References of "Mahy, Grégory"
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See detailConcilier la conservation des métallophytes et la phytoremédiation des sols pollués par les éléments traces métalliques
Boisson, Sylvain ULg; Ngoy Shutcha, Mylor; Mahy, Grégory ULg

in Colinet, Gilles; Mahy, Grégory; Bogaert, Jan (Eds.) Anthropisation des paysages katangais (R.D.C.) (in press)

La conservation de la biodiversité est devenue un challenge social, politique et économique au niveau mondial. Etant donné que certaines régions du monde sont fortement soumises à l’anthropisation et à ... [more ▼]

La conservation de la biodiversité est devenue un challenge social, politique et économique au niveau mondial. Etant donné que certaines régions du monde sont fortement soumises à l’anthropisation et à ses impacts, il est indispensable de modifier notre perception et notre réflexion en ce qui concerne la conservation de la biodiversité et la restauration écologique. Ce chapitre explore les possibilités existantes et les adapte pour associer la conservation des espèces végétales d’intérêt avec la phytoremédiation des sols pollués. Cette nouvelle stratégie semble encourageante pour conserver le lien entre la société et l’environnement. En utilisant la diversité végétale locale, il est possible de créer de nouvelles communautés végétales afin de réhabiliter des sols pollués par les éléments traces métalliques. Le cas de la ville de Lubumbashi et de la flore de l’Arc Cuprifère Katangais en est un exemple marquant qui a été récemment testé avec succès. Cependant, d’autres études sur les métallophytes sont essentielles pour les utiliser de manière appropriée. [less ▲]

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See detailLa place de l'arbre dans les systèmes agricoles par les populations locales
Hick, Aurélie ULg; Hallin, Maud; Tshibungu, Alain et al

in Mahy, Grégory; Colinet, Gilles; Bogaert, Jan (Eds.) Anthropisation au Katanga (in press)

Dans un contexte de déforestation massive dans les zones rurales adjacentes aux grandes métropoles de la République Démocratique du Congo (RDC), zones d’approvisionnement en bois-énergie, l’identification ... [more ▼]

Dans un contexte de déforestation massive dans les zones rurales adjacentes aux grandes métropoles de la République Démocratique du Congo (RDC), zones d’approvisionnement en bois-énergie, l’identification de la place et du rôle que prend l’arbre dans les villages constituent un préalable à tous plan de restauration forestière. Ce chapitre porte sur les connaissances taxonomiques, les usages et la distribution des espèces arborées indigènes au sein de quatre villages en zone rurale adjacente à la ville de Lubumbashi, chef-lieu de la province du Katanga en RDC. Un total de 49 espèces indigènes de la forêt claire a été identifié par les 51 familles interrogées. Les utilisations sont classées en 6 catégories. Neuf espèces sont connues par plus de 50% des familles et correspondent aux espèces les plus utilisées pour l’alimentation via la consommation de leurs fruits et pour la confection d’outils. Les espèces citées par les personnes interrogées ne sont pas présentes dans le système agricole. La densité d’arbre à l’hectare au sein des champs est faible. Les espèces présentes sont des espèces résistantes aux facteurs de dégradation. Cette étude a montré que la connaissance taxonomique est limitée aux espèces les plus utilisées. Il n’y a pas de gestion intégrée de l’arbre au sein du système agricole dans la zone rurale adjacente à la ville de Lubumbashi. [less ▲]

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See detailInterprétation paysagère du processus d’urbanisation à Lubumbashi (RD Congo): dynamique de la structure spatiale et suivi des indicateurs écologiques entre 2002 et 2008
Useni Sikuzani, Yannick; Andre, Marie ULg; Mahy, Grégory ULg et al

in Mahy, Grégory; Colinet, Gilles; Bogaert, Jan (Eds.) Anthropisation au Katanga (in press)

Lubumbashi is one of the fastest growing African cities with annual population growth rates of 5 %. Its urban population growth leads to a rapid urban growth associated with several environmental problems ... [more ▼]

