Résumé
White‐sand forests are thought to host many ectomycorrhizal fungi, as demonstrated by the numerous fruiting body collections made by Rolf Singer in the lower Rio Negro in the late 1970s. Despite recognition of the importance of ectomycorrhizal fungi in white‐sand forests, there has not yet been a systematic examination of diversity and taxonomic composition across white‐sand forests, or more widely across lowland Amazonian forests. In an effort to broaden our view of ectomycorrhizal fungal diversity and distribution on white‐sand forests, we collected ectomycorrhizal fruiting bodies in 10 plots of white‐sand forests in Brazil and French Guiana between 2012 and 2014. We collected 221 specimens and 62 morphospecies, from the 10 plots, confirming that all studied white‐sand forests host ectomycorrhizal fungi. Additionally, we searched for taxa associated with white sands among specimens deposited in Brazilian herbaria. We report 1006 unique ectomycorrhizal specimen records in 18 Brazilian herbaria, of which 137 specimens and 64 species are reported from white‐sand forests, mainly in the state of Amazonas, Brazil. Russulaceae and Amanitaceae were frequent in all habitats, and Cortinarius were more frequent on white sands. Our results highlight the high diversity and heterogeneity of ectomycorrhizal communities on white‐sand forests, and the wide distribution of ectomycorrhizal fungi throughout Brazil, irrespective of soil type.
Auteurs, date et publication :
Auteurs Mélanie Roy , Heidy Schimann , Ricardo Braga-Neto , Rosa A. E. Da Silva , Jaime Duque , Dawn Frame , Felipe Wartchow , Maria A. Neves
Publication : Biotropica
Date : 2016
Volume : 48
Issue : 1
Pages : 90–100
Catégorie(s)
#CIRAD #FORET ParacouAuteurs, date et publication :
Auteurs Heidy Schimann , Cyrille Bach , Juliette Lengelle , Eliane Louisanna , Sandra Barantal , Claude Murat , Marc Buée
Publication : Microbial Ecology
Date : 2017
Volume : 73
Issue : 2
Pages : 310–320
Catégorie(s)
#CIRAD #FORET ParacouRésumé
The study of decay resistance in wood is of interest for wood end-users but also for the global carbon balance since wood biodegradation is a key driver of forest ecosystem functioning through its impacts on carbon and nutrient cycling. We studied the density and wood extractive contents in order to understand decay resistance against soil microflora after 90 days exposure of sapwood and heartwood from three Neotropical wood species known for their decay resistance: Bocoa prouacensis, Vouacapoua americana, Inga alba. Decay resistance was correlated with density more than wood extractive content. The results highlighted different decay resistance strategies. In B. prouacensis, both sapwood and heartwood were highly resistant due to the high density and high content of antifungal wood extractives. In V. americana heartwood, decay resistance was due to the high synergistic-acting wood extractive content. Conversely, with the least dense wood species I. alba, we found that decay resistance was due to the antifungal wood extractives synthesized early in the sapwood. In conclusion, we showed that the three wood species with the same level of heartwood decay resistance performance had different decay resistance strategies according to the anatomic and defensive wood traits.
Auteurs, date et publication :
Auteurs N. Amusant , M. Nigg , B. Thibaut , J. Beauchene
Publication : International Biodeterioration & Biodegradation
Date : 2014
Volume : 94
Pages : 103–108
Catégorie(s)
#CIRAD #FORET ParacouRésumé
Human-caused alterations of the carbon and nutrient cycles are expected to impact tropical ecosystems in the near future. Here we evaluated how a combined change in carbon (C), nitrogen (N) and phosphorus (P) availability affects soil and litter microbial respiration and litter decomposition in an undisturbed Amazonian rainforest in French Guiana. In a fully factorial C (as cellulose), N (as urea), and P (as phosphate) fertilization experiment we analyzed a total of 540 litterbag-soil pairs after a 158-day exposure in the field. Rates of substrate-induced respiration (SIR) measured in litter and litter mass loss were similarly affected by fertilization showing the strongest stimulation when N and P were added simultaneously. The stimulating NP effect on litter SIR increased considerably with increasing initial dissolved organic carbon (DOC) concentrations in litter, suggesting that the combined availability of N, P, and a labile C source has a particularly strong effect on microbial activity. Cellulose fertilization, however, did not further stimulate the NP effect. In contrast to litter SIR and litter mass loss, soil SIR was reduced with N fertilization and showed only a positive effect in response to P fertilization that was further enhanced with additional C fertilization. Our data suggest that increased nutrient enrichment in the studied Amazonian rainforest can considerably change microbial activity and litter decomposition, and that these effects differ between the litter layer and the underlying soil. Any resulting change in relative C and nutrient fluxes between the litter layer and the soil can have important consequences for biogeochemical cycles in tropical forest ecosystems.
