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Essebtey, Salma El Idrissi ; Villard, Ludovic ; Borderies, Pierre ; Koleck, Thierry ; Burban, Benoït ; Le Toan, Thuy |
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Title |
Long-Term Trends of P-Band Temporal Decorrelation Over a Tropical Dense Forest-Experimental Results for the BIOMASS Mission |
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Journal Article |
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2021 |
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IEEE Transactions on Geoscience and Remote Sensing |
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60 |
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1-15 |
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Fostered by the upcoming BIOMASS mission, this article explores long-term trends of P-band temporal decorrelation over a tropical forest due to a time series of 617 days acquired during the TropiScat-2 experiment. The interest in this unique time series is twofold. First, it provides consistent statistics to monitor the yearly evolution of temporal coherences according to specific time scales of the BIOMASS tomographic and interferometric phases. Second, it provides key insights to explore new processing approaches with the combination of data from different orbit directions (ascending/descending) and different mission cycles separated by about seven months according to the current acquisition plan. For the first time, this study shows that 18-day coherences (corresponding to the time interval between the first and last acquisitions of the BIOMASS tomographic processing) can vary significantly according to rainy and dry seasons (medians from 0.3 to 0.9). The extension to time intervals of up to 90 days within both seasons and over two consecutive years puts forward the key role of the typical sporadic rainfalls occurring during dry periods in tropical rainforests, with a stronger impact on temporal coherence evolution compared to the more reproducible rainy seasons. Furthermore, outstanding values significantly above zero have been obtained for the 7- and 14-month coherences (medians of 0.35 and 0.2, respectively), opening the way to new methods of change detection. Overall, this study highlights the role of P-band temporal decorrelation not only as a disturbance factor for coherent applications but also as a relevant indicator of forest changes. |
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Institute of Electrical and Electronics Engineers |
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EcoFoG @ webmaster @ |
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1060 |
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Herault, B.; Beauchene, J.; Muller, F.; Wagner, F.; Baraloto, C.; Blanc, L.; Martin, J.M. |
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Title |
Modeling decay rates of dead wood in a neotropical forest |
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Journal Article |
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Year |
2010 |
Publication |
Oecologia |
Abbreviated Journal |
Oecologia |
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Volume |
164 |
Issue |
1 |
Pages |
243-251 |
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Amazonia; Carbon cycle; Decomposition; Selective logging; Rainforest; Coarse woody debris |
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Variation of dead wood decay rates among tropical trees remains one source of uncertainty in global models of the carbon cycle. Taking advantage of a broad forest plot network surveyed for tree mortality over a 23-year period, we measured the remaining fraction of boles from 367 dead trees from 26 neotropical species widely varying in wood density (0.23-1.24 g cm(-3)) and tree circumference at death time (31.5-272.0 cm). We modeled decay rates within a Bayesian framework assuming a first order differential equation to model the decomposition process and tested for the effects of forest management (selective logging vs. unexploited), of mode of death (standing vs. downed) and of topographical levels (bottomlands vs. hillsides vs. hilltops) on wood decay rates. The general decay model predicts the observed remaining fraction of dead wood (R (2) = 60%) with only two biological predictors: tree circumference at death time and wood specific density. Neither selective logging nor local topography had a differential effect on wood decay rates. Including the mode of death into the model revealed that standing dead trees decomposed faster than downed dead trees, but the gain of model accuracy remains rather marginal. Overall, these results suggest that the release of carbon from tropical dead trees to the atmosphere can be simply estimated using tree circumference at death time and wood density. |
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[Herault, Bruno; Wagner, Fabien; Martin, Jean-Michel] Univ Antilles Guyane, UMR EcoFoG, F-97387 Kourou, France, Email: bruno.herault@ecofog.gf |
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SPRINGER |
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0029-8549 |
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ISI:000280962200023 |
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EcoFoG @ eric.marcon @ |
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45 |
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Dejean, A.; Carpenter, J.M.; Gibernau, M.; Leponce, M.; Corbara, B. |
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Title |
Nest relocation and high mortality rate in a Neotropical social wasp: Impact of an exceptionally rainy La Nina year |
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Journal Article |
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Year |
2010 |
Publication |
