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On the relative role of abiotic and biotic controls on channel network development: insights from scaled tidal flume experiments
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Tidal marshes provide highly valued ecosystem services, which depend on variations in the geometric properties of the tidal channel networks dissecting marsh landscapes. The development and evolution of channel network properties are controlled by abiotic (dynamic flow-landform feedback) and biotic processes (e.g., vegetation-flow-landform feedback). However, the relative role of biotic and abiotic processes, and under which condition one or the other is more dominant, remains poorly understood. In this study, we investigated the impact of spatio-temporal plant colonization patterns on tidal channel network development through flume experiments. Four scaled experiments mimicking tidal landscape development were conducted in a tidal flume facility: two control experiments without vegetation, a third experiment with hydrochorous vegetation colonization (i.e., seed dispersal via the tidal flow), and a fourth with patchy colonization (i.e., by direct seeding on the sediment bed). Our results show that more dense and efficient channel networks are found in the vegetation experiments, especially in the hydrochorous seeding experiment with slower vegetation colonization. Further, an interdependency between abiotic and biotic controls on channel development can be deduced. Whether biotic factors affect channel network development seems to depend on the force of the hydrodynamic energy and the stage of the system development. Vegetation-flow-landform feedbacks are only dominant in contributing to channel development in places where intermediate hydrodynamic energy levels occur and mainly have an impact during the transition phase from a bare to a vegetated landscape state. Overall, our results suggest a zonal domination of abiotic processes at the seaward side of intertidal basins, while biotic processes dominate system development more towards the landward side.
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RBINS Staff Publications 2024
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Mangroves as nature-based mitigation for ENSO-driven compound flood risks in a river delta
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Densely populated coastal river deltas are very vulnerable to compound flood risks, coming from both oceanic and riverine sources. Climate change may increase these compound flood risks due to sea level rise and intensifying precipitation events. Here, we investigate to what extent nature-based flood defence strategies, through conservation of mangroves in a tropical river delta, can contribute to mitigate the oceanic and riverine components of compound flood risks. While current knowledge of estuarine compound flood risks is mostly focussed on short-term events such as storm surges (taking one or a few days), longer-term events, such as El Niño events (continuing for several weeks to months) along the Pacific coast of Latin America, are understudied. Here, we present a hydrodynamic modelling study of a large river delta in Ecuador aiming to elucidate the compound effects of El Niño driven oceanic and riverine forcing on extreme high water level propagation through the delta, and in particular, the role of mangroves in reducing the compound high water levels. Our results show that the deltaic high water level anomalies are predominantly driven by the oceanic forcing but that the riverine forcing causes the anomalies to amplify upstream. Furthermore, mangroves in the delta attenuate part of the oceanic contribution to the high water level anomalies, with the attenuating effect increasing in the landward direction, while mangroves have a negligible effect on the riverine component. These findings show that mangrove conservation and restoration programs can contribute to nature-based mitigation, especially the oceanic component of compound flood risks in a tropical river delta.
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RBINS Staff Publications 2024
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A global meta-analysis on the drivers of salt marsh planting success and implications for ecosystem services
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Planting has been widely adopted to battle the loss of salt marshes and to establish living shorelines. However, the drivers of success in salt marsh planting and their ecological effects are poorly understood at the global scale. Here, we assemble a global database, encompassing 22,074 observations reported in 210 studies, to examine the drivers and impacts of salt marsh planting. We show that, on average, 53% of plantings survived globally, and plant survival and growth can be enhanced by careful design of sites, species selection, and novel planted technologies. Planting enhances shoreline protection, primary productivity, soil carbon storage, biodiversity conservation and fishery production (effect sizes = 0.61, 1.55, 0.21, 0.10 and 1.01, respectively), compared with degraded wetlands. However, the ecosystem services of planted marshes, except for shoreline protection, have not yet fully recovered compared with natural wetlands (effect size = −0.25, 95% CI −0.29, −0.22). Fortunately, the levels of most ecological functions related to climate change mitigation and biodiversity increase with plantation age when compared with natural wetlands, and achieve equivalence to natural wetlands after 5–25 years. Overall, our results suggest that salt marsh planting could be used as a strategy to enhance shoreline protection, biodiversity conservation and carbon sequestration.