Auteurs, date et publication :
Auteurs Nicolas Fanin , Sandra Barantal , Nathalie Fromin , Heidy Schimann , Patrick Schevin , Stephan Hättenschwiler , Caroline P. Slomp
Publication : Plos One
Date : 2012
Volume : 7
Issue : 12
Pages : e49990
Catégorie(s)
#CIRAD #FORET ParacouRésumé
Phylogenetic patterns and the underlying speciation processes can be deduced from morphological, functional, and ecological patterns of species similarity and divergence. In some cases, though, species retain multiple similarities and remain almost indistinguishable; in other cases, evolutionary convergence can make such patterns misleading; very often in such cases, the “true” picture only emerges from carefully built molecular phylogenies, which may come with major surprises. In addition, closely related species may experience gene flow after divergence, thus potentially blurring species delimitation. By means of advanced inferential methods, we studied molecular divergence between species of the Virola genus (Myristicaceae): widespread Virola michelii and recently described, endemic V. kwatae, using widespread V. surinamensis as a more distantly related outgroup with different ecology and morphology—although with overlapping range. Contrary to expectations, we found that the latter, and not V. michelii, was sister to V. kwatae. Therefore, V. kwatae probably diverged from V. surinamensis through a recent morphological and ecological shift, which brought it close to distantly related V. michelii. Through the modeling of the divergence process, we inferred that gene flow between V. surinamensis and V. kwatae stopped soon after their divergence and resumed later, in a classical secondary contact event which did not erase their ecological and morphological differences. While we cannot exclude that initial divergence occurred in allopatry, current species distribution and the absence of geographical barriers make complete isolation during speciation unlikely. We tentatively conclude that (a) it is possible that divergence occurred in allopatry/parapatry and (b) secondary contact did not suppress divergence.
Auteurs, date et publication :
Auteurs Giorgio Binelli , William Montaigne , Daniel Sabatier , Caroline Scotti‐Saintagne , Ivan Scotti
Publication : Ecology and Evolution
Date : 2025
Volume : 10
Issue : 11
Pages : 4726-4738
Catégorie(s)
#CIRAD #FORET ParacouRésumé
Tropical forest mortality is controlled by both biotic and abiotic processes, but how these processes interact to determine forest structure is not well understood. Using long‐term demography data from permanent forest plots at the Paracou Tropical Forest Research Station in French Guiana, we analysed the relative influence of competition and climate on tree mortality. We found that self‐thinning is evident at the stand level, and is associated with clumped mortality at smaller scales (textless2 m) and regular spacing of living trees at intermediate (2.5–7.5 m) scales. A competition index (CI) based on spatial clustering of dead trees was used to build predictive mortality models, which also accounted for climate interactions. The model that most closely fitted observations included both the CI and climatic variables, with climate‐only and competition‐only models less informative than the full model. There was strong evidence for U‐shaped size‐specific mortality, with highest mortality for small and very large trees, as well as sensitivity of trees to drought, especially when temperatures were high, and when soils were water saturated. The effect of the CI was more complex than expected a priori: a higher CI was associated with lower mortality odds, which we hypothesize is caused by gap‐phase dynamics, but there was also evidence for competition‐induced mortality at very high CI values. The strong signature of competition as a control over mortality at the stand and individual scales confirms its important role in determining tropical forest structure. The complexity of the competition‐mortality relationship and its interaction with climate indicates that a thorough consideration of the scale of analysis is needed when inferring the role of competition in tropical forests, but demonstrates that climate‐only mortality models can be significantly improved by including competition effects, even when ignoring species‐specific effects. Synthesis. Empirical models such as the one developed here can help constrain and improve process‐based vegetation models, serving both as a benchmark and as a means to disentangle mortality processes. Tropical vegetation dynamic models would benefit greatly from explicitly considering the role of competition in stand development and self‐thinning while modelling demography, as well as its interaction with climate.
