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Effects of the earthworm Pontoscolex corethrurus on rice P nutrition and plant-available soil P in a tropical Ferralsol
No full textWe conducted a greenhouse experiment in mesocosms for 28 days to assess the effects of the endogeic earthworm Pontoscolex corethrurus on plant-available soil phosphorus (P) and rice (Oryza sativa) P nutrition in a Malagasy Ferralsol. To assess plant-available soil P, we determined the L-value by measuring the specific activity of P taken up from the soil by rice and by applying the isotopic dilution principle. Despite earthworm mortality, P. corethrurus significantly increased rice shoot biomass (+26%) and P nutrition (+65%), confirming that the soil used for the experiment was P-deficient. The L-value also markedly increased from 6.8 +/- 0.9 to 14.2 +/- 1.3 mg P mesocosm(-1) in the presence of P. corethrurus. We estimated that the orthophosphate ions released due to earthworm mortality contributed to 30% of the L-value increase. We attributed the remaining 70% increase to the solubilization of native soil P during its transit through the digestive tract. Thereafter, we discussed the sources of uncertainty associated with the L-value calculation and their utilization to assess earthworm effects on P availability in further studies
Surface and groundwater characteristics within a semi-arid environment using hydrochemical and remote sensing techniques
No full textThe understanding of hydro systems is of great importance in monitoring quantitative and qualitative changes in water resources. The Essaouira region at the edge of the Moroccan Atlantic Ocean is subject to a semi-arid climate. The decrease in rainfall as a result of climate change and the increase in the exploitation of surface and groundwater have disrupted the stability of these resources and threaten the socio-economic and environmental balance in the area under investigation. Climate scenarios estimate that precipitation will decrease by 10-20% while warming increases by 3 degrees C over the next 30 years. The physico-chemical parameters studied show that the evolution of the pH and temperature of the groundwater remained stable with a neutral (pH approximate to 7) and a hypothermal character (T < 30 degrees C). For the electrical conductivity, it showed an increasing trend from 2017 to 2020. A hydrochemical approach showed that the groundwater mineralization was controlled by the dissolution of evaporites and carbonates, by cation exchange processes, and by seawater contamination. A groundwater assessment for drinking use was made by comparing the concentrations of the chemical elements with the standards set by the World Health Organization. The results obtained show that the groundwater from the aquifers studied requires treatment before being consumed, in particular for Cl- and SO42-. Furthermore, the groundwater quality for irrigation was evaluated based on the parameters Na% and Sodium Adsorption Ratio (SAR). The results showed that the groundwater was adequate for agricultural purposes, especially for the plants that adapt to high salinity. The monitoring of surface water by processing the satellite images via the calculation of the normalized difference water index (NDWI) showed an increase in water surface areas in the region following the commissioning of two large dams (Zerrar and Igouzoullene). Despite the installation of these hydraulic structures, a drop of 4.85 km(2) in water surface area was observed beyond 2016. This situation requires intervention in order to preserve this vital resource
Synergistic impacts of global warming and thermohaline circulation collapse on amphibians
No full textImpacts on ecosystems and biodiversity are a prominent area of research in climate change. However, little is known about the effects of abrupt climate change and climate catastrophes on them. The probability of occurrence of such events is largely unknown but the associated risks could be large enough to influence global climate policy. Amphibians are indicators of ecosystems' health and particularly sensitive to novel climate conditions. Using state-of-the-art climate model simulations, we present a global assessment of the effects of unabated global warming and a collapse of the Atlantic meridional overturning circulation (AMOC) on the distribution of 2509 amphibian species across six biogeographical realms and extinction risk categories. Global warming impacts are severe and strongly enhanced by additional and substantial AMOC weakening, showing tipping point behavior for many amphibian species. Further declines in climatically suitable areas are projected across multiple clades, and biogeographical regions. Species loss in regional assemblages is extensive across regions, with Neotropical, Nearctic and Palearctic regions being most affected. Results underline the need to expand existing knowledge about the consequences of climate catastrophes on human and natural systems to properly assess the risks of unabated warming and the benefits of active mitigation strategies. Julian Velasco et al. use climate model simulations to show how the collapse of the Atlantic meridional overturning circulation and unabated global warming under the RCP 8.5 scenario affect the global distribution of 2509 amphibian species. These results show severe and synergistic impacts of global warming, with particularly strong effects shown in the Neotropical, Nearctic and Palearctic regions
