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Letort, V.; Heuret, P.; Zalamea, P.-C.; De Reffye, P.; Nicolini, E. |
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Analysing the effects of local environment on the source-sink balance of Cecropia sciadophylla: A methodological approach based on model inversion |
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Journal Article |
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2012 |
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Annals of Forest Science |
Abbreviated Journal |
Ann. Forest Sci. |
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69 |
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2 |
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167-180 |
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Cecropia; Functional-structural model; Model inversion; Morphology; Trophic competition |
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Context Functional-structural models (FSM) of tree growth have great potential in forestry, but their development, calibration and validation are hampered by the difficulty of collecting experimental data at organ scale for adult trees. Due to their simple architecture and morphological properties, “model plants” such as Cecropia sciadophylla are of great interest to validate new models and methodologies, since exhaustive descriptions of their plant structure and mass partitioning can be gathered. Aims Our objective was to develop a model-based approach to analysing the influence of environmental conditions on the dynamics of trophic competition within C. sciadophylla trees. Methods We defined an integrated environmental factor that includes meteorological medium-frequency variations and a relative index representing the local site conditions for each plant. This index is estimated based on model inversion of the GreenLab FSM using data from 11 trees for model calibration and 7 trees for model evaluation. Results The resulting model explained the dynamics of biomass allocation to different organs during the plant growth, according to the environmental pressure they experienced. Perspectives By linking the integrated environmental factor to a competition index, an extension of the model to the population level could be considered. © INRA and Springer Science+Business Media B.V. 2011. |
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UMR ECOFOG Campus Agronomique, INRA, BP 316, 97379 Kourou cedex, French Guiana |
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12864560 (Issn) |
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Cited By (since 1996): 1; Export Date: 20 June 2012; Source: Scopus; Coden: Afosf; doi: 10.1007/s13595-011-0131-x; Language of Original Document: English; Correspondence Address: Letort, V.; Department of Applied Mathematics and Systems (MAS), Ecole Centrale Paris, Grande voie des Vignes, Chatenay-Malabry 92295, France; email: veronique.letort@centraliens.net |
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EcoFoG @ webmaster @ |
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405 |
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Siebicke, L.; Hunner, M.; Foken, T. |
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Title |
Aspects of CO 2 advection measurements |
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Journal Article |
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2012 |
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Theoretical and Applied Climatology |
Abbreviated Journal |
Theor. Appl. Climatol. |
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109 |
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1-2 |
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109-131 |
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Observations of vegetation-atmosphere exchange of carbon dioxide (CO 2) by the eddy covariance (EC) technique are limited by difficult conditions such as nighttime and heterogeneous terrain. Thus, advective flux components are included into the net ecosystem exchange (NEE) budget. However, advection measurements are experimentally challenging and do not always help to solve the night flux problem of the EC technique. This study investigates alternative methods for the observation of horizontal advection, in particular horizontal concentration gradients, as well as different approaches to coordinate rotation and vertical advection. Continuous high-frequency measurements of the horizontal CO 2 concentration field are employed and compared to the often used discontinuous sequential sampling. Significant differences were found in the case of 30-min mean concentration values between the conventional discontinuous sampling approach and the complete observation of the time series by continuous sampling. Estimates of vertical advection rely on accurate estimates of vertical wind velocity (W). Therefore, different approaches to the planar fit coordinate rotation have been investigated. Sector-wise rotation was able to eliminate directional dependencies of mean W. Furthermore, the effect of the data set length used for rotation (window length) was investigated and was found to have significant impact on estimates of vertical advection, with larger window lengths yielding about 50% larger vertical advection. A sequential planar fit with controlled window length is proposed to give reproducible results. The different approaches to the measurement and calculation of horizontal and vertical advection presented are applied to data obtained during the exchange processes in mountainous region experiment at the FLUXNET site Waldstein-Weidenbrunnen (DE-Bay). Estimates of NEE including advection are compared to NEE from turbulent and storage flux alone without advection. NEE including vertical advection with sector-wise planar fit rotation and controlled window length and including horizontal advection from continuous gradient measurements, which were comprehensively bias corrected by a new approach, did compare well with the expected night flux error, with meteorological drivers of the fluxes and with soil chamber measurements. Unrealistically large and noisy values of horizontal advection from the conventional discontinuous sampling approach, which lead to unrealistic values of NEE, could be eliminated by the alternative approaches presented. We therefore suggest the further testing of those approaches at other sites in order to improve the accuracy of advection measurements and, subsequently, estimates of NEE. © 2011 Springer-Verlag. |
