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Talaga, S., Dezerald, O., Carteron, A., Petitclerc, F., Leroy, C., Céréghino, R., et al. (2015). Tank bromeliads as natural microcosms: A facultative association with ants influences the aquatic invertebrate community structure. Comptes Rendus – Biologies, 338(10), 696–700.
Abstract: Many tank bromeliads have facultative relationships with ants as is the case in French Guiana between Aechmea aquilega (Salib.) Griseb. and the trap-jaw ant, Odontomachus haematodus Linnaeus. Using a redundancy analysis, we determined that the presence of O. haematodus colonies is accompanied by a greater quantity of fine particulate organic matter in the water likely due to their wastes. This increase in nutrient availability is significantly correlated with an increase in the abundance of some detritivorous taxa, suggesting a positive bottom-up influence on the aquatic macroinvertebrate communities living in the A. aquilega wells. On the other hand, the abundance of top predators is negatively affected by a lower number of available wells due to ant constructions for nesting, releasing a top-down pressure that could also favor lower trophic levels. © 2015 Académie des sciences.
Keywords: Aechmea; Ant-bromeliad associations; Aquatic communities; Odontomachus; Phytotelm
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Rutishauser, E., Herault, B., Baraloto, C., Blanc, L., Descroix, L., Sotta, E. D., et al. (2015). Rapid tree carbon stock recovery in managed Amazonian forests. Current Biology, 25(18), R787–R788.
Abstract: Summary While around 20% of the Amazonian forest has been cleared for pastures and agriculture, one fourth of the remaining forest is dedicated to wood production [1]. Most of these production forests have been or will be selectively harvested for commercial timber, but recent studies show that even soon after logging, harvested stands retain much of their tree-biomass carbon and biodiversity [2,3]. Comparing species richness of various animal taxa among logged and unlogged forests across the tropics, Burivalova et al.[4] found that despite some variability among taxa, biodiversity loss was generally explained by logging intensity (the number of trees extracted). Here, we use a network of 79 permanent sample plots (376 ha total) located at 10 sites across the Amazon Basin [5] to assess the main drivers of time-to-recovery of post-logging tree carbon (Table S1). Recovery time is of direct relevance to policies governing management practices (i.e., allowable volumes cut and cutting cycle lengths), and indirectly to forest-based climate change mitigation interventions. © 2015 Elsevier Ltd.
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Dejean, A., Groc, S., Herault, B., Rodriguez-Pérez, H., Touchard, A., Céréghino, R., et al. (2015). Bat aggregation mediates the functional structure of ant assemblages. Comptes Rendus – Biologies, 338(10), 688–695.
Abstract: In the Guianese rainforest, we examined the impact of the presence of guano in and around a bat roosting site (a cave). We used ant communities as an indicator to evaluate this impact because they occupy a central place in the functioning of tropical rainforest ecosystems and they play different roles in the food web as they can be herbivores, generalists, scavengers or predators. The ant species richness around the cave did not differ from a control sample situated 500m away. Yet, the comparison of functional groups resulted in significantly greater numbers of detritivorous fungus-growing and predatory ant colonies around the cave compared to the control, the contrary being true for nectar and honeydew feeders. The role of bats, through their guano, was shown using stable isotope analyses as we noted significantly greater δ15N values for the ant species captured in and around the cave compared to controls. © 2015 Académie des sciences.
Keywords: Ant functional groups; Bat roosts; Biogeochemical hotspots; Bioindicators; Stable isotopes
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Dezerald, O., Céréghino, R., Corbara, B., Dejean, A., & Leroy, C. (2015). Temperature: Diet Interactions Affect Survival through Foraging Behavior in a Bromeliad-Dwelling Predator. Biotropica, 47(5), 569–578.
Abstract: Temperature, food quantity and quality play important roles in insect growth and survival, influencing population dynamics as well as interactions with other community members. However, the interaction between temperature and diet and its ecological consequences have been poorly documented. Toxorhynchites are well-known biocontrol agents for container-inhabiting mosquito larvae. We found that Toxorhynchites haemorrhoidalis larvae (Diptera: Culicidae) inhabiting water-filled rosettes of tank bromeliads catch and eat prey of both aquatic (mosquito larvae) and terrestrial origin (ants), using distinct predatory methods. They carried out frontal attacks on ants, but ambushed mosquito larvae. In choice tests, T. haemorrhoidalis favored terrestrial prey. Temperature had a significant effect on predator development and survival through its interaction with diet, but did not alter the preference for ants. T. haemorrhoidalis larvae emerged quickly when fed only mosquito larvae, whereas all individuals died before pupation when fed only ants. We conclude that behavioral factors (i.e., attraction to ants that disturb the surface of the water) overtake physiological factors (i.e., the adverse outcome of elevated temperature and an ant-based diet) in determining a predator's response to temperature:diet interactions. Finally, because T. haemorrhoidalis larvae preferentially feed on terrestrial insects in tank bromeliads, mosquito larvae may indirectly benefit from predation release. © 2015 Association for Tropical Biology and Conservation Inc.