Comptes Rendus Biologies |
Abbreviated Journal |
C. R. Biol. |
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333 |
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1 |
Pages |
35-40 |
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Vespidae; Population size variation; Microevolution; La Nina; French Guiana |
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After noting the forecast of a La Nina episode, associated with heavy rainfall in French Guiana, we monitored the fate of wasp nests before and during the 2006 short rainy season. The population of the most abundant epiponine wasp species, Polybia bistriata, decreased dramatically during the short rainy season (60.6% of the nests disappeared) then remained low for at least 18 months. Colonies that survived moved from the shelter of large, low leaves (a situation well adapted to the previous dry season) of the most frequent substrate tree, Clusia grandiflora (Clusiaceae), to upper leaves, better ventilated and whose orientation provides good protection from the rain. Therefore, the possibility of moving the nest higher during the first rains following the dry season seems very adaptive as colonies that do not do so are eliminated during the La Nina years, whose frequency will increase with global climate change. (C) 2009 Academie des sciences. Published by Elsevier Masson SAS. All rights reserved. |
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[Dejean, Alain; Gibernau, Marc] CNRS, UMR Ecofog 8172, F-97387 Kourou, France, Email: alain.dejean@wanadoo.fr |
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ELSEVIER FRANCE-EDITIONS SCIENTIFIQUES MEDICALES ELSEVIER |
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1631-0691 |
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ISI:000275984200006 |
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EcoFoG @ eric.marcon @ |
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64 |
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Chave, J.; Navarrete, D.; Almeida, S.; Alvarez, E.; Aragao, L.E.O.C.; Bonal, D.; Chatelet, P.; Silva-Espejo, J.E.; Goret, J.Y.; von Hildebrand, P.; Jimenez, E.; Patino, S.; Penuela, M.C.; Phillips, O.L.; Stevenson, P.; Malhi, Y. |
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Title |
Regional and seasonal patterns of litterfall in tropical South America |
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Journal Article |
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Year |
2010 |
Publication |
Biogeosciences |
Abbreviated Journal |
Biogeosciences |
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7 |
Issue |
1 |
Pages |
43-55 |
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The production of aboveground soft tissue represents an important share of total net primary production in tropical rain forests. Here we draw from a large number of published and unpublished datasets (n=81 sites) to assess the determinants of litterfall variation across South American tropical forests. We show that across old-growth tropical rainforests, litterfall averages 8.61 +/- 1.91 Mg ha(-1) yr(-1) (mean +/- standard deviation, in dry mass units). Secondary forests have a lower annual litterfall than old-growth tropical forests with a mean of 8.01 +/- 3.41 Mg ha(-1) yr(-1). Annual litterfall shows no significant variation with total annual rainfall, either globally or within forest types. It does not vary consistently with soil type, except in the poorest soils (white sand soils), where litterfall is significantly lower than in other soil types (5.42 +/- 1.91 Mg ha(-1) yr(-1)). We also study the determinants of litterfall seasonality, and find that it does not depend on annual rainfall or on soil type. However, litterfall seasonality is significantly positively correlated with rainfall seasonality. Finally, we assess how much carbon is stored in reproductive organs relative to photosynthetic organs. Mean leaf fall is 5.74 +/- 1.83 Mg ha(-1) yr(-1) (71% of total litterfall). Mean allocation into reproductive organs is 0.69 +/- 0.40 Mg ha(-1) yr(-1) (9% of total litterfall). The investment into reproductive organs divided by leaf litterfall increases with soil fertility, suggesting that on poor soils, the allocation to photosynthetic organs is prioritized over that to reproduction. Finally, we discuss the ecological and biogeochemical implications of these results. |
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[Chave, J.] CNRS UPS, Lab Evolut & Divers Biol, UMR 5174, Toulouse, France, Email: chave@cict.fr |
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COPERNICUS GESELLSCHAFT MBH |
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1726-4170 |
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ISI:000274058100004 |
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EcoFoG @ eric.marcon @ |
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70 |
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Baraloto, C.; Paine, C.E.T.; Patino, S.; Bonal, D.; Herault, B.; Chave, J. |
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Title |
Functional trait variation and sampling strategies in species-rich plant communities |
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Journal Article |
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2010 |
Publication |
Functional Ecology |
Abbreviated Journal |
Funct. Ecol. |
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24 |
Issue |
1 |
Pages |
208-216 |
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French Guiana; functional diversity; plant traits; specific leaf area; wood density; sampling design; tropical forest |