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Wind Cert Services, TÜV SÜD Industrie Service GmbH, Ludwig-Eckert-Str. 10, 93049 Regensburg, Germany |
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0177798x (Issn) |
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Export Date: 27 June 2012; Source: Scopus; doi: 10.1007/s00704-011-0552-3; Language of Original Document: English; Correspondence Address: Siebicke, L.; Department of Micrometeorology, University of Bayreuth, Universitätsstr. 30, 95440 Bayreuth, Germany; email: lukas.siebicke@uni-bayreuth.de |
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EcoFoG @ webmaster @ |
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406 |
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Coq, S.; Weigel, J.; Bonal, D.; Hattenschwiler, S. |
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Title |
Litter mixture effects on tropical tree seedling growth – a greenhouse experiment |
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Journal Article |
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2012 |
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Plant Biology |
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Plant Biol. |
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14 |
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4 |
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630-640 |
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Amazonian lowland rain forest; Autotoxicity; Belowground/aboveground interactions; Litter decomposition; Plant nutrition; Plant-soil feedback |
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Decomposing litter provides critical nutrients for plants, particularly in nutrient-poor ecosystems such as tropical forests. We hypothesised that decomposing litter improves the performance of a variety of tropical tree seedlings, and that this litter effect varies depending on the species of litter present in litter mixtures. We addressed these hypotheses with a large pot experiment manipulating a range of different litter mixtures of contrasting quality and using seedlings of four tree species from the Amazonian forest of French Guiana. In contrast to our initial hypothesis, decomposing litter had either neutral or negative impacts on seedling growth, despite strongly different growth rates, biomass allocation patterns and leaf and root traits among tree species. Tree species varied in their responses to litter additions, which were further modified by species identity of the added litter. Our data show litter species-specific effects on growth, biomass allocation and leaf and root traits of tropical tree seedlings. These results suggest that a net nutrient release from decomposing litter does not necessarily improve tree seedling growth, even under nutrient-limiting conditions. In conclusion, litter layer composition may affect seedling establishment and recruitment success beyond litter-derived plant nutrient availability, which may contribute to tree species composition and dynamics in the studied tropical forest. © 2012 German Botanical Society and The Royal Botanical Society of the Netherlands. |
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INRA, UMR, Écologie et Écophysiologie, Champenoux, France |
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14358603 (Issn) |
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Export Date: 27 June 2012; Source: Scopus; Coden: Pbiof; doi: 10.1111/j.1438-8677.2011.00534.x; Language of Original Document: English; Correspondence Address: Coq, S.; Laboratoire d'Ecologie Alpine (LECA), CNRS, Université Joseph Fourier, BP 53, F-38042 Grenoble, Cedex 09, France; email: sylvain.coq@gmail.com |
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EcoFoG @ webmaster @ |
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407 |
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Baraloto, C.; Herault, B.; Paine, C.E.T.; Massot, H.; Blanc, L.; Bonal, D.; Molino, J.-F.; Nicolini, E.A.; Sabatier, D. |
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Contrasting taxonomic and functional responses of a tropical tree community to selective logging |
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Journal Article |
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2012 |
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Journal of Applied Ecology |
Abbreviated Journal |
J. Appl. Ecol. |
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49 |
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4 |
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861-870 |
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Canopy gap dynamics; Disturbance; French Guiana; Functional diversity; Functional evenness; Functional traits; Light partitioning; Species richness; Tropical rain forest |
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1.Considerable debate surrounds the extent to which tropical forests can be managed for resource extraction while conserving biodiversity and ecosystem properties, which depend on functional composition. Here we evaluate the compatibility of these aims by examining the effects of logging on taxonomic and functional diversity and composition in a tropical forest. 2.Twenty years after selective logging, we inventoried 4140 stems regenerating in logging gaps and adjacent undisturbed areas, and we integrated a database of 13 functional traits describing leaf and wood economics of tropical trees. 3.We found no differences in taxonomic and functional richness among habitats, but logging gaps had significantly higher taxonomic and functional evenness. 4.Logging also effected striking, long-term changes in both species and functional composition. In particular, the xylem density of recruits in logging gaps was 6% less than in unlogged forests, leaves were 11% less tough and had 6-13% greater mineral nutrient concentrations. 5.Synthesis and applications. Our results suggest that managers of tropical forests should limit overall surface area converted to logging gaps by creating fewer, larger gaps during selective logging, to reduce impacts on the taxonomic and functional composition of the regenerating stand. Our results suggest that managers of tropical forests should limit overall surface area converted to logging gaps by creating fewer, larger gaps during selective logging, to reduce impacts on the taxonomic and functional composition of the regenerating stand. © 2012 The Authors. Journal of Applied Ecology © 2012 British Ecological Society. |
