References of "Piqueray, Julien"
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See detailRapid restoration of a species-rich ecosystem assessed from soil and vegetation indicators: the case of calcareous grasslands restored from forest stands
Piqueray, Julien ULg; Bottin, Gaëtan; Delescaille, Louis-Marie et al

in Ecological Indicators (2011), 11

Calcareous grasslands have long been recognized as biodiversity hotspots in Europe. However, in recent decades these ecosystems have seen rapid decline. In Belgium, more than 100 ha of calcareous ... [more ▼]

Calcareous grasslands have long been recognized as biodiversity hotspots in Europe. However, in recent decades these ecosystems have seen rapid decline. In Belgium, more than 100 ha of calcareous grasslands have been restored from oak coppices and pine forests since the 1990s. The aim of the present study was to provide a quantitative assessment of the success of these restoration efforts, using two sets of indicators: one related to soil conditions, the other related to vascular plant communities. Soil conditions were evaluated by comparing soil samples from pre-restoration forest stands, restored grasslands (3 age classes: 2-4 years; 5-8 years, 10-15 years) and reference grasslands. The analysis revealed no significant differences in soil N, P and K contents between pre-restoration forests and restored and reference grasslands. We observed a decrease in the mineralization rate indicators in both pre-restoration forests and recent grassland restorations, which was resorbed in older restorations. Floristic surveys revealed that plant species composition of older restorations was most like reference grasslands. However, some differences in species composition persisted after 15 years. Moreover, a few rare species did not colonise restored grasslands despite a close seed source. Non-recolonization by a set of species expected on calcareous grasslands may be due to dispersal limitation and higher cover by native invasive grasses in restored parcels. These results were discussed in term of implications for management. [less ▲]

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See detailCotoneaster horizontalis on calcareous grasslands in Belgium : from ornament to management
Frisson, Gwenn ULg; Piqueray, Julien ULg; Halford, Mathieu ULg et al

Poster (2010, September)

Cotoneaster horizontalis DECAISNE, a Rosaceae coming from Asia, was introduced in Belgium as an ornamental species. Different sides of the invasion were studied, from the distribution of the species and ... [more ▼]

Cotoneaster horizontalis DECAISNE, a Rosaceae coming from Asia, was introduced in Belgium as an ornamental species. Different sides of the invasion were studied, from the distribution of the species and the invasion status, the impacts, to management methods. To describe the invasion status, information was gathered about the occurrence and the distribution of the species in Belgium by compiling various databases. The naturalization status in calcareous grasslands, high-value habitats recognized as biodiversity hotspots, was assessed. Occurrence, population status, preferred habitats, invaded communities, growth rate and fruiting capacity were characterized. Once naturalization established, we investigated its impacts on calcareous grasslands communities, individual species and pollinators. C. horizontalis occurred in seven of the nine studied calcareous grasslands, with densities from 0.34 to 10 individuals/ha. In the most invaded sites, an ongoing colonization process was suggested by a high proportion of small individuals. Moreover, 3-year-old individuals already showed fruiting capacities. Germination rate reached about 30%. Significant impacts on habitat structure and vegetation were showed. Community structure and composition changes were demonstrated in invaded sites by decreasing species richness and diversity. As calcareous grasslands are priority Natura2000 habitats, measures must be taken to control the spread of C. horizontalis. For this purpose, we performed management tests to identify the most efficient techniques that would help the restoration of calcareous grasslands. Both mechanical and chemical management techniques were tested. Methods choice was driven by the environmental constraints of calcareous grasslands, which require highly selective techniques, and by species characteristics. Tested methods were cuttings, stump burning, spraying, cutting plus glyphosate application on stump and glyphosate application on stem basis. Efficiency, cost, feasibility and side-effects on ecosystems were estimated. Management tests are still ongoing but some results have already been drawn: spraying and single cutting are not efficient, the last one generating production of numerous sprouts. Finding the best management method will not be sufficient to stop the invasion. C. horizontalis is still present in 53% of the sale catalogs of horticulturists in Southern Belgium. As long as the species is used in the vicinity of calcareous grasslands, propagules are continuously provided, jeoparding management actions. [less ▲]