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RBINS Staff Publications 2024
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Vegetation controls on channel network complexity in coastal wetlands
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Channel networks are key to coastal wetland functioning and resilience under climate change. Vegetation affects sediment and hydrodynamics in many different ways, which calls for a coherent framework to explain how vegetation shapes channel network geometry and functioning. Here, we introduce an idealized model that shows how coastal wetland vegetation creates more complexly branching networks by increasing the ratio of channel incision versus topographic diffusion rates, thereby amplifying the channelization feedback that recursively incises finer-scale side-channels. This complexification trend qualitatively agrees with and provides an explanation for field data presented here as well as in earlier studies. Moreover, our model demonstrates that a stronger biogeomorphic feedback leads to higher and more densely vegetated marsh platforms and more extensive drainage networks. These findings may inspire future field research by raising the hypothesis that vegetation-induced self-organization enhances the storm surge buffering capacity of coastal wetlands and their resilience under sea-level rise.
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RBINS Staff Publications 2024
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Mangrove ecosystem properties regulate high water levels in a river delta
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Intertidal wetlands, such as mangroves in the tropics, are increasingly recognized for their role in nature-based mitigation of coastal flood risks. Yet it is still poorly understood how effective they are at attenuating the propagation of extreme sea levels through large (order of 100 km2) estuarine or deltaic systems, with complex geometry formed by networks of branching channels intertwined with mangrove and intertidal flat areas. Here, we present a delta-scale hydrodynamic modelling study, aiming to explicitly account for these complex landforms, for the case of the Guayas delta (Ecuador), the largest estuarine system on the Pacific coast of Latin America. Despite coping with data scarcity, our model accurately reproduces the observed propagation of high water levels during a spring tide. Further, based on a model sensitivity analysis, we show that high water levels are most sensitive to the mangrove platform elevation and degree of channelization but to a much lesser extent to vegetation-induced friction. Mangroves with a lower surface elevation, lower vegetation density, and higher degree of channelization all favour a more efficient flooding of the mangroves and therefore more effectively attenuate the high water levels in the deltaic channels. Our findings indicate that vast areas of channelized mangrove forests, rather than densely vegetated forests, are most effective for nature-based flood risk mitigation in a river delta.
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RBINS Staff Publications 2024
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Influence of an urbanization gradient on the vertical stratification of arboreal ants in green areas
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EVALUATION OF DIFFERENT TAXONOMIC LEVELS AS SURROGATES OF ANT DIVERSITY IN GREEN AREAS IN AN URBANIZED ENVIRONMENT E. B. A. KOCH1, T. S. MELO2,3,4, A. R. S. ANDRADE2,3, M. LEPONCE5 & J. H. C. DELABIE2,4 1Programa de Pós-graduação em Ecologia e Evolução, Universidade Estadual de Feira de Santana (UEFS), CEP: 44.036-900 - Feira de Santana, Bahia, Brazil, e-mail: elmoborges@gmail.com; 2Programa de Pós-graduação em Ecologia, Universidade Federal da Bahia (UFBA), Salvador, Bahia, Brazil; 3Centro de Ecologia e Conservação Animal, Universidade Católica do Salvador (UCSal), Salvador, Bahia, Brazil; 4Laboratório de Mirmecologia, Convênio Universidade Estadual de Santa Cruz (UESC)/Comissão Executiva do Plano da Lavoura Cacaueira (CEPLAC), Ilhéus, Bahia, Brazil; 5Biodiversity Monitoring & Assessment, Royal Belgian Institute of Natural Sciences (RBINS), Bruxelas, Belgium. In cities located in environments of high biological importance, urbanization leads to changes in biotic diversity, while monitoring these changes can be difficult. Studies have pointed to the use of metrics that replace species as an alternative. Surrogate models are easily determined measures of biodiversity that correlate strongly with species richness and with what you want to investigate, being useful for detecting or monitoring environmental changes. The use of higher taxonomic levels has been applied to groups of megadiverse organisms, such as arthropods, since difficulties in identifying species are predictable. The aim of this study was to evaluate the practicality of using taxonomic diversity of ants as a surrogate of green area coverage in an urban environment. Four levels of "surrogate resolutions" (subfamily, genus, indicator taxa, and intermediate resolution) were assessed to the taxonomic diversity of ants across three levels of urban green areas (Small = 0 to 35%