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P> Despite considerable interest in the application of plant functional traits to questions of community assembly and ecosystem structure and function, there is no consensus on the appropriateness of sampling designs to obtain plot-level estimates in diverse plant communities. We measured 10 plant functional traits describing leaf and stem morphology and ecophysiology for all trees in nine 1-ha plots in terra firme lowland tropical rain forests of French Guiana (N = 4709). We calculated, by simulation, the mean and variance in trait values for each plot and each trait expected under seven sampling methods and a range of sampling intensities. Simulated sampling methods included a variety of spatial designs, as well as the application of existing data base values to all individuals of a given species. For each trait in each plot, we defined a performance index for each sampling design as the proportion of resampling events that resulted in observed means within 5% of the true plot mean, and observed variance within 20% of the true plot variance. The relative performance of sampling designs was consistent for estimations of means and variances. Data base use had consistently poor performance for most traits across all plots, whereas sampling one individual per species per plot resulted in relatively high performance. We found few differences among different spatial sampling strategies; however, for a given strategy, increased intensity of sampling resulted in markedly improved accuracy in estimates of trait mean and variance. We also calculated the financial cost of each sampling design based on data from our 'every individual per plot' strategy and estimated the sampling and botanical effort required. The relative performance of designs was strongly positively correlated with relative financial cost, suggesting that sampling investment returns are relatively constant. Our results suggest that trait sampling for many objectives in species-rich plant communities may require the considerable effort of sampling at least one individual of each species in each plot, and that investment in complete sampling, though great, may be worthwhile for at least some traits. |
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[Baraloto, Christopher; Patino, Sandra; Bonal, Damien] INRA, UMR Ecol Forets Guyane, F-97387 Kourou, French Guiana, Email: chris.baraloto@ecofog.gf |
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WILEY-BLACKWELL PUBLISHING, INC |
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0269-8463 |
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ISI:000273455500024 |
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EcoFoG @ eric.marcon @ |
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72 |
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Conte, D.E.; Aboulaich, A.; Robert, F.; Olivier-Fourcade, J.; Jumas, J.C.; Jordy, C.; Willmann, P. |
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Title |
Sn-x[BPO4](1-x) composites as negative electrodes for lithium ion cells: Comparison with amorphous SnB0.6P0.4O2.9 and effect of composition |
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Journal Article |
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Year |
2010 |
Publication |
Journal of Solid State Chemistry |
Abbreviated Journal |
J. Solid State Chem. |
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Volume |
183 |
Issue |
1 |
Pages |
65-75 |
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Sn-based composites; Lithium-ion batteries; Negative electrodes; Mossbauer spectroscopy; LixSn alloys |
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Abstract |
A comparative study of two Sn-based composite materials as negative electrode for Li-ion accumulators is presented. The former SnB0.6P0.4O2.9 obtained by in-situ dispersion of SnO in an oxide matrix is shown to be an amorphous tin composite oxide (ATCO). The latter Sn-0.72[BPO4](0.28) obtained by ex-situ dispersion of Sri in a borophosphate matrix consists of Sri particles embedded in a crystalline BPO4 matrix. The electrochemical responses of ATCO and Sn-0.72.[BPO4](0.28) composite in galvanostatic mode show reversible capacities of about 450 and 530 mAhg(-1), respectively, with different irreversible capacities (60% and 29%). Analysis of these composite materials by Sn-119 Mossbauer spectroscopy in transmission (TMS) and emission (CEMS) modes confirms that ATCO is an amorphous Sn-II composite oxide and shows that in the case of Sn-0.72[BPO4](0.28), the Surface of the tin clusters is mainly formed by Sn-II in an amorphous interface whereas the bulk of the clusters is mainly formed by Sn-0. The determination of the recoilless free fractions f (Lamb-Mossbauer factors) leads to the effective fraction of both Sn-0 and Sn-II species in such composites. The influence of chemical composition and especially of the surface-to-bulk tin species ratio oil the electrochemical behaviour has been analysed for several Sn-x[BPO4](1-x) composite materials (0.17 < x < 0.91). The cell using the compound Sn-0.72[BPO4](0.28) as active material exhibits interesting electrochemical performances (reversible capacity of 500 mAh g(-1) at C/5 rate). (C) 2009 Elsevier Inc. All rights reserved. |
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[Conte, Donato Ercole; Aboulaich, Abdelmaula; Robert, Florent; Olivier-Fourcade, Josette; Jumas, Jean-Claude] Univ Montpellier 2, CNRS, UMR 5253,Inst Charles Gerhardt, Equipe Agregats Interfaces & Mat Energie, F-34095 Montpellier, France, Email: iguanasornione@libero.it |
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ACADEMIC PRESS INC ELSEVIER SCIENCE |
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0022-4596 |
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ISI:000273834600010 |
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EcoFoG @ eric.marcon @ |
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83 |
