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van Gorsel, E.; Delpierre, N.; Leuning, R.; Black, A.; Munger, J.W.; Wofsy, S.; Aubinet, M.; Feigenwinter, C.; Beringer, J.; Bonal, D.; Chen, B.Z.; Chen, J.Q.; Clement, R.; Davis, K.J.; Desai, A.R.; Dragoni, D.; Etzold, S.; Grunwald, T.; Gu, L.H.; Heinesch, B.; Hutyra, L.R.; Jans, W.W.P.; Kutsch, W.; Law, B.E.; Leclerc, M.Y.; Mammarella, I.; Montagnani, L.; Noormets, A.; Rebmann, C.; Wharton, S. |
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Title |
Estimating nocturnal ecosystem respiration from the vertical turbulent flux and change in storage of CO2 |
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Journal Article |
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Year |
2009 |
Publication |
Agricultural and Forest Meteorology |
Abbreviated Journal |
Agric. For. Meteorol. |
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Volume |
149 |
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11 |
Pages |
1919-1930 |
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Ecosystem respiration; Micrometeorology; Advection; u-star correction; Eddy covariance; Chamber; Process-based modelling |
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Micrometeorological measurements of night time ecosystem respiration can be systematically biased when stable atmospheric conditions lead to drainage flows associated with decoupling of air flow above and within plant canopies. The associated horizontal and vertical advective fluxes cannot be measured using instrumentation on the single towers typically used at micrometeorological sites. A common approach to minimize bias is to use a threshold in friction velocity, u*, to exclude periods when advection is assumed to be important, but this is problematic in situations when in-canopy flows are decoupled from the flow above. Using data from 25 flux stations in a wide variety of forest ecosystems globally, we examine the generality of a novel approach to estimating nocturnal respiration developed by van Gorsel et al. (van Gorsel, E., Leuning, R., Cleugh, H.A., Keith, H., Suni, T., 2007. Nocturnal carbon efflux: reconciliation of eddy covariance and chamber measurements using an alternative to the u*-threshold filtering technique. Tellus 59B, 397-403, Tellus, 59B, 307-403). The approach is based on the assumption that advection is small relative to the vertical turbulent flux (F-C) and change in storage (F-S) of CO2 in the few hours after sundown. The sum of F-C and F-S reach a maximum during this period which is used to derive a temperature response function for ecosystem respiration. Measured hourly soil temperatures are then used with this function to estimate respiration R-Rmax. The new approach yielded excellent agreement with (1) independent measurements using respiration chambers, (2) with estimates using ecosystem light-response curves of F-c + F-s extrapolated to zero light, R-LRC, and (3) with a detailed process-based forest ecosystem model, R-cast. At most sites respiration rates estimated using the u*-filter, R-ust, were smaller than R-Rmax, and R-LRC. Agreement of our approach with independent measurements indicates that R-Rmax, provides an excellent estimate of nighttime ecosystem respiration. (C) 2009 Elsevier B.V. All rights reserved. |
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[van Gorsel, Eva; Leuning, Ray] CSIRO Marine & Atmospher Res, Canberra, ACT 2061, Australia, Email: Eva.vangorsel@csiro.au |
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ELSEVIER SCIENCE BV |
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0168-1923 |
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ISI:000270640300013 |
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EcoFoG @ eric.marcon @ |
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102 |
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Wagner, F.; Herault, B.; Stahl, C.; Bonal, D.; Rossi, V. |
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Title |
Modeling water availability for trees in tropical forests |
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Journal Article |
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Year |
2011 |
Publication |
Agricultural and Forest Meteorology |
Abbreviated Journal |
Agric. For. Meteorol. |
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Volume |
151 |
Issue |
9 |
Pages |
1202-1213 |
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Keywords |
Water balance model; Amazonian rainforest; Time domain reflectometer; Bayesian inference; Tree drought stress |
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Modeling soil water availability for tropical trees is a prerequisite to predicting the future impact of climate change on tropical forests. In this paper we develop a discrete-time deterministic water balance model adapted to tropical rainforest climates, and we validate it on a large dataset that includes micrometeorological and soil parameters along a topographic gradient in a lowland forest of French Guiana. The model computes daily water fluxes (rainfall interception, drainage, tree transpiration and soil plus understorey evapotranspiration) and soil water content using three input variables: daily precipitation, potential evapotranspiration and solar radiation. A novel statistical approach is employed that uses Time Domain Reflectometer (TDR) soil moisture data to estimate water content at permanent wilting point and at field capacity, and root distribution. Inaccuracy of the TDR probes and other sources of uncertainty are taken into account by model calibration through a Bayesian framework. Model daily output includes relative extractable water, REW, i.e. the daily available water standardized by potential available water. The model succeeds in capturing temporal variations in REW regardless of topographic context. The low Root Mean Square Error of Predictions suggests that the model captures the most important drivers of soil water dynamics, i.e. water refilling and root water extraction. Our model thus provides a useful tool to explore the response of tropical forests to climate scenarios of changing rainfall regime and intensity. (C) 2011 Elsevier B.V. All rights reserved. |
