Auteurs, date et publication :
Auteurs Lena Gustafsson , Susan C. Baker , Jürgen Bauhus , William J. Beese , Angus Brodie , Jari Kouki , David B. Lindenmayer , Asko Lõhmus , Guillermo Martínez Pastur , Christian Messier , Mark Neyland , Brian Palik , Anne Sverdrup-Thygeson , W. Jan A. Volney , Adrian Wayne , Jerry F. Franklin
Publication : BioScience
Date : 2012
Volume : 62
Issue : 7
Pages : 633–645
Catégorie(s)
#CIRAD #FORET ParacouRésumé
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).
Auteurs, date et publication :
Auteurs Alain Dejean , Jacques H. C. Delabie , Bruno Corbara , Fréderic Azémar , Sarah Groc , Jérôme Orivel , Maurice Leponce , William Hughes
Publication : Plos One
Date : 2012
Volume : 7
Issue : 5
Pages : e37683
Catégorie(s)
#CIRAD #CNRS #FORET Nouragues #FORET ParacouAuteurs, date et publication :
Auteurs C. Albinet , P. Borderies , T. Koleck , F. Rocca , S. Tebaldini , L. Villard , T. Le Toan , A. Hamadi , D. Ho Tong Minh
Publication : IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing
Date : 2012
Volume : 5
Issue : 3
Pages : 1060–1066
Catégorie(s)
#CIRAD #FORET ParacouAuteurs, date et publication :
Auteurs Nathalie Fromin , Benjamin Porte , Robert Lensi , Jérôme Hamelin , Anne-Marie Domenach , Bruno Buatois , Jean-Christophe Roggy
Publication : Journal of Soils and Sediments
Date : 2012
Volume : 12
Issue : 7
Pages : 1030–1039
Catégorie(s)
#CIRAD #FORET ParacouRésumé
In this paper we present results from the ground-based ESA campaign TropiScat, aimed at evaluating the temporal coherence at P-band in a tropical forest in all polarizations and at different heights within the vegetation layers. The TropiScat equipment has been operated since October 2011 at the Paracou field station, French Guiana, to continuously produce height-range images of the forest below with a temporal sampling of 15 minutes. The forest temporal behaviour can then be captured by analyzing the interferometric coherence between images gathered at different times, considering time scales on the order of hours, days, and months. Temporal coherence at the ground level was found to be higher than 0.8 at 27 days in all polarimetric channels, whereas temporal coherence at canopy height was found to be about 0.8 at 4 days and about 0.65 at 27 days, witnessing coherence sensitivity to height. © 2013 IEEE.
Auteurs, date et publication :
Auteurs D. Ho Tong Minh , S. Tebaldini , F. Rocca , T. Le Toan , P. Borderies , T. Koleck , C. Albinet , L. Villard , A. Hamadi
Publication : International Geoscience and Remote Sensing Symposium (IGARSS)
Date : 2025
Pages : 1206–1209
Catégorie(s)
#CIRAD #FORET ParacouRésumé
Brazilian Eucalyptus plantations are some of the most productive forest plantations in the world, sustaining mean growth rates of 25 Mg ha_1 year_1 (50 m3 ha_1 year_1) over the 4.7 million hectares planted across the country. To better understand forest productivity, studies at the stand scale need to be coupled with tree level evaluations of the production ecology (the assessment of wood production as a function of crown light absorption and light use efficiency). The soil clay content (_20% to _40%), topography and historical land use of the experimental site generated a natural gradient in productivity. We measured (from 6 to 7 years after planting) stem wood dry biomass growth and estimated light absorption and light use efficiency at the tree level with a three-dimensional array model (MAESTRA) in 12 plots within a seed-origin Eucalyptus grandis plantation. We investigated the hypothesis that dominant trees (the 20% largest) are