Éditeur(s) : INRA : Institut National de la Recherche Agronomique Université des Antilles. Service commun de la documentation INRA : Institut National de la Recherche Agronomique Université des Antilles. Service commun de la documentation
Extrait de : 52e congrès annuel de la Société caribéenne des plantes alimentaires / 52nd annual meeting of the Caribbean food crops society (CFCS), du 10 au 16 juillet 2016. INRA, CFCS
Description : The importance of longevity as an economically trait gives a picture of the flock efficiency and adaptation in a particular environment. A study was conducted in the experimental herd of Creole goats at INRA in Guadeloupe in order to test environmental (year and season at first kidding, age at first kidding and weight at first mating as well as genetic (index of resistance, sire) factors that affect longevity of does. Lifetime data set of 387 Creole does, reared at pasture all year long, was recorded over a period of 11 years (2001-2012). Does were bred for reproduction at 11months of age. Three mating periods were organized per year, corresponding to 3 climatic seasons, using buck effect. Data were analyzed using survival models (Survival Kit 6.1). The average age for culling was 5.03 years. The culling rate was higher for goats between 2 and 3 years (17 and 24%) and then gradually decreased. Year and season at first kidding did not have a long term influence on does? longevity; neither does age at first kidding. In contrast, weight at first mating had a significant effect and it can be recommended to farmers to mate primiparous goats heavier than 17 kg. Heritability was estimated to 0.16 allowing some genetic progress. No significant correlation was shown with the genetic breeding value of resistance to gastrointestinal parasitism. This study gave indications to breeders to improve their female flock management and increase does? longevity. L'importance de la longévité comme trait économique donne une image de l'efficacité et de l'adaptation de troupeau dans un environnement particulier. Une étude a été entreprise dans le troupeau expérimental de chèvres créoles à l'AICN en Guadeloupe afin d'examiner ambiant (l'année et la saison d'abord badiner, âge d'abord badiner et poids d'abord joindre aussi bien que (index de résistance, de père) les facteurs génétiques affectez dont la longévité fait. L'ensemble de données de vie du Créole 387 fait, élevé au pâturage tout au long de l'année, a été enregistré pendant 11 ans (2001-2012). Fait ont été multipliés pour la reproduction à 11months d'âge. Trois périodes d?accouplement ont été organisées par an, correspondant à 3 saisons climatiques, utilisant l'effet de mâle. Des données ont été analysées utilisant des modèles de survie (trousse de survie 6,1). L'âge moyen pour cueillir était de 5,03 ans. Le taux de cueillage était plus haut pour des chèvres entre 2 et 3 ans (17 et 24%) et alors graduellement diminué. L'année et la saison à premier badiner n'ont pas eu une influence à long terme sur la longévité des does ; ni l'un ni l'autre ne vieillit d'abord badiner. En revanche, le poids au premier accouplement a eu un effet significatif et il peut recommander aux agriculteurs de joindre les chèvres primipares des que 17 kilogrammes plus lourds. L'héritabilité a été estimée à 0,16 permettant du progrès génétique. Aucune corrélation significative n'a été montrée avec la valeur d'élevage génétique de la résistance au parasitisme gastro-intestinal. Cette étude a donné des indications aux éleveurs afin d'améliorer la gestion féminine de troupeau et d'augmenter la longévité de ces dernières.
Siècle(s) traité(s) : 21
Droits : CC-BY-NC-ND - Attribution - Pas d'utilisation commerciale - Pas de modification
Permalien : http://www.manioc.org/fichiers/V16262
V16262
V16262

Éditeur(s) : University of Florida Université des Antilles. Service commun de la documentation
Extrait de : 52e congrès annuel de la Société caribéenne des plantes alimentaires / 52nd annual meeting of the Caribbean food crops society (CFCS), du 10 au 16 juillet 2016. INRA, CFCS
Description : Under tropical and sub-tropical climates, a sustainable development of agriculture is challenging because of the pest pressure with favorable weather conditions. Implementation of appropriate cropping systems including growing cover crops and crop rotation plays a critical role, which can break up the food chain and life cycles of field pests. Some field trials have demonstrated that among all tested summer cover crops, sunn hemp (Crotalaria juncea L. cv. Tropic sun) can grow vigorously during the rainy summer, cover the land quickly and densely, and it can produce a large quantity of biomass in two to three months. More importantly, sunn hemp can suppress soil root-knot nematodes via releasing some nematicides through its roots and through the decomposition of plant residues. Therefore, growing cover crop â? ? sunn hemp during the crop off season and rotating with valuable vegetable crops in the growing season has become a promising cropping system under the subtropical climate. Such a result may have a potential to be implemented in Caribbean countries to improve the sustainable development of agriculture.

