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How topography drives ecosystem nutrient provision in a tropical rain forest ecosystem
No full textIntroduction. Chemical weathering is the transformation of rocks into soils, a process that not only consumes atmospheric CO2 but also releases nutrients from rock minerals and makes them available for life, creating the critical zone, the habitable part of the planet. Forest ecosystem services are limited by water and nutrient stresses. While the water, carbon, and nitrogen cycles have been and continue to be the subject of numerous studies, not enough attention has been paid to essential mineral nutrients including Ca, Mg, K, and P, whose ultimate origin can only be rock weathering. Chemical weathering is controlled by a number of factors including climate, landscape position, parent material, precipitation rates of secondary minerals, ecosystem productivity, and residence time of water in the critical zone. In this study, we investigate, under the favorable conditions of a tropical rain forest, the relationships among critical zone architecture, landscape position, hydrological flow path and river water chemistry.Study site. The Quiock stream site is a small monitored catchment (8 ha) in the island of Basse Terre, French West Indies, part of the ObsErA Observatory, OZCAR critical zone observatory network (https://www.ozcar-ri.org). The whole catchment is underlain by 1 Myr old volcanic rocks and the rainfalls exceed 3500 mm/yr. Located in the National Parc of Guadeloupe, the catchment is covered by a primary rain forest. The Quiock stream is characterized by a 50 m-wide knickzone located 200 m upstream to the catchment outlet, indicating a transient river profile where the upper reaches are non-equilibrated. Geophysical investigations have revealed that the weathered mantle or saprolite is deep, reaching 40 m (Pasquet et al. 2022).Analytical tools. We measured different elemental and isotopic tracers along the Quiock river from the spring to the catchment outlet and in various compartments of the system (soil, rain, vegetation, rocks). We were particularly interested in Strontium (Sr) and Uranium (U) isotopes as tracers of bedrock weathering vs. atmospheric inputs for mineral nutrients to ecosystems.Results. The study shows that the chemistry of the river changes along the 700 m length from spring to mouth, indicating the contribution of waters with different origins. Sr isotopes vary from 87Sr/86Sr = 0.709 in the headwaters to 0.7055 at mouth. U isotopes increase from (234U/238U) = 1.15 in the headwaters to 1.30 at mouth. Upstream of the knickzone, most of the nutrients measured in the river are originating from marine aerosols in rainwater. Below the knickzone, nutrients are enriched and display a clear bedrock origin, despite the thickness of the weathered zone.Discussion. U and Sr isotopes in the river water define a mixing line between a seawater-like endmember and a volcanic rock endmember. This mixing line allows us to calculate at each sampling location how much of the Sr, U and the other major nutrients are released by rock weathering and how much are added to the ecosystem by the dissolution of atmospheric marine aerosols. These results were compared with water flow lines simulated by a steady-state groundwater numerical model developed for the Quiock catchment. Modflow was used to solve the groundwater flow equations and Modpath to determine the flow lines (Abhervé et al. 2023). The hydrological model clearly shows a strong vertical partitioning of water and nutrients between the weathered zone and the bedrock, controlled by a hydraulic conductivity that is 150 times higher in the saprolite. While only 4% of the water, characterized by long residence time, circulates through the unweathered bedrock,this small fraction interacts with fresh minerals and releases nutrients. The model shows that the spatial distribution of water and nutrient fluxes is controlled by the surface topography, in particular the knickzone. Indeed, the ability of groundwater flowpaths to cross the weathered zone-bedrock interface and to discharge into the river is mainly controlled by the change in the hydraulic gradient associated with the knickzone.This study therefore shows that even in deep mantle zones, the shape of the landscape controls groundwater flow paths and creates hot spots of weathering and nutrient release that can benefit and sustain ecosystem productivity
Causal Xwildfire: Causality-instilled fire spread modelling for extreme events