Auteurs, date et publication :
Auteurs Michiel Pillet , Emilie Joetzjer , Camille Belmin , Jérôme Chave , Philippe Ciais , Aurélie Dourdain , Margaret Evans , Bruno Hérault , Sebastiaan Luyssaert , Benjamin Poulter , Shurong Zhou
Publication : Journal of Ecology
Date : 2018
Volume : 106
Issue : 3
Pages : 1165–1179
Catégorie(s)
#CIRAD #FORET ParacouRésumé
Tropical soils are a major contributor to the balance of greenhouse gas (GHG) fluxes in the atmosphere. Models of tropical GHG fluxes predict that both the frequency of drought events and changes in atmospheric deposition of nitrogen (N) will significantly affect dynamics of soil carbon dioxide (CO2) and methane (CH4) production and consumption. In this study, we examined the combined effect of a reduction in precipitation and an increase in nutrient availability on soil CO2 and CH4 fluxes in a primary French Guiana tropical forest. Drought conditions were simulated by intercepting precipitation falling through the forest canopy with tarpaulin roofs. Nutrient availability was manipulated through application of granular N and / or phosphorus (P) fertilizer to the soil. Soil water content (SWC) below the roofs decreased rapidly and stayed at continuously low values until roof removal, which as a consequence roughly doubled the duration of the dry season. After roof removal, SWC slowly increased but remained lower than in the control soils even after 2.5 months of wet-season precipitation. We showed that drought-imposed reduction in SWC decreased the CO2 emissions (i.e CO2 efflux), but strongly increased the CH4 emissions. N, P and N × P (i.e. NP) additions all significantly increased CO2 emission but had no effect on CH4 fluxes. In treatments where both fertilization and drought were applied, the positive effect of N, P and NP fertilization on CO2 efflux was reduced. After roof removal, soil CO2 efflux was more resilient in the control plots than in the fertilized plots while there was only a modest effect of roof removal on soil CH4 fluxes. Our results suggest that a combined increase in drought and nutrient availability in soil can locally increase the emissions of both CO2 and CH4 from tropical soils, for a long term.
Auteurs, date et publication :
Auteurs Laëtitia Bréchet , Elodie A. Courtois , Thomas Saint-Germain , Ivan A. Janssens , Dolores Asensio , Irene Ramirez-Rojas , Jennifer L. Soong , Leandro Van Langenhove , Erik Verbruggen , Clément Stahl
Publication : Frontiers in Environmental Science
Date : 2025
Volume : 7
Catégorie(s)
#CIRAD #FORET ParacouRésumé
1. The potential for competition is highest among species in close association. Despite net benefits for both parties, mutualisms can involve costs, including food competition. This might be true for the two neotropical ants Camponotus femoratus and Crematogaster levior, which share the same nest in a presumably mutualistic association (parabiosis). 2. While each nest involves one Crematogaster and one Camponotus partner, both taxa were recently found to comprise two cryptic species that show no partner preferences and seem ecologically similar. Since these cryptic species often occur in close sympatry, they might need to partition their niches to avoid competitive exclusion. 3. Here, we investigated first, is there interference competition between parabiotic Camponotus and Crematogaster, and do they prefer different food sources under competition? And second, is there trophic niche partitioning between the cryptic species of either genus? 4. Using cafeteria experiments, neutral lipid fatty acid and stable isotope analyses, we found evidence for interference competition, but also trophic niche partitioning between Camponotus and Crematogaster. Both preferred protein- and carbohydrate-rich baits, but at protein-rich baits Ca. femoratus displaced Cr. levior over time, suggesting a potential discovery-dominance trade-off between parabiotic partners. Only limited evidence was found for trophic differentiation between the cryptic species of each genus. 5. Although we cannot exclude differentiation in other niche dimensions, we argue that neutral dynamics might mediate the coexistence of cryptic species. This model system is highly suitable for further studies of the maintenance of species diversity and the role of mutualisms in promoting species coexistence.