Towards a better integration of local populations in the design of projects to manage the massive aggradation of rivers stemming from mining activity in Thio, New Caledonia
No full textNickel mining in New Caledonia has largely contributed to the supply of sediment to watercourses, so that some of the main watercourses of the island are considerably aggraded. One of the consequences of this massive aggradation is the elevation and widening of river beds and creeks, thus increasing the flood hazard and the associated risks for people and goods. In addition, it changes the aquatic ecosystems, deteriorates the quality of drinking water supplies, causes the deposit of mud on crops during floods, damages communication networks and affects customary practices and activities. In this context, remediation measures are needed on a local level and they are required to consider technical aspects as well as social and cultural ones. Because of these requirements, the CNRT "Nickel and Environment" funds an applied and interdisciplinary research project with both physical and social sciences in order to (a) better understand local dynamics, and to (b) identify key factors for implementing remediation measures. In addition to physical observation and the modelling of aggradation, observations and experiences concerning river and creek aggradation were collected from the inhabitants of six tribes (Kanak villages) in the Thio Valley. It was equally important to record their perception regarding possible remediation measures, some of which having already been put in practice. In these testimonies, people often referred to 'water holes' in the rivers. These are socially important for inhabitants, and their sedimentary dynamics are well known to local people and could represent interesting markers of morphodynamic evolution. Linking lessons learned from both the physical and the social sciences approaches has led to the elaboration of a methodological guide dedicated to the management of sedimentary heritage from mining. This guide was presented to various actors in New Caledonia in 2018. Through the example of water holes as 'shared objects', this paper describes why and how the involvement of the inhabitants in the design and implementation of observations and monitoring is necessary and discusses the need to fully integrate people's perceptions into the project design
"Health in" and "Health of" social-ecological systems : a practical framework for the management of healthy and resilient agricultural and natural ecosystems
No full textThe past two decades have seen an accumulation of theoretical and empirical evidence for the interlinkages between human health and well-being, biodiversity and ecosystem services, and agriculture. The COVID-19 pandemic has highlighted the devastating impacts that an emerging pathogen, of animal origin, can have on human societies and economies. A number of scholars have called for the wider adoption of "One Health integrated approaches" to better prevent, and respond to, the threats of emerging zoonotic diseases. However, there are theoretical and practical challenges that have precluded the full development and practical implementation of this approach. Whilst integrated approaches to health are increasingly adopting a social-ecological system framework (SES), the lack of clarity in framing the key concept of resilience in health contexts remains a major barrier to its implementation by scientists and practitioners. We propose an operational framework, based on a transdisciplinary definition of Socio-Ecological System Health (SESH) that explicitly links health and ecosystem management with the resilience of SES, and the adaptive capacity of the actors and agents within SES, to prevent and cope with emerging health and environmental risks. We focus on agricultural transitions that play a critical role in disease emergence and biodiversity conservation, to illustrate the proposed participatory framework to frame and co-design SESH interventions. Finally, we highlight critical changes that are needed from researchers, policy makers and donors, in order to engage communities and other stakeholders involved in the management of their own health and that of the underpinning ecosystems
Agroecological modeling of nitrogen and carbon transfers between decomposer micro-organisms, plant symbionts, soil and atmosphere in an intercropping system