No full textIntroductionExtreme wildfires are increasingly prevalent worldwide, driving significant forest area loss and severe environmental and socioeconomic impacts (Cunningham et al. 2024). The Mediterranean, in particular, is projected to face heightened fire risks due to climate change-induced drier conditions and lower fuel moisture (de Rivera et al. 2020). However, the drivers of extreme wildfires remain poorly understood. Current fire models, typically calibrated on global fire datasets, are primarily designed to estimate annual total burned areas and struggle to capture the unique behaviours of extreme wildfires (Forrest et al. 2024). Furthermore, correlation-based approaches, which dominate current modelling efforts, may fail to identify the underlying causal drivers of these events and are poorly suited for extrapolation to changing conditions.Causal discovery methods, which aim to identify cause-and-effect relationships from observational data, offer a promising pathway to uncover the mechanisms driving extreme wildfires. While increasingly applied in environmental sciences, their use in wildfire prediction remains limited (de Rivera et al. 2020, Zhang et al. 2024, Zhao et al. 2024).This study will use causal discovery to identify key drivers of extreme wildfire in the Mediterranean, and further integrate the causal graphs into a stand-alone model of wildfire spread. This approach aims to move beyond correlation-based models, improve our understanding of extreme wildfire behaviour and inform more robust mitigation strategies.Study Area and DataWe will use the Mesogeos dataset (Kondylatos et al. 2023), designed for wildfire modelling in the Mediterranean region. Spanning 17 years (2006–2022) at a 1 km² spatial and daily temporal resolution, it includes meteorological variables (e.g., temperature, wind speed), vegetation indices (e.g., NDVI, LAI), and human activity indicators (e.g., population density, road proximity). Wildfire data include MODIS fire ignitions and burned areas from EFFIS.MethodsExtreme Wildfire Definition and SamplingIn this study, we define extreme wildfires as those that are exceptionally large in size. To identify these events, we will first extract the final burned areas associated with each fire ignition recorded in the Mesogeos dataset. Since the classification of large fires is inherently subjective and varies by region, we will adopt a data-driven approach based on an absolute quantitative threshold. Specifically, we will define extreme wildfires as those exceeding the 99th percentile of fire sizes, though this threshold may be adjusted to align with extreme fire events documented in national fire reports. While this method provides a straightforward and reproducible way to define extreme events, we acknowledge its limitations. Future work will refine this approach by incorporating region-specific thresholds and additional contextual factors to improve geographic relevance.Phase I: Causal DiscoveryUsing local variables from Mesogeos, averaged over final burned areas and lagged to time t, we will estimate causal graphs for extreme events via Python’s Tigramite library with the PCMCI method (Runge et al. 2019). PCMCI detects time-lagged causal associations in large nonlinear datasets through iterative conditional independence testing. To ensure robustness, we will assess graph stability across hyperparameters and selected drivers, and validate graphs through expert knowledge.Phase II: Causal Fire Spread ModelWe will develop a fire spread model incorporating causal mechanisms from Phase I. This model will integrate spatiotemporal fire dynamics, causal dependencies constraining fire spread, and dynamic weather and fuel inputs. By explicitly modeling causal interactions, it aims to improve early warning systems and risk assessments under future climate scenarios. The causal model’s performance will be benchmarked against statistical models to evaluate its predictive accuracy and robustness.Expected ResultsWe expect that the data-driven approach proposed in this study will enhance the predictability of extreme wildfires by reducing confounding effects and capturing key drivers of extreme fire events. Compared to purely statistical approaches, incorporating causal structures should lead to more reliable predictions, particularly in out-of-sample applications or under changing environmental conditions. Furthermore, the causal fire spread model will provide insights into how climate, vegetation, and anthropogenic factors interact to drive fire spread, supporting fire prevention and mitigation strategies
An Autonomous Sensor to Monitor In Situ Soil Moisture, Salinity, and Temperature Profiles for Wireless Networks