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[Wagner, F; Herault, B] Univ Antilles Guyane, UMR Ecol Forets Guyane, F-97387 Kourou, France, Email: fabien.wagner@ecofog.gf |
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Elsevier Science Bv |
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0168-1923 |
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WOS:000294032000005 |
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EcoFoG @ webmaster @ |
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337 |
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Aguilos, M.; Hérault, B.; Burban, B.; Wagner, F.; Bonal, D. |
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Title |
What drives long-term variations in carbon flux and balance in a tropical rainforest in French Guiana? |
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Journal Article |
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Year |
2018 |
Publication |
Agricultural and Forest Meteorology |
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253–254 |
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114-123 |
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Tropical rainforest; Nee; Gpp; Ecosystem respiration; Radiation; Drought |
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A thorough understanding of how tropical forests respond to climate is important to improve ecosystem process models and to reduce uncertainties in current and future global carbon balance calculations. The Amazon rainforest, a major contributor to the global carbon cycle, is subject to strong intra- and interannual variations in climate conditions. Understanding their effect on carbon fluxes between the ecosystem and the atmosphere and on the resulting carbon balance is still incomplete. We examined the long-term (over a 12-year period; 2004–2015) variations in gross primary productivity (GPP), ecosystem respiration (RE) and net ecosystem exchange (NEE) in a tropical rainforest in French Guiana and identified key climatic drivers influencing the changes. The study period was characterized by strong differences in climatic conditions among years, particularly differences in the intensity of the dry and wet seasons, as well as differences in annual carbon fluxes and balance. Annual average GPP varied from 3384.9?g?C?m-2?yr?1 (95% CI [3320.7, 3445.9]) to 4061.2?g?C?m-2?yr?1 (95% CI [3980.1, 4145.0]). RE varied even more than GPP, with a difference of 933.1?C?m-2?yr?1 between the minimum (3020.6?g?C?m-2?yr?1; 95% CI [2889.4, 3051.3]) and maximum (3953.7?g?C?m-2?yr?1; 95% CI [3887.6, 4019.6]) values. Although NEE showed large interannual variability (nine-fold), from ?65.6?g?C?m-2?yr?1 (95% CI [?4.4, ?126.0]) to ?590.5?g?C?m-2 yr?1 (95% CI [?532.3, ?651.6]), the forest remained a carbon sink over the 12-year period. A combination of global radiation (Rg), relative extractable water (REW) and soil temperature (Ts) explained 51% of the daily variations for GPP, 30% for RE and 39% for NEE. Global radiation was always the best predictor of these variations, but soil water content and temperature did also influence carbon fluxes and balance. Seasonally, Rg was the major controlling factor for GPP, RE and NEE during the wet season. During the dry season, variations in carbon fluxes and balance were poorly explained by climate factors. Yet, REW was the key driver of variations in NEE during the dry season. This study highlights that, over the long-term, carbon fluxes and balance in such tropical rainforest ecosystems are largely controlled by both radiation and water limitation. Even though variations in Rg have a greater impact on these fluxes, water limitation during seasonal droughts is enough to reduce ecosystem productivity, respiration and carbon uptake. The reduced precipitation expected in tropical rainforest areas under future climatic conditions will therefore strongly influence carbon fluxes and carbon uptake. This study also highlights the importance for land surface or dynamic global vegetation models to consider the main drivers of carbon fluxes and balance separately for dry and wet seasons. |
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EcoFoG @ webmaster @ |
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792 |
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Perrin, A.-S.; Fujisaki, K.; Petitjean, C.; Sarrazin, M.; Godet, M.; Garric, B.; Horth, J.-C.; Balbino, L.C.; Filho, A.S.; de Almeida Machado, P.L.O.; Brossard, M. |
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Title |
Conversion of forest to agriculture in Amazonia with the chop-and-mulch method: Does it improve the soil carbon stock? |
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Journal Article |
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Year |
2014 |
Publication |
Agriculture, Ecosystems and Environment |
Abbreviated Journal |
Agric. Ecosyst. Environ. |
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184 |
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101-114 |
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Annual crops; Brachiaria; Deforestation; Fire-free; French Guiana; No-tillage |
