Search

International audience; Dans les zones où la pression foncière est forte, l’espace disponible pour les forêts riveraines (ripisylves) est souvent réduit, et les endiguements et protections de berges associées sont fréquents. La place disponible pour la préservation ou la restauration d’un espace de mobilité pour le cours d’eau est ainsi souvent limitée. Des aménagements sont construits dans l’objectif de protéger les enjeux humains (habitations, infrastructures...) des risques d’érosion et d’inondation. D’une façon générale, les ouvrages de protection de berge sont de trois types : les ouvrages de génie civil constitués de maçonneries en pierre ou en béton, de gabions ou d’enrochements ; les ouvrages de génie végétal constitués de végétaux vivants et qui utilisent les caractéristiques des plantes pour protéger les berges contre l’érosion ; et les ouvrages mixtes qui associent ces deux techniques.Le génie végétal fait l’objet de multiples travaux de recherche depuis de nombreuses années. Mais qu’est-ce que le génie végétal ? Quels sont les avantages des ouvrages en génie végétal pour la biodiversité par rapport à d’autres techniques ? Quelle est leur résistance mécanique ? Quelles préconisations peut-on formuler en ce qui concerne leur entretien ? Cette publication a pour objectif d’apporter des éléments de réponse à ces questions.

International audience; In neotropical area, soil bioengineering techniques, using vegetation to protect embankments from the problems associated with erosion, are currently developing. They remain to be adapted in the Caribbean islands where the lack of knowledge on native species constrain their implementation. Among species presenting a high potential for soil bioengineering, legumes trees appear particularly relevant. Indeed, various species are used in tropical restoration programs because of their ability to improve soil quality and their ecological tolerance. Thus, legume trees appear particularly interesting in a soil bioengineering context where designs are often implemented in poor and degraded soils. Among the Caribbean Island hotspot, Guadeloupe shows a remarkable biodiversity and 40 native legume tree species are harbored in 34 types of ecosystems. In the context of global change and the erosion of biodiversity, conserving and restoring degraded ecosystems, particularly those under anthropogenic pressure such as riparian areas, must become a priority. Soil bioengineering techniques can be efficient tools to reestablish successional trajectories. The breadth of indigenous legumes tree species richness carries the promise of finding suitable species for the development of such techniques in Guadeloupe.In order to provide tools for the use of legumes tree in soil bioengineering in the Caribbean, germination, growth, morphological traits and traces of herbivory were assessed during the first stage of development. Five native legumes trees species (Inga ingoides, Inga laurina, Lonchocarpus heptaphyllus, Lonchocarpus roseus, Pterocarpus officinalis) adapted to riverine environments of different ecosystems (Swamp forest, Seasonal evergreen forest, Rainforest) were selected. Thirty seeds per species were sown in nursery. Germination rate, herbivory injuries, survival, growth, root traits, shoot and root biomass were measured on 3-month-old seedlings. A Principal Component Analysis and Kruskal-Walis tests were conducted to test interspecific differences.All the species have shown high germination and survival rate but distinct performance and traits were observed. Lonchocarpus heptaphyllus appeared to be the most sensitive species to herbivory and also shown the lower growth rate with the less developed root system. L. roseus, a critical endangered species, invested in its aerial parts more than in its root system. Inga ingoides and Inga laurina have shown a fast growth rate and a fast root development. Pterocarpus officinalis had the highest growth rate with a fastest development of its root system.The selected legume tree species presented characteristics compatible with a use in soil bioengineering in Guadeloupe and in the Caribbean at large.