No full textThe in situ sensor we develop is aimed at monitoring continuously essential variables of the soil such as its moisture, salinity, and temperature at different horizons or depths up to 60 cm. Its capability permits to follow accurately water movements in soil resulting from such events as rain infiltration, evapotranspiration or intrusions of underground saltwater (Fig. 1). It is intended for industrial-scale duplication and deployment (series of several tens) (Chavanne and Frangi 2024). The instrument principle relies on soil permittivity to determine water content and salinity like many others. However, its unique measurement technique presents an output linear to the complex permittivity with a large resolution, not possible with other techniques. Conversions are based on physical laws to reach high accuracy and made instrument bias negligible. Hence are deduced soil real permittivity (for water molecules) and conductivity (for ions). Conversion of permittivity into soil water content should be based on established relations like Archie’s law or even Topp’s correlation, that are independent of the instrument. Soil temperature gradients are measured owing to thermocouples offering also unique precision and resolution without the need of a calibration. The device profits from recent advances in Information and Communication Technology, namely LoRaWAN, for autonomous operations and communication. Data are transferred over several km and made available in real time on Internet. Consumption is minimized to permit operations over a year without intervention at a sampling frequency as low as 5 min. Both rare but intense events and long term trends are captured. The technology allows equally to manage networks of several tens of sensors such as those in a catchment for mapping spatial variability. Sensor features a compact design with a water proof box of 12 x 12 cm2 area housing on ground all electronics and power supply, and connected to low-cost modular electrodes inserted into soil. Installation labor and invasiveness are minimized. Electronic simplification and integration on one board, as well as standardized components and procedures of assembly reduce costs and labors. Tight tolerances for key characteristics and a on-board reference limit time spent on quality control for each device of a series while maintaining a low sensor-to-sensor variability. Prototypes are operating presently at different observatories, some in mountains, to test their robustness and to identify further improvements before industrial duplication. They also start to provide data
Hyper-resolution decametric modelling of alpine catchments: development of a data processing framework to represent small scale-snow hydrological processes, over complex topography
No full textMountain ecosystems are under increasing pressure from anthropogenic forcings including warming, precipitation change and nutrient inputs. Understanding and projecting the consequences of these changes requires to be able to model transfer of energy and water (as a resource and the main agent of transport) both through vertical and lateral fluxes. The determination of these water paths is particularly challenging in complex mountain terrains, where small scale snow, topographic and geomorphological processes drive hydrology. Conceptual and semi-distributed hydrological models fail to represent the complexity of these water paths and land surface model often neglect lateral fluxes, making both approaches limited in studying trajectories of mountain ecosystems.To overcome these limitations, we applied the data-intensive and calibration-light critical zone model ParFlow-CLM3.5, to a highly instrumented alpine catchment (6.2 km² area between 1950 and 3100 m.a.s.l) close to the Lautaret Pass, in the French Alps. Specific efforts have been directed toward the representation and definition of small-scale snow hydrological processes, that modify significantly the timing, amount, and location of water fluxes above and below the surface.The representation of snow accumulation, redistribution, and melt was a key point of improvement in this model. Limitations of the initial snow scheme were overcome by refining the snow/rain transition dependencies on meteorological factors, by improving the snow albedo aging routine, by accounting for Saharan dust events and by selecting relevant spatial distribution methods for meteorological forcings over the watershed. The snow/rain transition was evaluated with disdrometer measurements. Meteorological forcings are distributed based on topography (slope effect on radiation and windspeed, shading, reillumination by longwave radiation), altitude (precipitation, temperature and humidity gradients), and remote sensing measurements (Leaf Area Index, snow redistribution maps).In this presentation we will focus on snow scheme improvements, and the ability of the model to represent the dynamic of the snow cover during the season at decametric resolution. This will be evaluated spatially with drone, Sentinel-2, MODIS and Pleiades images (snow height, snow cover and albedo), locally with albedo, snow height and Snow Water Equivalent, and hydrologically with streamflow observations. Further on, this work aims to show that distributed and physics-based hydrological modelling is feasible over complex alpine terrain, with reduced field data needs, and to provide a reproducible framework. Future work will look at subsurface hydrological consequencies of snow melt spatial patterns on water paths
Can high-resolution monitoring provide a better understanding of the hyporheic zone in Groundwater Dependent Ecosystems?