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See detailSoil-plants relations diversity in extreme ecsystems and implications for restoration: the case of the cupriferous vegetation, in Katanga, D.R. Congo
Seleck, Maxime ULg; Guillaume, Arielle; Lebrun, Julie ULg et al

Conference (2010, August 25)

Katangan copper and cobalt hills in the D. R. Congo are isolated ecosystems on highly toxics substrates (>10.000 ppm Cu, with strongly marked gradients). As a result, those outcrops host singular vegetal ... [more ▼]

Katangan copper and cobalt hills in the D. R. Congo are isolated ecosystems on highly toxics substrates (>10.000 ppm Cu, with strongly marked gradients). As a result, those outcrops host singular vegetal communities – with a diversity of specialized metallophytes species – related to soil metals content. Recent resumption of mining activities in the area threatens those ecosystems. To allow the restoration of those communities a fine understanding of the relationship maintained with the edaphic factors is required, as well as a characterization of the intra and inter sites variation. Three outcrops have been studied on the basis of a systematic grid, following the a priori trace elements gradient. In 1m² quadrats, a composite soil sample (0-15 cm depth) was taken and the cover (%) of each species of vascular plants was recorded. Soils were analyzed for pH, C, N, and bioavailables Cu, Co, Zn, Mn, Fe, K, Mg, Ca and P. The cluster analysis and Canonical Correspondence Analysis show that different sites present different soil conditions and vegetation. Concentrations in Cu are an important explicative factor of the flora’s variation but gradients in others edaphic parameters (pH, Mg, Mn, K, Ca) appear to be essential. However, parameters explaining the diversity of communities vary from one site to another indicating a great diversity of those ecosystems and the need to develop restoration strategies relevant for each site. [less ▲]

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See detailDiversité des relations sol plantes dans les écosystèmes extrémophiles et implications pour la restauration : le cas des végétations cupricoles du Katanga, RDC.
Seleck, Maxime ULg; Lebrun, Julie ULg; Guillaume, Arielle ULg et al

Conference (2010, March 31)

Les collines de cuivre et de cobalt du Katanga (RDC) sont des milieux isolés présentant des substrats hautement toxiques (>10.000 ppm cuivre, gradients très marqués). De ce fait, ces gisements hébergent ... [more ▼]

Les collines de cuivre et de cobalt du Katanga (RDC) sont des milieux isolés présentant des substrats hautement toxiques (>10.000 ppm cuivre, gradients très marqués). De ce fait, ces gisements hébergent des communautés végétales originales, avec une diversité d’espèces métallophytes spécialisées, en relation étroite avec la concentration en métaux du sol. La récente reprise des activités minières dans la région menace grandement ces écosystèmes. La restauration de ces communautés végétales nécessite une compréhension fine des relations entretenues avec leur environnement édaphique et la caractérisation de la diversité intra et inter sites de ces communautés. Trois gisements ont fait l’objet d’une étude détaillée sur base d’un échantillonnage systématique en fonction du gradient à priori d’ETM. Dans des placette de 1m², un échantillon composite de sols a été prélevé à deux profondeurs : 0-15 cm et 30-45 cm et analysé pour : pH, Corg, N tot, Cu, Co, Zn, Mn, Fe, K, Mg, Ca et P biodisponibles. L’abondance des espèces présentes au sein des quadrats a été mesurée selon leur pourcentage de recouvrement. L’analyse en groupement et la mise en relation flore-sol par les méthodes de CCA indiquent que les sites présentent des conditions de sol et des végétations bien différenciées bien que les deux mêmes formations sont présentes. Les concentrations en cuivre sont un facteur explicatif important de la variation de la flore mais d’autres paramètres édaphiques s’avèrent également essentiels (Mg, Mn, K, Ca). Toutefois la sélection des paramètres édaphique expliquant la variation de la flore diffère d’un site à l’autre indiquant la grande diversité de ces écosystèmes et la nécessité de développer des approches de restauration spécifiques à chaque site. [less ▲]