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Aimene, Y.; Vidal-Salle, E.; Hagege, B.; Sidoroff, F.; Boisse, P. |
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Title |
A Hyperelastic Approach for Composite Reinforcement Large Deformation Analysis |
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Journal Article |
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Year |
2010 |
Publication |
Journal of Composite Materials |
Abbreviated Journal |
J. Compos Mater. |
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Volume |
44 |
Issue |
1 |
Pages |
5-26 |
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Keywords |
hyperelasticity; woven reinforcements; forming; fabric mechanical behavior; finite element |
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Abstract |
A hyperelastic constitutive model is developed for textile composite reinforcement at large strain. A potential is proposed, which is the addition of two tension and one shear energies. The proposed potential is a function of the right Cauchy Green and structural tensor invariants whose choice corresponds to textile composite reinforcement mechanical behavior which exhibits weak elongations in the fiber directions and large angular variations in the fabric plane. The model is implemented in a Vumat user routine of ABAQUS/Explicit. Some elementary tests are performed in order to identify the model and verify its validity. It is then used to simulate the hemispherical punch forming of balanced and unbalanced fabrics. A correct agreement is obtained with experimental forming processes. |
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[Aimene, Y.; Vidal-Salle, E.; Boisse, P.] Univ Lyon, INSA Lyon, LaMCoS, F-69621 Villeurbanne, France, Email: philippe.boisse@insa-lyon.fr |
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SAGE PUBLICATIONS LTD |
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0021-9983 |
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ISI:000273509100001 |
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EcoFoG @ eric.marcon @ |
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84 |
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Ferrer, A.; Dixon, A.F.; Gibernau, M.; Hemptinne, J.L. |
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Title |
Ovarian dynamics and specialisation in ladybirds |
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Journal Article |
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Year |
2010 |
Publication |
Ecological Entomology |
Abbreviated Journal |
Ecol. Entomol. |
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35 |
Issue |
1 |
Pages |
100-103 |
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Keywords |
Ladybird beetles; oocyte resorption; ovarian dynamics; specialisation |
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2. This hypothesis was tested by comparing a generalist and a specialist ladybird species belonging to the same genus. 3. A resorption index was calculated for females of both species subjected to several starvation regimes. This index indicated that over a period of fasting of 3 days, the intensity of resorption was greater in the generalist than the specialist. When food was again supplied, oogenesis resumed and within 1 day was faster in the generalist than in the specialist. 4. As predicted, the resorption of oocytes and replenishment occurred faster in the generalist than in the specialist species. This is the first time, to our knowledge, that the speed and intensity of the ovarian dynamics of a predatory insect have been linked to its way of life. |
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[Ferrer, Aurelie; Hemptinne, Jean-Louis] Univ Toulouse ENFAT, CNRS, UMR 5174, F-31326 Castanet Tolosan, France, Email: jean-louis.hemptinne@educagri.fr |
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WILEY-BLACKWELL PUBLISHING, INC |
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0307-6946 |
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ISI:000273454300013 |
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no |
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EcoFoG @ eric.marcon @ |
Serial |
86 |
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Author |
Ferry, B.; Morneau, F.; Bontemps, J.D.; Blanc, L.; Freycon, V. |
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Title |
Higher treefall rates on slopes and waterlogged soils result in lower stand biomass and productivity in a tropical rain forest |
Type |
Journal Article |
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Year |
2010 |
Publication |
Journal of Ecology |
Abbreviated Journal |
J. Ecol. |
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Volume |
98 |
Issue |
1 |
Pages |
106-116 |
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Keywords |
biomass; community ecology; growth; mortality; productivity; soil waterlogging; topography; treefall; tropical moist forest; wood density |
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Abstract |
