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Longo, M., Saatchi, S., Keller, M., Bowman, K., Ferraz, A., Moorcroft, P. R., et al. (2020). Impacts of Degradation on Water, Energy, and Carbon Cycling of the Amazon Tropical Forests. J. Geophys. Res. Biogeosci., 125(8), e2020JG005677.
Abstract: Selective logging, fragmentation, and understory fires directly degrade forest structure and composition. However, studies addressing the effects of forest degradation on carbon, water, and energy cycles are scarce. Here, we integrate field observations and high-resolution remote sensing from airborne lidar to provide realistic initial conditions to the Ecosystem Demography Model (ED-2.2) and investigate how disturbances from forest degradation affect gross primary production (GPP), evapotranspiration (ET), and sensible heat flux (H). We used forest structural information retrieved from airborne lidar samples (13,500 ha) and calibrated with 817 inventory plots (0.25 ha) across precipitation and degradation gradients in the eastern Amazon as initial conditions to ED-2.2 model. Our results show that the magnitude and seasonality of fluxes were modulated by changes in forest structure caused by degradation. During the dry season and under typical conditions, severely degraded forests (biomass loss ≥66%) experienced water stress with declines in ET (up to 34%) and GPP (up to 35%) and increases of H (up to 43%) and daily mean ground temperatures (up to 6.5°C) relative to intact forests. In contrast, the relative impact of forest degradation on energy, water, and carbon cycles markedly diminishes under extreme, multiyear droughts, as a consequence of severe stress experienced by intact forests. Our results highlight that the water and energy cycles in the Amazon are driven by not only climate and deforestation but also the past disturbance and changes of forest structure from degradation, suggesting a much broader influence of human land use activities on the tropical ecosystems. ©2020. The Authors.
Keywords: Amazon; drought; ecosystem modeling; evapotranspiration; forest degradation; remote sensing; carbon cycle; deforestation; dry season; evapotranspiration; hydrological cycle; logging (timber); net primary production; remote sensing; sensible heat flux; tropical forest; understory; water stress; Amazon River
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Marino, N. A. C., Céréghino, R., Gilbert, B., Petermann, J. S., Srivastava, D. S., de Omena, P. M., et al. (2020). Species niches, not traits, determine abundance and occupancy patterns: A multi-site synthesis. Global Ecol. Biogeogr., 29(2), 295–308.
Abstract: Aim: Locally abundant species are usually widespread, and this pattern has been related to properties of the niches and traits of species. However, such explanations fail to account for the potential of traits to determine species niches and often overlook statistical artefacts. Here, we examine how trait distinctiveness determines the abilities of species to exploit either common habitats (niche position) or a range of habitats (niche breadth) and how niche position and breadth, in turn, affect abundance and occupancy. We also examine how statistical artefacts moderate these relationships. Location: Sixteen sites in the Neotropics. Time period: 1993–2014. Major taxa studied: Aquatic invertebrates from tank bromeliads. Methods: We measured the environmental niche position and breadth of each species and calculated its trait distinctiveness as the average trait difference from all other species at each site. Then, we used a combination of structural equation models and a meta-analytical approach to test trait–niche relationships and a null model to control for statistical artefacts. Results: The trait distinctiveness of each species was unrelated to its niche properties, abundance and occupancy. In contrast, niche position was the main predictor of abundance and occupancy; species that used the most common environmental conditions found across bromeliads were locally abundant and widespread. Contributions of niche breadth to such patterns were attributable to statistical artefacts, indicating that effects of niche breadth might have been overestimated in previous studies. Main conclusions: Our study reveals the generality of niche position in explaining one of the most common ecological patterns. The robustness of this result is underscored by the geographical extent of our study and our control of statistical artefacts. We call for a similar examination across other systems, which is an essential task to understand the drivers of commonness across the tree of life. © 2019 John Wiley & Sons Ltd
Keywords: abundance; environmental niche; functional distinctiveness; functional traits; metacommunity; niche breadth; niche position; occupancy; abundance; biodiversity; functional group; geographical distribution; invertebrate; Neotropical Region; niche breadth; Invertebrata
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Medjigbodo, G., Rozière, E., Charrier, K., Izoret, L., & Loukili, A. (2018). Hydration, shrinkage, and durability of ternary binders containing Portland cement, limestone filler and metakaolin. Construction and Building Materials, 183, 114–126.