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See detailColonization Credit in Restored Wet Heathlands
Cristofoli, Sara ULg; Piqueray, Julien ULg; Dufrêne, Marc ULg et al

in Restoration Ecology (2010), 18(5), 645-655

Although human-driven landscape modification is generally characterized by habitat destruction and fragmentation, it may also result in the creation of new habitat patches, providing conditions conducive ... [more ▼]

Although human-driven landscape modification is generally characterized by habitat destruction and fragmentation, it may also result in the creation of new habitat patches, providing conditions conducive to spontaneous colonization. In this article, we propose the concept of ‘‘colonization credit’’ (i.e., the number of species yet to colonize a patch, following landscape changes) as a framework to evaluate the success of colonization, in terms of species richness, in new/restored habitats, taking into account the spatial structure of landscapes. The method mirrors similar approaches used to estimate extinction debt in the context of habitat fragmentation, that is, comparisons, between old and new habitat patches, of the relationships among spatial patch metrics and patch species richness. We applied our method to the case of spontaneous colonization of newly created habitat patches suitable for wet heathland plant communities in South Belgium. Colonization credit was estimated for the total species richness, the specialist species richness, and the species richness of three emergent groups (EGs) of specialist species, delineated on the basis of dispersal traits. No significant colonization credit was identified either in patches created 25–55 years ago or in those created within the past 25 years, with the exception of species from our first EG (mostly anemochorous species with long-term persistent seed bank). However, the differential response of species in that first EG could not be explained through their characteristic life history traits. The results of this study are encouraging and suggest that deliberate, directed restoration activities could yield positive developments in a relatively short period of time. [less ▲]

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See detailIdentification des menaces sur la diversité floristique des pelouses calcicoles de Belgique et opportunités pour la restauration : de l'espèce au paysage
Piqueray, Julien ULg

Doctoral thesis (2010)

Current human activities can be responsible either of the loss or promotion of biodiversity at the regional scale. The study of the influence of human activities on patterns of biological diversity is ... [more ▼]

Current human activities can be responsible either of the loss or promotion of biodiversity at the regional scale. The study of the influence of human activities on patterns of biological diversity is therefore of primary importance in order to set up conservation strategies. We studied the influence of human activities on calcareous grassland floristic diversity in Belgium. During the past century, a high fragmentation of this habitat occurred within the study region. There was a delay between the process of fragmentation and the subsequent response in terms of species richness, which created an “extinction debt” in remnant calcareous grasslands. Although fragmentation was the main process involved, we also showed that some new habitat patches were created thanks to human activities during this period. These new habitat patches exhibited a species richness and composition that was found similar to old habitat patches. In the face of fragmentation, restoration programs were launched in the study region. Restored areas exhibited similar soil conditions as compared to reference grasslands. Plant species communities found in the oldest restorations tend to resemble reference grassland communities. However, some differences in species composition persisted after 15 years. It was also shown that some species did not colonize restored sites at all. With this respect, seed and germination microsite availability could be limiting factors for the colonization of restored sites. However, the absence or the lower colonization in restored areas compared to reference grasslands following seed addition and disturbance suggested that habitat quality could be considered as lower in restored habitats. Our results suggest therefore that restoration effort should be maintain in the study site. This effort is not vain as many species are able to colonize newly created sites. Finally, another threat to calcareous grasslands was studied i.e. the naturalization of the ornamental species Cotoneaster horizontalis. The analysis revealed that, although being at an early stage of naturalization, the species had an impact on vegetation structure and composition and on grassland diversity. Trade limitation for this species should be promoted in addition to management. [less ▲]

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See detailRevue bibliographique sur la restauration des pelouses calcicoles en Europe : contraintes rencontrées et solutions proposées
Piqueray, Julien ULg; Mahy, Grégory ULg

in Biotechnologie, Agronomie, Société et Environnement = Biotechnology, Agronomy, Society and Environment [=BASE] (2010), 14(3), 471-484

Calcareous grasslands, that are considered as biodiversity hotspots in Europe, have suffered an important decline during the last century. In this context, restoration of suitable habitats has been ... [more ▼]