Auteurs, date et publication :
Auteurs Philipp P. Sprenger , Christian Müsse , Juliane Hartke , Barbara Feldmeyer , Thomas Schmitt , Gerhard Gebauer , Florian Menzel
Publication : Ecological Entomology
Date : 2025
Volume : n/a
Issue : n/a
Catégorie(s)
#CIRAD #FORET ParacouRésumé
Volatile terpenes are among the most diverse class of defensive compounds in plants, and they are implicated in both direct and indirect defense against herbivores. In terpenes, both the quantity and the diversity of compounds appear to increase the efficiency of defense as a diverse blend of compounds provides a more efficient protection against a broader range of herbivores and limits the chances that an enemy evolves resistance. Theory predicts that plant defensive compounds should be allocated differentially among tissues according to the value of the tissue, its cost of construction and the herbivore pressure on it. We collected volatile terpenes from bark and leaves of 178 individual tree belonging to 55 angiosperm species in French Guiana and compare the kind, amount, and diversity of compounds in these tissues. We hypothesized that in woody plants, the outermost part of the trunk should hold a more diverse blend of volatile terpenes. Additionally, as herbivore communities associated with the leaves is different to the one associated with the bark, we also hypothesized that terpene blends should be distinct in the bark vs. the leaves of a given species. We found that the mixture of volatile terpenes released by bark is different and more diverse than that released by leaves, both in monoterpenes and sesquiterpenes. This supports our hypothesis and further suggests that the emission of terpenes by the bark should be more important for trunk defense than previously thought.
Auteurs, date et publication :
Auteurs Elodie A. Courtois , Christopher Baraloto , C.E. Timothy Paine , Pascal Petronelli , Pierre-Alain Blandinieres , Didier Stien , Emeline Höuel , Jean-Marie Bessière , Jérôme Chave
Publication : Phytochemistry
Date : 2012
Volume : 82
Pages : 81–88
Catégorie(s)
#CIRAD #CNRS #FORET Nouragues #FORET ParacouRésumé
Tropical rainforests harbor a particularly high plant diversity. We hypothesize that potential causes underlying this high diversity should be linked to distinct overall functionality (defense and growth allocation, anti-stress mechanisms, reproduction) among the different sympatric taxa. In this study we tested the hypothesis of the existence of a metabolomic niche related to a species-specific differential use and allocation of metabolites. We tested this hypothesis by comparing leaf metabolomic profiles of 54 species in two rainforests of French Guiana. Species identity explained most of the variation in the metabolome, with a species-specific metabolomic profile across dry and wet seasons. In addition to this “homeostatic” species-specific metabolomic profile significantly linked to phylogenetic distances, also part of the variance (flexibility) of the metabolomic profile was explained by season within a single species. Our results support the hypothesis of the high diversity in tropical forest being related to a species-specific metabolomic niche and highlight ecometabolomics as a tool to identify this species functional diversity related and consistent with the ecological niche theory.
Auteurs, date et publication :
Auteurs Albert Gargallo-Garriga , Jordi Sardans , Victor Granda , Joan Llusià , Guille Peguero , Dolores Asensio , Romà Ogaya , Ifigenia Urbina , Leandro Van Langenhove , Lore T. Verryckt , Jérome Chave , Elodie A. Courtois , Clément Stahl , Oriol Grau , Karel Klem , Otmar Urban , Ivan A. Janssens , Josep Peñuelas
Publication : Scientific Reports
Date : 2020
Volume : 10
Issue : 1
Pages : 6937