Droits : CC-BY-NC-ND - Attribution - Pas d'utilisation commerciale - Pas de modification
Permalien : http://www.manioc.org/fichiers/V16313
V16313

Éditeur(s) : HAL CCSD European Geosciences Union
Résumé : International audience
The seasonal climate drivers of the carbon cycle in tropical forests remain poorly known, although these forests account for more carbon assimilation and storage than any other terrestrial ecosystem. Based on a unique combination of seasonal pan-tropical data sets from 89 experimental sites (68 include aboveground wood productivity measurements and 35 litter productivity measurements), their associated canopy photosynthetic capacity (enhanced vegetation index, EVI) and climate, we ask how carbon assimilation and aboveground allocation are related to climate seasonality in tropical forests and how they interact in the seasonal carbon cycle. We found that canopy photosynthetic capacity seasonality responds positively to precipitation when rainfall is < 2000 mm yr(-1) (water-limited forests) and to radiation otherwise (light-limited forests). On the other hand, independent of climate limitations, wood productivity and litterfall are driven by seasonal variation in precipitation and evapotranspiration, respectively. Consequently, light-limited forests present an asynchronism between canopy photosynthetic capacity and wood productivity. First-order control by precipitation likely indicates a decrease in tropical forest productivity in a drier climate in water-limited forest, and in current light-limited forest with future rainfall < 2000 mm yr(-1).
ISSN: 1726-4170

hal-01557759
https://hal.univ-lorraine.fr/hal-01557759
https://hal.univ-lorraine.fr/hal-01557759/document
https://hal.univ-lorraine.fr/hal-01557759/file/bg-13-2537-2016.pdf
DOI : 10.5194/bg-13-2537-2016

Éditeur(s) : HAL CCSD Springer Verlag
Résumé : Coarse woody debris (CWD, dead wood sections a parts per thousand yen10 cm diameter) represents a large store of carbon in tropical forests; however, estimates of the flux of carbon from CWD in these forests remain poorly constrained. The objective of this study was to resolve the dry/wet season response of respiration in CWD (R (cwd)), and investigate the importance of biotic and abiotic factors for predicting the seasonal change of R (cwd) at the ecosystem level. This study presents a 4-month time series of R (cwd) measurements conducted on 42 dead trees (26 species) at the Paracou Research Station in French Guiana. R (cwd) measurements were repeated 13 times on each CWD sample from July to November 2011, spanning the transition from wet to dry season, and then from dry season to the following wet season. Seasonal drought caused monthly R (cwd) to drop by 20.5 +/- A 5.1% over the wet-dry transition. Changes in woody tissue moisture content explained 41.9% of the measured seasonal variability in R (cwd), but 60% of the seasonal variability in mean forest R (cwd) rates could be modelled using surface soil water content. We estimate that R (cwd) is approximately 5% of annual ecosystem respiration (R (eco)) and that seasonal variations in R (cwd) contribute appreciably to seasonal variations of R (eco), and should be included in functional models simulating the response of tropical rainforest ecosystems to current and future climate.
ISSN: 1432-9840

hal-01032431
https://hal.archives-ouvertes.fr/hal-01032431
DOI : 10.1007/s10021-013-9684-x

Éditeur(s) : Wiley-Blackwell
Résumé : The Climate Forecast System Reanalysis (CFSR) provides a wealth of information spanning 1979–2009 for investigation of ocean wind and wave climate. Preprocessing of the data is necessary to remove the dominant seasonal signals and to create time series of semimonthly averaged wind speed and significant wave height over a 0.5° global grid. We perform an empirical orthogonal function (EOF) analysis to extract the dominant space-time patterns. The results for the three major ocean basins show strong zonal structures in the winds and saturation of the swells corroborating prior works with various data sets. We reexamine the CFSR data in the frequency domain to identify periodic signals associated with published climate indices. The Fourier transform of the preprocessed time series generates spectra ranging from 1 month to 15 years period for an EOF analysis. The results demonstrate the spatial structures and periods of climate phenomena. The Arctic Oscillation dominates the Atlantic basin with a broad range of intra-annual signals off the European coasts. The Indian and Pacific Oceans are strongly influenced by inter-annual cycles of the El Niño Southern Oscillation (ENSO) and the Antarctica Oscillation. The Indian Ocean also has strong intra-annual components ranging from 50 to 80 days period. The ENSO proves to be a ubiquitous signal around the globe, and in particular, saturates the Pacific with strong influences in the equatorial region and the Southern Hemisphere Westerlies. A commonality of all basins is that the magnitude and the spatial structure of the intra-annual and inter-annual signals are similar suggesting a wide range of periods in each of the climate cycles examined.
Journal of Geophysical Research: Oceans (21699275) (Wiley-Blackwell), 2014-08 , Vol. 119 , N. 8 , P. 5563-5584

Droits : 2014. American Geophysical Union. All Rights Reserved.
http://archimer.ifremer.fr/doc/00210/32149/30606.pdf
http://archimer.ifremer.fr/doc/00210/32149/30607.pdf
DOI:10.1002/2013JC009729
http://archimer.ifremer.fr/doc/00210/32149/