No full textThe hyporheic zone is an essential component of river ecosystems, yet it is often overlooked in environmental studies. A comprehensive understanding of the interactions between surface water (SW) and groundwater (GW), as well as the role of Groundwater Dependent Ecosystems (GDEs) in providing essential ecosystem services, is crucial for informed and effective land and water management (Yang and 2017).GDEs are influenced by local hydrogeology and climate, necessitating detailed spatial and temporal monitoring of the physical and chemical interactions occurring within these systems. Traditional monitoring methods, which typically rely on individual sensors to collect point data, can overlook important variations across different sections of a stream. By integrating continuous high-resolution longitudinal stream temperature monitoring with Electrical Conductivity (EC) and discharge measurements, more comprehensive data can be collected. This approach provides both high spatial and temporal resolution, capturing small-scale interactions and patterns that are crucial for understanding the SW-GW interface. Such methods are particularly valuable for localising SW-GW interactions and assessing their seasonal impact on GDEs' baseflow.To investigate these interactions, we employed a multidisciplinary approach combined with continuous high-resolution longitudinal stream temperature monitoring in the headwater stream of the Wüstebach Catchment, located within the TERENO Observatory in Eifel National Park, Germany. In October 2022, a Fibre Optic Distributed Temperature Sensing (FO-DTS) system (Silixa XT) was installed along a 500-meter-long stream section to monitor temperature changes over a hydrological year. Stream temperature measurements were recorded every 15 minutes at a resolution of 25 cm. Sampling was conducted at 18 sites distributed along the stream, tributaries, and existing groundwater wells, in conjunction with weekly sampling coordinated by site managers. Additionally, two intensive field campaigns were carried out during the wet and dry seasons, incorporating high-frequency EC measurements and tracer tests to capture specific hydrological events such as snowmelt and intense rainfall. These efforts aimed to deepen the understanding of groundwater recharge and discharge processes. Additional discharge and precipitation data were obtained from the TERENO Eifel database.Despite the limited groundwater network at the study site, this approach significantly enhanced our understanding of SW-GW interactions and their role in driving the seasonal flow variations of GDEs. It also led to the quantification of SW-GW interactions and the development of standardised methods that can be applied and scaled to larger areas, complementing and strengthening existing monitoring efforts
The Mental’eau project: what is the relationship between aquatic ecosystem health and human well-being?
No full textBackground In a global context undergoing profound transformation (climate change, collapse of biodiversity, new pandemics, social changes, etc.), the 'One Health' concept (World Health Organization 2023) may appear relevant both from a scientific point of view, to think about (and prevent) these crises, but also from a social - or even political - point of view, by proposing an additional way of making visible the ecosystemic interactions and interdependencies in which humans are involved. We explore this dual social and scientific aspect of the 'One Health' concept in Mental'Eau project, which focuses on the interface between humans and aquatic ecosystems (rivers, water bodies, canals). A preliminary literature review has shown that few studies have focused on the link between well-being and health in aquatic ecosystems. Co-funded by the Rhine-Meuse Water Agency, our 4-yr project proposes an interdisciplinary approach based on environmental sciences, human sciences and scientific mediation. It brings together a multidisciplinary research team (LIEC - Université de Lorraine CNRS, LHAC - Ecole Nationale Supérieure d'Architecture de Nancy, EABX and Beta - INRAE, ICube and LinCS - Université de Strasbourg CNRS) and the ‘Vigie de l'Eau’ association (Vittel), and involves local stakeholders.Objectives In this interdisciplinary research project, we are investigating the relationship that individuals have with aquatic ecosystems, as landscapes and environments for a variety of recreational practices. How can these ecosystems be a source of well-being for humans, and conversely, how can users' perceptions help to improve the quality of aquatic ecosystems? To what extent can we link human health and ecosystem health, from the perspective of the 'One Health' concept? Finally, how is this concept perceived and integrated (or not) by individuals, with possible implications for their practices and their experience of these environments?This research aims to link indicators of well-being (relaxation, ability to concentrate, happiness, serenity, creativity, etc.), as expressed by individuals frequenting places linked to water (rivers, lakes, etc.) with measurable indicators of the functionality and quality of these aquatic ecosystems (Observatoire National de la Biodiversité 2025) such as physico-chemical parameters, biodiversity.These scientific research objectives are complemented by more operational ones, which anchor the project presented in the field of action research. The project has three main operational targets:to raise awareness of the 'One Health' concept among the public visiting the various sites, through events, serious games, etc.to support local authorities in their