Abstract: A partial replacement of the clinker by latent hydraulic or pozzolanic materials is encouraged due to environmental and specific technical requirements. Such substitution remains limited to a relatively low level (less than 30% by mass of cementitious materials). An experimental research work was carried out on mortars made with binary and ternary binders (Portland cement; metakaolin; limestone filler) to reach 45% total replacement. In order to investigate the activating effect of reduced water-to-cement ratio, two series of mixtures were designed with W/C0 of 0.42 and 0.5. Their heat of hydration, portlandite content, shrinkage, porosity, and carbonation were monitored. The tests were performed to understand the evolution of their relative strength (activity index) and durability parameters. The strength development of mortars with ternary binders was found to depend on metakaolin properties, including manufacturing process and particle size distribution. Reducing W/C0 ratio accelerated pozzolanic reaction and allowed improving early-age strength and durability parameters. © 2018 Elsevier Ltd
Keywords: Durability; Limestone filler; Metakaolin; Shrinkage; Strength; Ternary binders
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Dejean, A., Delabie, J. H., Corbara, B., Azémar, F., Groc, S., Orivel, J., et al. (2012). The ecology and feeding habits of the arboreal trap-jawed ant Daceton armigerum. PLoS ONE, 7(5), e37683.
Abstract: Here we show that Daceton armigerum, an arboreal myrmicine ant whose workers are equipped with hypertrophied trap-jaw mandibles, is characterized by a set of unexpected biological traits including colony size, aggressiveness, trophobiosis and hunting behavior. The size of one colony has been evaluated at ca. 952,000 individuals. Intra- and interspecific aggressiveness were tested and an equiprobable null model used to show how D. armigerum colonies react vis-à-vis other arboreal ant species with large colonies; it happens that D. armigerum can share trees with certain of these species. As they hunt by sight, workers occupy their hunting areas only during the daytime, but stay on chemical trails between nests at night so that the center of their home range is occupied 24 hours a day. Workers tend different Hemiptera taxa (i.e., Coccidae, Pseudococcidae, Membracidae and Aethalionidae). Through group-hunting, short-range recruitment and spread-eagling prey, workers can capture a wide range of prey (up to 94.12 times the mean weight of foraging workers).
Keywords: animal; ant; article; ecology; feeding behavior; Hemiptera; physiology; predation; Animals; Ants; Ecology; Feeding Behavior; Hemiptera; Predatory Behavior
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Fox Ramos, A. E., Alcover, C., Evanno, L., Maciuk, A., Litaudon, M., Duplais, C., et al. (2017). Revisiting Previously Investigated Plants: A Molecular Networking-Based Study of Geissospermum laeve. Journal of Natural Products, 80(4), 1007–1014.
Abstract: Three new monoterpene indole alkaloids (1-3) have been isolated from the bark of Geissospermum laeve, together with the known alkaloids (−)-leuconolam (4), geissolosimine (5), and geissospermine (6). The structures of 1-3 were elucidated by analysis of their HRMS and NMR spectroscopic data. The absolute configuration of geissolaevine (1) was deduced from the comparison of experimental and theoretically calculated ECD spectra. The isolation workflow was guided by a molecular networking-based dereplication strategy using an in-house database of monoterpene indole alkaloids. In addition, five known compounds previously undescribed in the Geissospermum genus were dereplicated from the G. laeve alkaloid extract network and were assigned with various levels of identification confidence. The antiparasitic activities against Plasmodium falciparum and Leishmania donovani as well as the cytotoxic activity against the MRC-5 cell line were determined for compounds 1-5. © 2017 The American Chemical Society and American Society of Pharmacognosy.
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Bordenave, B., Lehir, F., & Lorans, M. (2012). Current knowledge on threatened plant species of French Guiana. Rev. Ecol. Terre Vie, 67(Suppl.2), 29–45.
Abstract: The elaboration of a first list of the most threatened species of the overseas territory of French Guyana was undertaken in 2009 by the Association for Botanical Conservation in French Guiana in collaboration with the National Botanical Conservatory of Brest. Carried out in synergy with the updating of the species list for Natural Areas of Ecological, Faunistic and Floritic Interests supervised by the Region Science Council for Natural Heritage, this work includes 97 vascular plants, 18 of which can be considered as threatened in the state of current knowledge, according to the IUCN criteria which are recommended by the Federation of National Botanical Conservatories. Among these 18 taxa, threatened because of their rarity and the fragility of their natural habitats, 17 are already protected by a 2001 ministry decree and one is from a new genus, Hekkingia bordenavei; nine of these appear to be of high concern for conservation: Cleistes grandifiora (Orchidaceae), Cornutia pubescens (Verbenaceae), Antirhea triflora (Rubiaceae), Himathantus drasticus (Apocynaceae), Axonopus oiapocensis (Poaceae), Psychotria granvillei (Rubiaceae), Eriocaulon guyanense (Eriocaulaceae) along with two palm species subject to National Action Plans for their conservation since 2009, Astrocaryum minus and Bactris nancibaensis. This study also contributes to the on-going “regional Red List” of the French Guiana flora.
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Degen, B., Bandou, E., & Caron, H. (2004). Limited pollen dispersal and biparental inbreeding in Symphonia globulifera in French Guiana. Heredity, 93(6), 585–591.