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Fire-free forest conversion with organic inputs as an alternative to slash-and-burn could improve agro-ecosystem sustainability. We assessed soil carbon mass changes in a sandy-clayey and well-drained soil in French Guiana after forest clearing by the chop-and-mulch method and crop establishment. At the experimental site of Combi, native forest was cut down in October 2008; woody biomass was chopped and incorporated into the top 20cm of soil. After about one year of legume and grass cover, three forms of land management were compared: grassland (Urochloa ruziziensis), maize/soybean crop rotation with disk tillage and in direct seeding without tillage. There were four replicates. We measured 14.16kgm-2 of carbon in 2mm-sieved soil down to 2m depth for the initial forest. Forest clearing did not induce significant soil compaction; neither did any specific agricultural practice. In converted soils, C stocks were measured in the 0-30cm layer after each crop for three years. Carbon mass changes for soil fractions <2mm (soil C stock) and >2mm (soil C pool) in the 0-5, 5-10, 10-20 and 20-30cm soil layers were assessed on an equivalent soil mass basis. One year and 1.5 years after deforestation, higher C stocks (+0.64 to 1.16kgCm-2yr-1) and C pools (+0.52 to 0.90kgCm-2yr-1) were measured in converted soils, compared to those of the forest into the top 30cm of soil. However, the masses of carbon in these converted soils declined later. The highest rates of carbon decrease were measured between 1.5 and 2 years after forest conversion in the <2mm soil fraction, from 0.46kgCm-2yr-1 (in grassland soils) to 0.71kgCm-2yr-1 (in cropland under no tillage). The carbon pool declined during the third year at rates of 0.41kgCm-2yr-1 (cropland under disk tillage) to 0.76kgCm-2yr-1 (grassland soils). Three years after forest conversion, C masses in the top 30cm of soils for grassland showed similar values than for forest. In comparison, the carbon stock in cropped soils managed under no tillage in direct seeding (without mulch) was significantly 17% and 16% lower than in forest and grassland soils, respectively. None of the studied agricultural practices succeeded in accumulating carbon from the chopped forest biomass. © 2013 Elsevier B.V. |
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EMBRAPA Arroz e Feijao, Cx Postal 179, CEP 75375-000 Santo Antonio de Goias, GO, Brazil |
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01678809 (Issn) |
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Export Date: 2 January 2014; Source: Scopus; Coden: Aeend; doi: 10.1016/j.agee.2013.11.009 |
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EcoFoG @ webmaster @ |
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521 |
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Leroy, C.; Sabatier, S.; Wahyuni, N.S.; Barczi, J.F.; Dauzat, J.; Laurans, M.; Auclair, D. |
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Title |
Virtual trees and light capture: a method for optimizing agroforestry stand design |
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Journal Article |
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2009 |
Publication |
Agroforestry Systems |
Abbreviated Journal |
Agrofor. Syst. |
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77 |
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1 |
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37-47 |
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Acacia mangium; Tectona grandis; Agroforestry; Light interception; Plant architecture; Simulation; 3D virtual plant |
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In agroforestry systems, the distribution of light transmitted under tree canopies can be a limiting factor for the development of intercrops. The light available for intercrops depends on the quantity of light intercepted by tree canopies and, consequently, on the architecture of the tree species present. The influence of tree architecture on light transmission was analysed using dynamic 3D architectural models. The architectural analysis of Acacia mangium and Tectona grandis was performed in Indonesian agroforestry systems with trees aged from 1 to 3 years. 3D virtual trees were then generated with the AmapSim simulation software and 3D virtual experiments in which tree age, planting density, planting pattern and pruning intensity varied were reconstructed in order to simulate light available for the crop. Canopy closure of trees was more rapid in A. mangium than in T. grandis agroforestry systems; after 3 years the quantity of light available for A. mangium intercrops was three times lower than under T. grandis. Simulations with A. mangium showed that practices such as pruning and widening tree spacing enable to increase the total transmitted light within the stand. On T. grandis, modification of the tree row azimuth resulted in changes in the spatial and seasonal distribution of light available for the intercrops. These results are discussed in terms of agroforestry system management. |
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[Sabatier, Sylvie; Barczi, Jean-Francois; Dauzat, Jean; Laurans, Marilyne] CIRAD, UMR AMAP Botan & Bioinformat Architecture Plantes, F-34398 Montpellier 5, France, Email: sylvie-annabel.sabatier@cirad.fr |
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SPRINGER |
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0167-4366 |
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ISI:000268865600004 |
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EcoFoG @ eric.marcon @ |
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199 |
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Nirma, C.; Eparvier, V.; Stien, D. |
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Antifungal agents from Pseudallescheria boydii SNB-CN73 isolated from a nasutitermes sp. termite |
