Pierre Roger - Academia.edu (original) (raw)

Papers by Pierre Roger

Biology and Fertility of Soils, 1993

The density and composition of ricefield oligochaete populations were estimated in 33 farmers' fi... more The density and composition of ricefield oligochaete populations were estimated in 33 farmers' fields in the Philippines and related to physicochemical properties of the soils and agrochemical use. The spatial distribution of organisms and the investigative sampling strategy were determined from a high-intensity sampling in a single ricefield. Species diversity was low. The dominant species were Limnodrilus hoffmeisteri and Branchiura sowerbyi. The spatial distribution of populations was contagious and densities ranged from O to 35000 m-2 (maximum 620 kg ha-'). Mean population density was positively correlated with soil moisture, organic matter, and the quantity of N fertilizer applied. No pesticide impacts were observed.

− Using peptides as energy sources, H 2 as electron donor, thiosulfate as electron acceptors, we ... more − Using peptides as energy sources, H 2 as electron donor, thiosulfate as electron acceptors, we isolated, from four ricefield soils originating from France and the Philippines, 52 strains of anaerobes, among which 18 reduced thiosulfate but not sulfate. These 18 strains were strict proteolytic asaccharolytic anaerobes producing H 2 S when grown on thiosulfate + H 2 . They exhibited the same restriction fragment length polymorphism (RFLP) profile (11 restriction enzymes tested). Partial sequencing of the 16S rDNA showed that they belonged to the genus Clostridium and were phylogenetically related to C. subterminale. DNA-DNA hybridization of a representative strain with the closest C. subterminale strain (DSM 6970 T ) yielded a value of 68.9%. Previous counts of thiosulfate reducers unable to reduce sulfate (TSRnSR) in ricefield soils, their identification as Clostridium strains, and the known ubiquity of this genus in such soils indicate that TSRnSR of the genus Clostridium may play...

We investigated the effects of N fertiliser and pesticide applications on the population dynamics... more We investigated the effects of N fertiliser and pesticide applications on the population dynamics of benthic molluscs in a tropical wetland rice field. Populations were monitored for two consecutive dry seasons in selected treatments during a study on the effects of agricultural practices on the floodwater ecology of tropical rice fields. The most abundant species recorded in the ricefields were the snails Melanoides tuberculata and fifelanoides granifera. Population densities and biomass values in planted plots ranged between O and i530 individuals m-2 and O and 1060 kg ha-', respectively. Snails were more abundant in unplanted than planted plots (1991: 170-2040 versus 0-1040 individuals m-2, respectively). Populations in planted plots declined as the crop season progressed. Snail populations were significantly reduced by the broadcast application of mineral N fertiliser at 110 kg N ha-'. There was little evidence that snails were affected by carbofuran or butachlor applications. Key words Benthic molluscs Snails-Melanoides spp. Wetland rice * Nitrogen fertiliser-Pesticide Carbofuran * Butachlor

Algal, zooplankton, and mollusc populations were monitored over a crop cycle in the floodwater of... more Algal, zooplankton, and mollusc populations were monitored over a crop cycle in the floodwater of a tropical ricefield subject to various N-management and pesticide regimes. This paper gives the results on dynamics of microcrustanceans and dipteran larvae. Dominant groups developed in the succession mosquito + chironomid larvae -+ ostracods + copepods + cladocerans. Populations of ostracods and mosquito + chironomid larvae expanded rapidly after broadcast N applications. Deep placement of N avoided the proliferation of ostracods and dipteran larvae. With the exception of chironomid larvae early in the crop cycle, aquatic invertebrates were generally less abundant in treatments where AzolZa sp. was incorporated. When considered at the crop cycle level, aquatic invertebrate populations were not significantly affected by applications of butachlor and carbofuran.

impliquant principalement des champignons et des groupes bacteriens tels que les bacteries lactiq... more impliquant principalement des champignons et des groupes bacteriens tels que les bacteries lactiques. Ces deux orientations conditionnent le classement en trois grands groupes des residus agricoles et agro-industriels pouvant constituer une source de pollution importante dans les pays du Sud et du Nord (Tableau 1).