Lubumbashi is one of the fastest growing African cities with annual population growth rates of 5 %. Its urban population growth leads to a rapid urban growth associated with several environmental problems. This study test hypothesis that rapid built-up growth is followed by natural habitats decrease and creates favorable conditions for the spread of Tithonia diversifolia, an invasive specie. From two SPOT satellite images from 2002 and 2008 supported by field visits, seven land cover classes were obtained and the accuracy of the classification was verified. Landscape dynamic has been demonstrated through a transition matrix, by calculating spatial pattern metrics and identification of spatial transformation processes. The results obtained show that built-up covering 32 % of the landscape in 2008 against 22.6 % of the landscape in 2002. Its growth, followed by Tithonia diversifolia and anthropogenic vegetation, operates to the detriment of natural classes. The effect of human impact was translated by the increase of disturbance index which increased from 1.9 to 3.3 in six years, confirming that in the study area, natural classes are removed parallel to aggregation and creating of anthropogenic classes. The study area has undergone significant changes related to urban growth, which implies establishing efficient urban planning and management policies to reverse this trend. [less ▲]

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See detailQuantification of anthropogenic effects in the landscape of Lubumbashi
Andre, Marie ULg; Vranken, Isabelle ULg; Boisson, Sylvain ULg et al

in Mahy, Grégory; Colinet, Gilles; Bogaert, Jan (Eds.) Anthropisation au Katanga (in press)

In order to understand the dynamic of the (sub)urbanisation and so, to quantify the anthropogenic effects of the rapid growth of tropical cities, it is crucial to find and apply valuable methods. In this ... [more ▼]

In order to understand the dynamic of the (sub)urbanisation and so, to quantify the anthropogenic effects of the rapid growth of tropical cities, it is crucial to find and apply valuable methods. In this contribution, the transferability of the Rüdisser et al. (2012) «Distance to Nature» hemeroby assessment method to the landscape surrounding the city of Lubumbashi (DRC) is evaluated. That methodology has the advantage of taking structural connectivity into account by computing the distance to natural habitats. As it had never been applied to an African city before, some adjustments (fitting of the local land uses types into the hemeroby levels designed to Austria) and amendments (suppression of the final classification into hemeroby level simplification) are proposed. Moreover, an analysis of the decanal (2002-2013) hemeroby dynamics is presented. Results suggest that the Distance to Nature methodology is transferable but requires good field knowledge to define reference habitats and identify them in the Landsat classified images. There was a dramatic decrease of the «natural» and «near-natural» levels in the study extent during the studied period. In addition, 32% of the land underwent anthropisation increase, mostly around cities and following a ribbon development. [less ▲]

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See detail4th Doctoral Seminar on Sustainability Research in the Built Environment Book of Abstracts
Attia, Shady ULg; Teller, Jacques ULg; Mahy, Grégory ULg

Book published by SBD Lab (2017)

The DS2BE is a joint initiative of research groups working on sustainability issues at 8 Belgian universities: ULBruxelles, VUBrussel, KULeuven, UCLouvain, ULiège, UHasselt, UAntwerpen and UGent ... [more ▼]

The DS2BE is a joint initiative of research groups working on sustainability issues at 8 Belgian universities: ULBruxelles, VUBrussel, KULeuven, UCLouvain, ULiège, UHasselt, UAntwerpen and UGent. Conceived as a platform for PhD researchers whose work engages the built environment at different scales in the framework of sustainability, these seminars provide an excellent opportunity for the doctoral students of the partner institutions to present their ongoing research. They will get feedback from a broad panel of sustainability experts, including invited specialists and peers, for furthering their research. PhD candidates can provide submissions that concern topics, such as: - Sustainable Architecture and Resources, materials, re-cycling /re-use, building elements and envelope, building physics, building construction technology, building renovation, drawing lessons from vernacular, bioclimatic design, regenerative design, biomimetic and integrated design, …, - Sustainability theory, sustainability / environmental assessment at building and neighborhood scales, and at the scale of city and regions, - Sustainable urbanism, urban form, landscape and urban ecology, urban green infrastructure and ecosystem services, public space, density, urban infrastructure & transportation, water urbanism, retrofitting of buildings to the built environment, - Methodologically oriented PhDs focusing on issues related to LCA (Life Cycle Analysis), I-O (Input-Output Analysis), MFA (Material Flow Analysis), simulation techniques, to exploring urban metabolism, industrial ecology, environmental modelling, GIS-based land-use change modelling, to Research by Design. [less ▲]