Éditeur(s) : HAL CCSD European Geosciences Union (EGU)
Résumé : International audience
Pollen and clay mineralogical analyses of a Holocene sequence from Sebkha Boujmel (southern Tunisia) traces the climatic and environmental dynamics in the lower arid bioclimatic zone over the last 8000 years. During the Mid- to Late Holocene transition, between 8 and 3 ka, a succession of five wet/dry oscillations is recorded. An intense arid event occurs between 5.7 and 4.6 ka. This episode marks the onset of a long-term aridification trend with a progressive retreat of Mediterranean woody xerophytic vegetation and of grass steppes. It ends with the establishment of pre-desert ecosystems around 3 ka. The millennial-scale climate change recorded in the data from Sebkha Boujmel is consistent with records from the south and east Mediterranean, as well as with climatic records from the desert region for the end of the African Humid Period (AHP). Eight centennial climatic events are recorded at Sebkha Boujmel and these are contemporary with those recorded in the Mediterranean and in the Sahara. They indicate a clear coupling between the southern Mediterranean and the Sahara before 3 ka. The event at 4.2 ka is not evidenced and the link between events recorded in Sebkha Boujmel and the North Atlantic Cooling events is clearer from 3 ka onwards. These variations indicate the importance of climatic determinism in the structuring of landscapes, with the establishment of the arid climatic conditions of the Late Holocene. It is only from 3 ka onwards that the dynamic of plant associations is modified by both human activity and climatic variability. The climatic episodes identified during the historic period indicate strong regionalisation related to the differential impact of the North Atlantic Oscillation (NAO) and the Mediterranean Oscillation (MO) on the Mediterranean basin. The local human impact on regional ecosystems is recorded in the form of episodes of intensification of pastoral and/or agricultural activities. The development of olive production and of several taxa associated with agriculture attest to increasing sedentism among human populations during Classical Antiquity. The significant increase in Artemisia (wormwood) between 1.1 and 0.8 ka (850–1150 AD) is linked to intensive pastoral activity, associated with heightened interannual and/or seasonal climatic instability. A complete re-shaping of the landscape is recorded during the 20th century. The remarkable expansion of the olive tree, and the deterioration of regional ecosystems with the spread of desert species, is linked to recent local socio-economic changes in Tunisia.
ISSN: 1814-9324

hal-01319967
https://hal.archives-ouvertes.fr/hal-01319967
https://hal.archives-ouvertes.fr/hal-01319967/document
https://hal.archives-ouvertes.fr/hal-01319967/file/cp-12-1339-2016.pdf
DOI : 10.5194/cp-12-1339-2016

Éditeur(s) : HAL CCSD Elsevier
Résumé : Vegetation phenology is the study of the timing of seasonal events that are considered to be the result of adaptive responses to climate variations on short and long time scales. In the field of remote sensing of vegetation phenology, phenological metrics are derived from time series of optical data. For that purpose, considerable effort has been specifically focused on developing noise reduction and cloud-contaminated data removal techniques to improve the quality of remotely-sensed time series. Comparative studies between time series composed of satellite data acquired under clear and cloudy conditions and from radiometric data obtained with high accuracy from ground-based measurements constitute a direct and effective way to assess the operational use and limitations of remote sensing for predicting the main plant phenological events. In the present paper, we sought to explicitly evaluate the potential use of MODerate resolution Imaging Spectroradiometer (MODIS) remote sensing data for monitoring the seasonal dynamics of different types of vegetation cover that are representative of the major terrestrial biomes, including temperate deciduous forests, evergreen forests, African savannah, and crops. After cloud screening and filtering, we compared the temporal patterns and phenological metrics derived from in situ NDVI time series and from MODIS daily and 16-composite products. We also evaluated the effects of residual noise and the influence of data gaps in MODIS NDVI time series on the identification of the most relevant metrics for vegetation phenology monitoring. The results show that the inflexion points of a model fitted to a MODIS NDVI time series allow accurate estimates of the onset of greenness in the spring and the onset of yellowing in the autumn in deciduous forests (RMSE <= one week). Phenological metrics identical to those provided with the MODIS Global Vegetation Phenology product (MDC12Q2) are less robust to data gaps, and they can be subject to large biases of approximately two weeks or more during the autumn phenological transitions. In the evergreen forests, in situ NDVI time series describe the phenology with high fidelity despite small temporal changes in the canopy foliage. However, MODIS is unable to provide consistent phenological patterns. In crops and savannah, MODIS NDVI time series reproduce the general temporal patterns of phenology, but significant discrepancies appear between MODIS and ground-based NDVI time series during very localized periods of time depending on the weather conditions and spatial heterogeneity within the MODIS pixel. In the rainforest, the temporal pattern exhibited by a MODIS 16-day composite NDVI time series is more likely due to a pattern of noise in the NDVI data structure according to both rainy and dry seasons rather than to phenological changes. More investigations are needed, but in all cases, this result leads us to conclude that MODIS time series in tropical rainforests should be interpreted with great caution. (C) 2013 Elsevier Inc. All rights reserved.
ISSN: 0034-4257

hal-01032407
https://hal.archives-ouvertes.fr/hal-01032407
DOI : 10.1016/j.rse.2013.01.010

