ORCHIDS AS INVASIVE PLANTS

Wojciech Adamowski

Bialowieza Geobotanical Station, Warsaw University Ul. Sportowa 19 17-230 Bialowieza
Poland
Tel +48 85 68 12 548, Fax +48 85 68 12 479
adamowsk@tilia.bsg.bialowieza.pl
 

Extinction or endangerment of many orchid species is well known fact. However, also in this group one can find invasive species. The paper include list of more than twenty taxons, spreading in new countries and even invading natural plant communities.
European Epipactis helleborine occurs in a variety of anthropogenic habitats and broad-leaved forests in Eastern part of Northern America. In western Europe, on pine and spruce plantations, boreal orchids Goodyera repens and Listera cordata are spreading. In tropical zone most successful invaders are African species: Oeceoclades maculata in Southern and Central America and Monadenia bracteata in Western and Southern Australia. Some orchids, commonly cultivated, escape in two geographical regions, e.g. Epidendrum o'brienianum in Eastern Australia and Hawaii Islands. Most rich in naturalised orchids are Central America and Hawaii Islands.
Common characters of many invading orchids are:
- quick development (Oeceoclades maculata 1 year from seed to flower in favourable conditions!)
 - autogamy
- apomixis
- wide ecological amplitudes
- broad natural distribution
In most cases, intentional human activity (cultivation) was very important factor for further successful spreading. Unintentional activity (transformation of habitats, accidental introductions) seems to be of similar importance.
This phenomenon can be more common, particularly in tropical countries, where orchid flora is rich, and conditions for cultivation more favourable.

Wojciech Adamowski and Piotr Medrzycki

Bialowieza Geobotanical Station, Warsaw University Ul. Sportowa 19 17-230 Bialowieza, Poland
Tel +48 85 68 12 548, Fax +48 85 68 12 479
adamowsk@tilia.bsg.bialowieza.pl,
piotrmed@tilia.bsg.bialowieza.pl

English landscape parks, botanical gardens and arboreta are widely known to be sources of propagules of alien plants being cultivated there and the susceptible habitat for first invasion steps. This is an effect of the high number of cultivated taxa and the diversity of habitats, including these almost natural.
These processes occurs also in all landscape parks in Bialowieza Forest. This is the especially the case with the Manor Park (ca. 50 ha). When it was established in the end of XIX century around the Russian tsar's hunting palace, several species of non-indigenous trees and shrubs have been planted. Many of them perfectly regenerated, created self-sustainable populations and spread widely around the park, including the most valuable in the all Bialowieza Forest primeval stands of the Strict Preserve.
The paper contains the complete list of the woody species being considered non-native in the Bialowieza Forest, that occur in the Manor Park and colonise natural or semi-natural plant communities. Data on the time and the range of their invasion are provided, together with maps of distribution for selected taxa. Most widespread woody alien taxa are Sambucus racemosa, Acer negundo, A. pseudoplatanus and Quercus rubra (Adamowski, Medrzycki and Luczaj, 1998). However, juvenile individuals of some woody cultivars are also observed, e.g.: Quercus robur 'Fastigiata', Fraxinus excelsior 'Pendula'.
The special meaning of the Manor Park as the nascent focus of invasions is additionally determined by following factors:
- the localisation in the centre of forest complex;
- the presence of abandoned farmlands in the close vicinity of the Park;
- the intensity of the tourism within the park (hotels, restaurants).
Taking into consideration all these facts makes it possible to treat the landscape mosaic of 100-year-old English park as model object for studying alien species' invasions and predicting their further behaviour.

 SUCCESS OF EARLY ERADICATION: THE CASE OF IMPATIENS PARVIFLORA IN BIALOWIEZA NATIONAL PARK (NE POLAND)

Wojciech Adamowski (1) and Andrzej Keczynski (2)

(1) - Bialowieza Geobotanical Station, Warsaw University Ul. Sportowa 19 17-230 Bialowieza
Poland
Tel +48 85 68 12 548, Fax +48 85 68 12 479
adamowsk@tilia.bsg.bialowieza.pl
(2) - Bialowieza National Park, Park Palacowy 5, 17-230 Bialowieza
Poland
Tel +48 85 68 12 306
kecz@lynx.bpn.bialowieza.pl

Impatiens parviflora, one of the most common invaders in Europe (Trepl 1984) has been spreading in the Bialowieza Forest for about 25 years. Having encountered a site of its occurrence in the Strict Reserve of Bialowieza National Park, attempts were made to stop its expansion (Adamowski and Keczynski, 1998). Every year (1991 - 1998; one to four surveys in summer months) the individuals of this species found in the National Park were carefully removed; plant material was dried in 105 °C, to prevent dissemination of viable seeds. This led to almost complete extirpation of Impatiens parviflora population. Surveys will be continued several years after extirpation to prevent reappearance of the species from seed bank.
The wide spread of the species in the western part of the Bialowieza Forest makes impossible its total elimination. However, every effort is undertaken to prevent the expansion of the species at least in the close vicinity of the Strict Reserve, e.g. at the Bialowieza Clearing, to build a buffer zone. A significant delay of spread of Impatiens parviflora into forest communities of the Bialowieza National Park is expected.
The success of this action is an example, that early start is a warranty of efficient eradication, achieved with simple, non-destructive and non-expensive methods.

 ALIEN PERENNIAL PLANTS IN AN IBERIAN REGULATED RIVER

F. Aguiar (1), T. Ferreira and I. Moreira

(1) Instituto Superior de Agronomia
Departemento de Engenharia Florestal
Tapada da Ajuda
1300-596 Lisboa
Portugal
fraguiar@mail.telepac.pt

