5 62 26 99 71 / (33) 5 62 26 99 72; Fax: (33) 5 62 26 99 99
am.tabacchi@cesac.cemes.fr
tabacchi@cesac.cemes.fr

Patterns of plant species richness and community composition were studied along several riparian zones belonging to river systems from SW France and NW USA. Our findings suggest that riparian zones are among the most invasible ecosystems under oceanic climate influences. In SW France, 420 exotic species were found on 245 sites distributed along 7 rivers. Very few of them were pre-adapted with respect to the specificities of riparian ecosystems. At the scale of the entire corridor, exotics accounted between 25 to 30 % of the total number of species. This overall proportion as well as the patterns of longitudinal trends were consistent between the Adour River (France) and the MacKenzie River (Oregon), where the percentage of exotics at the local scale could respectively reach up to 40% and 60%. Due to intermediate levels of disturbance, spatial patterns at the local scale of a stretch of the middle Adour River showed a very complex mosaic of 45 different plant communities. As a result, the species richness was high (702 species on 200 ha). The highest species richness was found along the main channel in fragmented and disturbed patches, which were also the most invasible. Regional and local patterns of invasion by exotic plants are analysed and possible causes and consequences are discussed.
 

Fugo Takasu (1), Namiko Yamamoto (1), Kohkichi Kawasaki (2) and Nanako Shigesada (1)

(1) Department of Information and Computer Sciences, Nara Women's University, Kita-Uoya Nishimachi, Nara 630-8506,
Japan
(2) Department of Knowledge Engineering and Computer Sciences, Doshisha University Tanabe, Kyoto, 610-0321
Japan
Tel and Fax: +81 - 742 - 20- 3983
takasu@ics.nara-wu.ac.jp
kkawasak@duaic.doshisha.ac. jp
sigesada@ics.nara-wu.ac.jp

Pine wilt disease is caused by the pinewood nematode, Bursaphelenchus xylophilus, that is vectored by a pine sawyer beetle, Monochamus alternatus.
Japanese native pinewood, black pine (Pinus thunbergii Parl.) and red pine (P. densiflora Sieb. et Zucc.) are extremely sensitive to the nematode infection and the disease damage has been expanding nation-wide in the last several decades despite the intensive effort to control the disease. To gain insight into the range expansion of the disease in Japan, we modeled the dynamics of the pinewoods and the vector beetles that carry the nematode using integro-difference equation in one dimensional space. We focused on the speed of the range expansion of the disease and investigated the dependence of the expanding speed on the eradication rate of the beetles, the initial pinewood density, and the beetle's ability to disperse, based on detailed data set collected in Japan. From the model analyses, we obtained the following results.
(1) The Allee effect operates on the beetle reproduction and hence the disease cannot invade a pinewood stand, once the beetle density decreases below a certain threshold.
(2) The distribution of the travel distance of the beetles critically affects the expanding speed of the disease. As the fraction of the beetles that travel over long distance (long range dispersal) is increased from zero, the expanding speed is sharply amplified, i.e., occasional long distance dispersal greatly accelerates the disease range expansion.
(3) However, too much long range dispersals results in a failure of the disease invasion due to the Allee effect, suggesting the importance of correct assessment of the beetle's mobility to predict the disease expanding speed. Based on the model analyses, we discuss the effective control of the disease.

C. Tauleigne-Gomes, D. Draper and A. Rossellu

Museu, Laboraturio e Jardim Botânico da Universidade de Lisboa, Rua da Escola Politècnica, 58 - 1250-102 Lisboa
Portugal
ctgomes@fc.ul.pt

The aim of this work is to evaluate the alteration of the floristic diversity caused by Carpobrotus edulis (L.) N. E. Br. growth on the autochtone vegetation of the protected area, the archipelago Reserva Natural das Berlengas. This protected area is located along the portuguese Estremadura littoral (39° 24' 49"" N - 9° 30' 29'' W) and is formed by rocky islands. The height of the islands is under 100 m and Berlenga, the largest one, has an area of 76 ha. A seasonally occuped fishermen village is located in this island and the others are uninhabited.
In the 50th Carpobrotus edulis (L.) N. E. Br. as been introducted in order to avoid the overthrow of rocks in the leasure areas of the island, it as been planted in two islands, Berlenga and Farilho Grande and has successfully established. Presently Carpobrotus edulis as spread out over the cliffs and hillsides mainly in those with south exposition. Spontaneous occurences of this specie have been observed in three other islands of the archipelago. Carpobrotus edulis establishes a monospecific cover that obstructs the occurence of the autochtone vegetation. The Flora of this protected area consists of around a hundred species mainly annuals and few perennials, three species are endemic from the archipelago.

Linear transepts were done in order to collect the data, they were made inside and outside the area covered with Carpobrotus edulis, in both islands Berlenga and Farilho Grande. The results allow to obtain a quantitative assessment of the reduction in frequency and covering area of the native Flora. They also indicate that Carpobrotus edulis presents a different soil occupation pattern on the different islands.