Calcareous grasslands, that are considered as biodiversity hotspots in Europe, have suffered an important decline during the last century. In this context, restoration of suitable habitats has been promoted as a conservation strategy. Restoration consists in the recreation of favourable abiotic and biotic conditions that permit the recolonization by typical species. Depending on the degradations, several constraints can be encountered during restoration, such as soil enrichment, the presence of competitive species, or harsh conditions for plant growth. In order to overcome these constraints, scientists have proposed techniques that were demonstrated to be more or less efficient. In this article, the different constraints that can occur while restoring calcareous grasslands are described as well as the techniques proposed in the scientific literature. We also describe restoration objectives specific to calcareous grasslands, taking the history of these habitats into account and considering global change issue. Different parameters can be considered to value restoration success. Here again, an analysis of the scientific literature is needed in order to best assess restoration monitoring. [less ▲]

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See detailExtinction debt and colonization credit: When both phenomena are integrated
Piqueray, Julien ULg; Cristofoli, Sara; Bisteau, Emmanuelle et al

Conference (2010)

Calcareous grasslands are among the most species-rich ecosystems in temperate countries. These ecosystems suffered a high fragmentation process during the last century. Fragmentation can lead to the ... [more ▼]

Calcareous grasslands are among the most species-rich ecosystems in temperate countries. These ecosystems suffered a high fragmentation process during the last century. Fragmentation can lead to the creation of an extinction debt in remaining habitat patches. In our study site, it was shown in a previous study that Fragmented habitat patches (area loss since 1965 >80%) exhibited an extinction debt in comparison to Stable habitat patches (area loss since 1965 <80%). However, human activities also created new habitat patches in the landscape and provided therefore opportunities for calcareous grassland plant species to colonize new sites. They also provide opportunities for studying species colonization abilities in the context of habitat restoration. We analyzed species richness in these new patches in comparison to old patches in order to detect colonization credit. When taking as reference Fragmented patches (that exhibit an extinction debt) or all old patches (Fragmented and Stable), we concluded to the occurrence of a colonization credit in New patches. However, when the reference is Stable patches (the less likely to exhibit an extinction debt) alone, no colonization credit could be detected. Moreover, correspondence analysis revealed that New patches were similar to old patches in term of species composition. These results are encouraging for restoration programs. They also showed that the presence of an extinction debt in reference habitats can lead to mistaken conclusion in restoration monitoring. Extinction debt occurrence should be taken into account in the choice of reference habitats for evaluation of restoration success. [less ▲]

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See detailPlant species extinction debt in a biodiversity hotspot: community and species approaches
Piqueray, Julien ULg; Bisteau, Emmanuelle; Cristofoli, Sara et al

Conference (2009, April)

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See detailLe cotoneaster horizontal sur pelouses calcicoles: de l'ornement à la gestion
Piqueray, Julien ULg; Halford, Mathieu ULg; Massoz, Aurélie ULg et al

in Parcs & Réserves (2009), 64(4), 23-26

Detailed reference viewed: 45 (8 ULg)
See detailDette d'extinction dans un hotspot de biodiversité: approches communauté et espèces
Piqueray, Julien ULg; Bisteau, Emmanuelle; Cristofoli, Sara et al

Conference (2009)

Detailed reference viewed: 64 (5 ULg)
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See detailNaturalization and impact of a horticultural species, Cotoneaster horizontalis (Rosaceae) in biodiversity hotspots in Belgium
Piqueray, Julien ULg; Mahy, Grégory ULg; Vanderhoeven, Sonia

in Belgian Journal of Botany (2008), 141

Cultivation of ornamental plant species has been recognized to foster plant naturalization of exotics by counteracting environmental stochasticity and continuously providing propagules. As a preliminary ... [more ▼]