The River Mondego (CW of Portugal) has been subjected to regularisation of its lowlands on the late seventies, for flood defence, irrigation and land drainage purposes. The alluvial flood plain, Baixo Mondego, has about 15,000 hectares occupied mainly by rice and other highly water-consuming Mediterra-nean crops (INE, 1993), crossed by drainage and irrigation channels and ditches, and by the resectioned river (‘New Mondego’) in a extension of about 40 km. This segment was subjected to mechanical reprofiling by dredging, straightening and to a two-stage bank reinforcement. Some promoted stone areas were positioned on the riverbed.
A detailed survey of aquatic and riparian plants was performed in May-June 1999, on six reaches along the New Mondego. On each site, three longitudinal transepts (A, B and C) were studied, with five 5 x 25 m plots. The first transept was positioned on the water and the in-stream side of the bank and the others on the two-stage terraces of the bank.
All species were identified. Its cover was visually estimated, as well as the total tree cover and herbaceous cover. Distance and height above the water were measured for each plot, and substrate composition was visually estimated. For each site, the following variables were considered: distance to the sea, water conductivity, type of land use, average depth and average bank width.
A canonical correspondence analysis using Program CANOCO ver. 4.0 1998 (Ter Braak, 1995) was used to analyse the relations between species and environmental variables and NTSYSpc ver. 2.0 1997 (Numerical Taxonomy System) was used for the hierarchical classification of the data.
Alien cover was dominant in many plots, though alien plant richness was only about 10% of the total flora. Dominant alien species were Acacia dealbata Link and Eryngium pandanifolium Cham. and Schlecht., however Paspalum paspalodes (Michx) Scribner and Tradescantia fluminensis Velloso were also largely disseminated.
Results of multivariate analysis are displayed in Figure 1: eight variables explained 40.3% of the total species variation. The first axis shows a clear transversal variation, with a high correlation with the transept height and distance to the water (0.93 and 0.97 of inter set correlation, respectively), showing the effects of river regularisation on the species composition. The second axis illustrates the longitudinal variation, opposing conductivity, depth and bedrock substrate to distance to the sea.
The invasiveness of the South American alien E. pandanifolium was clearly defined on the two reaches closer to the sea (transepts A and B) and was progressively substituted by P. paspalodes, corresponding to a promoted area. T. fluminensis was dominant on transept B along all the studied area. A. dealbata  invades specially the transepts more distant from the water, and on reaches with more intensive agricultural use and further away from the sea.

Figure 1: Axis I and Axis II of the canonical correspondence analysis, showing the position of the environmental variables, species and plots (ordered by increasing distance to the sea); only dominant alien species are indicated. DSEA-distance to the sea; COND-water conductivity; LAND USE-land use; DEPTH-average depth; BWIDTH- average bank width; SAND/CLAY-fine substract elements;BEDROCK-bedrock; HEIGTHW-height above water; DISTW- distance to the water

References
INE (Instituto Nacional de Estatística). 1993. Portugal Agrícola. Instituto Nacional de Estatística, Lisboa, 258 p.
Ter Braak, C.J.F. (1995). Ordination. In Jongman, R.H.G., Ter Braak, C.J.F. and Van Tongeren, O.F.R. (eds.) Data analysis in Community and Landscape Ecology. Cambridge University Press, Cambridge, UK: 91-173.

 THE EXOTIC AND INVASIVE FLORA OF PORTUGAL

J. Almeida (1).and H. Freitas

(1) Department of Botany, Faculty of Sciences and Technology, University of Coimbra. 3049 Coimbra
Portugal
hfreitas@ci.uc.pt

This survey of the introduction of exotic plants in Portugal in the last two centuries showed an important increment during the last decades, reaching now a preoccupying figure of more than 14 % of the Portuguese flora. In this paper we present a report of the actual situation in Portugal, based on a large amount of bibliography, herbarium specimens and field studies. We have also considered the distribution of these species according to the Portuguese administrative regions (provinces), and the effect of their different demographic and social patterns.

 ACACIA INVASION ON PENA PARK (CENTRE OF PORTUGAL)

J. Alves (1), Ilídio Moreira (2), Maria Cristina Duarte (3) and J. Monjardino (4)

(1) Parque Natural de Sintra-Cascais - Instituto da Conservação da Natureza Rua General Alves Roçadas, 10 - 2º Esq., 2710 SINTRA
Portugal
tel.: (351 1) 9235116 fax: (351 1) 9235141
pnsc.alvesj@icn.pt
(2) Departamento de Protecção das Plantas e de Fitoecologia - Instituto Superior de Agronomia. Tapada da Ajuda, 1349-018 LISBOA
Portugal
tel.: (351 1) 3602019 fax: (351 1)
ilidimor@esoterica.pt
(3) Centro de Botânica - Instituto de Investigação Científica Tropical Travessa Conde da Ribeira, 71349-142 LISBOA
Portugal
tel.: (351 1) 3616340 fax: (351 1) 3622626
mcduarte@ip.pt
(4) Parque Natural de Sintra-Cascais - Instituto da Conservação da Natureza Rua General Alves Roçadas, 10 - 2º Esq., 2710 SINTRA
Portugal
tel.: (351 1) 9235141 fax: (351 1) 9235141

The "Parque da Pena" is a historical park situated in the stony slopes of Serra de Sintra, a coastal granitic mountain at west from Lisbon. It was founded by the king D. Fernando II at the middle of the XIX century. This park is included in the "Parque Natural de Sintra-Cascais", a natural park under the administration of the Instituto da Conservação da Natureza, a state department for nature conservation. The topography and the mild climate of this region allowed the successfully establishment of species from all over the world. The diversity and the notability of the introduced flora turned this park not only a space for leisure but also a field laboratory for research studies. In the last years the floristic richness of the Parque da Pena has been reduced. The naturalisation of some of the cultivated species and the lack of control measures are some of the main causes for the present situation. In the sixties Azevedo Gomes published a monograph about the flora of this park. This work is noteworthy for the accuracy of the descriptions. Gomes (1960) pointed out the most notable trees and made some remarks about invading alien species, such as Acacia melanoxylon, Acacia dealbata, Hakea salicifolia and Pittosporum undulatum. The comparative analysis of the data published by Gomes in 1960 and those acquired in field work in 1999 will allow to study the evolution of the invading woody flora in the last forty years. In 1967 a fire caused severe damages in some areas of the park. The consequences of this fire in the spread of alien species would also be evaluated. Finally the field survey will allow the recognition of the presently naturalised woody species and the assessment of its invading potential. A better knowledge of these topics would be very useful to establish priorities for the control of alien species and to prevent the spread of new invaders throughout the area.