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CIRAD-ES, Research Unit 'Biens et Services des Ecosystémes Forestiers tropicaux', Embrapa Amazonia Oriental, Caixa Postal, 48, Belem, Para – CEP 66095-100, Brazil |
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00218901 (Issn) |
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Export Date: 30 July 2012; Source: Scopus; Coden: Japea; doi: 10.1111/j.1365-2664.2012.02164.x; Language of Original Document: English; Correspondence Address: Baraloto, C.; INRA, UMR 'Ecologie des Forêts de Guyane', 97387 Kourou Cedex, French Guiana; email: chris.baraloto@ecofog.gf |
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EcoFoG @ webmaster @ |
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410 |
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Fromin, N.; Porte, B.; Lensi, R.; Hamelin, J.; Domenach, A.-M.; Buatois, B.; Roggy, J.-C. |
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Spatial variability of the functional stability of microbial respiration process: A microcosm study using tropical forest soil |
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Journal Article |
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2012 |
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Journal of Soils and Sediments |
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J. Soils Sed. |
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12 |
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7 |
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1030-1039 |
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Disturbance; Diversity-stability relationship; Microbial diversity; Substrate-induced respiration |
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Purpose: Understanding the ability of ecosystem processes to resist to and to recover from disturbances is critical to sustainable land use. However, the spatial variability of the stability has rarely been addressed. Here, we investigated the functional stability of a soil microbial process for 24 soils collected from adjacent locations from a 0. 3 ha tropical rainforest plot in Paracou, French Guiana. Materials and methods: The 24 locations were characterized regarding soil chemical and biological (microbial diversity) parameters and forest structure. The corresponding soils were submitted to an experimental transient heat disturbance during a microcosm experiment. The response of the respiration process was followed using substrate-induced respiration (SIR). Results and discussion: The response of soil SIR to heat disturbance varied widely between samples. The variability of the SIR response increased just after the disturbance, and a global rather homogeneous decrease in SIR rates was observed 15 and 30 days after. The stability of SIR in response to heat disturbance could not be related to either the genetic or the metabolic diversity of the microbial community. The initial level of SIR before the disturbance was the soil variable that best correlated with the impact of the disturbance: the soil locations with the highest initial SIR rates were the most affected 15 and 30 days after the heat disturbance. Conclusions: Such a heterogeneous response suggests that the response of soil processes to a disturbance will be difficult to assess from only local-scale analyses and highlights the need for spatial explicitness in understanding biogeochemical processes. © 2012 Springer-Verlag. |
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UMR EcoFoG, BP 709, 97387 Kourou, French Guiana |
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14390108 (Issn) |
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Export Date: 30 July 2012; Source: Scopus; doi: 10.1007/s11368-012-0528-7; Language of Original Document: English; Correspondence Address: Fromin, N.; CEFE, CNRS UMR 5175, 1919 Route de Mende, 34293 Montpellier cedex 5, France; email: nathalie.fromin@cefe.cnrs.fr |
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EcoFoG @ webmaster @ |
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415 |
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Barthe, S.; Gugerli, F.; Barkley, N.A.; Maggia, L.; Cardi, C.; Scotti, I. |
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Always look on both sides: Phylogenetic information conveyed by simple sequence repeat allele sequences |
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Journal Article |
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2012 |
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PLoS ONE |
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PLoS ONE |
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7 |
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7 |
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e40699 |
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Simple sequence repeat (SSR) markers are widely used tools for inferences about genetic diversity, phylogeography and spatial genetic structure. Their applications assume that variation among alleles is essentially caused by an expansion or contraction of the number of repeats and that, accessorily, mutations in the target sequences follow the stepwise mutation model (SMM). Generally speaking, PCR amplicon sizes are used as direct indicators of the number of SSR repeats composing an allele with the data analysis either ignoring the extent of allele size differences or assuming that there is a direct correlation between differences in amplicon size and evolutionary distance. However, without precisely knowing the kind and distribution of polymorphism within an allele (SSR and the associated flanking region (FR) sequences), it is hard to say what kind of evolutionary message is conveyed by such a synthetic descriptor of polymorphism as DNA amplicon size. In this study, we sequenced several SSR alleles in multiple populations of three divergent tree genera and disentangled the types of polymorphisms contained in each portion of the DNA amplicon containing an SSR. The patterns of diversity provided by amplicon size variation, SSR variation itself, insertions/deletions (indels), and single nucleotide polymorphisms (SNPs) observed in the FRs were compared. Amplicon size variation largely reflected SSR repeat number. The amount of variation was as large in FRs as in the SSR itself. The former contributed significantly to the phylogenetic information and sometimes was the main source of differentiation among individuals and populations contained by FR and SSR regions of SSR markers. The presence of mutations occurring at different rates within a marker's sequence offers the opportunity to analyse evolutionary events occurring on various timescales, but at the same time calls for caution in the interpretation of SSR marker data when the distribution of within-locus polymorphism is not known. |
