References of "Mahy, Grégory"
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See detailExtent of intra-population functional variability along a local environmental gradient for four calcareous grasslands species
Harzé, Mélanie ULg; Monty, Arnaud ULg; Mahy, Grégory ULg

Conference (2013, August 19)

In the last few years, an increasing body of evidence has highlighted the role of functional traits as reliable predictors of species resistance to disturbance and response to environmental gradients ... [more ▼]

In the last few years, an increasing body of evidence has highlighted the role of functional traits as reliable predictors of species resistance to disturbance and response to environmental gradients. However, most studies focused on functional comparisons at the interspecific level while intraspecific functional trait variation has received remarkably little attention. As intraspecific traits variability is a necessary condition for species to adapt to environmental changes, studying intraspecific functional traits variation along environmental gradients is a major issue in a context of global change. The aim of our study was to evaluate the extent of intraspecific functional variability of four species along an environmental gradient of water stress at a local scale and to compare species response to the gradient. Calcareous grasslands species are present along a xeric gradient from mesophilous to xerophilous grasslands. Changes of exposure, slope and soil depth lead to differences of water availability for plants along the gradient. We measured the maximum vegetative height (MVH), the specific leaf area (SLA, one side area of a fresh leaf divided by its oven-dry mass) and the leaf dry matter content (LDMC, leaf oven-dry mass divided by its water-saturated fresh mass) on randomly selected individuals along a gradient of xericity on three study sites located in south Belgium. Functional traits were measured on about 60 individuals per site and per species. The soil depth was measured around each individual. The exposure and the slope were measured in order to calculate a heat load index for each individual. The extent of local intraspecific functional variability of our data was compared to data covering the species European range. Results are species dependent but for some study species intraspecific functional variability at local scale is not negligible compared to European data. Species functional responses to the gradient (soil depth and heat load index) showed a decrease in SLA and MVH and an increase in LDMC with increasing xericity for all study species. Response extent was species dependent. Main implications for species resistance to disturbance and climate change adaptation will be discussed. [less ▲]

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See detailPerformance Indicators Framework for Biodiversity Management in Gypsum Quarries Throughout Europe
Pitz, Carline ULg; Marlet, Christine; Chevalier, Philippe et al

Report (2013)

This study aims to establish a common Key Performance Indicators (KPIs) framework to report biodiversity for the Gypsum Industry at the European level. An original approach of participatory process has ... [more ▼]

This study aims to establish a common Key Performance Indicators (KPIs) framework to report biodiversity for the Gypsum Industry at the European level. An original approach of participatory process has been developed in order to integrate the different opinions and to reach a consensus framework between different stakeholders’ groups: - Eurogypsum stakeholders - European and local authorities - Scientific panel : universities and consulting offices - European and local associations for the conservation of nature - Stakeholders from the mining sector The strategy is based on five main steps: (i) To Build a stakeholders’ network; (ii) To build a framework proposal to be submitted to stakeholders by selecting a maximum set of indicators based on the literature and reaching an agreement on indicators with Eurogypsum (Focus Group); (iii) Reaching a consensus framework with all the stakeholders and evaluating feasibility by a Delphi Policy survey, by the analysis of the EIAs of the Gypsum Industry and by visiting three European quarries; (iv) Final validation with Eurogypsum (meeting); (v) Creating indicators’ Factsheets and a Eurogyspum report to the destination of the public. The resulting framework contains eleven indicators which are the most acceptable set of indicators for all the stakeholders. It answers to European legislation and strategies for biodiversity. It is intended to improve sustainability in the quarries and to help managing biodiversity, to allow setting up of appropriate reporting systems. The aim is to maintain the biodiversity status of the gypsum quarries. It is a flexible framework adaptable given the local context of each gypsum quarry in order to prove if a No Net Loss has been reached at a quarry’s scale. [less ▲]

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See detailSynthesis and new definition of the areas included in the urban-rural gradient
Andre, Marie ULg; Mahy, Grégory ULg; Lejeune, Philippe ULg et al

Conference (2013, July 26)

Every scientific studies should begin with the delimitation of the studied system. Ours aims at evaluating and quantifying the resistence of landscape classes and ecosystems to the urbanization process ... [more ▼]