A. Attardo(1) and A. Trigilia (2)

(1) Assessorato Agricoltura e Foreste of the Region of Sicily
Italy
Tel. 0931-38234
fwjaat@tin.it
(2) Assessorato Beni Culturali e Ambientali of the Region of Sicily
Italy
 

The presence of weedy vegetation on monuments, on buildings of historical and artistic interest, on archeological sites, in nature reserves and historical gardens, poses evident problems for management, conservation and restoration, because of possible transformations undergone both by materials and other living organisms.  In Sicily today, Ailanthus altissima, Robinia pseudoacacia, as well as Broussonetia papyrifera and Nicotiana glauca, are favoured by the light conditions and by their capacity to produce root-shoots and disseminate seeds.  Fighting the spread of these species is particularly difficult because new plants shoot from even the most minute fragment of root left in the soil.  The authors have been observing the behaviour of Ailanthus altissima in the
territory of the province of Siracusa for several years.  Recent formations have been located in the territory of Buscemi-Palazzolo Acreide in the upper valley of the river Anapo, in agricultural areas along the banks of the river, not far from the nature reserve of Pantalica. Decades of colonies are spreading in Contrada Rinaura, less than 500 m away from the ruins of the temple of Jove and the Ciane salt pans nature reserve.  Entire architectural complexes ("masserie" farms, olive presses, houses in the country), but also simple stone constructions such as stables, sheds, cisterns, wells, irrigation systems and dry-stone walls are seriously damaged.  Ailanthus is not only spreading in agricultural and forestry areas, but is also increasingly present in areas within the urban perimeter of Siracusa, colonising empty urban spaces in the heart of Ortigia (the abandoned church of San Giovannello in Via Minerva), the most important historic public (Villa Landolina) and private gardens (Villa Annino), as well as the most interesting and evocative archeological sites of the ancient city of Siracusa, Akradina (Latomie dei Cappuccini and the Balza Akradina).  The acquisition of more knowledge concerning the relationship between the vegetal, biological components, the substrates and environmental factors will permit the individuation of the ability of this species to cause damage, but also its potential for propagation. This scientific knowledge can benefit the society only if it is sustained by suitable political and legislative actions.

 IPOMOEA MUTABILIS LINDL. (CONVOLVULACEAE) COLTIVATA SPONTANEIZZATA A SASSARI (SARDEGNA, ITALIA)

Aldo Domenico Atzei

Dip. Scienze del Farmaco
Università degli Studi di Sassari
Italia

Viene segnalata come coltivata spontaneizzata a Sassari (Sardegna, Italia) Ipomoea mutabilis Lindl. (=I. dealbata Hemsl. = I. leàrii Meiss. non Paxt. = Pharbitis mutabilis Bojer) (Convolvulaceae), dell'America tropicale, che non ci risulta segnalata come spontaneizzata in Italia nè nel bacino del Mediterraneo. La stazione è ubicata alla periferia della città, in zona Baldedda, su un terreno comprendente la siepe stradale, una zona incolta degradante in un ampio fossato in parte adibita a discarica abusiva, e un piccolo tratto confinante coltivato ad oliveto, su una superificie di circa 1200 m2, nonché dal lato opposto della strada e confinante con la ferrovia, un giardino abbandonato, anche questo parzialmente utilizzato come discarica, su una superficie minore diu circa 150 m2, per un totale di circa 1350 m2. Nel periodo vegetativo (fine primavera - inizio autunno) la specie ricopre interamente il terreno e le piante spontanee presenti, raggiungendo la chioma degli alberi di olivo coltivato.
La specie presente è perenne, munita di rizoma lungo e grosso da cui si dipartono lunghissimi esili fusti rampicanti fioriferi, afoglia in prevalenza profondamente 3-loba ma anche intera o con lobi accennati, fiori in grappoli di (1-)3-5(-7), corolla lunga 6,5-7,5 cm e larga 8-9 cm, azzurra, a tubo e 5 costolature rosee, diventante rosea con l'essicamento. Per alcuni caratteri (lunghezza della foglia e del calice, costole rosee rispetto al resto azzurro della corolla) si avvicina a I. indica (Burm.) Murr. (= I. acuminata (Vahl) Roemer and Schultes = I. leàrii Paxton = Pharbitis cathartica (Poiret) Choisy = Convolvolus indicus Burm.), naturalizzata alle Azzorre, Baleari, Portogallo, Francia, Malta e Sicilia, ma presenta la pagina superiore della foglia minutamente peloso-sericea (e non glabra), quella inferiore canescente argentina. D'altra parte i campioni non rientrano in nessuna delle altre specie perenni trattate dalla Letteratura consultata.
Attualmente sono in corso lavori di riempimento del fossato interssato e la specie è rimasta accantonata su una superficie residua, ma ancora rappresentativa della spontaneizzazione.

Harald Auge, Uwe Amarell, Roland Brandl, Stefan Klotz, Jutta Stadler

UFZ Centre for Environmental Research Leipzig-Halle, Department of Community Ecology, Theodor-Lieser-Straße 4, D-06120 Halle
Germany
Phone ++49 - 3 45 - 55 85 309; Fax ++49 - 55 85 329
aug@oesa.ufz.de
http://www.ufz.de/spb/bioz/index.e.html

Invasive species are not randomly distributed over biological communities. Thus, one major question concerning success or failure of invasions is: What characteristics make a community invasible by alien species? Theoretical considerations predict a higher chance of establishment of alien species in species-poor communities compared to communities of a high diversity of native species. We tested this prediction for invasive plants using (1) species lists of 20 political districts in south-western Kenya, (2) the flora of 17 cities in central and eAstern Germany, and (3) a gradient of floristic diversity across 400 pine forest sites in central Germany.
Compiling the three data sets, we found a consistent pattern despite the different spatial scales and biogeographic regions considered: In each case, species richness of alien plants was positively correlated with species richness of native plants. Moreover, the proportion of alien plant species increased significantly with increasing diversity of native plants. Thus, in contrast to our prediction, the species-rich communities or regions investigated are not more resistant against biological invasions than the species-poor ones.