Abstract: In this paper, we report a study of the mating system and gene flow of Symphonia globulifera, a hermaphroditic, mainly bird-pollinated tree species with a large geographic distribution in the tropical Americas and Africa. Using three microsatellites, we analysed 534 seeds of 28 open pollinated families and 164 adults at the experimental site 'Paracou' in French Guiana. We observed, compared to other tropical tree species, relatively high values for the effective number of alleles. Significant spatial genetic structure was detected, with trees at distances up to 150 m more genetically similar than expected at random. We estimated parameters of the mating system and gene flow by using the mixed mating model and the TwoGener approach. The estimated multilocus outcrossing rate, t(m), was 0.920. A significant level of biparental inbreeding and a high proportion of full-sibs were estimated for the 28 seed arrays. We estimated mean pollen dispersal distances between 27 and 53 m according to the dispersal models used. Although the adult population density of S. globulifera in Paracou was relatively high, the joint estimation of pollen dispersal and density of reproductive trees gave effective density estimates of 1.6 and 1.3 trees/ha. The parameters of the mating system and gene flow are discussed in the context of spatial genetic and demographic structures, flowering phenology and pollinator composition and behaviour.
Keywords: gene flow; microsatellites; mixed mating; spatial autocorrelation; tropical tree; twogener
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Degen, B., Blanc, L., Caron, H., Maggia, L., Kremer, A., & Gourlet-Fleury, S. (2006). Impact of selective logging on genetic composition and demographic structure of four tropical tree species. Biol. Conserv., 131(3), 386–401.
Abstract: Over-exploitation and fragmentation are serious problems for tropical forests. Most sustainable forest management practices avoid clear-cuts and apply selective logging systems focused on a few commercial species. We applied a simulation model to estimate the impact of such selective logging scenarios on the genetic diversity and demography of four tropical tree species from French Guiana. The simulations used data on genetic and demographic composition, growth, phenology and pollen and seed dispersal obtained for Dicorynia guianensis, Sextonia rubra, Symphonia globulifera and Vouacapoua americana at the experimental site in Paracou. Whereas Symphonia globulifera serves as a model for a species with low logging pressure, the other three species represent the most exploited tree species in French Guiana. In simulations with moderate logging, typical for French Guiana, with large cutting diameter (> 60 cm diameter) and long cutting cycles (65 years), the two species V. americana and Sextonia rubra were not able to recover their initial stock at the end of the rotation period, with a large decrease in the number of individuals and in basal area. Under a more intensive logging system (cutting diameter > 45 cm diameter, cutting cycles of 30 years) that is common practice in the Brazilian Amazon, only Symphonia globulifera showed no negative impact. Generally, the differences between the genetic parameters in the control scenarios without logging and the logging scenarios were surprisingly small. The main reasons for this were the overlapping of generations and the effective dispersal ability of gene vectors in all species, which guarantee relative homogeneity of the genetic structure in different age classes. Nevertheless, decreasing the population size by logging reduced the number of genotypes and caused higher genetic distances between the original population and the population at the end of the logging cycles. Sensitivity analysis showed that genetic changes in the logging scenarios were principally determined by the growth, densities and cutting diameter of each species, and only to a very small extent by the reproductive system including factors such as pollen and seed dispersal and flowering phenology. (c) 2006 Elsevier Ltd. All rights reserved.
Keywords: demography; genetic diversity; logging; phenology; pollen and seed dispersal; simulation; trees; tropics
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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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Ruiz-González, M. X., Leroy, C., Dejean, A., Gryta, H., Jargeat, P., Carrión, A. D. A., et al. (2019). Do host plant and associated ant species affect microbial communities in myrmecophytes? Insects, 10(11), 391.
Abstract: Ant-associated microorganisms can play crucial and often overlooked roles, and given the diversity of interactions that ants have developed, the study of the associated microbiomes is of interest. We focused here on specialist plant-ant species of the genus Allomerus that grow a fungus to build galleries on their host-plant stems. Allomerus-inhabited domatia, thus, might be a rich arena for microbes associated with the ants, the plant, and the fungus. We investigated the microbial communities present in domatia colonised by four arboreal ants: Allomerus decemarticulatus, A. octoarticulatus, A. octoarticulatus var. demerarae, and the non-fungus growing plant-ant Azteca sp. cf. depilis, inhabiting Hirtella physophora or Cordia nodosa in French Guiana. We hypothesized that the microbial community will differ among these species. We isolated microorganisms from five colonies of each species, sequenced the 16S rRNA or Internal TranscribedSpacer (ITS) regions, and described both the alpha and beta diversities. We identified 69 microbial taxa, which belong to five bacterial and two fungal phyla. The most diverse phyla were Proteobacteria and Actinobacteria. The microbial community of Azteca cf. depilis and Allomerus spp. differed in composition and richness. Geographical distance affected microbial communities and richness but plant species did not. Actinobacteria were only associated with Allomerus spp.
Keywords: Allomerus decemarticulatus; Allomerus octoarticulatus; Azteca sp; Cf; Cordia nodosa; Depilis; Domatia; Hirtella physophora; Microbial diversity
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