Every scientific studies should begin with the delimitation of the studied system. Ours aims at evaluating and quantifying the resistence of landscape classes and ecosystems to the urbanization process. This is done by studying a dozen cities in sub-Saharan Africa, conducting a diachronic (2000 - 2010) landscape evolution analysis from SPOT satellite imagery. Paradoxaly, when tackling this subject, one must recognize that no consensus exists about the definition and localization of the areas included in the urban-rural gradient. This prevents from comparing the results of different cities. A bibliography analysis has been conducted in order to 1) identify the different areas in the urban-rural gradient, the characteristics and types of characteristics used to define the most cited ones (i.e. urban, suburbs, sprawl, exurban, rurban, periurban and rural) ; 2) Through citation frequency indexes, evaluate the relative importance of characteristics and types of characteristics for every area and then for the whole gradient; 3) Evaluate the principal characteristics according to a series of criteria (the best characteristic is supposed to be quantitative, integrative, marking a consensus, discriminative and easy to apply on the field); 4) On the basis of retained characteristics, propose single and simple definitions to the most cited areas. These new definitions aim at enable areas identification on the field and on satellite images. These new definitions have been applied to the field study of the city of Lubumbashi (D.R.C) and seem to be convenient. Retained characteristics have then been translated into landscape composition indexes for the future study of the following cities on basis of satellite imagery, without field research. Indeed, such indexes are commonly used in landscape ecology because they allow the description of the urban landscape pattern or structure which, according to the central hypothesis of landscape ecology, i.e. “pattern-process paradigm”, influence landscape ecological processes. [less ▲]

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See detailPlant ecological niche distribution along heavy metal gradients
Boisson, Sylvain ULg; Monty, Arnaud ULg; Seleck, Maxime ULg et al

Conference (2013, June 26)

Why species do not occur everywhere? The concept of ecological niche is central to understand relationships among biotic/abiotic factors and species distribution. Gradients of environmental stress ... [more ▼]

Why species do not occur everywhere? The concept of ecological niche is central to understand relationships among biotic/abiotic factors and species distribution. Gradients of environmental stress associated to interspecific interactions generate testable patterns of specie’s response curves. Distribution of response curves have been seldom tested along toxicity gradient, in contrast to resource gradients. On Katangan copper hills (south R.D.C.), natural copper and cobalt concentrations span a large range: 2 - 1000 mg kg-1 for cobalt and 30 - 10 000 mg kg-1 for copper. In this study, we evaluate three hypotheses related to niche distributions and shapes along metal toxic gradients: (1) Species optima are uniformly distributed over copper-cobalt gradient. (2) Realized niche width varies in relation to the niche optimum along copper and cobalt gradient. (3) Absolute values of skewness coefficient are higher when plant species optima are in the extremes of cobalt gradient with a niche tails toward mesic conditions. Realized niches of 80 taxa were modeled with general additive models (GAM) using presence/absence data in 172 1m² plots. Niche optima, niche widths and skewness coefficients were estimated from species response curves. The three hypotheses were globally validated. Three groups of species were distinguished according to their optima position along metal gradient with packed optima on intermediate concentrations suggesting higher interspecific competition in low metal concentrations. Niche width increased with metal concentrations. Highest metal tolerant plant species had broader niches. Skewness coefficient was inversely related to niche optima positions. Our study demonstrates that species distribution pattern on toxicity gradient presents similarities with resource gradient. Broad realized amplitude of species adapted to high levels of copper cobalt concentrations suggests that fundamental niche of specialist metallophytes may be larger than expected. This should be further tested in controlled conditions in association to competition tests. [less ▲]

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See detailGradient urbain-rural de la ville de Lubumbashi: dynamique entre 2002 et 2009
Andre, Marie ULg; Bogaert, Jan ULg; Mahy, Grégory ULg et al

in Ernoult, Aude (Ed.) Dynamiques écologiques des paysages: de l'agricole à l'urbain (2013, June 12)

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See detailSpecies delimitation and diversification in the widespread tree genus Milicia (Moraceae)
Daïnou, Kasso ULg; Mahy, Grégory ULg; Duminil, Jérôme et al

Conference (2013, June)

The long generation time and large effective size of widespread forest tree species can result in slow evolutionary rate and incomplete lineage sorting, complicating species delimitation. We addressed ... [more ▼]