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See detailNo copper required for germination of an endangered endemic species from the Katangan Copperbelt (Katanga, DR Congo): Diplolophium marthozianum
Boisson, Sylvain ULg; Ortmans, William ULg; Maréchal, Justine et al

in Tropical Ecology (2017), 58(1), 193-198

Two hypotheses were tested with respect to the germination of Diplolophium marthozianum, an endemic plant species of the copper-cobalt outcrops in Katanga, Democratic Republic of Congo: (1) germination of ... [more ▼]

Two hypotheses were tested with respect to the germination of Diplolophium marthozianum, an endemic plant species of the copper-cobalt outcrops in Katanga, Democratic Republic of Congo: (1) germination of copper-endemics is limited by fungal infection in the absence of pathogen control and (2) the germination success of this copper-endemic species is copper-dependent. Seed lots of twenty seeds were weighed, soaked in different disinfection treatments and then placed in a germination medium containing four distinct copper concentrations for 30 days. Seed viability was measured at the beginning and at the end of the experiment by a cut test. Final germination percentage (15.2 ± 8.2 %) and seed viability (24.2 ± 10.3 %) were not affected by copper concentration or disinfection treatments. D. marthozianum is able to germinate in a substrate without added copper, despite pervasive fungal infection. However, seed mass had a significant positive effect on seed germination suggesting that selecting the largest seeds may ensure the highest germination success in ex situ conservation programs. [less ▲]

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See detailEffects of seed traits variation on seedling performance of the invasive weed, Ambrosia artemisiifolia
Monty, Arnaud ULg; Mahy, Grégory ULg; Ortmans, William ULg

Poster (2016, September 14)

Seedling performance can determine the survival of a juvenile plant and impact adult plant performance. Understanding the factors that may impact seedling performance is thus critical, especially for ... [more ▼]

Seedling performance can determine the survival of a juvenile plant and impact adult plant performance. Understanding the factors that may impact seedling performance is thus critical, especially for annuals, opportunists or invasive plant species. Seedling performance can vary among mothers or populations in response to environmental conditions or under the influence of seed traits. However, very few studies have investigated seed traits variations and their consequences on seedling performance. Specifically, the following questions have been addressed by this work: 1) How the seed traits of the invasive Ambrosia artemisiifolia L. vary among mothers and populations, as well as along the latitude; 2) How do seed traits influence seedling performance; 3) Is the influence on seedlings temperature dependent. With seeds from nine Western Europe ruderal populations, seed traits that can influence seedling development were measured. The seeds were sown into growth chambers with warmer or colder temperature treatments. During seedling growth, performance-related traits were measured. A high variability in seed traits was highlighted. Variation was determined by the mother identity and population, but not latitude. Together, the temperature, population and the identity of the mother had an effect on seedling performance. Seed traits had a relative impact on seedling performance, but this did not appear to be temperature dependent. Seedling performance exhibited a strong plastic response to the temperature, was shaped by the identity of the mother and the population, and was influenced by a number of seed traits. [less ▲]

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See detailFirst come first served: “priority effect“ benefits Ambrosia artemisiifolia L. more than other ruderal Asteraceae species
Ortmans, William ULg; Mahy, Grégory ULg; Monty, Arnaud ULg

Poster (2016, September 14)