B. B. Baki

Institute of Biological Sciences
University of Malaya, 50603 Kuala Lumpur
Malaysia
baki@botany.um.edu.my

Mimosa quadrivalvis L. var. leptocarpa (DC.) Barneby was first detected in Peninsular Malaysia in by Baki et al. (1993). It was a new species record for Malaysia and Malaesia. Subsequent field surveys conducted in 1994 and 1998 recorded increased infestation of the weed from small localised pockets in Penang to areas hitherto uncolonised in Perlis, Kedah and Penang states in northern Peninsular Malaysia, usually on inseptisol, vertisol, ultisol and entisol soils. The weed populations were highly clustered with Ip (Lloydís patchiness index) values ranging from 64.89 to 121.84. The Lloydís mean crowding (m*)-to-Lloydís mean density (m) ratios of fruit-bearing populations registered values ranging from 31.08 to 57.86. Field populations displayed erratic oscillations and this apparently was due to high mortality of seedlings. Each plant produced ca. 11,550 seeds/year with 98.23% viability. Only about 5.75% of the seeds produced emerged as seedlings out of which only 24.85% became successful colonisers of open space. There is a slight increase in fruit-bearing adult populations of 2.54%/year over the 1994-1998 period. This was translated as an increase of seed bank populations in soils (5.95%/year) over the same period. The seeds display both primary and secondary dormancy. The plant exhibited robust clonal growth producing many primary and higher order stolons, which in turn act as fruit- and seed-bearing entities and resource-capture. Arguably, high seed production capacity coupled with robust and aggressive clonal growth identify M. quadrivalvis as an invasive weed to watch in Peninsular Malaysia.

Key words: Mimosa quadrivalvis var. leptocarpa, Shrankia leptocarpa, spatio-temporal dynamics, seed banks

G. Balent (1) and J. Tassin (2)

(1) INRA-SAD Toulouse, CNRS-UMR 5552 Ecologie Terrestre
France.
Phone: +33 5 6128 52 58 ; Fax: +33 5 61 73 20 77
Balent@toulouse.inra.fr
(2) CIRAD-ForÍt, La RÈunion
France.
Phone : +262 35 76 62 ; +262 35 76 41
Tassin@cirad.fr

Hierarchy theory, which suggests that higher levels of organization incorporate and constrain the behaviour of lower levels, highlights the interest to assess plant invasions at different levels of organization, including landscape level. The paper presents the integration of landscape level in order to assess the process and the impact of Acacia mearnsii in the western and southern slopes of Reunion Island (French Overseas Territory, Indian ocean).
In Reunion Island, the patterns of A. mearnsii invasion are highly correlated to landscape changes and landscape structure. Introduced in 1887, this exotic species was planted in the 1950s by forestry services, mainly on high slopes above the pelargonium cropping zones. In 1962, an important crisis of pelargonium production provided many safe sites, lands relinquished by farmers, where the invasion began. The colonisation of landscape was then spatially correlated to the organisation of ravines, riparian corridors and gullies. Today, A. mearnsii is observed in ravines at a very low altitude, probably with the help of hurricanes (as Firinga in 1989) which facilitate the transport of pods. Mainly from these corridors, this plant has then colonised new safe sites in rural areas. There, main invasion patches consist of long and narrow bands limited by the boundaries of abandoned land ownerships.
In return, landscape attributes are modified by A. mearnsii invasion. Species richness of birds is lower in areas with A. mearnsii stands. Total plant cover at the ground level is lower, though aboveground phytomass is higher. On the other hand, this invasion doesn't seem to have incidence on fire propagation.
Both process and impact of A. mearnsii are still very linked to the evolution of agriculture. Some economic opportunities can favourish A. mearnsii clearing in order to produce new crops, but A. mearnsii woods can recover very quickly from seed-banks if land is abandoned again.

 INVASIVE ALIEN PLANTS THREATENED THE NATURAL VEGETATION OF ÖRSÉG LANDSCAPE PROTECTION AREA (WESTERN HUNGARY)

Lajos Balogh

Department of Natural History, Savaria Museum, PO Box 14, Szombathely 9701
Hungary
Tel.: 36-94-312-554, Fax: 36-94-313-736
savmuz@c3.hu

Örség Landscape Protection Area (ÖLPA) (380 km2) is situated in Western Hungary, along the Austrian-Slovenian border (h. a.s.l. 194-386 m). The landscape is characterised by deep valleys and flat-ridged hills. The northern part lowers to the flood plain of Rába, which is the greatest river in Western Hungary. Its natural conditions are determined by the transitional situation between the Alps and Transdanubia. Rivers and streams belong to the drainage area of Rába, Lake Balaton and of the Mura-Drava river-system. The original flora can be characterised as a mixture of Atlantic, Submediterranean and Central European floristic elements. Great number of dealpine-montane elements, postglacial relicts and more than a hundred protected or endangered species make it one of the most valuable and beautiful area in Hungary. The most typical plant associations, according to Kovács (1999), are as follows: Genisto-Pinetum, Galio rotundifolio-Fagetum, Luzulo-Querco-Carpinetum in the woody vegetation; Carici brizoidis-Alnetum, Molinion, Filipendulo-Petasition in valleys; Leucojo aestivi-Salicetum albae along the rivers and Caricion fuscae, Deschampsion, Arrhenatherion, Nardetalia in herbaceous vegetation. Our examinations were carried out between 1993 and 1998. The main aim was to investigate the role these adventive invasive plants play in the transformation of the original vegetation. Recent distribution of adventive invasive species was illustrated on UTM maps. There are also registered those associations that are invaded by these taxa entered into the various units of natural vegetation. On the basis of the coverage degree, these plant taxa can be ordered as follows: Solidago gigantea Ait. has the largest distribution, often forming (sub)monodominant stands; mainly in the flood areas of rivers and streams, mostly endangering the associations that belong to Phragmitetea australis R. Tx. et Preising 1942 and Molinio-Arrhenatheretea R. Tx. 1937, and secondly along the roadsides by the sides of abandoned fields. Fallopia x bohemica (Chrtek and Chrtková) J. Bailey frequently forms monodominant stands, mainly in the flood area of Rába, often invading the lower layers of Leucojo aestivi-Salicetum albae Kevey in Borhidi et Kevey 1996. (The hybrid's parent species F. japonica and F. sachalinensis are unknown from the area.) Helianthus tuberosus L. agg. and Impatiens glandulifera Royle often form (sub)monodominant stands mainly in the flood areas of Rába and Zala, endangering mostly the associations that belong to Phragmitetea australis and Salicetea purpureae Moor 1958. Similar habitats are colonised by the following species, but less frequently than the previous ones: Aster lanceolatus Willd., Echinocystis lobata (Michx.) Torr. et Gray and Rudbeckia laciniata L. Only a few localities of Asclepias syriaca L., Amorpha fruticosa L., Heracleum mantegazzianum Somm. and Lev. are recently known. It became clear that there is a slight difference only between the degree of invasion of natural / seminatural habits of Ölpa and other parts of Western Hungary. The exsiccata are deposited in the herbarium of the Savaria Museum (Szombathely).