Keywords: Toxorhynchites haemorrhoidalis; Biocontrol agent; Development; French Guiana; Selective feeding behavior; Tank bromeliad
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Rivalland, C., Madhkour, S., Salvin, P., & Robert, F. (2015). Electrochemical and microbial monitoring of multi-generational electroactive biofilms formed from mangrove sediment. Bioelectrochemistry, 106, 125–132.
Abstract: Electroactive biofilms were formed from French Guiana mangrove sediments for the analysis of bacterial communities' composition. The electrochemical monitoring of three biofilm generations revealed that the bacterial selection occurring at the anode, supposedly leading microbial electrochemical systems (MESs) to be more efficient, was not the only parameter to be taken into account so as to get the best electrical performance (maximum current density). Indeed, first biofilm generations produced a stable current density reaching about 18A/m2 while second and third generations produced current densities of about 10A/m2. MES bacterial consortia were characterized thanks to molecular biology techniques: DGGE and MiSeq® sequencing (Illumina®). High-throughput sequencing data statistical analysis confirmed preliminary DGGE data analysis, showing strong similarities between electroactive biofilms of second and third generations, but also revealing both selection and stabilization of the biofilms. © 2015 Elsevier B.V.
Keywords: Dissimilarity; High-throughput sequencing; Mes; Microbial diversity; Syntrophism
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Lambs, L., Bompy, F., Imbert, D., Corenblit, D., & Dulormne, M. (2015). Seawater and freshwater circulations through coastal forested wetlands on a Caribbean Island. Water, 7(8), 4108–4128.
Abstract: Structure and composition of coastal forested wetlands are mainly controlled by local topography and soil salinity. Hydrology plays a major role in relation with tides, seaward, and freshwater inputs, landward. We report here the results of a two-year study undertaken in a coastal plain of the Guadeloupe archipelago (FWI). As elsewhere in the Caribbean islands, the study area is characterized by a micro-tidal regime and a highly seasonal climate. This work aimed at understanding groundwater dynamics and origin (seawater/freshwater) both at ecosystems and stand levels. These hydrological processes were assessed through 18O/16O and 2H/1H isotopic analyses, and from monthly monitoring of water level and soil salinity at five study sites located in mangrove (3) and swamp forest (2). Our results highlight the importance of freshwater budget imbalance during low rainfall periods. Sustained and/or delayed dry seasons cause soil salinity to rise at the mangrove/swamp forest ecotone. As current models on climate change project decreasing rainfall amounts over the inner Caribbean region, one may expect for this area an inland progression of the mangrove forest to the expense of the nearby swamp forest. © 2015 by the authors.
Keywords: 18O/2H stable isotope; Hydrology; Mangrove; Salinity; Swamp forest; Water level
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Guitet, S., Pélissier, R., Brunaux, O., Jaouen, G., & Sabatier, D. (2015). Geomorphological landscape features explain floristic patterns in French Guiana rainforest. Biodiversity and Conservation, 24(5), 1215–1237.
Abstract: Geomorphic landscape features have been suggested as indicators of forest diversity. However, their explanatory power has not yet been explicitly tested at a regional scale in tropical rainforest. We used forest inventories conducted according to a stratified sampling design (3,132 plots in 111 transects at 33 sites) and holistic multi-scale geomorphological mapping derived from a Shuttle Radar Topography Mission digital elevation model to describe and explain spatial patterns in floristic composition across French Guiana (80,000 km2). We measured and identified 123,906 trees with DBH ≥20 cm and used constrained and unconstrained ordinations to analyze variations in the abundance of 221 taxa and 51 families. Variance partitioning and variograms were used to detect spatial patterns in species composition, compare the explanatory power of spatial and environmental factors, and select the variables that best explain forest composition. Strong floristic patterns corresponded to a major latitudinal gradient and significant sub-regional floristic structure. Geomorphological landscapes shaped by historic climate fluctuations and major geological events successfully captured these patterns and explained the variation in abundance of 80 taxa, corresponding to 65 % of the inventoried trees. Our findings suggest that long-term forest dynamics are under substantial “geomorphographic control”. A geomorphological perspective on landscapes that incorporates current and past environmental filters and historical biogeographical processes could thus be used more systematically in tropical regions for regional planning and forest conservation. © 2014, Springer Science+Business Media Dordrecht.