Ambrosia artemisiifolia L. (common ragweed, Asteraceae) is an invasive weed causing a health crisis in Europe, due to its highly allergenic pollen. In Western Europe the invaded range covers most of ... [more ▼]

Ambrosia artemisiifolia L. (common ragweed, Asteraceae) is an invasive weed causing a health crisis in Europe, due to its highly allergenic pollen. In Western Europe the invaded range covers most of central and southern France, and northern Italy. Northwards beyond the edge of this range, occurrence of casual population have been described for years, but these populations do not appear to become invasive, and the species does not seem to spread. This situation raises the following question: Has the invaded range reached a limit or will the species continue its invasion northwards? To answer this question, we followed two complementary approaches. First we set up an experimental garden in Belgium, 250 km north to the current invaded range, to see if the local climate allows the completion of the species reproduction cycle. Second, we performed an in situ measurement campaign in 12 population located beyond the edge, within the range but near the margin, and in the center of the invaded range. The aim of this campaign was to test whether the species had reduced plant performance towards range margins. The results showed that the species is able to establish populations with high growth rates in Belgium. Furthermore, the species expressed similar performance across the considered areas, even beyond the current invasion front. No evidence of processes constraining the invasion was found, which suggests a great potential for invasion north to the current invaded range. In this uncertain situation, awareness actions should be considered in the northern countries. [less ▲]

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See detailIs Ambrosia artemisiifolia L. able to expand its invaded range northward in Western Europe?
Ortmans, William ULg; Mahy, Grégory ULg; Monty, Arnaud ULg

Conference (2016, September 13)

Ambrosia artemisiifolia L. (common ragweed, Asteraceae) is an invasive weed causing a health crisis in Europe, due to its highly allergenic pollen. In Western Europe the invaded range covers most of ... [more ▼]

Ambrosia artemisiifolia L. (common ragweed, Asteraceae) is an invasive weed causing a health crisis in Europe, due to its highly allergenic pollen. In Western Europe the invaded range covers most of central and southern France, and northern Italy. Northwards beyond the edge of this range, occurrence of casual population have been described for years, but these populations do not appear to become invasive, and the species does not seem to spread. This situation raises the following question: Has the invaded range reached a limit or will the species continue its invasion northwards? To answer this question, we followed two complementary approaches. First we set up an experimental garden in Belgium, 250 km north to the current invaded range, to see if the local climate allows the completion of the species reproduction cycle. Second, we performed an in situ measurement campaign in 12 population located beyond the edge, within the range but near the margin, and in the center of the invaded range. The aim of this campaign was to test whether the species had reduced plant performance towards range margins. The results showed that the species is able to establish populations with high growth rates in Belgium. Furthermore, the species expressed similar performance across the considered areas, even beyond the current invasion front. No evidence of processes constraining the invasion was found, which suggests a great potential for invasion north to the current invaded range. In this uncertain situation, awareness actions should be considered in the northern countries. [less ▲]

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See detailLandscape diversity, better for biodiversity? - hoverflies and butterflies in different agri-environment schemes
Pécheur, Emilie ULg; Piqueray, Julien; Dopagne, Claude ULg et al

Conference (2016, August 31)

In Europe, agri-environment schemes (AES) are designed to give credit to environmental issues in agricultural practices. Among the different Walloon AES, some are dedicated to enhance and preserve ... [more ▼]