more productive than non-dominant trees (the 20% smallest) as a result of greater light absorption and light use efficiency; and that with increasing productivity across plots, dominant trees would show larger increases in light use and light use efficiency in comparison to non-dominant trees. The 20% smallest of the trees averaged 10.6 kg of stem wood dry biomass (1.6 kg of stem wood growth during the last year of the rotation), compared with 185 kg per stem wood in the 20% largest of trees (34 kg of stem wood growth over the same period). The smallest trees contained 7.2% of the leaf area as compared to the largest trees (3.0 m2 versus 41.7 m2), and they absorbed only 6.7% as much light (2.2 versus 32.8 GJ year_1). The smallest trees grew at about 4.7% of the rate of the largest trees, which is a smaller percentage than the difference in absorbed photosynthetically active radiation; therefore the light use efficiency was lower for the smallest trees (0.75 kg GJ_1 versus 1.03 kg GJ_1). Our results show the significant contribution of dominant trees to stand productivity and the importance of evaluating production ecology at the individual tree scale. (Résumé d'auteur)
Auteurs, date et publication :
Auteurs Otávio Camargo Campoe , Jose Luiz Stape , Yann Nouvellon , Jean-Paul Laclau , William L. Bauerle , Dan Binkley , Guerric Le Maire
Publication : Forest Ecology and Management
Date : 2025
Volume : 288
Pages : 14-20
Catégorie(s)
#CIRAD #FORET Itatinga #INRAERésumé
Natural rubber is a valuable source of income in many tropical countries and rubber trees are increasingly planted in tropical areas, where they contribute to land-use changes that impact the global carbon cycle. However, little is known about the carbon balance of these plantations. We studied the soil carbon balance of a 15-year-old rubber plantation in Thailand and we specifically explored the seasonal dynamic of soil CO2 efflux (FS) in relation to seasonal changes in soil water content (WS) and soil temperature (TS), assessed the partitioning of FS between autotrophic (RA) and heterotrophic (RH) sources in a root trenching experiment and estimated the contribution of aboveground and belowground carbon inputs to the soil carbon budget. A multiplicative model combining both TS and WS explained 58 % of the seasonal variation of FS. Annual soil CO2 efflux averaged 1.88 kg C m−2 year−1 between May 2009 and April 2011 and RA and RH accounted for respectively 63 and 37 % of FS, after corrections of FS measured on trenched plots for root decomposition and for difference in soil water content. The 4-year average annual aboveground litterfall was 0.53 kg C m−2 year−1 while a conservative estimate of belowground carbon input into the soil was much lower (0.17 kg C m−2 year−1). Our results highlighted that belowground processes (root and rhizomicrobial respiration and the heterotrophic respiration related to belowground carbon input into the soil) have a larger contribution to soil CO2 efflux (72 %) than aboveground litter decomposition.
Auteurs, date et publication :
Auteurs Duangrat Satakhun , Frédéric Gay , Naruenat Chairungsee , Poonpipope Kasemsap , Pisamai Chantuma , Sornprach Thanisawanyangkura , Philippe Thaler , Daniel Epron
Publication : Ecological Research
Date : 2025
Volume : 28
Issue : 6
Pages : 969-979
Catégorie(s)
#CIRAD #FORET RubberfluxAuteurs, date et publication :
Auteurs Junior C. R. Sette , J. P. Laclau , M. Tomazello Filho , R. M. Moreira , J. P. Bouillet , J. Ranger , J. C. Raposo Almeida
Publication : Trees
Date : 2025
Volume : 27
Issue : 4
Pages : 827-839.