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RBINS Staff Publications 2023
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Evaluation of different taxonomic levels as surrogates of ant diversity in green areas in an urbanized environment
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EVALUATION OF DIFFERENT TAXONOMIC LEVELS AS SURROGATES OF ANT DIVERSITY IN GREEN AREAS IN AN URBANIZED ENVIRONMENT E. B. A. KOCH1, T. S. MELO2,3,4, A. R. S. ANDRADE2,3, M. LEPONCE5 & J. H. C. DELABIE2,4 1Programa de Pós-graduação em Ecologia e Evolução, Universidade Estadual de Feira de Santana (UEFS), CEP: 44.036-900 - Feira de Santana, Bahia, Brazil, e-mail: elmoborges@gmail.com; 2Programa de Pós-graduação em Ecologia, Universidade Federal da Bahia (UFBA), Salvador, Bahia, Brazil; 3Centro de Ecologia e Conservação Animal, Universidade Católica do Salvador (UCSal), Salvador, Bahia, Brazil; 4Laboratório de Mirmecologia, Convênio Universidade Estadual de Santa Cruz (UESC)/Comissão Executiva do Plano da Lavoura Cacaueira (CEPLAC), Ilhéus, Bahia, Brazil; 5Biodiversity Monitoring & Assessment, Royal Belgian Institute of Natural Sciences (RBINS), Bruxelas, Belgium. In cities located in environments of high biological importance, urbanization leads to changes in biotic diversity, while monitoring these changes can be difficult. Studies have pointed to the use of metrics that replace species as an alternative. Surrogate models are easily determined measures of biodiversity that correlate strongly with species richness and with what you want to investigate, being useful for detecting or monitoring environmental changes. The use of higher taxonomic levels has been applied to groups of megadiverse organisms, such as arthropods, since difficulties in identifying species are predictable. The aim of this study was to evaluate the practicality of using taxonomic diversity of ants as a surrogate of green area coverage in an urban environment. Four levels of "surrogate resolutions" (subfamily, genus, indicator taxa, and intermediate resolution) were assessed to the taxonomic diversity of ants across three levels of urban green areas (Small = 0 to 35%
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RBINS Staff Publications 2023
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Importance of green area rate nesting site and exotic species on native ants in an urban environment
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EVALUATION OF DIFFERENT TAXONOMIC LEVELS AS SURROGATES OF ANT DIVERSITY IN GREEN AREAS IN AN URBANIZED ENVIRONMENT E. B. A. KOCH1, T. S. MELO2,3,4, A. R. S. ANDRADE2,3, M. LEPONCE5 & J. H. C. DELABIE2,4 1Programa de Pós-graduação em Ecologia e Evolução, Universidade Estadual de Feira de Santana (UEFS), CEP: 44.036-900 - Feira de Santana, Bahia, Brazil, e-mail: elmoborges@gmail.com; 2Programa de Pós-graduação em Ecologia, Universidade Federal da Bahia (UFBA), Salvador, Bahia, Brazil; 3Centro de Ecologia e Conservação Animal, Universidade Católica do Salvador (UCSal), Salvador, Bahia, Brazil; 4Laboratório de Mirmecologia, Convênio Universidade Estadual de Santa Cruz (UESC)/Comissão Executiva do Plano da Lavoura Cacaueira (CEPLAC), Ilhéus, Bahia, Brazil; 5Biodiversity Monitoring & Assessment, Royal Belgian Institute of Natural Sciences (RBINS), Bruxelas, Belgium. In cities located in environments of high biological importance, urbanization leads to changes in biotic diversity, while monitoring these changes can be difficult. Studies have pointed to the use of metrics that replace species as an alternative. Surrogate models are easily determined measures of biodiversity that correlate strongly with species richness and with what you want to investigate, being useful for detecting or monitoring environmental changes. The use of higher taxonomic levels has been applied to groups of megadiverse organisms, such as arthropods, since difficulties in identifying species are predictable. The aim of this study was to evaluate the practicality of using taxonomic diversity of ants as a surrogate of green area coverage in an urban environment. Four levels of "surrogate resolutions" (subfamily, genus, indicator taxa, and intermediate resolution) were assessed to the taxonomic diversity of ants across three levels of urban green areas (Small = 0 to 35%