The long generation time and large effective size of widespread forest tree species can result in slow evolutionary rate and incomplete lineage sorting, complicating species delimitation. We addressed this issue with the African timber tree genus Milicia that comprises two morphologically similar and often confounded species: M. excelsa, widespread from West to East Africa, and M. regia, endemic to West Africa. We combined information from nuclear microsatellites (nSSRs), nuclear and plastid DNA sequences, and morphological systematics to identify significant evolutionary units and infer their evolutionary and biogeographical history. We detected five geographically coherent genetic clusters using nSSRs and three levels of genetic differentiation. First, one West African cluster matched perfectly with the morphospecies M. regia, which formed a monophyletic clade at both DNA sequences. Second, a West African M. excelsa cluster formed a monophyletic group at plastid DNA and was more related to M. regia than to Central African M. excelsa, but shared many haplotypes with the latter at nuclear DNA. Third, three Central African clusters appeared little differentiated and shared most of their haplotypes. Although gene tree paraphyly could suggest a single species in Milicia following the Phylogenetic Species Concept, the existence of mutual haplotypic exclusivity and non-admixed genetic clusters in the contact area of the two taxa indicate strong reproductive isolation, and thus, two species following the Biological Species Concept. Molecular dating of the first divergence events showed that speciation in Milicia is ancient (Tertiary), indicating that long-living tree taxa exhibiting genetic speciation may remain similar morphologically. [less ▲]

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See detailTrees communities and filters to restoration along a periurban gradient of tropical forest degradation
Hick, Aurélie ULg; Tooth, Martin; Tshibungu, Alain et al

Conference (2013, June)

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See detailIntegrated management of wild chamomile populations by tillage
Jaunard, Delphine ULg; Monty, Arnaud ULg; Mahy, Grégory ULg et al

in Agricultural and Apllied Biological Sciences (2013, May 21)

Gembloux, Belgium Chemical weeding in agriculture increasingly raises environmental, health and economic preoccupations. European authorities has set up legislations (directive 91/414, settlement 1107 ... [more ▼]

Gembloux, Belgium Chemical weeding in agriculture increasingly raises environmental, health and economic preoccupations. European authorities has set up legislations (directive 91/414, settlement 1107/2009, directive 2009/128) aiming to reduce risks related to the use of pesticides and encouraging integrated pest management. This situation leads professionals and scientists to take interest in the biology and population dynamics of weeds and to study the impacts of integrated pest management on weeds and crops. Tillage can potentially be an efficient weed control method in winter wheat (Triticum aestivum L.). We studied wild chamomile (Matricaria chamomilla L.) population dynamics and crop yields in an experimental winter wheat crop, in relation to tillage methods. Five modalities (i.e. different combinations of a stubble cultivator and/or a moldboard plow, including a no-tillage control) were applied during three years (2009-2012), with four replications, in Gembloux (Belgium). In each plot, M. chamomilla density was recorded throughout the seasons. In summer 2012, wild chamomile density was significantly lower in plots tilled with a moldboard plow. The use of a stubble cultivator did not significantly affect M. chamomilla density. In addition, we found higher wheat yields in ploughed plots, indicating that the decrease in M. chamomilla density reduced competition for wheat. To confirm these results, experiments are still under investigation in similar conditions. [less ▲]

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See detailA comparison of soil properties under four vegetation units from six metalliferous hills in Katanga
Kaya Muyumba, Donato ULg; Mahy, Grégory ULg; Ngongo Luhembwe, Michel et al

Conference (2013, April 12)

In Katanga (Democratic Republic of Congo), numerous metalliferous hills are distributed along what is called the copperhill belt from Kolwezi to Lubumbashi. Very specific vegetation developed on these ... [more ▼]

In Katanga (Democratic Republic of Congo), numerous metalliferous hills are distributed along what is called the copperhill belt from Kolwezi to Lubumbashi. Very specific vegetation developed on these hills within the miombo forest in response to very specific soil conditions, among which the copper content. Previous studies have already shown the existence of gradients of copper from the mineralized rocks outcropping at the top of the hills to the foot slopes on colluviums. After a characterization of the vertical variability of soil properties in pits distributed along the main slopes, we investigated the soil-vegetation relationships in six hills located between the towns of Tenke and Fungurume. Observation 1-square meter plots were installed in four vegetation units and sixty of them were selected according to their relative importance on the six hills. The soil from the top 10cm was sampled and analyzed for pH, Total Organic Carbon, available P, K, Mg, Ca, Cu, Co and Mn and soluble Cu and Co. Analysis of variance was performed in order to assess whether the effects of the “Hill” and of the “Vegetation Unit” were significant to explain soil chemical variability. Additionally, short transects were sampled at the boundaries from adjacent vegetation units in order to evaluate the gradual or rough nature of change in soil properties under these units. [less ▲]