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Journal Article |
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2013 |
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Journal of Natural Products |
Abbreviated Journal |
J. Nat. Prod. |
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76 |
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5 |
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988-991 |
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Defense mutualisms between social insects and microorganisms have been described in the literature. The present article describes the discovery of a Pseudallescheria boydii strain isolated from Nasutitermes sp. The microbial symbiont produces two antifungal metabolites: tyroscherin and N-methyltyroscherin, a compound not previously described in the literature. Methylation of tyroscherin has confirmed the structure of N-methyltyroscherin. Both compounds are effective antifungal agents with favorable selectivity indices for Candida albicans and Trichophyton rubrum. © 2013 The American Chemical Society and American Society of Pharmacognosy. |
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UMR Ecofog, Institut Pasteur de la Guyane, Université des Antilles et de la Guyane, 23 Avenue Pasteur, 97306 Cayenne, France |
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01633864 (Issn) |
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Export Date: 6 June 2013; Source: Scopus; Coden: Jnprd; :doi 10.1021/np4001703; Language of Original Document: English; Correspondence Address: Eparvier, V.; CNRS, Institut de Chimie des Substances Naturelles, UPR 2301, 1 Avenue de la Terrasse, 91198 Gif-sur-Yvette, France; email: veronique.eparvier@icsn.cnrs-gif.fr |
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EcoFoG @ webmaster @ |
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491 |
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Rodrigues, A.M.S.; Theodoro, P.N.E.T.; Eparvier, V.; Basset, C.; Silva, M.R.R.; Beauchene, J.; Espindola, L.S.; Stien, D. |
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Search for Antifungal Compounds from the Wood of Durable Tropical Trees |
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Journal Article |
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2010 |
Publication |
Journal of Natural Products |
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J. Nat. Prod. |
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73 |
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10 |
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1706-1707 |
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Research on antifungal compounds from the durable wood from French Guiana Amazonian forest trees highlights the correlation between the activity of their extracts against wood-rotting fungi and human pathogens. The fractionation of an ethyl acetate extract of Sextonia rubra wood led to the isolation of rubrenolide (1) and rubrynolide (2). The potential of compounds 1 and 2 is described through the evaluation of their activity against 16 pathogenic fungi and their cytotoxicity toward NIH-3T3 mammalian fibroblast cells. |
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[Rodrigues, Alice M. S.; Eparvier, Veronique; Basset, Charlie; Espindola, Laila S.; Stien, Didier] Univ Antilles Guyane, CNRS, UMR ECOFOG, F-97300 Cayenne, France, Email: darvenne@unb.br |
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AMER CHEMICAL SOC |
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0163-3864 |
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ISI:000283288900015 |
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EcoFoG @ eric.marcon @ |
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25 |
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Cabanillas, B.J.; Le Lamer, A.C.; Castillo, D.; Arevalo, J.; Rojas, R.; Odonne, G.; Bourdy, G.; Moukarzel, B.; Sauvain, M.; Fabre, N. |
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Caffeic Acid Esters and Lignans from Piper sanguineispicum |
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Journal Article |
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2010 |
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Journal of Natural Products |
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J. Nat. Prod. |
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73 |
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11 |
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1884-1890 |
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Three new caffeic acid esters (1-3), four new lignans (4-7), and the known compounds (7'S)-parabenzlactone (8), dihydrocubebin (9), and justiflorinol (10) have been isolated from leaves of Piper sanguineispicum. Their structures were determined by spectroscopic methods, including 1D and 2D NMR, HRCIMS, CD experiments, and chemical methods. Compounds 1-10 were assessed for their antileishmanial potential against axenic amastigote forms of Leishmania amazonensis. Caffeic acid esters 1 and 3 exhibited the best antileishmanial activity (IC50 2.0 and 1.8 μM, respectively) with moderate cytotoxicity on murine macrophages. |
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[Cabanillas, Billy Joel; Le Lamer, Anne-Cecile; Odonne, Guillaume; Bourdy, Genevieve; Moukarzel, Beatrice; Sauvain, Michel; Fabre, Nicolas] Univ Toulouse, UPS, UMR 152, Lab Pharmacochim Subst Nat & Pharmacophores Redox, F-31062 Toulouse 9, France, Email: michel.sauvain@ird.fr |
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AMER CHEMICAL SOC |
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0163-3864 |