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RBINS Staff Publications 2023
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Chièvres/Chièvres : témoins archéobotaniques d'un tannage végétal complexe à l'époque contemporaine
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Entre 2013 et 2015, une opération d'archéologie préventive d'envergure a été menée dans la commune de Chièvres par le Service Archéologique de Wallonie. Lors des travaux d’installation du collecteur d’eaux usées pour la station d’épuration, deux cuves d’une tannerie datant du 19ème siècle ont été découvertes. L'une des deux cuves a pu faire l’objet d’une fouille exhaustive et son remplissage a livré des matériaux organiques propices aux études archéobotaniques. Celles-ci ont été entreprises afin d'éclairer le fonctionnement de la tannerie et de fournir des informations sur le type de tannage utilisé. Le tannage est l'opération qui consiste à transformer la peau en cuir grâce aux tanins ; ces substances de différentes natures (végétales, minérales ou combinées) permettent la transformation d'une peau putrescible en un matériau durable et imputrescible. Sans surprise, les assemblages polliniques enregistrent de nombreux taxons riches en tanin tels que les arbres forestiers chêne, hêtre et châtaignier, et les fruitiers de type Prunus sp.. Parallèlement, des écorces de feuillus indéterminés ont été trouvées au sein des macrorestes végétaux. Ont aussi été identifiés dans les spectres polliniques certaines espèces herbacées (Artemisia, Plantago, Filipendula) et d'autres microfossiles intéressants, qui ont également pu jouer un rôle dans le processus de tannage étant donné leurs propriétés astringentes, antiseptiques, ou encore colorantes. Mais les découvertes les plus frappantes concernent le matériel carpologique avec l’identification de nombreux noyaux de dattes (Phoenix dactylifera) et de noyaux très fragmentés de Myrobolan ou cadou (Terminalia chebula), deux espèces exotiques importées. Autant la présence de la datte suscite des interrogations, autant la présence du Myrobolan ou cadou a toute sa place dans ce contexte. En effet, dès le début du 20ème siècle, le fruit séché du Myrobolan est l'une des matières tannantes les plus connues, exportée de manière considérable, principalement de Bombay (Brandis 1906). Au cours de cette présentation, nous essayerons également de reconstituer, ou tout du moins d'appréhender, le mode de tannage pratiqué à Chièvres, grâce aux analyses des micro- et macro-restes botaniques retrouvés. De plus, sur la base de recherches historiques et archivistiques, nous tenterons de comprendre l'importation, la distribution et l'utilisation du cadou en Belgique à l'époque contemporaine.
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RBINS Staff Publications 2024
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Predynastic and Early Dynastic plant economy in the Nile Delta: archaeobotanical evidence from Tell el-Iswid
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The large-scale excavation at the prehistoric site of Tell el-Iswid made it possible to undertake a systematic archaeobotanical study of different structures covering the Predynastic and Early Dynastic period (Lower Egyptian Cultures (Buto II) to Naqada III Culture. Here we present the results of the analysis of carpological remains preserved mostly in charred state and coming from 62 samples processed by manual flotation, with total volume of 615 litres and containing a total of 9672 identifiable and quantifiable items. Further ca. 650 wood fragments (or woody vegetative remains) were subject to anthracological analysis. Besides the aim of overall characterising and exploring the plant economy of the site, the macrobotanical assemblages were also considered in relation to the structures from which they were uncovered. The study revealed that the agricultural economy of both studied periods relied on emmer, barley, lentils, and pea, but from the Early Dynastic times onwards also flax and condiments (like Anethum graveolens and cf. Origanum sp.) played a certain role. Together with the cultivated fields also the surrounding wetlands were an important part of the plant resources utilized at site. The stems of Phragmites are also the most common among the anthracological remains, together with a small proportion of Tamarix and Acacia charcoal fragments. The overall composition of the plant assemblages (charred and mineralised chaff, small weed or wild growing seeds capable to pass the herbivore digestion, dung fragments, awns) suggest that the major source of the retrieved plant remains was dung fuel.
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RBINS Staff Publications 2023 OA