No full textThe modeling of continuous transfers of carbon (C) and nitrogen (N) previously published in the literature has paid little attention to the functional role of micro-organisms. In general, only monoculture systems have been modeled. Furthermore, there have been few experiments under field conditions at farm scale, where clear evidence for the benefits of intercropping is lacking. This work focus on mechanistic modeling approaches based on the ecological functioning of the microbial biomass, to quantify the daily exchange of C and N between plant organs, micro-organisms, rhizobial symbionts, soil compartments and the atmosphere in an arable intercropping system. The MOMOS model was validated on C and N data collected from a common bean (Phaseolus vulgaris L. cv. El Djadida) and maize (Zea mays L. cv. Filou) intercropping system. The experiment was performed at two field sites that were chosen with farmers to represent both high and low soil P availability. The results show that all C and N exchanges were successfully predicted at 5% significance and that they depend on the phenological stage, especially the flowering stage. Increased C allocation from photosynthesis to roots contributed to increasing both grain yield and N grain for intercropped maize. C and N stocks in the common bean nodules were lower in intercropping than in monocultures, and this is associated with the decrease of total atmospheric nitrogen (N-2) fixation by intercropped common beans, in particular with a high soil P. However, the rate of N-2 fixation was higher in the intercrops than in the monoculture when the soil is P-deficient. Micro-organisms were responsible for most of the C losses from the soil to the atmosphere but intercropping significantly reduced the C losses by improving micro-organism C use efficiency. These results uncover the strong link between N and C stocks, confirming the robustness of the newly formulated MOMOS equations that are validated in this paper. This agroecological modeling experiment demonstrated the functional role of microbial biomass, in both the growth of the intercrops crop and their symbiosis, improving the prediction of the daily C and N flows between plant organs, soil compartments and the atmosphere
Overview of the French operational network for in situ observation of PM chemical composition and sources in urban environments (CARA Program)
No full textThe CARA program has been running since 2008 by the French reference laboratory for air quality monitoring (LCSQA) and the regional monitoring networks, to gain better knowledge-at a national level-on particulate matter (PM) chemistry and its diverse origins in urban environments. It results in strong collaborations with international-level academic partners for state-of-the-art, straightforward, and robust results and methodologies within operational air quality stakeholders (and subsequently, decision makers). Here, we illustrate some of the main outputs obtained over the last decade, thanks to this program, regarding methodological aspects (both in terms of measurement techniques and data treatment procedures) as well as acquired knowledge on the predominant PM sources. Offline and online methods are used following well-suited quality assurance and quality control procedures, notably including inter-laboratory comparison exercises. Source apportionment studies are conducted using various receptor modeling approaches. Overall, the results presented herewith underline the major influences of residential wood burning (during the cold period) and road transport emissions (exhaust and non-exhaust ones, all throughout the year), as well as substantial contributions of mineral dust and primary biogenic particles (mostly during the warm period). Long-range transport phenomena, e.g., advection of secondary inorganic aerosols from the European continental sector and of Saharan dust into the French West Indies, are also discussed in this paper. Finally, we briefly address the use of stable isotope measurements (delta N-15) and of various organic molecular markers for a better understanding of the origins of ammonium and of the different organic aerosol fractions, respectively
A genomic amplification affecting a carboxylesterase gene cluster confers organophosphate resistance in the mosquito Aedes aegypti : from genomic characterization to high-throughput field detection
