Articles of the day

Global parameterization and validation of a two-leaf light use efficiency model for predicting gross primary production across fluxnet sites

Z.Nagy , G.Kiely , J.Olejnik , Y.Zhou , X.Wu , W.Ju , J.M. , S.Wang , H.Wang , W.Yuan , T.Andrew , R.Jassal , A.Ibrom , S.Han , J.Yan , H.Margolis , O.Roupsard , Y.Li , F.Zhao , G.Starr , M.Pavelka , L.Montagnani , G.Wohlfahrt , P.D'Odorico , D.Cook , M.Altaf , D.Bonal , J.Beringer , P.D. , B.Loubet , M.Y. , G.Matteucci , K.Tha , A.Varlagin


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Light use efficiency models are widely used to simulate gross primary production. However, the treatment of the plant canopy as a big leaf by these models can introduce large uncertainties in simulated GPP. Recently, a two-leaf light use efficiency model was developed to simulate GPP separately for sunlit and shaded leaves and has been shown to outperform the big-leaf MOD17 model at six FLUX sites in China. In this study we investigated the performance of the TL-LUE model for a wider range of biomes. For this we optimized the parameters and tested the TL-LUE model using data from 98 FLUXNET sites which are distributed across the globe. The results showed that the TL-LUE model performed in general better than the MOD17 model in simulating 8 day GPP. Optimized maximum light use efficiency of shaded leaves ) was 2. 63 to 4. 59 times that of sunlit leaves ). Generally, the relationships of epsilon and epsilon with epsilon were well described by linear equations, indicating the existence of general patterns across biomes. GPP simulated by the TL-LUE model was much less sensitive to biases in the photosynthetically active radiation input than the MOD17 model. The results of this study suggest that the proposed TL-LUE model has the potential for simulating regional and global GPP of terrestrial ecosystems, and it is more robust with regard to usual biases in input data than existing approaches which neglect the bimodal within-canopy distribution of PAR.

Adoption des reseaux sociaux numeriques par les bibliothecaires des universites ivoiriennes : une approche par lutaut

K.Sylvestre


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AbstractAcceptance of digital social networks by Ivorian universities librarians: an approach by the UTAUT This article aims to identify and evaluate the factors influencing the intention of adopting the RSN by librarians Ivorian universities. Drawing on the theory of UTAUT, we developed a research model whose validation was done by combining the methods of analysis of simple and multiple linear regressions. The study shows that the main factors that determine the intention of adopting the RSN in the context of the Ivorian university libraries are technology task compatibility, the perceived usefulness, the perceived ease of use, the hoped image, the involvement of management and availability of technical assistance. Resume : FrancaisCet article vise a identifier et a evaluer les facteurs influencant lintention dadoption des RSN par les bibliothecaires des universites ivoiriennes. En nous appuyant sur la theorie de lUTAUT, nous avons elabore un modele de recherche dont la validation sest fait en combinant les methodes danalyses de regressions lineaires simple et multiple. Letude montre que les principaux facteurs qui determinent lintention dadoption des reseaux sociaux numeriques dans le contexte des bibliotheques universitaires ivoiriennes sont la compatibilite tache technologie , l utilite percue , la facilite dutilisation percue , l image esperee , l implication de la direction et la disponibilite dune assistance technique.

Behavioral responses of juvenile golden grey mullet liza aurata to changes in coastal temperatures and consequences for benthic food resources

C.Lefrancois , D.Christine , S.Como , E.Maggi , F.Antognarelli


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Temperature is an important factor for fish. Yet, little is known about its effects on the feeding behavior of fish and the subsequent consequences of these behavioral changes on the spatial distribution of resources. We analyzed the differences in the feeding behavior of two sizes of juvenile Liza aurata at two water temperatures , using laboratory mesocosms. We also examined whether temperature-induced changes in feeding behavior of the smaller size of L. aurata would affect the spatial distribution of the microphytobenthos biomass, an important resource in coastal systems. Both the number of feeding events and the swimming velocity during feeding in juvenile L. aurata were higher at 20C than at 10C, independently of the fish size. The time spent feeding did not vary between 10C and 20C, while the distance covered during feeding was significantly smaller at 20C than at 10C. Grazing did not affect the mean MPB biomass, but did increase its spatial variance at the smaller scale at 20C. A high number of feeding events, a high swimming velocity during feeding and a small distance covered during feeding in 20C-acclimated L. aurata most likely represented an adaptation to an increase in metabolism, as well as to the need to reduce the energy costs of feeding at 20C. Results also indicated that changes in feeding behavior of the 20C-acclimated L. aurata were responsible for the increase in small-scale spatial variability in the MPB biomass. We suggested that the enhanced spatial patchiness due to grazing by fish at 20C might yield a local increase in the mean MPB biomass, probably increasing photosynthetic efficiency of cells and algal growth that counterbalance the negative effect of algal removal by fish, and resulting in the lack of an overall significant effect on the mean.

Plio-pleistocene mammalian biostratigraphy of atlantic morocco

D.Geraads


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The recent Moroccan-French cooperation programme has brought about the discovery and excavation of several rich sites in the area of Casablanca. The earliest of these is the newly discovered locality of Lissasfa, which is at least 5 Myr old, and shows that the "Quaternary" sequence of Atlantic Morocco is at least twice as long as previously thought. The other localities provide a biochronological frame for the North-African Upper Pliocene and Quaternary. Ahl al Oughlam, dated to about 2. 5 Myr, is one of the richest faunal localities in the whole African Cenozoic, but man had probably not arrived in North Africa at that time. In Thomas Quarry 1, the earliest archaeological level in Morocco, level L, is probably of lower Pleistocene age. In the same complex of quarries, the faunas of cave fillings, of which the Homo erectus level of Thomas 1 looks the oldest, can be grouped within a single faunal unit. Resume : Le recent programme de cooperation franco-marocain a permis la decouverte et la fouille de plusieurs riches sites dans la region de Casablanca. Le plus ancien d'entre eux est celui de Lissasfa, age d'au moins 5 M. a. , qui montre que la sequence "quaternaire" du Maroc atlantique est au moins deux fois plus longue qu'on ne le pensait naguere. Les autres sites permettent l'etablissement d'un cadre biochronologique pour le Pliocene superieur et le Quaternaire nord-africain. Ahl al Oughlam, date d'environ 2,5 M. a. , est l'une des plus riches localites de tout le Cenozoique africain, mais l'Homme n'avait sans doute pas encore gagne l'Afrique du Nord a cette epoque. Dans la carriere Thomas 1, le plus ancien niveau archeologique du Maroc, le niveau L, est probablement d'age pleistocene inferieur. Dans le meme ensemble de carrieres, les faunes de remplissages de fissures, dont la plus ancienne est associee a l' Homo erectus de Thomas 1, peuvent etre regroupees dans un meme ensemble.
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