Tecco, P.A. and M. Rouges.

Laboratorio de Investigaciones Ecologicas de las Yungas Fac. Ciencias Naturales e IML - UNT, C.C 34 - 4107 Yerba Buena, Tucuman
Argentina
Tel/Fax: 54 381 4304957
piaya@mail.satlink.com

Citrus aurantium is a common exotic treelet in NW Argentina subtropical montane forests, native from SE Asia. It was introduced in the area as for orchard plantations and as a urban tree. Is the only exotic tree species frequently found in the understory of mature forests, including long lasting National Parks. We examined the size distribution of C. aurantium populations in two types of forest at El Rey National Park of NW Argentina: mature (MF) and second growth forest (SGF) with about 40 years of abandonement, in order to make inferences about population trends. We censused a total of 9.2 ha of forests (1.9 and 2.2 ha in two sites of MF; 2 and 3 ha in two sites in SGF) using 20 x 100 meters transects. We registered a total of 1011 individuals in the four areas sampled. Densities were significantly very different among sites (385 and 107ind/ha for MF; 19 and 3.6 ind/ha in SGF). The number of individuals of less than 1.5 m represented from about 92 to 58 % of the total at each site. The size distribution suggest that population is increasing, particularly in the mature forests. We found only 17 plants with fruits, 16 of those in one of the mature forest sites. According to its demographic patterns, C. aurantium can be characterised as a mature-forest species, which makes it particularly difficult to control in natural areas. High densities of C. aurantium juveniles in the mature forest may be attributed to the shade tolerance of this species and to the effective dispersal by native animals. The results emphasise the importance of prevention as a way to avoid invasion of this species. Future research should aim to quantify large scale patterns of distribution of the species and to identify natural pathogens and predators that could potentially reduce the expansion into more areas.

David Tickner (1), Owen Mountford (2), Penny Angold (1), Angela Gurnell (1) and Tim Sparks (2)

(1) School of Geography and Environmental Sciences, University of Birmingham, Edgbaston, Birmingham, B15 2TT
United Kingdom
Tel.: +44 (0)121 414 6869; Fax: +44 (0)121 414 5528
d.p.tickner@bham.ac.uk
(2) Ecological Processes and Management, NERC Institute of Terrestrial Ecology, Monks Wood, Abbots Ripton, Huntingdon, Cambridgeshire, PE17 2LS
United Kingdom

Hydrogeomorphological processes are key influences on the structure of riparian plant communities. Research has pointed to disturbance regimes and the availability of vacant habitat niches as factors which make river margins prone to invasion by alien species.
However, most European research on invasive riparian plants has focused on their biology, autecology and biogeography. The interactions between invasion and factors such as flood frequency and duration, sediment transport processes and water-table regime requires further exploration.

Himalayan balsam (Impatiens glandulifera) is an alien annual herb which has colonised lowland riverbanks across much of the UK. Because it forms dense monospecific stands it is considered a threat to riparian biodiversity. Previous research and informal observations on riverbanks have tentatively suggested that Impatiens may even be able to out-compete native perennial species such as the common nettle (Urtica dioica).

The aim of this study was to assess competition between Impatiens and Urtica under a variety of hydrogeomorphological situations. Two separate mesocosm experiments were undertaken to investigate the influence on growth of the two species of depth to water-table and occurrence and timing of inundation. In the first experiment, three species-mixes were subjected to four different water-table regimes ranging from near-surface to beneath rooting zone. In the second experiment, treatments using the same species mixes were subjected to a number of different flood events. Data from these experiments indicated, inter alia, that once established, presence of Impatiens could have a significant negative impact on growth of Urtica. This impact was especially important when the water-table was low. These results were then related to field investigations.
 

David Tickner (1), Penelope Angold (1), Angela Gurnell( 1) and Owen Mountford (2)

(1) School of Geography and Environmental Sciences, University of Birmingham, Edgbaston, Birmingham, B15 2TT
United Kingdom
Tel.: +44 (0)121 414 6869; Fax: +44 (0)121 414 5528
d.p.tickner@bham.ac.uk
(2) Ecological Processes and Management, NERC Institute of Terrestrial Ecology, Monks Wood, Abbots Ripton, Huntingdon, Cambridgeshire, PE17 2LS
United Kingdom

In several regions of the world it has been shown that riparian habitats are especially prone to invasion. It is often asserted that this vulnerability is, in part, due to the role of rivers in transporting propagules of alien species from upstream sources and depositing them during flood events. However, evidence of this process is difficult to find in the literature.

