Meunier J.D.,Aix - Marseille University |
Keller C.,Aix - Marseille University |
Guntzer F.,Aix - Marseille University |
Riotte J.,Indian Institute of Science |
And 4 more authors.
Geoderma | Year: 2014
Amorphous silica (ASi) pool and fluxes have become parameters of a growing interest in the understanding of the biogeochemical cycle of Si and the modeling of anthropogenic impacts. Extraction by 1% Na2CO3 followed by a correction for crystalline Si (DeMaster, 1981) has recently become widely used and is proposed as the standard technique for quantifying amorphous silica (ASi) pools in soil and continental aquatic environments. However, the 1% Na2CO3 method was developed to quantify diatom frustules and not phytoliths (PhSi), which constitute the most common fraction of ASi in soils. The aim of this study was to assess the 1% Na2CO3 method for fresh and aged phytoliths. We founded a significant positive correlation between Si extracted by the 1% Na2CO3 method and Si extracted by other standard procedures (Guntzer et al., 2010) for various shoot samples (elm, horsetail, fern and larch). Because the Si shoot samples are mainly composed of phytoliths, we concluded that the 1% Na2CO3 method was well adapted for the determination of PhSi of fresh phytoliths containing less than 70mg Si g-1. To assess the 1% Na2CO3 method for PhSi of aged phytoliths, we used artificial mixtures of soil phytoliths from La Réunion (Meunier et al., 1999) and quartz. Our results showed that the 1% Na2CO3 method underestimated PhSi for aged phytoliths by a factor of 3.7. Combining the 1% Na2CO3 method and a physical method of extraction using samples of various origins showed a dispersion of the data that can be explained by a combination of several factors including loss during physical extraction and the presence of resistant phytoliths. In the absence of standard technique, we recommend to check the nature of the particles using physical extraction in combination with the 1% Na2CO3 in order to provide a more careful analysis of ASi. © 2013 Elsevier B.V. Source
Attewell G.,French Institute of Pondicherry
Culture, Medicine, and Psychiatry | Year: 2014
This is a study of the emergence of new institutional arenas for ayurveda and yunani medicine, collectivized at the time as 'indigenous medicine,' in a semi-autonomous State (Mysore) in late colonial India. The study argues that the characteristic dimensions of this process were compromise and misalignment between ideals of governance and modes of pedagogy and practice. Running counter to a narrative that the Princely States such as Mysore were instrumental for the 'preservation' of ayurveda, this study analyzes the process of negotiation and struggle between a variety of actors engaged with shaping the direction of institutionalized 'indigenous medicine'. In examining the entanglements over the priorities of the state administration and the conflicting desires and ideals of protagonists, the study problematizes the idea of studying the encounter between the 'state' and 'indigenous medicine,' in order rather to highlight their co-production and the tensions which were generated in the process. While institution-making for ayurveda and yunani in Mysore State assumed distinctive translocal forms, themes of divergence that were unresolved during the time of this study, over the role of the state, the politics of validation, appropriate curricula and pedagogy, and their relation to practice and employment, continue to inform the trajectories of state-directed health provision through 'indigenous medicine' on larger scales [India, health-care, ayurveda, yunani, education]. © 2014 Springer Science+Business Media New York. Source
Gritti E.S.,CNRS Center of Evolutionary and Functional Ecology |
Gritti E.S.,Montpellier SupAgro |
Gaucherel C.,French National Institute for Agricultural Research |
Gaucherel C.,French Institute of Pondicherry |
And 2 more authors.
PLoS ONE | Year: 2013
Today, more than ever, robust projections of potential species range shifts are needed to anticipate and mitigate the impacts of climate change on biodiversity and ecosystem services. Such projections are so far provided almost exclusively by correlative species distribution models (correlative SDMs). However, concerns regarding the reliability of their predictive power are growing and several authors call for the development of process-based SDMs. Still, each of these methods presents strengths and weakness which have to be estimated if they are to be reliably used by decision makers. In this study we compare projections of three different SDMs (STASH, LPJ and PHENOFIT) that lie in the continuum between correlative models and process-based models for the current distribution of three major European tree species, Fagus sylvatica L. We compare the consistency of the model simulations using an innovative comparison map profile method, integrating local and multi-scale comparisons. The three models simulate relatively accurately the current distribution of the three species. The process-based model performs almost as well as the correlative model, although parameters of the former are not fitted to the observed species distributions. According to our simulations, species range limits are triggered, at the European scale, by establishment and survival through processes primarily related to phenology and resistance to abiotic stress rather than to growth efficiency. The accuracy of projections of the hybrid and process-based model could however be improved by integrating a more realistic representation of the species resistance to water stress for instance, advocating for pursuing efforts to understand and formulate explicitly the impact of climatic conditions and variations on these processes. © 2013 Gritti et al. Source
Saltre F.,French National Center for Scientific Research |
Saint-Amant R.,Natural Resources Canada |
Gritti E.S.,Montpellier SupAgro |
Brewer S.,University of Utah |
And 3 more authors.