Éditeur(s) : HAL CCSD
Résumé : International audience
The challenge is to implement research that can estimate the consequences ofclimate changes in terms of impact on terrestrial environments and resources.Emphasis should be placed on regions dependent on natural resources and forwhich demographic pressure is strong. Simulations obtained from climate modelprojections (using different Representative Concentration Pathways (RCPs))predict that the Mediterranean basin and its southern periphery are particularlyvulnerable to water resources and environmental impact (IPCC, AR5, 2013).An annual rainfall decrease by 30% is found for the projection period 2070-2099(IPCC, AR5, 2013) associated with a decrease in water resources by 30 to 50%(Milano, 2012). In addition, several studies using regional atmospheric modelsindicate an increase in the precipitation inter-annual variability with extremeevents and a spatial heterogeneous signature, superimposed on a decrease in thetotal precipitation amount (Giorgi and Lionello, 2008; Raible et al. 2010).Currently, regional climate projections are highly sensitive to the climate modelused. In particular, spatial resolution as well as local climate conditions seemto impact significantly on the simulations (Jacob et al. 2014).The Mediterranean region, at the interface between arid and temperate climateswith several mountainous areas, is a complex climate system affected by theinteractions between mid-latitude and sub-tropical processes. In this context,Morocco, located at the transition between a temperate climate to the North anda tropical climate to the south constitutes a key area for an impact and sensitivitystudy to global climate changes. The climate is influenced by the Atlantic Ocean,the Mediterranean Sea and the Sahara, together with a very steep orography inthe Atlas region. The precipitation distribution is therefore characterised by greatspatial variability, and exhibits a marked seasonality, a strong inter-annualvariability (Ouda et al. 2005) and in general a pronounced gradient from northto south and west to east. At a broader scale, Morocco is located on the subtropicalsubsidence path and between the Acores High and the Saharan Low (Agoussine,2003). Several studies have also identified strong links with inter-annualprecipitation variability and NAO index (Knippertz, 2003) as well as remoteclimate modes (Esper et al. 2007).Continental climate variability at a local/regional scale, if it is to be integratedin climate predictions, needs to be supported by long-term observation.Meteorological stations in Morocco provide climatic data mainly for the last40 years with only a few stations located in the mountainous region (Tramblayet al. 2012; 2013; Driouech et al. 2010). This climate database is also supportedby the IAEA network providing stations for which isotope tracers have beenapplied to daily/monthly rain and water vapour samples over 2 to 3 years between2000 and 2004. Besides the poor coverage of instrumented areas, lacustrinesystems can provide a climatic data set that offers access to short and long-termtime series of climate parameters when knowledge of modern lake water balanceis combined with lacustrine sedimentary-climate records. Lake sediment recordsideally provide high resolution climate/environmental information of the last10,000 years (Magny et al. 2013). This time interval (corresponding to theHolocene) is a key period to investigate short and long-term climate variabilityand to improve prediction in a warming climate.In this study we present an integrated approach focusing on a mountainous lake(Aguelmam Azigza). The modern lake system study is based on site monitoring(2012-2016) and available regional hydro-climatic data. These data show thatlake level changes during the instrumented period were mainly driven byprecipitation following the high inter-annual variability. These data are thencompared with accurately dated short sediment cores retrieved in the same lake.Micro-scale geochemical and sedimentological analyses of these sequencesenable us to identify various sedimentary facies that can be linked with periodsof high (low) lake levels over the past decades.
The Mediterranean Region under Climate ChangeLa méditerranée face au changement climatique

insu-01394690
https://hal-insu.archives-ouvertes.fr/insu-01394690
https://hal-insu.archives-ouvertes.fr/insu-01394690/document
https://hal-insu.archives-ouvertes.fr/insu-01394690/file/Vidaletal.2016-COP22-Chap1.pdf

Éditeur(s) : HAL CCSD Public Library of Science
Résumé : Climate models predict a range of changes in tropical forest regions, including increased average temperatures, decreased total precipitation, reduced soil moisture and alterations in seasonal climate variations. These changes are directly related to the increase in anthropogenic greenhouse gas concentrations, primarily CO2. Assessing seasonal forest growth responses to climate is of utmost importance because woody tissues, produced by photosynthesis from atmospheric CO2, water and light, constitute the main component of carbon sequestration in the forest ecosystem. In this paper, we combine intra-annual tree growth measurements from published tree growth data and the corresponding monthly climate data for 25 pan-tropical forest sites. This meta-analysis is designed to find the shared climate drivers of tree growth and their relative importance across pan-tropical forests in order to improve carbon uptake models in a global change context. Tree growth reveals significant intra-annual seasonality at seasonally dry sites or in wet tropical forests. Of the overall variation in tree growth, 28.7% was explained by the site effect, i.e. the tree growth average per site. The best predictive model included four climate variables: precipitation, solar radiation (estimated with extrasolar radiation reaching the atmosphere), temperature amplitude and relative soil water content. This model explained more than 50% of the tree growth variations across tropical forests. Precipitation and solar radiation are the main seasonal drivers of tree growth, causing 19.8% and 16.3% of the tree growth variations. Both have a significant positive association with tree growth. These findings suggest that forest productivity due to tropical tree growth will be reduced in the future if climate extremes, such as droughts, become more frequent.
ISSN: 1932-6203

hal-01268529
https://hal.archives-ouvertes.fr/hal-01268529
https://hal.archives-ouvertes.fr/hal-01268529/document
https://hal.archives-ouvertes.fr/hal-01268529/file/journal.pone.0092337.PDF
DOI : 10.1371/journal.pone.0092337

Éditeur(s) : HAL CCSD
Résumé : In a perfect-deficit approach (Yi, 2012), the daily maximum carbon storage capacity (CPC) of a given ecosystem for each year defines the perfect annual CPC curve. Deficits are the differences in the daily observational data for a given year against a perfect curve. The area between this curve and instantaneous canopy photosynthetic rates represents the potential productivity. Using an 11-year (2004 – 2014) eddy covariance flux and meteorological data, this perfect-deficit approach was used to examine the relationship between potential productivity and droughts occurring in 2005 and 2010 in a tropical rainforest of French Guiana, South America. Surprisingly, CPC deficits were only reduced by 24% (2005) and 19% (2010) from their respective perfect CPCs, indicating a subtle effect of drought to ecosystem productivity. Highest precipitation occurred in 2010 but precipitation deficits dropped drastically during this year (71% reduction from its perfect value) which reflects a drought condition. However, its deficits showed no correlation annually and seasonally. Soil water content (SWC) appeared to be the single driver for CPC deficits during long dry periods but is weakly correlated (r = 0.30; P <0.01 and r = 0.31; P <0.01, in 2005 and 2010, respectively). These results indicate that soil water is not a major limiting factor for productivity of this ecosystem during drought periods. In contrast, global radiation (Rg) corresponds to the peak of CPC deficits in 2010, but only 19% had been reduced from its ideal value. Yet, highest gross primary production (GPP) of 4106±231 gCm−2yr−1 occurred this year (mean 3753±231 gCm−2yr−1). Therefore, smaller deficits in Rg coupled with sufficient water may have induced higher productivity in 2010. Nevertheless, weaker correlations between potential productivity and climatic drivers may imply that other controlling aspects such as biological constraints may also have an effect to the dynamics of potential productivity during drought events, hence, must also be considered.
AGU Fall Meeting 2015
San Francisco, United States