David Bass

School of Geography, Population and Environmental Management,
Flinders University,
GPO Box 2100  Adelaide SA 5001
Australia.
Tel. +61 8 8201 2107
Fax +61 8 8201 3521
david.bass@flinders.edu.au

Environmental weeds are almost universally regarded as detrimental. These weeds modify ecosystems, alter natural biodiversity, and promote landscape degradation. In many disturbed ecosystems, especially those that have suffered significant native plant clearance, weeds may provide significant habitat resources. Data from camphor laurel (Cinnamomum camphora) invaded sub tropical NE NSW, and olive (Olea europaea) invaded woodland in SA reveal that these environmental weeds provide shelter, feeding substrates, sites for social interaction and vegetation corridors for a range of bird species. These resources are in addition to fruit, which may be very significant for native birds that have lost significant habitat from widespread clearance for agriculture. The implications for weed management and landscape rehabilitation are profound. Where weeds are to be removed there should be an assessment of the ecological role they play. There is a significant spatial and temporal scale to this issue. The lag between weed removal and establishment of mature native vegetation may exert significant stress on local fauna, which may already be suffering stress from the previous clearance of native vegetation. A program of weed removal should plan the location of its activities not just to take advantage of access but provide a level of continuity of vegetation for use by birds. The lesson to be learned from this approach is to realise that animals are more likely to recognise a weed as a plant rather than some noxious entity. The rate of vegetation change from a native to more weedy state has been detrimental; the rate of change from weedy to rehabilitated vegetation may be the last nail in the coffin for some threatened species.

David Bass

School of Geography, Population and Environmental Management,
Flinders University,
GPO Box 2100  Adelaide SA 5001
Australia.
Tel. +61 8 8201 2107
Fax +61 8 8201 3521
david.bass@flinders.edu.au

This paper examines the relative invasiveness of two woody species, Crataegus monogyna and Prunus mahaleb and highlights implications for assessing invasion risk. The species are closely related and have similar habits and overlapping home ranges in Europe. The species have fleshy fruits and vertebrate dispersed seeds characteristic of many ornamental escapes. C. monogyna was introduced to Australia mainly as an ornamental and hedge plant with extensive plantings throughout southeastern Australia. P. mahaleb was introduced as rootstock for orchard trees and has only one recorded infestation in Australia. The project was focused on the Northern Tablelands of New South Wales. C. monogyna is very invasive in the region, having spread rapidly and conspicuously throughout northern New South Wales and elsewhere in southern Australia at rates of 80 - 120 m yr-1. P. mahaleb is far less invasive, being restricted to a small population near Armidale, which is expanding at 20 m yr-1. Demographic analysis utilising modified Leslie matrices showed that potential growth rates (expressed as the dominant latent root of transition matrix) of P. mahaleb (1.713 - 1.490) are greater than those for C. monogyna (1.138 - 1.103). Assessment of the seed dispersal ecology of both species revealed that C. monogyna, an autumn-winter fruiting species, had seeds dispersed by one bird and three mammals over many kilometres. P. mahaleb, a summer fruiting species, had seeds dispersed by six birds and four mammals over distances generally less than 100 m.
The main factors determining the difference in invasiveness between the two species relate directly to the changing nature of human management of each species and the ecological interactions between the plants and the invaded environment. C. monogyna was widely and extensively planted in hedges and gardens that provided many foci for further and accelerated spread facilitated by vertebrate seed dispersal. P. mahaleb was not planted widely and as result spread relatively slowly from a single focus. Despite a more rapid population growth rate P. mahaleb had seeds dispersed only relatively short distances compared to C. monogyna that has seed dispersed over many kilometres. This research has implications for the prediction and management of biological invasions; emphasising the importance of seed dispersal and human activities in determining the course of invasions: both of which cannot be readily predicted.

J.G.Virtue (1) and D. A. Bass (2)

(1) Animal and Plant Control Commission, Primary Industries and Resources South Australia - GPO Box 1671 - Adelaide SA 5001
Australia
Tel. +61 8 8303 9502
Fax +61 8 8303 9500
virtue.john@pi.sa.gov.au
(1) School of Geography, Population and Environmental Management,
Flinders University,
GPO Box 2100  Adelaide SA 5001
Australia.
Tel. +61 8 8201 2107
Fax +61 8 8201 3521
david.bass@flinders.edu.au

The '1st International Workshop on Weed Risk Assessment' was held in Adelaide, Australia in February 1999. Weed risk assessment (WRA) is the use of a standard, scientifically-based, decision making process to determine the relative weed threats posed by various plant species. The Workshop brought together 55 scientific and policy experts from eight countries to discuss best practice techniques to predict weediness and to prioritise weed species for control. The Workshop first considered three major criteria of WRA systems; invasiveness, impacts and potential distribution.
Important factors identified for invasiveness were weed history, reproductive ability, dispersal ability, habitat invasibility, native latitude range and introduction pressure. Types of impacts needing assessment were competition with desired vegetation, changes to ecosystem structure and functioning, effects on animal and human health, reductions in biodiversity, restrictions on movement, hosts for pests and diseases, loss of markets, cost of control measures and beneficial uses. The potential distribution session reviewed climate-based models to predict weed distribution, with CLIMEX and CLIMATE being most useful. Discussion on predicting weediness examined the strengths and weaknesses of the system recently implemented by Australia. The final session compared USA, New Zealand and Australian WRA systems to prioritise weeds for control, recognising many similarities. Issues frequently raised were the need to share weed data for WRA decisions (e.g.. weed lists, distributions, biology, impacts), to develop standard approaches between States and Countries, to ensure research meets the needs of policy makers, and to keep WRA decisions transparent to the community. Working groups were formed with actions beyond the Workshop to develop international standards for WRA, improve global sharing of weed data and develop a protocol for early action against new weed incursions. The proceedings of the Workshop are to be published, with details on the Workshop's website (http://www.hear.org/iwraw/index.html).
 