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ISI:000284559100024 |
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EcoFoG @ eric.marcon @ |
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74 |
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Verbeeck, H.; Peylin, P.; Bacour, C.; Bonal, D.; Steppe, K.; Ciais, P. |
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Seasonal patterns of CO2 fluxes in Amazon forests: Fusion of eddy covariance data and the ORCHIDEE model |
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Journal Article |
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2011 |
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Journal Of Geophysical Research-Biogeosciences |
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J. Geophys. Res.-Biogeosci. |
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116 |
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2 |
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G02018 |
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[1] In some regions of the Amazon, global biogeophysical models have difficulties in reproducing measured seasonal patterns of net ecosystem exchange (NEE) of carbon dioxide. The global process-based biosphere model Organizing Carbon and Hydrology in Dynamic Ecosystems (ORCHIDEE) used in this study showed that a standard model parameterization produces seasonal NEE patterns that are opposite in phase to the eddy flux data of the tropical evergreen forest at the Tapajos km 67 site (Brazil), like many other global models. However, we optimized several key parameters of ORCHIDEE using eddy covariance data of the Tapajos km 67 site in order to identify the driving factors of the seasonal variations in CO2 flux in this tropical forest ecosystem. The validity of the retrieved parameter values was evaluated for two other flux tower sites in the Amazon. The different tested optimization scenarios showed that only a few parameters substantially improve the fit to NEE and latent heat data. Our results confirm that these forests have the ability to maintain high transpiration and photosynthesis during the dry season in association with a large soil depth (D-soil = 10 m) and a rooting system density that decreases almost linearly with depth (H-root = 0.1). Previous analyses of seasonal variations in eddy covariance fluxes indicated that higher GPP levels were reached in the dry season compared to the wet season. Our optimization analysis suggests that this pattern could be caused by a leaf flush at the start of the dry season increasing the photosynthetic capacity of the canopy. Nevertheless, the current model structure is not yet able to simulate such a leaf flush, and we therefore suggest improving the ORCHIDEE model by including a specific phenology module that is driven by light availability for the tropical evergreen plant functional types. In addition, our results highlight both the potential and the limitations of flux data to improve global terrestrial models. Several parameters were not identifiable, and the risk of overfitting of the model was illustrated. Nevertheless, we conclude that these models can be improved substantially by assimilating site level flux data over the tropics. |
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[Verbeeck, Hans; Steppe, Kathy] Univ Ghent, Plant Ecol Lab, Dept Appl Ecol & Environm Biol, Fac Biosci Engn, B-9000 Ghent, Belgium, Email: hans.verbeeck@ugent.be |
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Amer Geophysical Union |
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0148-0227 |
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ISI:000290933500002 |
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EcoFoG @ webmaster @ |
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321 |
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Author |
Gond, V.; Bartholome, E.; Ouattara, F.; Nonguierma, A.; Bado, L. |
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Monitoring and mapping of waters and wetlands in arid regions using the SPOT-4 VEGETATION imaging system |
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2004 |
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International Journal of Remote Sensing |
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Int. J. Remote Sens. |
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25 |
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5 |
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987-1004 |
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Monitoring the state of small waterbodies and wetlands is very useful in dry regions, because their existence is entirely controlled by the rhythm of local rainfall. On VEGETATION image colour composites, waterbodies and marshy vegetation show up clearly. Yet simple image classification does not yield sufficiently good results because 'spectral signatures' vary significantly together with the ecological conditions of these surfaces. A robust contextual procedure taking into account local contrast was successfully developed and tested. A systematic validation was carried out and a map of waterbodies and wetlands was produced for Burkina Faso and neighbouring regions. |
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Ctr Commun Rech, I-21020 Ispra, VA, Italy, Email: valery.gond@cirad.fr |
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TAYLOR & FRANCIS LTD |
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0143-1161 |
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ISI:000187996500007 |
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EcoFoG @ eric.marcon @ |
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266 |
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