hal-01269439
https://hal.archives-ouvertes.fr/hal-01269439
PRODINRA : 338570

Éditeur(s) : HAL CCSD Public Library of Science
Résumé : Climate models for the coming century predict rainfall reduction in the Amazonian region, including change in water availability for tropical rainforests. Here, we test the extent to which climate variables related to water regime, temperature and irradiance shape the growth trajectories of neotropical trees. . We developed a diameter growth model explicitly designed to work with asynchronous climate and growth data. Growth trajectories of 205 individual trees from 54 neotropical species censused every 2 months over a 4-year period were used to rank 9 climate variables and find the best predictive model. . About 9% of the individual variation in tree growth was imputable to the seasonal variation of climate. Relative extractable water was the main predictor and alone explained more than 60% of the climate effect on tree growth, i.e. 5.4% of the individual variation in tree growth. Furthermore, the global annual tree growth was more dependent on the diameter increment at the onset of the rain season than on the duration of dry season. . The best predictive model included 3 climate variables: relative extractable water, minimum temperature and irradiance. The root mean squared error of prediction (0.035 mm.d(-1)) was slightly above the mean value of the growth (0.026 mm.d(-1)). . Amongst climate variables, we highlight the predominant role of water availability in determining seasonal variation in tree growth of neotropical forest trees and the need to include these relationships in forest simulators to test, in silico, the impact of different climate scenarios on the future dynamics of the rainforest.
ISSN: 1932-6203

hal-01268350
https://hal.archives-ouvertes.fr/hal-01268350
DOI : 10.1371/journal.pone.0034074
PRODINRA : 215438
PUBMED : 22506012

Éditeur(s) : Université de La Rochelle
Résumé : Shrimp aquaculture in New Caledonia is a developing industry, exclusively based on the species Litopenaeus stylirostris. However, it is subject to mortalities during grow out as observed all over the world. Since 1993, shrimp reared during the cold period are affected by a disease named "syndrome 93". As a consequence, the whole industry has become seasonal and produces essentially during the warm season. The climatic conditions during the periods of transition between the two main seasons could be responsible for an environmental stress and the origin reason for mortality outbreaks. Stocking density is the main risk factor. It increases the probability of the appearance and development of the epizooty in the pond. The "Summer Syndrome", a septicemic vibriosis caused by Vibrio nigripulchritudo, was identified for the first time in December 1997 in an intensive shrimp farm (DF). It has become enzootic ever since and is expressed after 50d of rearing. Since 2003, two others farms located near DF have developed the disease. As a consequence, the summer syndrome is considered to be a potential threat for all the industry. Between 1991 and 2005, the increase of feed input and nitrogen levels in feed has led to a significant increase in the growth rate over the years in the farms affected by the disease. In consequence, an early eutrophication of the water is observed, which is concomitant with the beginning of the mortality outbreaks. An early eutrophication and the virulence level of the pathogen are considered as the main risk factors of the disease. Factors may act synergistically to explain the summer syndrome. As part of a multidisciplinary approach (pathology – physiology – environment), two high-frequency surveys were carried out to analyse the pond ecosystem. Since the feed quantity increases with the biomass of shrimp, the eutrophication level of the pond ecosystem will also tend to increase with the duration of rearing. During the first part of the rearing, the abundance of each picoplankton type is exceptionally high and picophytoplankton dominated the autotrophic compartment. The nanophytoplankton dominated the second part of the rearing and was more unstable. The shift from pico to nanophytoplankton could be considered as an environmental stress and was observed in relation to the beginning of the mortalities, whatever the disease. Shift intensity could play a role by inducing directly or indirectly a stress for shrimp and/or a growth and/or virulence factors of the pathogen. Results from sediment studies show that mortality was best characterized by TAN concentration in pore water and even more when the TAN concentration was high. TAN and pH are potential stress factors for shrimp reared in ponds affected by these diseases.
L'aquaculture mondiale de crevettes est un secteur à très forte croissance. Toutefois, les problèmes liés aux maladies dans les élevages ne cessent d'augmenter depuis 1980. Au cours du développement de la filière de Nouvelle-Calédonie, deux épisodes saisonniers de mortalités associées à la présence de Vibrio pathogènes sont apparus et ont fortement perturbé les techniques et les schémas de production. Les premières mortalités hivernales, décrites sous le nom de « syndrome 93 » ont été observées en mai 1993. Elles ont affecté depuis tous les élevages de saison froide de toutes les fermes de production. Les conditions climatiques pendant les périodes de transitions entre les deux principales saisons caractérisant le climat de la Nouvelle-Calédonie, seraient responsables d'un stress environnemental à l'origine du déclenchement du syndrome 93. La densité initiale d'ensemencement, apparaît comme le principal facteur de risque, augmentant la probabilité d'apparition de la maladie et l'ampleur de ses effets. Le « syndrome d'été » a été identifié pour la première fois en 1997 dans une ferme pratiquant une production intensive. Il s'est déclaré depuis 2003 dans deux autres fermes géographiquement proches. Les mortalités apparaissent 58 jours en moyenne après l'ensemencement des post-larves dans les bassins. La recherche d'une croissance maximale des animaux a induit, avec les années, une intensification progressive du système caractérisée par une augmentation de la quantité d'aliment distribuée. L'examen des données historiques fait apparaître une eutrophisation du milieu de plus en plus précoce concomitante au déclenchement des mortalités. En l'état actuel de nos connaissances, cette évolution précoce de l'écosystème en présence de façon récurrente de la souche hautement pathogène du Vibrio incriminé et à une période où la fréquence des mues des crevettes est élevée, constitue le principal facteur de risque de la maladie. Avec l'apport croissant en aliment, la colonne d'eau évolue vers une autotrophie croissante alors que le sédiment devient de plus en plus hétérotrophe au fur et à mesure que l'élevage progresse. Au cours du processus d'eutrophisation, le compartiment autotrophe montre une succession de deux assemblages. Le picophytoplancton domine sur la première partie de l'élevage et laisse place à du nanophytoplancton en seconde partie. Cette phase de transition, concomitante à l'apparition des mortalités quel que soit le syndrome, caractérise un stress environnemental dont l'intensité pourrait favoriser ou non le déclenchement des mortalités. Les suivis de différents indicateurs dans les sédiments - pH, potentiel d'oxydoréduction et concentration en ammoniaque dans l'eau interstitielle – indiquent dans les bassins déclarant les épizooties des conditions qui ont été définies expérimentalement comme potentiellement plus stressantes pour les animaux.