Its membership comprises donor countries, international and regional organizations, and private f... more Its membership comprises donor countries, international and regional organizations, and private foundations. As listed in its most recent Corporate Report, IRRI receives support, through the CGIAR, from a number of donors including UNDP, World Bank, European Union, Asian Development Bank, Rockefeller Foundation, and Ford Foundation, and the international aid agencies of the following governments: Australia,

Roger et al. a water microflora. The first section presents a brief summary of the major environm... more Roger et al. a water microflora. The first section presents a brief summary of the major environments of the wetland rice field ecosystem and the major microbial activities they host, and a short overview of research on microbiological management of rice fields. The next sections discuss in detail potential and adopted practices, including (1) the utilization of symbiotic and free-living N,-íìxing blue-green algae as biofertilizers, (2) the inoculation of rice with heterotrophic bacteria and the potential for rhizosphere microflora management, and (3) the utilization of bacterial and algal inhibitors to decrease N fertilizer losses. II. A. Diffusion of air into soil is reduced about 10,000 times when a rice field is flooded and O, supply cannot meet the demand of soil aerobic organisms. Facultative and strict anaerobes proliferate , using oxidized soil substrates for respiration, reducing the soil in a sequence predicted by thermodynamics, and creating anaerobic conditions in a reduced layer a few millimeters beneath the soil surface (Yoshida, 1975). Flooding and crop growth lead to the differentiation of macroenvironments differing in physicochemical and trophic properties: floodwater, surface-oxidized soil, reduced soil, rice plants (submerged parts and rhizosphere), plow layer, and subsoil (Fig. 1). Although those environments can be macroscopically differentiated, they are more or less continuous. In particular, continuous exchanges take place between floodwater and oxidized soil (Watanabe and Furasaka, 1980). Macroenvironments might also be heterogeneous in their oxidation-reduction status at the microsite level because the activity of soil fauna creates microaerophilic sites in the reduced layer, while organic matter debris and aggregates might provide anaerobic microsites in the oxidized soil layer and the water.

Les sols, exondés ou inondés, abritent à la fois des populations de bactéries méthanogènes anaéro... more Les sols, exondés ou inondés, abritent à la fois des populations de bactéries méthanogènes anaérobies, responsables de la production de méthane (CH 4) et des bactéries méthanotrophes aérobies, responsables de son oxydation en CO 2. Les sols submergés sont des sources de CH 4 où l'émission de ce gaz est la résultante d'une production dans les zones anaérobies et d'une réoxydation importante (60 à > 90%) dans les zones aérobies que sont la rhizosphère des plantes aquatiques et l'interface sol-eau. Les émissions de CH 4 par les sols submergés (rizières, zones marécageuses, sols d'estuaires, tourbières...) s'expriment en mg CH 4 m-2 h-1 avec une médiane inférieure à 10 mg CH 4 m-2 h-1. Les sols continuellement exondés consomment le CH 4 atmosphérique, mais les activités sont très faibles, difficiles à mesurer et les micro-organismes impliqués ne sont que très imparfaitement caractérisés. La consommations de CH 4 dans ces sols ne dépasse qu'exceptionnellement 0,1 mg de CH 4 m-2 h-1. Elle décroît des sols de forêt aux sols de prairie et aux sols cultivés. Les sols agricoles, source de CH 4 , sont essentiellement les rizières où la submersion et l'utilisation d'engrais organiques favorisent l'émission de CH 4. L'introduction d'à-secs dans le cycle cultural et l'utilisation d'engrais sulfatés permettent de réduire l'émission de CH 4 par les rizières. Le potentiel méthanotrophe des sols exondés est réduit par la mise en culture et principalement par l'apport d'azote ammoniacal. Les estimations au niveau régional et planétaire des émissions et consommations de CH 4 par les sols sont encore extrêmement imprécises en raison de difficultés méthodologiques aussi bien au niveau de l'évaluation des activités locales que de celle des superficies concernées.

… of systematic and …, 2000

A rod (03-04 µmi3-10 µm) to filamentous (up to 40 µm) non-motile methanogenic bacterium, designat... more A rod (03-04 µmi3-10 µm) to filamentous (up to 40 µm) non-motile methanogenic bacterium, designated strain FPi T (T l type strain), was isolated from ricefield soil in the Philippines. The strain uses H 2 MCO 2 or formate for growth and produces CH 4. Optimum growth temperature is 40 SC ; no growth is observed at 15 SC or 45 SC. Optimum pH for growth is 7 ; no growth is observed at pH 55 or 90. Strain FPi T is halotolerant and grows at NaCl concentrations of 0-25 g l N1. The GMC content of its DNA is 31 mol %. Based on 16S rRNA gene sequence analysis, the isolate was identified as a new species of the genus Methanobacterium : Methanobacterium oryzae sp. nov. The type strain is FPi T (l DSM 11106 T).

Bulletin de la Société Botanique de France. Actualités Botaniques

Bulletin of Japanese Society of Microbial Ecology, May 1, 1990

Biology and Fertility of Soils, Dec 4, 1985

Biology and Fertility of Soils, Feb 1, 1994