 

Carl E. Bell

University of California Cooperative Extension, Holtville, CA and Ann M. Howald, Santa Rosa Junior College, Santa Rosa, CA
U.S.A.
cebell@ucdavis.edu

The natural landscape of California, with more than 5,800 native species, 24% of whom are endemic, is one of the most biologically rich in the temperate climate zones in the world. Human settlement has disrupted much of this landscape, principally by physical alteration, but also by the widespread introduction of non-native plants. At present, over 1,000 non-native species have become established in California. In response to this impact on biological diversity, particularly in natural areas, a group of concerned citizens, scientists, and land managers came together in 1992 to create the California Exotic Pest Plant Council (CalEPPC). The objectives of CalEPPC are to facilitate communication about invasive pest plants, to educate professionals and the lay public on this issue, and to facilitate and help coordinate detection, research, and control efforts. Important activities of CalEPPC include hosting an annual Symposium, co-hosting symposia and workshops with other groups, publishing an educational newsletter and other documents, maintaining a website, managing and soliciting grant funds for control projects, and providing expert testimony for political entities on public policy issues relating to exotic pest plants. The diversity of CalEPPC's membership, currently at 800, which includes academics, public agency professionals, private environmental consultants, members of environmental organisations, and many private citizens, strengthens the CalEPPC's ability to educate and to influence public policy. The problem of invasive species is larger than the ability and resources of public agencies to solve alone. CalEPPC, by providing a forum for common interests and action, has assumed a vital role in the management of exotic plants in California.
 

Karolina Bendova and Helena Gruberova

Department of Botany, Faculty of Biological Sciences, University of Ceske Budejovice, Branisovska 31, Ceske Budejovice, CZ - 370 05
Czech Republic
pes183b@tix.bf.jcu.cz
Helena.Gruberova@tix.bf.jcu.cz

Bidens frondosa is an annual species of Asteraceae, of the North American origin. It occurs from the north Canada to the south of U.S.A., where it growths mainly on riversides, at the shores of water reservoirs, in pastures, along roads, in gardens, in fields and in various waste places, all with higher soil moisture. The genus Bidens has three native representatives in Czech Republic, namely B. tripartita, B. cernua and B. radiata, but alien B. frondosa is more successful in competition with them. It expands to the detriment of the native species. In comparison with the native species, typically occurring only on wet sites, B. frondosa is able to grow also in relatively dry, mostly ruderal sites. Two species - B. frondosa and B. tripartita - were experimentally grown in a greenhouse, in mixture and separately. Two substrate types, differing in the amount of nutrients, were used and two types of moisture regime were applied: the variant receiving 0.5 litre of water three times a week and the variant with water level permanently at the soil surface. B. frondosa grew better under lower water table, on the other hand B. tripartita needed permanently wet soil to be able to grow successfully. Phytosociological data were collected in the field and elaborated by the PCA (Principal Components Analysis) ordination method. The results also illustrate that B. tripartita, B. cernua and B. radiata require higher site moisture than B. frondosa, occurring together with species such as Lemna minor, Glyceria maxima and Polygonum hydropiper. Based on the results of the experiments and the analysis of the phytosociological data it can be concluded that B. frondosa grows well and occurs in a broader variety of site moisture conditions than the native Bidens species, which are restricted to stands with high water level. Thus the occurrence of native species seems to be more limited by site conditions in comparison to B. frondosa.

Department of Botany, Faculty of Biological Sciences, University of Ceske Budejovice, Branisovska 31, Ceske Budejovice, CZ - 370 05
Czech Republic
pes183b@tix.bf.jcu.cz
Helena.Gruberova@tix.bf.jcu.cz

In its secondary range, B. frondosa invades natural stands of native species Bidens cernua, Bidens radiata and Bidens tripartita, and often outcompetes them. Seed production and dispersibility were suspected to contribute to its success. Together 30 individuals of each species were randomly selected in the field at the time of ripening. Plant height, number of heads and number of seeds in 30 randomly selected heads in the particular order were determined. There were differences within species and among the species in the number of seeds in heads of different order. The highest number of seeds was found in the heads of B. radiata followed by B. cernua and the last was Bidens frondosa. B. frondosa was found to be the highest among the all Bidens species and possessed the highest number of heads. It resulted into the highest average seed production per plant of this alien species among the all Bidens species. The potential for epizoochory was evaluated by an experiment in which we threw seeds from the height of 65 cm on the piece of cloth: fleece, and 100% PAD, which differed in their surface structure. The cloth was then lifted to the vertical position and seeds that remained on the cloth were counted. The seeds of Bidens cernua with four "teeth", were found to be the best attached to fleece, a cloth with long hair. B. frondosa was most successful on the 100% PAD, which is a completely smooth cloth. The two species seem to be the best adapted to epizoochoric dispersal. As our results suggest, high reproductive capacity of B. frondosa and the good ability to spread by epizoochory can play important role in invasive success of this alien species.

James P. Bennett

Institute for Environmental Studies
University of Wisconsin
504 Walnut St., Rm. 103
Madison, Wisconsin 53705
U.S.A.
(608) 262-5489 or 270-2442
jpbennet@facstaff.wisc.edu

Non-native plant species are increasing in frequency and abundance in many natural areas. In Midwestern National Parks, as much as one third of a park flora may be non-native. It was hypothesised that botanical characters of these species could be used to typify them and improve the methods of predicting invasions. Data on 20 characters of 341 non-native species from the four Great Lakes national lake shores (Apostle Islands, Indiana Dunes, Pictured Rocks, and Sleeping Bear Dunes) and invasive non-native species for the State of Wisconsin were collected and studied. For many of the species, little data could be collected, but for 139 of them, data were collected for at least 80% of the characters. The frequencies of classes of the characters were tabulated and ranked in order to typify the most common non-native species. This type species will be described in the presentation. Three species of Cirsium, including Canada (C. arvense), marsh (C. palustre), and bull thistle (C. vulgare), matched the type species better than other species. Cirsium vulgare occurs in more national parks than the other thistles.