In Europe, agri-environment schemes (AES) are designed to give credit to environmental issues in agricultural practices. Among the different Walloon AES, some are dedicated to enhance and preserve biodiversity linked to the agroecosystems. This study wishes to explore, at a landscape scale, how do different AES perform regarding butterflies and syrphidae diversity. Data collection occurred in five categories of ecological infrastructures (EI): four types of agri-environmental schemes (grassy strips, wildflower strips, bird-feeding margins, species-rich meadows) and cereal crops. Five replicates were selected for each category. Syrphidae were collected in water traps once per month, from May to July. Butterflies were monitored along transects from May to Augustus. Plant species were identified in every plot, within a 1-m radius around the traps and along a transect through every plot. Preliminary results show that abundance and species diversity of butterflies is significantly higher in parcels with floral resources. Moreover, hosts plants for larvae and foraging plants for adults are significantly more present in two types of AES: the wildflower strips and the species-rich meadows. Regarding the identified plant species, categories are divided in three groups (crops apart): bird-feeding margins; species-rich meadows and grassy strips; wildflower strips (Fig.1). Concerning hoverflies, a significantly higher abundance is observed in the wildflower strips compared to the crops in June (p= 0.008). Other abundance values in May and July show no difference. These results suggest that wildflower strips are performing infrastructures for biodiversity conservation in agroecosystems. As the presence of floral resources seem to be an important factor for the presence of foraging of adults, attention should be paid to the provisioning of food resources for the larval stages, especially butterflies, at a landscape scale in order to assure a sustainable approach in biodiversity support. [less ▲]

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See detailOccurrence rates of invasive plants in limestone quarries (Southern Belgium)
Pitz, Carline ULg; Jorion, Alexis ULg; Mahy, Grégory ULg et al

Conference (2016, August 23)

In quarries, invasive plant species can slow down the installation of high conservation value vegetation. Successful management of invasive requires, at first, a quantitative assessment of invasion levels ... [more ▼]

In quarries, invasive plant species can slow down the installation of high conservation value vegetation. Successful management of invasive requires, at first, a quantitative assessment of invasion levels. Although European legislation has adopted an ambitious strategy against invasive species, there is still a lack of knowledge about their occurrence in quarries. The aim of this study was to evaluate occurrence rates of invasive plant species in limestone quarries throughout Wallonia (Southern Belgium) and identify high priority and emerging invasive plants for adapted management. During 2016 vegetation period, forty quarries were selected by stratified sampling, using abandoned and active quarries as strata. Within selected quarries, two-meter wide transects were established to cross all activity sectors. Transects were divided in 10x2m plots, resulting in 2% of total surface of each quarry being surveyed. Cover and number of individuals of invasive plants species were recorded in each plot. Species considered were those of Harmonia list (67 species), the reference at the Wallonia scale. More than 30 000 plots were surveyed. Results of our recent study are presented (occurrences rates by species, mean percentage cover per site). First results indicate that dominant invasive species originate from different introduction paths: (i) planted (Robinia pseudoacacia); (ii) ornamentals (Cotoneaster horizontalis) and (iii) spontaneous colonization (Senecio inaequidens) - and follow various invasion dynamics. We propose research and management methods to be directed towards limitation of top ten frequent species (e.g. Buddleia davidii, Senecio inaequidens), and to establish a detection system for the emerging invasive plants. [less ▲]

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See detailIs the observer effect significant in vegetation assessment of restored metallicolous grassland?
Boisson, Sylvain ULg; Mahy, Grégory ULg

Conference (2016, August 22)

Projects that prospects habitat restoration require protocols of vegetation assessment to monitor the evolution of the restored ecosystems over time. In most cases, multiple assessors are needed and some ... [more ▼]

Projects that prospects habitat restoration require protocols of vegetation assessment to monitor the evolution of the restored ecosystems over time. In most cases, multiple assessors are needed and some studies have shown that the variability among observer can be significant. In the context of tropical grassland, few studies quantified the impact of the observer on the results, reducing the capacity to replicate conclusions, and, therefore to plan restoration strategies at large scale. This study aims to quantify the variation among observers using two phytosociological methods on restored metallicolous grassland and to test whether variation in the assessment could involve the conclusions of the vegetation assessment. Four observers were selected to perform monitoring of quadrats in two distinct habitats identified in four restored ecosystems. All observers sampled seven metrics based on phytosociological methods and two of them also performed a complete vegetation sampling of the quadrat, including species identification and cover in quadrat. For metrics based on cover, variation of measure exists among the observers. For metrics based on counting, no variation is highlighted and the observers are able to distinguish and identify species. These results emphasize that a same method could lead to distinct results according to observer and, in restoration projects, it is crucial to ensure a correct transfer of protocols of vegetation assessment in order to reproduce equally the method. [less ▲]