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Unité Mixte de Recherche Ecologie des forêts de Guyane, Institut National de la Recherche Agronomique, Kourou, French Guiana |
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19326203 (Issn) |
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Export Date: 30 July 2012; Source: Scopus; Art. No.: e40699; doi: 10.1371/journal.pone.0040699; Language of Original Document: English; Correspondence Address: Scotti, I.; Unité Mixte de Recherche Ecologie des forêts de Guyane, Institut National de la Recherche Agronomique, Kourou, French Guiana; email: ivan.scotti@ecofog.gf |
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EcoFoG @ webmaster @ |
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416 |
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Dejean, A.; Corbara, B.; Azémar, F.; Carpenter, J.M. |
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When attempts at robbing prey turn fatal |
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Journal Article |
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2012 |
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Naturwissenschaften |
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Naturwissenschaften |
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99 |
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7 |
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579-582 |
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Ant predation; Azteca andreae; Cleptobiosis; Flies and dung beetles; Myrmecophyte; Reduviidae; Socialwasps; Stinglessbees |
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Because group-hunting arboreal ants spread-eagle insect prey for a long time before retrieving them, these prey can be coveted by predatory flying insects. Yet, attempting to rob these prey is risky if the ant species is also an effective predator. Here, we show that trying to rob prey from Azteca andreae workers is a fatal error as 268 out of 276 potential cleptobionts (97.1 %) were captured in turn. The ant workers hunt in a group and use the “Velcro®” principle to cling firmly to the leaves of their host tree, permitting them to capture very large prey. Exceptions were one social wasp, plus some Trigona spp. workers and flies that landed directly on the prey and were able to take off immediately when attacked. We conclude that in this situation, previously captured prey attract potential cleptobionts that are captured in turn in most of the cases. © Springer-Verlag 2012. |
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Division of Invertebrate Zoology, American Museum of Natural History, Central Park West at 79th Street, New York, NY 10024, United States |
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00281042 (Issn) |
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Export Date: 30 July 2012; Source: Scopus; Coden: Natwa; doi: 10.1007/s00114-012-0929-x; Language of Original Document: English; Correspondence Address: Dejean, A.; CNRS, Écologie des Forêts de Guyane (UMR-CNRS 8172), Campus agronomique, BP 316, 97379 Kourou cedex, France; email: alain.dejean@wanadoo.fr |
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EcoFoG @ webmaster @ |
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417 |
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Vincent, G.; Sabatier, D.; Blanc, L.; Chave, J.; Weissenbacher, E.; Pélissier, R.; Fonty, E.; Molino, J.-F.; Couteron, P. |
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Accuracy of small footprint airborne LiDAR in its predictions of tropical moist forest stand structure |
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Journal Article |
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2012 |
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Remote Sensing of Environment |
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Remote Sens. Environ. |
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125 |
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23-33 |
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Basal area; Lidar; Tropical moist forest |
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We predict stand basal area (BA) from small footprint LiDAR data in 129 one-ha tropical forest plots across four sites in French Guiana and encompassing a great diversity of forest structures resulting from natural (soil and geological substrate) and anthropogenic effects (unlogged and logged forests). We use predictors extracted from the Canopy Height Model to compare models of varying complexity: single or multiple regressions and nested models that predict BA by independent estimates of stem density and quadratic mean diameter. Direct multiple regression was the most accurate, giving a 9.6% Root Mean Squared Error of Prediction (RMSEP). The magnitude of the various errors introduced during the data collection stage is evaluated and their contribution to MSEP is analyzed. It was found that these errors accounted for less than 10% of model MSEP, suggesting that there is considerable scope for model improvement. Although site-specific models showed lower MSEP than global models, stratification by site may not be the optimal solution. The key to future improvement would appear to lie in a stratification that captures variations in relations between LiDAR and forest structure. © 2012 Elsevier Inc. |
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ONF, Direction régionale de la Guyane, Cayenne, 97300 France |
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00344257 (Issn) |
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Export Date: 9 August 2012; Source: Scopus; Article in Press; Coden: Rseea; doi: 10.1016/j.rse.2012.06.019; Language of Original Document: English; Correspondence Address: Vincent, G.; IRD AMAP CIRAD, TA A-51/PS2, 34398 Montpellier cedex 5, Franceemail: gregoire.vincent@ird.fr |