A. Bertacchi, T. Lombardi, A. Onnis

Dipartimento di Agronomia e Gestione dell'Agroecosistema - Università di Pisa
Italy
aber@agr.unipi.it

Introduction
This study is part of a larger research project on transformations in the forested agricultural landscape of the Pisan Hills in the course of the last 50 years. Over time, both soil utilisation for agricultural purposes and spontaneous ground cover have undergone substantial change and fluctuation in terms of the area occupied (Bertacchi et Onnis, 1995). One major aspect concerns Robinia pseudoacacia L, an exotic species of North American origin naturalised in Tuscany. Although its presence in Tuscany was reported as early as the beginning of the 1800's (Savi, 1801), it has spread extensively over vast stretches of formerly agricultural but now abandoned land, often giving rise to monophytic populations. These may at times be found within native phytocenoses but in many cases the Robinia pseudoacacia populations have fully replaced the original phytocenoses.

Area of study and methodology already adopted
A close investigation of the expansion dynamics of Robinia pseudoacacia within the agroforest environment was undertaken on a limited area measuring roughly 900 ha, located along the western ridge of the Pisan Hills ( 43° 33' 36'' Lat. N, 10° 28' 32'' Long. E Greenwich). This sector, which reaches a maximum elevation of 97 m. above sea level, is geopedologically characterised by sands and predominantly calcareous pleistocenic conglomerates (AAVV, 1965). Its climate belongs to the Sub-Humid type (C2 B'2  sb'4) (Vittorini, 1971).
Roughly 2/3 of the area studied presents mixed agricultural soil utilisation, although large expanses of agricultural land are in effect abandoned and/or converted to other uses (e.g.. riding stables, agritourism). Roughly 30% of the area is covered by woodland, represented at the higher elevations by mixed deciduous stands dominated by Quercus cerris L. These stands are generally managed as coppice, often with low density conifer plantations with Pinus pinAster Aiton, according to the Tuscan tradition. The valley floors present hygrophilous phytocenoses of Populus sppl., Salix sppl. and Alnus glutinosa (L.) Gaetner interspersed with the species that also cloak the hillsides, together with microcommunities composed of Carpinus betulus L., Ulmus minor Miller and Corylus avellana L. In addition, R. pseudoacacia is present throughout, although to various extents.
During the preliminary stage of research, the historical Land Registry and a comparison between 1954 and 1997 aerial photographs were used to determine past and present vegetational typologies, and a surface mapping was drawn up. Field trips were then undertaken to verify the correspondence between the mapping and actual conditions. A floristic-vegetational investigation was also conducted, with 30 phytosociological samplings using the Braun-Blanquet method. Of these, 8 were carried out on mixed deciduous stands with predominance of Q. cerris; 1 on a community with predominance of C. betulus; 1 on a hygrophilous valley-floor stand; 1 on a P. pinAster pine forest and the remaining 19 in R. pseudoacacia communities at different stages of maturity and degree of ground cover. In addition, several forest transects were carried out on ecotonal portions among the Robinia thickets and the adjacent phytocenoses.

Results and Discussion
Out of an increase, over the last 50 years, of roughly 93 ha in the area occupied by woodland (271 ha in 1954, 364 ha currently), approximately 50 ha are represented by stands of Robinia, which has completely invaded abandoned agricultural lands. Furthermore, in an additional total of about 25 ha, Robinia cenoses have almost completely replaced the previous Q. cerris-dominated deciduous stands.Vegetational and floristic analysis of Robinia stands reveals different aspects according to the age of the community. Overall, three different typologies can be identified:
(1) young stage - <5 years -: when maintained in this stage by extremely frequent cutting, Robinia gives rise to monophytic formations, which are virtually impenetrable and have extremely thorny suckers. No other phanerophytes or nanophanerophytes succeed in becoming established, except for Rubus ulmifolius Schott, Sambucus nigra L. and, among herbaceous plants, only a few species such as Stellaria media (L.) Will. and Galium aparine L.
(2) Robinia stands aged 10-15 years: Robinia is dominant, but other species are present, deriving from adjacent cenoses. Among arboreal species Q. cerris is found, but also U. minor, C. betulus, Laurus nobilis L., Ilex aquilfolium L. There is greater presence and development of S. nigra, and to a lesser extent R. ulmifolius. Among herbaceous plants Muscari comosum (L.) Miller, Rubia peregrina L., Hedera elix L are found. Seedlings of the above cited phanerophytes are also present.
3) "Mature" Robinia stands, aged 20-25 years: Robinia loses its structural and numerical dominance, with the resurgence of native formations.
Out of the cases investigated in this study, almost all - 17 - belonged to the first or second typology, in roughly equal quantities. In none of the cases studied were Robinia seedlings germinated from seed observed.

Conclusions
The rapid spread of R. pseudoacacia in the area studied has been caused predominantly by the direct or indirect action of man. It appears that in the 1930s and '40s, a limited number of Robinia trees were planted close to farmhouses for use as forage and for stake and pole production, but then they rapidly grew out of control as a result of bad management practices, or as surrounding land was left to go wild. The former case, corresponding to the first typology cited above, arose when Robinia was included in forest stands under assiduous coppice management (cut down at least every ten years), which allowed Robinia to penetrate agamously. Owing to its rapid growth habit, Robinia was thus able to compete successfully with the much slower suckering ability of the pre-existing coppice species. This phenomenon, together with repeated cuttings undertaken in the mistaken belief that such a procedure would control its growth, has led in many cases to the present situation in which Robinia has ousted the previous forest species. The second typology arose in cases where Robinia left on abandoned farms was cut down periodically as a marginal but continuous source of firewood or wood for stakes and poles. This favoured its rapid spread throughout uncultivated areas.
In agreement with findings from similar (Bertacchi et Onnis, in press; Arrigoni, 1997) or other geographic contexts (Mondino and Scotta, 1987; Corbetta and Pirone,1995; Gentile, 1995), Robinia communities show a floristic composition that is differentiated qualitatively and quantitatively according to the age and physiognomic structure of the community. In the mature stage, there is a preponderance of floristic-vegetational elements of native communities, suggesting that if Robinia stands are not constantly "rejuvenated" by human action, they are destined over time to lose their character of dominant communities and be replaced by the original cenoses.