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See detailA population approach to evaluate grassland restoration - a systematic review
Harzé, Mélanie ULg; Monty, Arnaud ULg; Boisson, Sylvain ULg et al

Conference (2016, August)

How do we know if restoration goals are achieved? In practice, the criteria used to evaluate the success of restoration actions are numerous and can be defined at different ecological scales, i.e. at the ... [more ▼]

How do we know if restoration goals are achieved? In practice, the criteria used to evaluate the success of restoration actions are numerous and can be defined at different ecological scales, i.e. at the population, community or ecosystem level. Most studies about restoration success monitoring assessed attributes corresponding to the community or ecosystem levels like species diversity, vegetation structure and ecological processes. Has the population approach been disregarded to evaluate restoration success? This systematic review of the literature aimed to identify how often plant population traits were used to monitor restoration of grasslands. Practically, 3133 papers were reviewed among which 1065 reported monitoring of plant species after a restoration action. Only 153 papers used a population approach and represent the core of this review. Detailed results and paper content will be presented with the aim to identify restoration protocols (with or without species addition), species of interest, population attributes and processes considered to evaluate restoration success. [less ▲]

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See detailDiaspore heteromorphism in the invasive Bromus tectorum L. (Poaceae): sterile fl orets increase dispersal propensity and distance
Monty, Arnaud ULg; Maebe, Laura ULg; Mahy, Grégory ULg et al

in Flora (2016)

Within a species, the distance travelled by a particular diaspore depends on its morphology. In Poaceae, the presence of terminal sterile florets can lead to diaspore heteromorphism, which may influence ... [more ▼]

Within a species, the distance travelled by a particular diaspore depends on its morphology. In Poaceae, the presence of terminal sterile florets can lead to diaspore heteromorphism, which may influence dispersal. We tested the hypothesis that the presence of sterile florets favored dispersal in Bromus tectorum L., an invasive grass in the Western US. We used field and controlled experiments to study the dispersal of caryopses with and without sterile florets attached (respectively complex and simple diaspores), as well as pieces of inflorescence that detached from the mother plants. We considered both primary and secondary dispersal, as well as abiotic and biotic dispersal agents. The distance travelled by the diaspores and their attachment to animal fur were related to the presence and number of sterile florets. Abiotic agents moved diaspores over relatively short distances, both in terms of primary and secondary dispersal. A significant proportion of diaspores attached to fur, suggesting a potential for dispersal over longdistances. Complex diaspores were better dispersers than simple ones (and pieces of inflorescence), and this pattern was consistent across the study. However, among complex diaspores, the number of sterile florets had little or no influence. Considering primary and secondary dispersal by abiotic and biotic agents provided a general picture of the dispersal ecology of B. tectorum. For all the dispersal steps and dispersal agents we studied, the presence of sterile florets favored dispersal. These results highlight the functional significance of diaspore heteromorphism induced by floret sterility in the dispersal of Poaceae. [less ▲]

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See detailUsing phytostabilisation as a way to conserve threatened endemic species from the Southeastern D.R. Congo
Boisson, Sylvain ULg; Le Stradic, Soizig ULg; Seleck, Maxime ULg et al

Conference (2016, June 22)

Metalliferous outcrops of the southeastern Democratic Republic of Congo are recognized as some of the largest copper-cobalt deposits of the world. They support unique vegetation with around 600 ... [more ▼]