Cultivation of ornamental plant species has been recognized to foster plant naturalization of exotics by counteracting environmental stochasticity and continuously providing propagules. As a preliminary attempt to describe the invasion status of C horizontalis, we gathered information on the occurrence of the species in Belgium by compiling various databases. We assessed the naturalization status of C. horizontalis in Belgian calcareous grasslands, high-value habitats recognized as biodiversity hotspots, by characterizing its occurrence, population status, preferred habitats, invaded communities, growth rate and fruiting capacity. We also assessed the impact of the species on calcareous grasslands communities and on individual species. Cotoneaster occurred in seven of the nine investigated sites, with densities varying from 0.34 to 10 individuals/ha. In the most invaded sites, the high proportion of small individuals suggests an important ongoing colonization process, emphasized by the fact that fruiting capacities were demonstrated for 3-year-old individuals. Invaded habitats were typically Mosan Xerobromion habitats, which are priority Natura 2000 habitats. The presence of C horizontalis was associated with changes in both the structure and composition of the community by decreasing species richness and diversity, and affecting grassland specialist species. These impacts are expected to intensify over time with population age and increasing propagule pressure due to close urbanization. [less ▲]

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See detailPlant species extinction debt in a biodiversity hotspot: community and species approaches
Piqueray, Julien ULg; Bisteau, Emmanuelle ULg; Cristofoli, Sara ULg et al

in Belgian Journal of Botany (2008), 141(2), 189

Destruction and fragmentation of natural and semi-natural habitats are considered as major threats for plant species richness. However, the response of plant species richness to habitat alteration is ... [more ▼]

Destruction and fragmentation of natural and semi-natural habitats are considered as major threats for plant species richness. However, the response of plant species richness to habitat alteration is sometimes delayed. This delay induces an extinction debt in plant communities that are thus prone to undergo species extinctions in the following years. Several methodologies were proposed to detect this extinction debt and estimate the mean number of species yet to disappear. In this study, we developed a new methodology for the estimation of the extinction debt extent. Moreover, we proposed a species approach aimed at determining which species are more sensitive to extinction as a consequence of habitat destruction and fragmentation. Finally, we explored the colonization ability of habitat specialist species. This aspect is of fi rst importance to counteract local species extinctions. Our model habitat is calcareous grasslands of Southeast Belgium that have suffered an important fragmentation process since the beginning of the twentieth century. We estimated that the mean extinction debt of the calcareous grassland patches was ca. 24 species, including ca. six specialist species. We showed that 16 of the 46 specialist species did not meet their area requirement anymore and were therefore considered as sensitive to extinction. However, the species composition of the more recent grasslands indicates a non-negligible recolonization potential of specialist species. There is thus a real possibility to reduce extinction risk by restoring suitable habitats. [less ▲]

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See detailRestoration assessment of calcareous grasslands in Belgium : soil conditions and floristic diversity
Piqueray, Julien ULg; Bottin, Gaëtan; Bisteau, Emmanuelle et al

Conference (2008)

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See detailPlant communities and species richness of the calcareous grasslands in southeast Belgium
Piqueray, Julien ULg; Bisteau, Emmanuelle ULg; Bottin, Gaëtan et al

in Belgian Journal of Botany (2007), 140(2), 157-173

Calcareous grasslands are biodiversity hotspots in Western Europe. In Belgium, a number of phytosociological surveys have been realized in these habitats, but none covers the whole range of calcareous ... [more ▼]

Calcareous grasslands are biodiversity hotspots in Western Europe. In Belgium, a number of phytosociological surveys have been realized in these habitats, but none covers the whole range of calcareous grasslands at the regional scale. The aim of this study was (i) to provide a synthesis of the floristic variation of calcareous grasslands of the Calestienne natural region using a uniform methodology; (ii) to relate floristic variation to environmental variables, and (iii) to characterize the specific diversity of the different grassland communities that occur in the study region. Seven different communities were identified with the TWINSPAN method. The originality of the grasslands on calcareous and calcareo-siliceous rocks was statistically confirmed. Significant differences for environmental variables were identified among the seven communities by a MANOVA. Main differences between communities were related to xericity and pH, although a north-south gradient was also identified. More xeric grasslands were located in the southern part of the study region while northern part was occupied by more mesophilous grasslands. Multiple regressions were used to describe the influence of the environmental conditions on plant species richness. The most mesophilous grasslands appeared to be the most species-rich while soil acidity negatively affected species richness. [less ▲]

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