Droits : info:eu-repo/semantics/openAccess
http://archimer.ifremer.fr/doc/2007/these-2643.pdf
http://archimer.ifremer.fr/doc/00000/2643/

Éditeur(s) : HAL CCSD Cambridge University Press (CUP)
Résumé : Patterns of leaf production and leaf fall directly influence leaf area index and forest productivity. Here, we focused on Cecropia sciadophylla individuals inhabiting the extremes of the gradient in seasonality in rainfall at which C. sciadophylla occurs. In Colombia and French Guiana we compared the intra-annual variation in leaf production as well as the intra-annual fluctuation in internode length on a total of 69 saplings ranging in size from 1 to 2 m. The mean rate of leaf production was similar to 2 leaves mo(-1) in both populations, and the rate of leaf production was constant throughout the year. Our results showed monthly variation in internode length and the number of live leaves per sapling in the seasonal habitat and variation only in internode length in the everwet habitat. Because the rate of leaf production is constant at both localities, the difference in number of live leaves per sapling at the seasonal site must reflect seasonal variation in leaf life span. We show that in Cecropia, internode length can serve as an indicator of precipitation seasonality. Finally an open question is whether leaf production in other pioneer species is also independent of climatic seasonal cues. This information could allow us to link growth and climate of secondary forest species and better understand how past and future climate can affect plant growth trajectories.
ISSN: 0266-4674

hal-01032402
https://hal.archives-ouvertes.fr/hal-01032402
DOI : 10.1017/S0266467413000394

Éditeur(s) : HAL CCSD
Résumé : International audience
ABSTRACT :A satellite retrieval of surface solar irradiance (SSI) based on GOES satellite data is presented and validated for the French Guiana with three years of in situ measurements from six ground stations. We propose a particle filter approach combining GOES satellite observations and in situ data. We propose an original observation function based on a joint probability distribution and taking advantages of the characteristics of both the involved type of data. The statistical results are compared with those of existing estimation methods and they are found to be in accordance with them. The daily bias ranges from -12 W/m² (-6% of the mean of measurements) to 12 W/m² (6%), depending on the stations. The daily root mean square difference ranges between 23 W/m² (10%) and 27 W/m² (15%). The correlation coefficient is close to 0.92. There is no seasonal climatic effect on the method, the bias and RMSD remain similar for both the rainy and the dry season, but better correlation is observed in the rainy season than in the dry season. Uncertainties are mainly due to the presence of specific tropical atmospheric conditions during the dry season. The method has been tested through various tests: cross-validation scheme has highlighted the potential generalization of the model in a temporal dimension; the ability of the method to effectively duplicate anomalies in surface solar irradiance time series has also been tested. The robustness of the results shows the interest of the method compared to other existing estimation methods. Because of its simplicity of implementation this method opens new prospects in estimating surface solar irradiance. It is concluded that using a particle filter and original observation function method allow a high-quality surface solar irradiance estimation in French Guiana.RESUMEUne méthode d'estimation de l'irradiance solaire de surface (SSI) à partir de données satellites GOES est présentée et validée par comparaison avec trois années de mesures in situ provenant de six stations météorologiques de Guyane Française. Dans cet article, nous proposons une approche par filtre particulaire combinant observations du satellite GOES et données in situ. Nous proposons une fonction d'observation originale basée sur une distribution de probabilité conjointe des deux types de données. Les résultats statistiques sont conformes à ceux des méthodes existantes. Le biais journalier varie de -16 W / m² (-7% de la moyenne des mesures) à 12 W / m² (6%). L'erreur quadratique moyenne (RMSD) est comprise entre 23 W / m² (10%) et 27 W / m² (15%). Le coefficient de corrélation est de 0,92. La méthode est peu sensible aux variations climatiques saisonnières, le biais et RMSD restent similaires en saison des pluies comme en saison sèche, mais une meilleure corrélation est observée pendant la saison des pluies. Les incertitudes sont principalement dues à la présence de conditions atmosphériques tropicales spécifiques en saison sèche. La méthode a été soumise à différents tests : un processus de validation croisée a mis en évidence la possible généralisation du modèle dans une dimension temporelle, la capacité du modèle à reproduire efficacement des anomalies dans les séries temporelles d'irradiance solaire de surface a aussi été testée. La robustesse des résultats obtenus montrent l'intérêt du modèle par rapport aux autres méthodes d'estimation existantes. A cause de sa simplicité de mise en oeuvre cette méthode ouvre de nouvelles perspectives en matière d'estimation de l'irradiance solaire au sol. Nous concluons que l'utilisation d'un filtre particulaire combinée à une fonction d'observation originale permet une estimation de haute qualité de l'irradiance solaire au sol en Guyane Française.
Canadian Journal of Remote Sensing