Metalliferous outcrops of the southeastern Democratic Republic of Congo are recognized as some of the largest copper-cobalt deposits of the world. They support unique vegetation with around 600 metallophyte species including rare and endemic species. Since 1900s, the exploitation of the Cu-Co outcrops in D.R. Congo has considerably increased, impacting environment and putting public health at risk. Phytostabilisation is a suitable technology to decrease the bioavailability of heavy metals in highly polluted soils. This technic has been successfully implemented in the vicinity of Lubumbashi with the grass Microchloa altera. The long term maintenance of such technic requires a good understanding of the interspecific relationship like competition and facilitation. This study aims to test the success of establishment of four herbaceous species from the southeastern DRC presenting conservation priority and to assess the potential role of M. altera as nurse plant in this context. Two annual species and two perennial species were sown in experimental design with soil amendments crossed with vegetation cover. The emergence, the growth and the survival were followed during the vegetation season and the resprout was measured for perennial species. M. altera had a distinct effect on the emergence and the survival of the annual and perennial species but affected negatively the growth of individuals for all species. [less ▲]

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See detailMonitoring the occurrence of invasive plants in different types of natural habitats
Monty, Arnaud ULg; Frisson, Gwenn; Delbart, Emmanuel et al

Conference (2016, April 19)

Protected areas and the Natura 2000 network are keystones of the EU nature and biodiversity policy. However, alien plants do not stop their spread at the border of protected areas and invasive plants are ... [more ▼]

Protected areas and the Natura 2000 network are keystones of the EU nature and biodiversity policy. However, alien plants do not stop their spread at the border of protected areas and invasive plants are reported to threaten many ecosystems, from aquatic and riparian areas to dry and xeric sites. The presentation summarizes three large-scale quantitative assessments of the occurrence of exotic plants in Wallonia, i.e. the southern part of Belgium. Three types of natural habitats were the focus of the assessments: i) ponds and lakes (400 sites); ii) river banks (187 sites); and iii) xeric ecosystems such dry grasslands, rocky habitats and screes (86 sites). In the three studies, sites were selected through a stratified sampling then visited. Exotic plants were recorded and their abundance assessed. Additional information about population dynamics, environmental conditions and visible impacts was recorded. Elodea spp. were the most common species in water bodies, with occurrence rates reaching 2.7%. Other aquatic alien species were found, but with an occurrence rate below 1%. Along rivers, 51 alien species were observed. Some were widespread (e.g. Impatiens glandulifera, with 17 % of linear banks invaded) whereas others were either rare or considered emergent alien species. Analyses showed that typical riparian species’ occurrence increased with the size of the watershed, indicating propagule pressure within protected areas through hydrochory. In xeric sites, the most common species were either cultivated or ornamental ones such as Juglans regia, Cotoneaster horizontalis, Prunus serotina, Robinia pseudoacacia and Buddleja davidii. The former was found in 15.1% of the visited sites. The implications of the different results, notably about emergent species, are related to the need for an effective early detection system. [less ▲]

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See detailIs Ambrosia artemisiifolia L. able to expand its invaded range northward in Western Europe?
Ortmans, William ULg; Mahy, Grégory ULg; Monty, Arnaud ULg

Poster (2016, April 19)

Ambrosia artemisiifolia L. (common ragweed, Asteraceae) is an invasive weed causing a health crisis in Europe, due to its highly allergenic pollen. In Western Europe the invaded range covers most of ... [more ▼]

Ambrosia artemisiifolia L. (common ragweed, Asteraceae) is an invasive weed causing a health crisis in Europe, due to its highly allergenic pollen. In Western Europe the invaded range covers most of central and southern France, and northern Italy. Northwards beyond the edge of this range, occurrence of casual population have been described for years, but these populations do not appear to become invasive, and the species does not seem to spread. This situation raises the following question: Has the invaded range reached a limit or will the species continue its invasion northwards? To answer this question, we followed two complementary approaches. First we set up an experimental garden in Belgium, 250 km north to the current invaded range, to see if the local climate allows the completion of the species reproduction cycle. Second, we performed an in situ measurement campaign in 12 population located beyond the edge, within the range but near the margin, and in the center of the invaded range. The aim of this campaign was to test whether the species had reduced plant performance towards range margins. The results showed that the species is able to establish populations with high growth rates in Belgium. Furthermore, the species expressed similar performance across the considered areas, even beyond the current invasion front. No evidence of processes constraining the invasion was found, which suggests a great potential for invasion north to the current invaded range. In this uncertain situation, awareness actions should be considered in the northern countries. [less ▲]