Keywords: Geodiversity; Geomorphology; Landscapes; Species distribution; Tree community
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Baraloto, C., Alverga, P., Quispe, S. B., Barnes, G., Chura, N. B., da Silva, I. B., et al. (2015). Effects of road infrastructure on forest value across a tri-national Amazonian frontier. Biological Conservation, 191, 674–681.
Abstract: Road construction demonstrably accelerates deforestation rates in tropical forests, but its consequences for forest degradation remain less clear. We estimated a series of forest value metrics including components of biodiversity, carbon stocks, and timber and non-timber forest product resources, along the recently paved Inter-Oceanic Highway (IOH) integrating Brazil and Peru along the Bolivian border. We installed 69 vegetation plots in intact terra firme forests representative of local community holdings near and far from the IOH, and we characterized 15 components of forest value for each plot.We observed strong geographic gradients in forest value components across the region, with increases from west to east in aboveground biomass and in the abundance of timber and non-timber forest product trees and regeneration. Plots in communities in Pando, Bolivia, where the IOH remains in part unpaved, had the highest aboveground biomass, standing timber volumes and Brazil nut tree density. In contrast, communities in Madre de Dios, Peru, where settlements and unpaved portions of the IOH have existed for decades, and in Acre, Brazil, where paving of the IOH has been underway for more than a decade, were more degraded. Seven of the fifteen forest value components we measured increased with increasing distance from the IOH, although the magnitude of these effects was weak. Landscape scale remote sensing analyses showed much stronger effects of road proximity on deforestation. We suggest that remote sensing techniques including canopy spectral signatures might be calibrated to characterize multiple components of forest value, so that we can estimate landscape scale impacts of infrastructure developments on both deforestation and forest degradation in tropical regions. © 2015 Elsevier B.V.
Keywords: Açai; Biodiversity; Brazil nut; Carbon stocks; Connectivity; Infrastructure; Livelihood; Ntfp; Redd; Road impact; Rubber; Timber; Tropical rainforest
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Moore, A. L., McCarthy, M. A., Parris, K. M., & Moore, J. L. (2014). The optimal number of surveys when detectability varies. PLoS ONE, 9(12), e115345.
Abstract: The survey of plant and animal populations is central to undertaking field ecology. However, detection is imperfect, so the absence of a species cannot be determined with certainty. Methods developed to account for imperfect detectability during surveys do not yet account for stochastic variation in detectability over time or space. When each survey entails a fixed cost that is not spent searching (e.g., time required to travel to the site), stochastic detection rates result in a trade-off between the number of surveys and the length of each survey when surveying a single site. We present a model that addresses this trade-off and use it to determine the number of surveys that: 1) maximizes the expected probability of detection over the entire survey period; and 2) is most likely to achieve a minimally-acceptable probability of detection. We illustrate the applicability of our approach using three practical examples (minimum survey effort protocols, number of frog surveys per season, and number of quadrats per site to detect a plant species) and test our model's predictions using data from experimental plant surveys. We find that when maximizing the expected probability of detection, the optimal survey design is most sensitive to the coefficient of variation in the rate of detection and the ratio of the search budget to the travel cost. When maximizing the likelihood of achieving a particular probability of detection, the optimal survey design is most sensitive to the required probability of detection, the expected number of detections if the budget were spent only on searching, and the expected number of detections that are missed due to travel costs. We find that accounting for stochasticity in detection rates is likely to be particularly important for designing surveys when detection rates are low. Our model provides a framework to do this. © 2014 Moore et al.
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Aimene, Y. E., & Nairn, J. A. (2015). Simulation of transverse wood compression using a large-deformation, hyperelastic–plastic material model. Wood Science and Technology, 49(1), 21–39.
Abstract: Transverse compression of wood is a process that induces large deformations. The process is dominated by elastic and plastic cell wall buckling. This work reports a numerical study of the transverse compression and densification of wood using a large-deformation, elastic–plastic constitutive law. The model is isotropic, formulated within the framework of hyperelasticity, and implemented in explicit material point method (MPM) software. The model was first validated for modeling of cellular materials by compression of an isotropic cellular model specimen. Next, it was used to model compression of wood by first validating use of isotropic, transverse plane properties for tangential compression of hardwood, and then by investigating both tangential and radial compression of softwood. Importantly, the discretization of wood specimens used MPM methods to reproduce accurately the complex morphology of wood anatomy for different species. The simulations have reproduced observations of stress–strain response during wood compression including details of inhomogeneous deformation caused by variations in wood anatomy. © 2014, Springer-Verlag Berlin Heidelberg.
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