No full textBy altering gene expression and creating paralogs, genomic amplifications represent a key component of short-term adaptive processes. In insects, the use of insecticides can select gene amplifications causing an increased expression of detoxification enzymes, supporting the usefulness of these DNA markers for monitoring the dynamics of resistance alleles in the field. In this context, the present study aims to characterize a genomic amplification event associated with resistance to organophosphate insecticides in the mosquito Aedes aegypti and to develop a molecular assay to monitor the associated resistance alleles in the field. An experimental evolution experiment using a composite population from Laos supported the association between the over-transcription of multiple contiguous carboxylesterase genes on chromosome 2 and resistance to multiple organophosphate insecticides. Combining whole genome sequencing and qPCR on specific genes confirmed the presence of a similar to 100-Kb amplification spanning at least five carboxylesterase genes at this locus with the co-existence of multiple structural duplication haplotypes. Field data confirmed their circulation in South-East Asia and revealed high copy number polymorphism among and within populations suggesting a trade-off between this resistance mechanism and associated fitness costs. A dual-color multiplex TaqMan assay allowing the rapid detection and copy number quantification of this amplification event in Ae. aegypti was developed and validated on field populations. The routine use of this novel assay will improve the tracking of resistance alleles in this major arbovirus vector
Multi-method investigation of mass transfer mechanisms in a retrogressive clayey landslide (Harmaliere, French Alps)
No full textThe mass transfer mechanisms in landslides are complex to monitor because of their suddenness and spatial coverage. The active clayey Harmaliere landslide, located 30 km south of Grenoble in the French Alps, exhibits two types of behavior: in its upper part, decameter-sized clay blocks slide along a listric slip surface, while a flow-like mechanism is observed in a clayey remolded material a few hundred meters below the headscarp. The landslide underwent a major retrogression affecting 45 ha in March 1981 and has experienced multiple reactivations since then. The last major event took place on the 26(th) of June 2016, and a large investigation survey was conducted to better understand the reactivation mechanism. A multi-method investigation was carried out at different temporal and spatial scales, including aerial photograph and light detection and ranging processing, correlation of optical satellite images, global navigation satellite system monitoring, continuous seismic monitoring, and passive seismic survey. The morphological evolution of the landslide was traced over the last 70 years, showing a headscarp retrogression of 700 m during multiple reactivations and a total mass transfer of more than 6 x 10(6) m(3). The detailed study of the 2016 event allowed to track and understand the mechanism of a mass transfer of 1 x 10(6) m(3) in 5 weeks, from a sliding mechanism at the headscarp to an earthflow at the toe
Calcium transfer and mass balance associated with soil carbonate in a semi-arid silicate watershed (North Cameroon) : an overlooked geochemical cascade ?
No full textCalcium is a key element of the Earth system and closely coupled to the carbon cycle. Weathering of silicate releases Ca, which is exported and sequestered in oceans. However, pedogenic calcium carbonate constitutes a second Ca-trapping pathway that has received less attention. Large accumulations of pedogenic calcium carbonate nodules, associated with palaeo-Vertisols, are widespread in North Cameroon, despite a carbonate-free watershed. A previous study suggested that a significant proportion of Ca released during weathering was trapped in palaeo-Vertisols but the pathways involved in the transfer of Ca from sources (the granite and the Saharan dust) to a temporary sink (the carbonate nodules) remain unclear. This study aims to compare the distribution of elements in carbonate nodules and their associated past and present compartments for Ca in the landscape. These compartments are all characterised by a distinctive geochemical composition, resulting from specific processes. Three end members have been defined based on geochemical data: (a) the granite and its residual products, dominated by K2O and Na2O, Ti and Zr, HREE, and a positive Ce anomaly; (b) the soil parental material and the Saharan dust, dominated by Al2O3, Fe2O3 and MgO, V, HREE, and a positive Ce anomaly; and finally (c) the carbonate nodules, which are dominated by CaO, a depletion in V, Ti and Zr, and an enrichment in REE with a negative Ce anomaly. Mass balance calculations in soil profiles demonstrated that the accumulation of Ca in carbonate nodules exceeds the Ca released by chemical weathering of the parental material, because of a continuous accumulation and contribution from lateral transfers. Consequently, at the landscape scale, carbonate nodules associated with palaeo-Vertisols constitute a temporary sink for Ca. Such a spatial relationship between sources and transient compartments opens an avenue to the new concept of 'geochemical cascade', similar in terms of geochemistry, to the concept of 'sediment cascade' developed by continental sedimentologists