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See detailPerformance variation of common ragweed (Ambrosia artemisiifolia L.) across invasion levels in Western Europe
Ortmans, William ULg; Mahy, Grégory ULg; Chauvel, Bruno et al

in Flora (2016), 220

The occurrence of an invasive plant across a continent is generally not homogeneous; typically, some areas are highly invaded whereas others show moderate or low invasion levels. This situation might be a ... [more ▼]

The occurrence of an invasive plant across a continent is generally not homogeneous; typically, some areas are highly invaded whereas others show moderate or low invasion levels. This situation might be a snapshot of an ongoing spread, but it could also remain stable under the pressure of factors that constrain the invasion. Among those factors, plant performance variation among invasion levels can explain an invasion slowdown. However, few studies have investigated the large-scale variation of invasive plant performance in the field. Ambrosia artemisiifolia L. in Western Europe represents a good opportunity to address this issue, with areas of high, moderate and low invasion levels being documented across a ca. 1000 km transect. In this study, we compared in situ plant performance-related traits in 12 populations from areas of contrasting invasion levels. We also tested whether performance-related traits were influenced by the intra-and inter-specific competition, by the local climatic conditions or by latitude (a proxy for growing season length). Overall, we did not find differences in performance-related traits across invasion levels, and intra-and inter-specific competition had low effects on plant performance. This study highlights the fact that A. artemisiifolia individuals express similar performance across invasion levels, even beyond what can be considered the present invasion front. Further research has to expand this study northwards, and assess other factors that could constrain the invasion in order to highlight if the species invasion northward is constrained or if it has the potential to invade new areas. [less ▲]

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See detailEffects of seed traits variation on seedling performance of the invasive weed, Ambrosia artemisiifolia L.
Ortmans, William ULg; Mahy, Grégory ULg; Monty, Arnaud ULg

in Acta Oecologica: International Journal of Ecology (2016), 71

Seedling performance can determine the survival of a juvenile plant and impact adult plant performance. Understanding the factors that may impact seedling performance is thus critical, especially for ... [more ▼]

Seedling performance can determine the survival of a juvenile plant and impact adult plant performance. Understanding the factors that may impact seedling performance is thus critical, especially for annuals, opportunists or invasive plant species. Seedling performance can vary among mothers or populations in response to environmental conditions or under the influence of seed traits. However, very few studies have investigated seed traits variations and their consequences on seedling performance. Specifically, the following questions have been addressed by this work: 1) How the seed traits of the invasive Ambrosia artemisiifolia L. vary among mothers and populations, as well as along the latitude; 2) How do seed traits influence seedling performance; 3) Is the influence on seedlings temperature dependent. With seeds from nine Western Europe ruderal populations, seed traits that can influence seedling development were measured. The seeds were sown into growth chambers with warmer or colder temperature treatments. During seedling growth, performance-related traits were measured. A high variability in seed traits was highlighted. Variation was determined by the mother identity and population, but not latitude. Together, the temperature, population and the identity of the mother had an effect on seedling performance. Seed traits had a relative impact on seedling performance, but this did not appear to be temperature dependent. Seedling performance exhibited a strong plastic response to the temperature, was shaped by the identity of the mother and the population, and was influenced by a number of seed traits. [less ▲]

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Monty, Arnaud ULg; Garré, Sarah ULg; Bindelle, Jérôme ULg et al

in Biotechnologie, Agronomie, Société et Environnement = Biotechnology, Agronomy, Society and Environment (2016)

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