Global Ecology and Biogeography | Year: 2013
Aim: Despite the recent improvements made in species distribution models (SDMs), assessing species' ability to migrate fast enough to track their climate optimum remains a challenge. This study achieves this goal and demonstrates the reliability of a process-based SDM to provide accurate projections by simulating the post-glacial colonization of European beech. Location: Europe. Methods: We simulated the post-glacial colonization of European beech over the last 12,000 years by coupling a process-based SDM (PHENOFIT) and a new migration model based on Gibbs point processes, both parameterized with modern ecological data. Simulations were compared with palaeoarchives and phylogeographic data on European beech. Results: Model predictions are consistent with palaeoarchives and phylogeographic data over the Holocene. The results suggest that post-glacial expansion of European beech was limited by climate on its north-eastern leading edge, while limited by its migration abilities on its north-western leading edge. The results show a mean migration rate of beech varying from 270myr -1 to 280myr-1 and a maximum migration rate varying from 560myr-1 to 630myr-1, when limited and not limited by climate, respectively. They also highlight the relative contribution of known and suspected glacial refugia in present beech distribution and confirm the results of phylogeographic studies. Main conclusions: For the first time, we were able to reproduce accurately the colonization dynamics of European beech during the last 12kyr using a process-based SDM and a migration model, both parameterized with modern ecological data. Our methodology has allowed us to identify the different factors that affected European beech migration during its post-glaciation expansion in different parts of its range. This method shows great potential to help palaeobotanists and phylogeographers locate putative glacial refugia, and to provide accurate projections of beech distribution change in the future. © 2013 John Wiley & Sons Ltd. Source
Lo Seen D.,CIRAD - Agricultural Research for Development |
Ramesh B.R.,French Institute of Pondicherry |
Nair K.M.,National Bureau of Soil Survey and Land Use Planning |
Martin M.,French National Institute for Agricultural Research |
And 2 more authors.
Global Change Biology | Year: 2010
Habitat loss and soil organic carbon (SOC) stock variations linked to land-cover change were estimated over two decades in the most densely populated biodiversity hotspot in the world, in order to assess the possible influence of conservation practices on the protection of SOC. For a study area of 88 484 km2, 70% of which lie inside the Western Ghats Biodiversity Hotspot (WGBH), land-cover maps for two dates (1977, 1999) were built from various data sources including remote sensing images and ecological forest maps. SOC stocks were calculated from climatic parameters, altitude, physiography, rock type, soil type and land-cover, with a modelling approach used in predictive learning and based on Multiple Additive Regression Tree. The model was trained on 361 soil profiles data, and applied to estimate SOC stocks from predictor variables using a Geographical Information System (GIS). Comparison of 1977 and 1999 land-cover maps showed 628 km2 of dense forests habitat loss (6%), corresponding to an annual deforestation rate of 0.44%. This was found consistent with other studies carried out in other parts of the WGBH, but not with FAO figures showing an increase in forest area. This could be explained by the different forest definitions used, based on ecological classification in the former, and on percentage tree cover in the latter. Unexpectedly, our results showed that despite ongoing deforestation, overall SOC stock was maintained (∼0.43 Pg). But a closer examination of spatial differences showed that soil carbon losses in deforested areas were compensated by sequestration elsewhere, mainly in recent plantations and newly irrigated croplands. This suggests that more carbon sequestration in soils could be achieved in the future through appropriate wasteland management. It is also expected that increasing concerns about biodiversity loss will favour more conservation and reinforce the already prevailing protective measures, thus further maintaining C stocks. © 2010 Blackwell Publishing Ltd. Source