As part of a wider study on the influence of hydrogeomorphology on competition between native and alien riparian plant species, field investigations were undertaken of the importance of the deposition of alien seeds during flooding. Artificial turf mats were placed on the banks of two UK rivers (the River Severn and the River Trent) such that they would trap sediment and plant propagules during flood events. Following inundation the mats were collected and cleaned and their contents analysed for particle size distribution, nutrient content and presence/absence of key species, notably the invasive alien Himalayan balsam (Impatiens glandulifera). These data were then related to data from botanical surveys along the same riverbanks. Initial results have suggested that there is considerable small-scale variation in the deposition of propagules and that the artificial turf mats are a useful tool for the study of deposited riparian seed banks.

Tokarska-Guzik Barbara

Department of Plant Systematics, Faculty of Biology and Environmental Protection, University of Silesia, Jagiellonska 28, 40-318 Katowice
Poland
Phone: +48 32 225 12 60 ext. 479; Fax: +48 32 255 58 73
tokarska@us.edu.pl

The subject of the paper is a concise review of  history, research trends and main methods used in studies of invasive alien plants in Poland. Some problems pertaining to methodological and nomenclatural classifications applied in Polish botanical literature against to the European ones are discussed.
Special attention is paid to the present studies which are intended to fill the gap in recognise recent distribution of about 250 species of invasive alien plants (kenophytes-neophytes) in Poland. The aims of these studies are: to present up-today distribution of kenophytes in Poland (the stations of species are plotted on the ATPOL grid - Atlas of distribution of vascular plants in Poland - 10 km square), to compare historical and recent spread of kenophytes, to give the general characteristic of this group of plants, to analyse of plant distribution data against historical, geographical, phytogeographical, man's activity factors.
The result of these studies have not only pure scientific value but can also serve as a basis to work out effective methods of management of the most invasive plants.
 

Valeri K. Tokhtar and Michael T. Khomyakov

Donetsk Botanical Gardens, Nat. Ukr. Acad. Sci., Illich's Avenue, 110, Donetsk, 340059
Ukraine
sad@botgar.donetsk.ua

Since the process of plants migration acquired global scales, microorganisms developing on plants spread with them in many regions. It is known that in some cases alien plants invasion may be even determined by them (Tokhtar, Burda, Kolomoets, 1998).
Practically complete absence of data on conjugated migrations of alien species and parasitic or saprophytic mycobiotic organisms made us study this problem. 305 alien species of plants from 103 genera and 52 families have been reported by us from the south-east of Ukraine. Most representatives of alien species belong to the families Asteraceae (50 species), Brassicaceae (40), Poaceae (33), Chenopodiaceae and Fabaceae (both have 17). However the majority of fungous pathogenes are found in cultivated representatives of the families Chenopodiaceae (63 injuries of species), Vitaceae (63), Fabaceae (61), Aceraceae (30), Poaceae (25), Juglandaceae (23), Grossulariaceae (22), Asteraceae and Brassicaceae (21).
If to analyze alien species according to the time of their emergence in the region, it should be noted that mycobiotic species parasitize chiefly on species-archeophytes which were brought here in the 17th century (67 species). Lower fungi have been also observed on 23 species-neophytes, 16 euneophytes and on 7 new species which have been recently found.
In species which are at different stages of invasion vegetative organs are injured most of all. An average number of injury by fungi per 1 plant species decreases during invasion: 9,5 damages were observed in 1 species-ephemerophyte (an unstable element of flora); 4,3 - were in 1 species-epecophyte ( the species is at an intermediate stage) and 4 were in 1 species-agriophyte (this species occurs already in local communities). It is highly probable that processes of coevolution and selection of alien species brought to the fact that species which got naturalised were less injured by fungi and adopted to the new conditions of the Ukrainian south-east best of all.
It is necessary to note that lower fungi are mainly observed on Mediterranean-Iranian-Turanian species of plants. This once again confirms correctness of ideas on common florogenetic roots of biotic complexes of the Ukrainian steppe zone and ancient Mediterranean region. Among alien species xero-and-hydrophytes are the least injured and xeromeso-and-mesophytes are the most damaged. It is explained by the fact that the fungi development cycle depends in many respects on moistening conditions. Some mycobiotic organisms brought into our region with alien plants occur only on these species and are narrowly specialised. Other species in the process of conjugated migration spread both on alien and local species of plants which is a certain menace for native ecosystems and has to be investigated in more detail.

H. Tremp

Institute of Landscape and Plant ecology (320), University of Hohenheim, 70593 Stuttgart
Germany
tremp@uni-hohenheim.de

Over a three years period 20 populations of Impatiens parviflora has been investigated. Monthly measured site specific factors as soil water content, light regime and nutrients are included in a model which describes the self thinning mortality of meta populations of Impatiens parviflora by a naturally given starting density of seedlings.
Relationships between productivity, self thinning mortality and seed production give hints about the strategy of survival of meta-populations of this species in a landscape section.
The investigation tries an integration of the species hierarchical features as germination properties, physiology, morphology, growth and  distribution patterns to select the most responsible for the species success.