P>1. Relationships between tropical rain forest biomass and environmental factors have been determined at regional scales, e.g. the Amazon Basin, but the reasons for the high variability in forest biomass at local scales are poorly understood. Interactions between topography, soil properties, tree growth and mortality rates, and treefalls are a likely reason for this variability. 2. We used repeated measurements of permanent plots in lowland rain forest in French Guiana to evaluate these relationships. The plots sampled topographic gradients from hilltops to slopes to bottomlands, with accompanying variation in soil waterlogging along these gradients. Biomass was calculated for > 175 tree species in the plots, along with biomass productivity and recruitment rates. Mortality was determined as standing dead and treefalls. 3. Treefall rates were twice as high in bottomlands as on hilltops, and tree recruitment rates, radial growth rates and the abundance of light-demanding tree species were also higher. 4. In the bottomlands, the mean wood density was 10% lower than on hilltops, the basal area 29% lower and the height:diameter ratio of trees was lower, collectively resulting in a total woody biomass that was 43% lower in bottomlands than on hilltops. 5. Biomass productivity was 9% lower in bottomlands than on hilltops, even though soil Olsen P concentrations were higher in bottomlands. 6. Synthesis. Along a topographic gradient from hilltops to bottomlands there were higher rates of treefall, which decreased the stand basal area and favoured lower allocation to height growth and recruitment of light-demanding species with low wood density. The resultant large variation in tree biomass along the gradient shows the importance of determining site characteristics and including these characteristics when scaling up biomass estimates from stand to local or regional scales. |
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Address |
[Ferry, Bruno; Morneau, Francois; Bontemps, Jean-Daniel] AgroParisTech, ENGREF Nancy, UMR 1092, CS 14216, F-54000 Nancy, France, Email: bruno.ferry@engref.agroparistech.fr |
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WILEY-BLACKWELL PUBLISHING, INC |
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0022-0477 |
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Notes |
ISI:000272657400012 |
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no |
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Call Number |
EcoFoG @ eric.marcon @ |
Serial |
87 |
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Author |
Gonzalez, M.A.; Roger, A.; Courtois, E.A.; Jabot, F.; Norden, N.; Paine, C.E.T.; Baraloto, C.; Thebaud, C.; Chave, J. |
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Title |
Shifts in species and phylogenetic diversity between sapling and tree communities indicate negative density dependence in a lowland rain forest |
Type |
Journal Article |
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Year |
2010 |
Publication |
Journal of Ecology |
Abbreviated Journal |
J. Ecol. |
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Volume |
98 |
Issue |
1 |
Pages |
137-146 |
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Keywords |
APG II plus rbcL megatree; density dependence; DNA barcoding; French Guiana; phylogenetic diversity; species diversity; tropical plant communities |
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Abstract |
P>1. As trees in a given cohort progress through ontogeny, many individuals die. This risk of mortality is unevenly distributed across species because of many processes such as habitat filtering, interspecific competition and negative density dependence. Here, we predict and test the patterns that such ecological processes should inscribe on both species and phylogenetic diversity as plants recruit from saplings to the canopy. 2. We compared species and phylogenetic diversity of sapling and tree communities at two sites in French Guiana. We surveyed 2084 adult trees in four 1-ha tree plots and 943 saplings in sixteen 16-m2 subplots nested within the tree plots. Species diversity was measured using Fisher's alpha (species richness) and Simpson's index (species evenness). Phylogenetic diversity was measured using Faith's phylogenetic diversity (phylogenetic richness) and Rao's quadratic entropy index (phylogenetic evenness). The phylogenetic diversity indices were inferred using four phylogenetic hypotheses: two based on rbcLa plastid DNA sequences obtained from the inventoried individuals with different branch lengths, a global phylogeny available from the Angiosperm Phylogeny Group, and a combination of both. 3. Taxonomic identification of the saplings was performed by combining morphological and DNA barcoding techniques using three plant DNA barcodes (psbA-trnH, rpoC1 and rbcLa). DNA barcoding enabled us to increase species assignment and to assign unidentified saplings to molecular operational taxonomic units. 4. Species richness was similar between saplings and trees, but in about half of our comparisons, species evenness was higher in trees than in saplings. This suggests that negative density dependence plays an important role during the sapling-to-tree transition. 5. Phylogenetic richness increased between saplings and trees in about half of the comparisons. Phylogenetic evenness increased significantly between saplings and trees in a few cases (4 out of 16) and only with the most resolved phylogeny. These results suggest that negative density dependence operates largely independently of the phylogenetic structure of communities. 6. Synthesis. By contrasting species richness and evenness across size classes, we suggest that negative density dependence drives shifts in composition during the sapling-to-tree transition. In addition, we found little evidence for a change in phylogenetic diversity across age classes, suggesting that the observed patterns are not phylogenetically constrained. |
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Address |
[Gonzalez, Mailyn A.; Roger, Aurelien; Courtois, Elodie A.; Jabot, Franck; Norden, Natalia; Thebaud, Christophe; Chave, Jerome] Univ Toulouse 3, Lab Evolut & Diversite Biol, UMR 5174, CNRS, F-31062 Toulouse, France, Email: gonzalez.mailyn@gmail.com |
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WILEY-BLACKWELL PUBLISHING, INC |
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0022-0477 |
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ISI:000272657400015 |
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EcoFoG @ eric.marcon @ |
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88 |
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