International audience; To respond to societal needs on erosion risk prevention and to guarantee the safety of human investments, local authorities must carry out works to protect the banks of watercourses and the slopes of gullies. These constructions are usually made of civil engineering mostly pure or concrete riprap. These techniques have a strong negative impact on riparian ecosystems. Soil bioengineering represents a softer and environmentally friendly option. In the Caribbean islands biodiversity hotspot, the natural flora of riverine network system has hardly been studied and native species are still poorly used in soil bioengineering. The lack of knowledge of the structure of riparian flora and the need for their restoration in Guadeloupe led to the emergence of the “Proteger” project in 2015 to develop and promote soil bioengineering techniques on riverbank of this territory and around. The first phase of this project (2016-2018) aimed to describe the riparian plant assemblages, and to identify the most suitable local species to maintain riverbanks. The second phase of the project (2019-2022) consists in controlling the multiplication of these species. We conducted a first ex situ experiment aiming to evaluate the vegetative propagation potential of cuttings from thirty-two native species. Experimental conditions were compatibles with soil bioengineering works settlement. Our results indicate that among the selected species, propagation of three trees, four shrubs and three herbs species can be controlled in low tech conditions, allowing the development of soil bioengineering techniques in Guadeloupe and in the Caribbean.

International audience; To guarantee the safety of property and people, Guadeloupe local authorities must carry out work to protect the banks of watercourses and gullies. In most cases, these constructions are made of pure or concrete riprap. Although these civil engineering techniques are well managed and sometimes indispensable, they have a strong negative impact on the functioning of riparian ecosystems. In relation to civil engineering, soil bioengineering represents a softer and more respectful option, from an environmental and landscape perspective, and is also generally less expensive. Soil bioengineering is both an old and innovative solution based on nature: its implementation imitates effective natural models to control and prevent erosion. In the West Indies, the natural flora of riverine network system has hardly been studied and local species are still not used extensively in the work of protecting watercourse. The lack of knowledge of riparian ecosystems in Guadeloupe led to the emergence of the “Proteger” project in 2015 to promote soil bioengineering techniques on riverbank of this territory. The first phase of this project (2016-2018) aimed to identify the thirty local species most suited to maintain riverbanks. Trees, shrubs, ferns and herbs owning to different riparian ecosystems were therefore selected.The second phase of the project (2019-2022) consists of control propagation of these species, in order to feed bioengineering works. Three different interconnected experimentations concerning germination ability, stem cuttings propagation, growth and development of seedlings of the selected species have been designed on a complex conceptual framework. Because stem cutting propagation is widely used for bioengineering works and because it represents a low cost, fast and effective way to obtain plant material, we conducted a first experiment aiming to evaluate the stem cutting propagation potential of twenty-six ligneous species. This communication presents cutting ability of these Antillean riverine forest species.

One of the major challenges in forest ecology is to understand the ecology, physiology and potential responses of the> 250000 species of vascular plants of the planet through the categorization of this diversity into functional groups. This approach is essentially based on functional traits analysis, but few investigations were made in tropical areas. The aim of this study was to determine functional groups in two contrasted tropical ecosystems, dry (DF) and mountain rain (MRF) forest (respectively rainfall of 1 200 mm/year and 10 000 mm/year). Guadeloupe Island in FWI presents both these ecosystems spread over less 100 km. In a first time, we developed an original species typology based on 7 "soft" traits, easy to measure (stomatal density, leaf trichom density, chlorophyll content, leaf nitrogen content, specific leaf area, wood density, leaf area, plant height). The method was based on principal component analysis (PCA) and agglomerative hierarchical clustering (AHC) applied to these traits measured at the individual level (Blazy et al., 2009). In a second time, we evaluated the relevance of these soft trait-based groups compared to a typology based on 5 "hard" ecophysiological traits, more costly to quantify but with higher functional significance (difference between predawn and minimum leaf water potential, stomatal conductance, maximal carbon assimilation rate, leaf water potential at 90% of loss of stem hydraulic conductivity). When performed on the dominant canopy species in DF and MRF (a total of 13 species and 60 mature individuals), the typological approach based on soft traits seems relevant to discriminate groups with a distinct functional reality. Through both ecosystems, we obtained 4 homogenous groups. Two were exclusively composed by DF's or MRF's species, indicating that a functional strategy can be linked to specific environmental conditions. The two other groups showed a mix of DF and MRF species indicating that different functional strategies can coexist in the same environment. These mixed groups seem distinct by their ecophysiological features, particularly in term of hydraulic characteristics. One group was composed by drought tolerant species, water spender species, with a high xylem embolism resistance, whereas the second one was composed by water saver species, less resistant to embolism. Therefore, a determination of functional groups based on soft traits could be useful to model ecosystem's responses to environmental changes on a global scale.