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See detail3. Contrôle des populations de mauvaises herbes
Jaunard, Delphine ULg; Monty, Arnaud ULg; Mahy, Grégory ULg et al

in Bodson, Bernard; Destain, Jean-Pierre (Eds.) Livre Blanc - Céréales (2013, February 27)

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See detailL'écologie du Paysage: un chaînon essentiel pour une gestion multiscalaire de l'hétérogénéité
Mahy, Grégory ULg; Bogaert, Jan ULg; Monty, Arnaud ULg

in Meerts, Pierre (Ed.) Vers une nouvelle synthèse écologique: de l'écologie scientifique au développement durable (2013)

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See detailSaving tropical copper grasslands: a comparison of vegetation and top soil translocation
Mahy, Grégory ULg; Seleck, Maxime ULg; Lebrun, Julie et al

Conference (2013)

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See detailSmall-scale diversity of plant communities and distribution of species niches on a copper rock outcrop in Upper Katanga, D.R.Congo
Ilunga wa Ilunga, Edouard; Seleck, Maxime ULg; Colinet, Gilles ULg et al

in Plant Ecology and Evolution (2013), 146(2), 173-182

Background and aims – In Katanga (D. R. Congo), outcrops of bedrocks naturally enriched in Cu and Co ("copper hills"), host unique plant communities. The spatial variation of vegetation has long been ... [more ▼]

Background and aims – In Katanga (D. R. Congo), outcrops of bedrocks naturally enriched in Cu and Co ("copper hills"), host unique plant communities. The spatial variation of vegetation has long been attributed almost exclusively to variation in Cu concentration in the soil, but this assumption has not been experimentally tested. We analysed the variation in plant communities and the niches of selected species in relation to edaphic factors within a copper hill. Methods – Forty-eight 1 m2 plots were sampled for plant community and soil mineral element composition, and classified with Unweighted Pair Group Method with Arithmetic mean (UPGMA) using the Bray-Curtis distance. Plant-edaphic relationships were examined using a Canonical Correspondence Analysis (CCA). Species niches were modelled with Generalized Additive Model (GAM). Mean edaphic factors between the soil of plant communities were compared with one-way Kruskal-Wallis non-parametric ANOVA. Key results – The diversity of communities at the site scale was higher than observed in previous studies at a larger scale. Cu was the most discriminating edaphic factor of plant communities. However, detailed comparisons of mean edaphic factors among communities revealed individual combinations of edaphic parameters for each community, as well as differences in soil Cu content. High covariation appears to be an essential trait of the edaphic factor variation of Katangan Cu-rich soils. This makes it difficult to examine separately the effect of these factors on plant community structures. A bimodal pattern of niche distribution was found for Cu and pH. For physical parameters, niche optima were normally distributed. Conclusions – Global variation in edaphic factors associated with variation in combinations of edaphic parameters generates a highly heterogeneous environment favourable to a high diversity of plant communities over limited areas. Conservation strategies or restoration actions to limit the impact of mining activities on Cu-enriched ecosystems should pay special attention to recreate heterogeneity, taking into account the covariation of edaphic factors. [less ▲]

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See detailImportance de la méthode de coupe sur la régénération de Combretaceae du Bassin arachidier sénégalais
Faye, E; Diallo, H; Samba, SAN et al

in Tropicultura (2013), 31(1), 44-52

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See detailApport de la surface terrière dans la dénomination des formations végétales dominées par le tapia (Uapaca bojeri) à Madagascar
Malaisse, François ULg; Rakotondrasoa, Olivia; Rakotoniaina, R.T. et al

in Verheggen, François; Bogaert, Jan; Haubruge, Eric (Eds.) Les vers à soie malgaches. Enjeux écologiques et socio-économiques. (2013)

Après avoir rappelé l’intérêt transcendant d’Uapaca bojeri, essence endémique malgache, pour les populations locales et avoir défini l’importance des apports écosystémiques des formations végétales où ... [more ▼]

Après avoir rappelé l’intérêt transcendant d’Uapaca bojeri, essence endémique malgache, pour les populations locales et avoir défini l’importance des apports écosystémiques des formations végétales où cette essence domine, la diversité des dénominations concernant ces dernières est mise en évidence et les causes sous-jacentes en sont analysées. Une situation analogue a été observée antérieurement pour les forêts claires de type miombo en Afrique continentale ; le concept de surface terrière a constitué pour ces dernières un apport pertinent et a autorisé une typologie valorisante des dénominations. Dès lors, l’application du concept de surface terrière aux formations végétales à dominance de tapia est examinée et son apport éventuel discuté. Un système original est proposé. [less ▲]

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