References
AA.VV.- 1965- Carta geologica d'Italia. Foglio 112. Servizio Geologico díItalia.
Arrigoni P.V. - 1997- Documenti per la carta della vegetazione delle Cerbaie. Parlatorea, II:39-41
Bertacchi A., Onnis A. - 1995 - Evoluzione dellíuso del territorio e della copertura vegetale delle Colline Pisane. Boll. A.I.C., n.93-94: 81-86.
Bertacchi A., Onnis A. - in press -  Changes in the forested agricultural landscape of the Pisan Hills (Tuscany, Italy)- Modificazioni del paesaggio agroforestale delle colline Pisane, in "Dynamics of Mediterranean Vegetation Landscape", S.Mazzoleni ed., Gordon and Breach Publ., Reading, UK.
Corbetta  F., Pirone G. - 1995- La dominanza della Robinia nel bosco di Agognate (Novara). Cause ed effetti. Monti e Boschi, 5:31-34
Gentile S. - 1995 - Robinia pseudoacacia L. in formazioni forestali miste dell'Italia Nord-occidentale. Coll.Phytosociol., XXIV:11-18.
Mondino G.P., Scotta M. - 1987- Robinia pseudoacacia L. nell'ambiente forestale piemontese. Inf. Bot. Ital.,19:43-49.
Savi G. - 1801- Trattato degli alberi della Toscana. Università di Pisa.
Vittorini S. - 1971- L'erosione del suolo e i suoi fattori . Ricerche sul clima della Toscana in base all'evapotraspirazione potenziale e al bilancio idrico. Riv.Geograf.Ital., LXXIX: 1-30.
 

Katerina Bímová (1), Bohumil Mandák (2) and Petr Pysek (2)

(1) Institute of Applied Ecology, Czech Agricultural University, CZ-281 63 Kostelec nad Cernymi lesy  Czech Republic  bimova@kostelec.czu.cz
(2) Institute of Botany, Academy of Sciences of the Czech Republic, CZ-252 43 Prùhonice
Czech Republic  mandak@ibot.cas.cz  pysek@ibot.cas.cz

The effects of various eradication methods were compared for three invasive Reynoutria species, i.e. R. japonica var. japonica, R. sachalinensis and their hybrid R. x bohemica. Five monospecific stands of each taxon were selected and subjected to the following treatments: (i) cutting, (ii) digging, (iii) combined cutting/spraying, and (iv) combined digging/spraying. Glyphosate was used for spraying. The trial was conducted over two growing seasons and the density of shoots, biomass production and performance of other species were used as measures of the control efficiency. Particular taxa responded in a different way to the treatments used.

Reinhard Böcker and Monika Dirk

Institute of landscape- and plant ecology
University of Hohenheim (320)
D-70593 Stuttgart
Germany
boeckerr@uni-hohenheim.de

In Germany more than 150 hardwood alien species are noted up to now. Only a very few escaped in natural and seminatural areas and may be classified as agriophytes. Most of these species which are causing problems were introduced for forest purposes and got naturalised after extensive planting. Following species are selected due to their importance in different types of stands:
Acer negundo
Prunus serotina
Quercus rubra
Robinia pseudoacacia
Populus x euamericana
Pseudotsuga menziesii
They all are occupying large patches of land and are more or less frequent spotted in parts with low altitudes all over. Their strategies of concurrence in relation to native trees are different but in general successfully. Their specific abilities are presented in this poster.

Françoise Boillot

Conservatoire Botanique national Méditérranéen de Porquerolles
Le Castel Sainte-Claire
Rue Sainte-Claire
83418 Hyères
France
cbn.siege@wanadoo.fr

The French Mediterranean area is facing a large problem with invasive plants. The action undertaken by the botanical conservancy unit of Porquerolles is developing according three directions : fight, monitoring and survey, prospective.
As we have some hundred invasive or potentially invasive species, we have develop a set of criterias to classify the so call species in order to establish priorities for monitoring and action. The criterias take on board :
* the plant capacity to colonise a not disturbed habitat.
* The speed of wide spreading
* The adaptation to a wide range of ecological conditions
* The behaviour in term of space occupation * The reproductive modes
* The longevity of individuals
* etc.
These criteria are used according a numerical system leading to a ranking of the invasive species in term of potential threats for habitats.

Zoltán Botta-Dukát (1) and István Dancza

(1) Ecological and Botanical Institute of Hungarian Academy of Sciences
Vácrátót, Alkotmány u. 2-4, H-2163,
Hungary
bdz@botanika.botanika.hu

Giant goldenrod (Solidago gigantea Ait) has a North American origin. Its occurrence in Hungary was observed in the middle of the last century. Nowadays it has been regarded as one of the most important weed species. In agricultural point of view it causes problems first of all in perennial cultures, sapling gardens (erdészeti csemetekertekben), young forests, pastures, meadows. It establishes monodominant fields whose area may be a few hectares. In this way it occupies the habitats of natural species. The growth of Solidago gigantea was studied from 1993 to 1996. It can be found that the biomass production per shoot is determined by the rainfall in the firs part of growing season.
The temperature seems to be important only early spring, when it determines the date of the begin of intensive growth. In summer the drought causes decrease of leaf area. The plant defends itself against the water deficit. The leaf death rate correlates with the rainfall but the development of new leaf seems to be independent of it. There is no tendency in the number of leaf in the year. The decrease of leaf area in the second part of growing season is caused by the decrease of average size of leaf. After cutting the production of Solidago became significantly less and the putting out the shoots in the next spring was significantly weaker.

John H. Brock

Environmental Sciences Program, Arizona State University.
P. O. Box 872005, Tempe, AZ 85287-2005
U.S.A
Tel. 602-965-7036, Fax 602-965-9656
john.brock@asu.edu

Elaeagnus angustifolia (Russian olive) was introduced to the United States as an ornamental and land conservation tree in the later half of the 19th century. It rapidly escaped and in the southwestern USA has become a major invader of riparian habitats. In addition to continued planting by humans, the plant readily spreads through wildlife ingestion of its relatively large fruits and by water along stream courses. The population of seeds in the soil was investigated along two streams in northeastern Arizona on the Navajo Indian Reservation. Soil, litter and seeds were collected to a depth of 1.0 cm depth from 0.5 m2 quadrats. A total of twenty  samples were taken from Chinle Creek and Ganado Wash. Seeds of Elaeagnus angustifolia were separated from the other materials and counted. Three sub-samples of seeds were placed in a germinator to determine the germination potential of the seed bank. There are numerous seeds in the seed bank and there are indications that those that are viable germinate readily.