Catégorie(s)
#CIRAD #FORET Itatinga #INRAERésumé
Understanding the light absorption and light use efficiency of each species at the tree scale is essential to disentangle the effects of intra- and inter-species interactions on productivity in mixed-species forest plantations. A complete randomized block design was set up using Eucalyptus grandis (E) and Acacia mangium (A), which is a N2-fixing species, planted in monospecific stands (100A, 100E) and in additive (25A:100E, 50A:100E, 100A:100E) and replacement (50A:50E) mixtures. Tree size and biomass were monitored over the complete rotation (6 years). The absorbed photosynthetically active radiation (APAR) for each tree in the experiment was simulated over the full rotation with the MAESTRA model. Measurements of tree leaf area, leaf angle distributions, leaf area density, and leaf and soil optical properties were performed to parameterize this model. The APAR and the ratio of stem biomass increment divided by the APAR (which is a measure of the Light Use Efficiency [LUE] for stem production) were calculated at tree and plot scales for each year of the rotation. The LUE of the 100E stand increased with age until stabilizing at 4 years of age, while the LUE of the 100A stand decreased between 2 and 4 years of age and increased between the two last years of the rotation. Eucalyptus trees dominated Acacia trees in mixed plantations. The stratification of the canopy led to an increase of stand Leaf Area Index (LAI) and APAR compared to monospecific plantations. However, both Eucalyptus and Acacia LUE decreased at the end of the rotation in the mixed-species stands, with the decrease occurring more markedly in Acacia, and the final stem biomass of the stand was not enhanced in mixed-species plantations compared with the average of the pure stands. Our results indicate that a stratified canopy may offer the potential benefit of capturing more light in mixed-species forests, but this may be negated if another resource deficiency prevents trees from converting intercepted radiation into dry matter. Mixed-species plantations should be established at sufficiently rainfed sites to maximize LUE, and appropriate fertilizer regimes should be applied. (Résumé d'auteur)
Auteurs, date et publication :
Auteurs Guerric Le Maire , Yann Nouvellon , Mathias Christina , Flávio Jorge Ponzoni , José Leonardo M. Gonçalves , Jean-Pierre Bouillet , Jean-Paul Laclau
Publication : Forest Ecology and Management
Date : 2025
Volume : 288
Pages : 31-42
Catégorie(s)
#CIRAD #FORET Itatinga #INRAERésumé
Aim: Edaphic heterogeneity may be an important driver of population differentiation in the Amazon but remains to be investigated in trees. We compared the phylogeographic structure across the geographic distribution of two Protium (Burseraceae) species with different degrees of edaphic specialization: Protium alvarezianum, an edaphic specialist of white-sand habitat islands; and Protium subserratum, an edaphic generalist found in white sand as well as in more widespread soil types. We predicted that in the edaphic specialist, geographic distance would structure populations more strongly than in the edaphic generalist, and that soil type would not structure populations in the edaphic generalist unless habitat acts as a barrier promoting population differentiation. Location: Tropical rain forests of the Peruvian and Brazilian Amazon, Guyana and French Guiana. Methods: We sequenced 1209—1211 bp of non-coding nuclear ribosomal DNA (internal transcribed spacer and external transcribed spacer) and a neutral low-copy nuclear gene (phytochrome C) from P. subserratum (n = 65, 10 populations) and P. alvarezianum (n = 19, three populations). We conducted a Bayesian phylogenetic analysis, constructed maximum parsimony haplotype networks and assessed population differentiation among groups (soil type or geographic locality) using analysis of molecular variance and spatial analysis of molecular variance. Results: The edaphic specialist exhibited considerable genetic differentiation among geographically distant populations. The edaphic generalist showed significant genetic differentiation between the Guianan and Amazon Basin populations. Within Peru, soil type and not geographic distance explained most of the variation among populations. Non-white-sand populations in Peru exhibited lower haplotype/nucleotide diversity than white-sand populations, were each other's close relatives, and formed an unresolved clade derived from within the white-sand populations. Main conclusions: Geographic distance is a stronger driver of population differentiation in the edaphic specialist than in the generalist. However, this difference did not appear to be related to edaphic generalism per se as adjacent populations from both soil types in the edaphic generalist did not share many haplotypes. Populations of the edaphic generalist in white-sand habitats exhibited high haplotype diversity and shared haplotypes with distant white-sand habitat islands, indicating that they have either efficient long-distance dispersal and/or larger ancestral effective population sizes and thus retain ancestral polymorphisms. These results highlight the importance of edaphic heterogeneity in promoting population differentiation in tropical trees. CR - Copyright © 2013 Wiley
Auteurs, date et publication :
Auteurs Paul V.A. A. Fine , Felipe Zapata , Douglas C. Daly , Italo Mesones , Tracy M. Misiewicz , Hillary F. Cooper , C. E.A. A. Barbosa
Publication : Journal of Biogeography
Date : 2013
Volume : 40
Issue : 4
Pages : 646–661