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EcoFoG @ webmaster @ |
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418 |
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Dubois-Fernandez, P.C.; Le Toan, T.; Daniel, S.; Oriot, H.; Chave, J.; Blanc, L.; Villard, L.; Davidson, M.W.J.; Petit, M. |
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The tropiSAR airborne campaign in French Guiana: Objectives, description, and observed temporal behavior of the backscatter signal |
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Journal Article |
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2012 |
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IEEE Transactions on Geoscience and Remote Sensing |
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IEEE Trans Geosci Remote Sens |
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50 |
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8 |
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3228-3241 |
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Forestry; interferometry; polarimetric synthetic aperture radar |
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The TropiSAR campaign has been conducted in August 2009 in French Guiana with the ONERA airborne radar system SETHI. The main objective of this campaign was to collect data to support the Phase A of the 7th Earth Explorer candidate mission, BIOMASS. Several specific questions needed to be addressed to consolidate the mission concept following the Phase 0 studies, and the data collection strategy was constructed accordingly. More specifically, a tropical forest data set was required in order to provide test data for the evaluation of the foreseen inversion algorithms and data products. The paper provides a description of the resulting data set which is now available through the European Space Agency website under the airborne campaign link. First results from the TropiSAR database analysis are presented with two in-depth analyses about both the temporal radiometric variation and temporal coherence at P-band. The temporal variations of the backscatter values are less than 0.5 dB throughout the campaign, and the coherence values are observed to stay high even after 22 days. These results are essential for the BIOMASS mission. The observed temporal stability of the backscatter is a good indicator of the expected robustness of the biomass estimation in tropical forests, from cross-polarized backscatter values as regarding environmental changes such as soil moisture. The high temporal coherence observed after a 22-day period is a prerequisite for SAR Polarimetric Interferometry and Tomographic applications in a single satellite configuration. The conclusion then summarizes the paper and identifies the next steps in the analysis. © 2012 IEEE. |
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Institut de Recherche Pour le Développement, 31062 Toulouse, France |
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Export Date: 9 August 2012; Source: Scopus; Art. No.: 6146421; Coden: Igrsd; doi: 10.1109/TGRS.2011.2180728; Language of Original Document: English; Correspondence Address: Dubois-Fernandez, P.C.; Office National d'Études et de Recherches Aérospatiales, Department of Electromagnetism and Radarh, 91761 Palaiseau, France; email: pdubois@onera.fr |
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EcoFoG @ webmaster @ |
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419 |
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Coté, G.G.; Gibernau, M. |
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Distribution of calcium oxalate crystals in floral organs of araceae in relation to pollination strategy |
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2012 |
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American Journal of Botany |
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Am. J. Bot. |
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99 |
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7 |
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1231-1242 |
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Araceae; Beetles; Calcium oxalate; Crystal; Defense; Flowers; Herbivory; Pollination |
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Premise of the study: Many flowers are pollinated by potentially hungry insects, yet flowers also contain gametes and embryos which must be protected from predation. Microscopic calcium oxalate crystals in plant tissues have been proposed to protect against herbivory. Aroids, which have an unusual diversity of such crystals, also exhibit diverse pollination strategies. Many species have pollinators that do not feed while visiting the flowers, while other species, especially those pollinated by beetles, offer sterile staminodia as food rewards. We examined flowers of 21 aroid species with various pollination strategies to test the hypothesis that crystals protect vital gametes and embryos while allowing consumption of food bribes.Methods: Aroid inflorescences collected from the field or from greenhouse material were sectioned, cleared, and examined by bright field and polarization microscopy.Key results: All species examined, regardless of pollination strategy, arrayed crystals around unshed pollen and ovules. Less vital tissues, such as odoriferous appendages, had few crystals. Staminodia offered as food to beetle pollinators, however, differed greatly between species in their crystal contents. Some had minimal crystals; some had crystals in patterns suggesting they limit beetle feeding; still others had abundant crystals in no obvious pattern.Conclusions: The results are consistent with crystals protecting against insect predation of gametes and embryos. However, the role of crystals in food-bribe staminodia is unclear. They may limit and direct feeding by beetles in some species, while in others they might have no protective role. © 2012 Botanical Society of America. |
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CNRS-Ecolog (UMR 8172), Campus Agronomique BP316, Korou cedex 97379, France |
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Export Date: 10 August 2012; Source: Scopus; Coden: Ajboa; doi: 10.3732/ajb.1100499; Language of Original Document: English; Correspondence Address: Coté, G. G.; Biology Department, Radford University, Radford, VA 24142-6931, United States; email: gcote@radford.edu |
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