meteo-01304574
https://hal-meteofrance.archives-ouvertes.fr/meteo-01304574
DOI : 10.1080/07038992.2015.1040150

Éditeur(s) : HAL CCSD
Résumé : International audience
Background: In French Guiana, a recent study has shown that a major part of the histoplasmosis incidence temporal fluctuations could be explained by climatic factors and thus postulated that disseminated histoplasmosis cases could be in a large proportion due to new infections. The description of the seasonal pattern of histoplasmosis could potentially help to test this new hypothesis. Patients and methods: A study using prospective data from the French Hospital Database for HIV was conducted in order to determine seasonal variations of the incidence of first cases of disseminated histoplasmosis in HIV persons in Cayenne, French Guiana. Single failure Cox proportional hazards models were used. Results: After adjusting for CD4 counts and antiretroviral treatment, the incidence of disseminated histoplasmosis was significantly higher during the Short Wet Season-Long Dry Season than during the Short Dry Season-Long Wet Season (Adjusted Hazard ratio 1.7 (1.1-2.5), P= 0.01). Conclusion: This result gives both valuable epidemiologic information to clinicians and a supplementary argument in favour of the hypothesis that an important proportion of cases were due to recent exposure. Therefore, the use of a primary prophylaxis must be discussed in French Guiana.
J AIDS Clinic Res

Droits : info:eu-repo/semantics/OpenAccess
inserm-00915009
http://www.hal.inserm.fr/inserm-00915009
http://www.hal.inserm.fr/inserm-00915009/document
http://www.hal.inserm.fr/inserm-00915009/file/2012_Hanf_-_Disseminated_Histoplasmosis_seasonal_incidence_variations_a_supplementary_argument_for_recent_infection.pdf
DOI : 10.4172/2155-6113.1000175

Éditeur(s) : HAL CCSD Public Library of Science
Résumé : International audience
Establishing a direct link between climate change and fluctuations in animal populations through long-term monitoring is difficult given the paucity of baseline data. We hypothesized that social wasps are sensitive to climatic variations, and thus studied the impact of ENSO events on social wasp populations in French Guiana. We noted that during the 2000 La Niña year there was a 77.1% decrease in their nest abundance along ca. 5 km of forest edges, and that 70.5% of the species were no longer present. Two simultaneous 13-year surveys (1997-2009) confirmed the decrease in social wasps during La Niña years (2000 and 2006), while an increase occurred during the 2009 El Niño year. A 30-year weather survey showed that these phenomena corresponded to particularly high levels of rainfall, and that temperature, humidity and global solar radiation were correlated with rainfall. Using the Self-Organizing Map algorithm, we show that heavy rainfall during an entire rainy season has a negative impact on social wasps. Strong contrasts in rainfall between the dry season and the short rainy season exacerbate this effect. Social wasp populations never recovered to their pre-2000 levels. This is probably because these conditions occurred over four years; heavy rainfall during the major rainy seasons during four other years also had a detrimental effect. On the contrary, low levels of rainfall during the major rainy season in 2009 spurred an increase in social wasp populations. We conclude that recent climatic changes have likely resulted in fewer social wasp colonies because they have lowered the wasps' resistance to parasitoids and pathogens. These results imply that Neotropical social wasps can be regarded as bio-indicators because they highlight the impact of climatic changes not yet perceptible in plants and other animals.
ISSN: 1932-6203

hal-00825825
https://hal.archives-ouvertes.fr/hal-00825825
https://hal.archives-ouvertes.fr/hal-00825825/document
https://hal.archives-ouvertes.fr/hal-00825825/file/Dejean2011_Climate.pdf
DOI : 10.1371/journal.pone.0027004

Éditeur(s) : HAL CCSD European Geosciences Union
Résumé : International audience
The exchanges of carbon, water and energy between the atmosphere and the Amazon basin have global implications for the current and future climate. Here, the global atmospheric inversion system of the Monitoring of Atmospheric Composition and Climate (MACC) service is used to study the seasonal and interannual variations of biogenic CO 2 fluxes in Amazonia during the period 2002–2010. The system assimilated surface measurements of atmospheric CO 2 mole fractions made at more than 100 sites over the globe into an atmospheric transport model. The present study adds measurements from four surface stations located in tropical South America, a region poorly covered by CO 2 observations. The estimates of net ecosystem exchange (NEE) optimized by the inversion are compared to an independent estimate of NEE upscaled from eddy-covariance flux measurements in Amazonia. They are also qualitatively evaluated against reports on the seasonal and interannual variations of the land sink in South America from the scientific literature. We attempt at assessing the impact on NEE of the strong droughts in 2005 and 2010 (due to severe and longer-than-usual dry seasons) and the extreme rainfall conditions registered in 2009. The spatial variations of the seasonal and in-terannual variability of optimized NEE are also investigated. While the inversion supports the assumption of strong spatial heterogeneity of these variations, the results reveal critical limitations of the coarse-resolution transport model, the surface observation network in South America during the recent years and the present knowledge of modelling uncertainties in South America that prevent our inversion from capturing the seasonal patterns of fluxes across Amazonia. However, some patterns from the inversion seem consistent with the anomaly of moisture conditions in 2009.
ISSN: 1680-7316

hal-01557375
https://hal.univ-lorraine.fr/hal-01557375
https://hal.univ-lorraine.fr/hal-01557375/document
https://hal.univ-lorraine.fr/hal-01557375/file/acp-15-8423-2015.pdf
DOI : 10.5194/acp-15-8423-2015-supplement

Éditeur(s) : HAL CCSD American Association for the Advancement of Science
Résumé :  
Amazon forests are a key but poorly understood component of the global carbon cycle. If, as anticipated, they dry this century, they might accelerate climate change through carbon losses and changed surface energy balances. We used records from multiple long-term monitoring plots across Amazonia to assess forest responses to the intense 2005 drought, a possible analog of future events. Affected forest lost biomass, reversing a large long-term carbon sink, with the greatest impacts observed where the dry season was unusually intense. Relative to pre-2005 conditions, forest subjected to a 100-millimeter increase in water deficit lost 5.3 megagrams of aboveground biomass of carbon per hectare. The drought had a total biomass carbon impact of 1.2 to 1.6 petagrams (1.2 × 1015 to 1.6 × 1015 grams). Amazon forests therefore appear vulnerable to increasing moisture stress, with the potential for large carbon losses to exert feedback on climate change.
ISSN: 0036-8075

hal-01032111
https://hal.archives-ouvertes.fr/hal-01032111
DOI : 10.1126/science.1164033

Éditeur(s) : HAL CCSD Elsevier Masson
Résumé : 14 pages
International audience
Central Africa hosts the world's second largest tropical forest after the Amazonian basin. However, as compared to its Amazonian counterpart, the Central Africa forests receive much less rain (∼1500 mm/year in mean spread over two rainy seasons in March-May and September-November, and two dry seasons). They also experience a slower deforestation rate, so that the main threat for the next decades might come from climate variations. Nonetheless, their response to the annual cycle of solar radiation and rainfall/clouds is still poorly known. Analysing high resolution remote sensing data of Enhanced Vegetation Index, rainfall, cloudiness, and solar radiation for a target region located between 0 and 5°N and 12–19°E, we explore the climatic drivers of the forests greenness mean annual cycle. Three main points emerge; first, the diurnal cycle is a key-scale for understanding the mean annual cycles of rainfall and incoming solar radiation at surface, then how climate shapes the greenness mean annual evolution; second, neither the two dry seasons nor the two rainy seasons resemble each other in terms of cloud cover, solar radiation and rainfall, and their links with greenness levels; third, whereas the first rainy season (March-May) appears optimal for greenness especially because of favorable light conditions, water availability is the main controlling factor during the main dry season and at the start of the first vegetative season (February). Regarding the little dry season (mid-June-mid-August) and the second rainy season (September-October), light availability might be the main limiting factor. These findings pave the way for further studies of the climate interannual variability and change impacts on the Central Africa forests, taking into account time-scale interactions.
ISSN: 0168-1923

hal-01309565
https://hal.archives-ouvertes.fr/hal-01309565
DOI : 10.1016/j.agrformet.2016.04.005

Éditeur(s) : HAL CCSD Springer Verlag
Résumé : International audience
Seasonal climate forecasts mainly rely on the atmospheric sensitivity to its lower boundary conditions and on their own predictability. Besides sea surface temperature (SST), soil moisture (SM) may be an additional source of climate predictability particularly during boreal summer in the mid-latitudes. In this work, we investigate the role of SM initial conditions on near-surface climate predictability during ten boreal summer seasons using three complementary ensembles of AMIP-type simulations performed with the Arpège-Climat atmospheric general circulation model. First we have conducted an assessment of the SM predictability itself through a comparison of simple empirical SM models with Arpège-Climat. The statistical and dynamical models reveal similar SM prediction skill patterns but the Arpège-Climat reaches higher scores suggesting that it is at least suitable to explore the influence of SM initialization on atmospheric predictability. Then we evaluate the relationships between SM predictability and some near surface atmospheric predictability. While SM initialization obviously improves the predictability of land surface evaporation, it has no systematic influence on the precipitation and near surface temperature skills. Nevertheless, the summer hindcast skill is clearly improved during specific years and over certain regions (mainly north America and eastern Europe in the Arpège-Climat model), when and where the SM forcing is sufficiently widespread and strong. In this case, a significant impact is also found on the occurrence of heat waves and heavy rains, whose predictability at the seasonal timescale is a crucial challenge for years to come.
ISSN: 0930-7575

meteo-00346948
https://hal-meteofrance.archives-ouvertes.fr/meteo-00346948
DOI : 10.1007/s00382-008-0375-9