decision-making on aquatic site development projects, through information meetings and the drafting of practical guidelines, andto provide scientific mediation for local residents in the vicinity of the sites studied, to present the research and its issues as well as its conclusions.Outcomes First, a corpus of around 30 aquatic ecosystems was selected in the river Moselle watershed (Figs 1, 2, 3). These sites were selected based on both frequentation and functional characteristics criteria.The second step was to design a method for characterizing the ‘health’ of aquatic ecosystems. This work was carried out as part of an end-of-study internship at INRAE Bordeaux (Paul et al. 2025). The proposed method integrates indicators of ecosystem ecological integrity such as naturalness, diversity, water quality and ecological interest. Metrics are calculated on the basis of both physico-chemical and ecological parameters, and are represented by radar diagrams that provide a synthetic visualization of the ecosystem's state of health. Metrics are assessed at the 3 scales of the landscape, the immediate environment and the aquatic environment itself. This multimetric and multiscalar method is currently being finalized and should enable us to estimate the state of health of the ecosystem and its utilization for the sociological part of the study.Sociological surveys combining observation, questionnaires (around 50 per site) and interviews (around 10 per site) will be carried out in situ. To date, a questionnaire has been designed by Caroline Denechaud (PhD student) and will be tested on the sites from spring 2025. The questionnaire covers various items, namely the perception of the characteristics of the site visited (sensory experience), the appreciation of the experience (effect of the experience), and the perception of the ecological quality of the site (individual assessment of the state of the ecosystem) (Denechaud et al. 2025). Survey results will be used to derive indicators of human well-being.The last step will focus on analyzing the links between indicators of well-being and ecosystem health. Interpretation of these results will reveal, among other things, whether individuals relate their well-being to the health of the ecosystem and the indicators used, and whether there is resonance or dissonance between the state of well-being of individuals and the health of the ecosystems they visit.We are also looking into ways of raising awareness of the 'One Health' concept among the general public. These awareness-raising activities will be carried out at selected sites, using a serious game built by the association ‘La Vigie de l'Eau’ (Fig. 4). The results of the awareness-raising study will help to answer the following question: is a citizen who is aware of the 'One Health' concept more sensitive to the well-being provided by a good-quality environment and, conversely, does he think he can influence the health of the ecosystems he visits
Livelihood benefits from commercialisation of mopane worms (Imbrasia belina) in the Mopani District Municipality, Limpopo Province of South Africa
No full textMopane worms have traditionally been harvested for subsistence purposes, however, in recent times, there has been increased commercialisation of these worms. In Muyexe and Nsavulani villages (falling under Mopani District), local communities have been selling mopane worms for the past two decades. A survey was undertaken in these two villages in June and July 2023 to document the process involved in the commercialisation of mopane worms—from raw material harvesting to a commodity sold to generate cash income, and to assess the importance of the trade for livelihoods and poverty allevia-tion of households. Interview-administered questionnaires were used as the main data collection tool, and systematic random sampling was used to select 161 households in Muyexe village and 82 households in Nsavulani village. The questionnaire that included closed- and open-ended questions covered the socio-economic profile of respondents, mopane worms’ availability and procurement, processing of mopane worms, market-ing, trading of mopane worms and livelihood benefits from selling mopane worms. Closed-ended questions were analysed using the Statistical Package for Social Sciences, while open-ended questions were analysed using thematic content analysis. The study found that most of the harvesters in Muyexe (69% n = 111) and Nsavulani (59% n = 48) villages were females. Most harvesters in Muyexe (97%; n = 156) and Nsavulani villages (98%; n = 80) preferred degutting mopane worms at home, whereas only five and two respondents in Muyexe and Nsavulani villages, respectively, degut them in the harvesting fields. The researcher found that mopane worms are harvested for both household consumption and trade—this is in line with Sustainable Development Goal 1 (no poverty) and 2 (zero hunger). Most harvesters in Nsavulani village who trade mopane worms reported making between R2,100 (162.55), whereas most harvesters in Muyexe village make between R1,000 ($54.18) and R2,000 (108.37) per season. The study found that 55% of households in Muyexe village and 70% in Nsavulani village derive income only from mopane worm sales. Although the income earned from the sale of mopane worms is seasonal, it is highly appreciated by communities and plays a significant role in alleviating poverty and improving their lives and livelihoods
Four new tube-nosed bat species of the genus Murina (Chiroptera, Vespertilionidae) from Xizang Autonomous Region, China, based on morphological and molecular data
No full textThe genus Murina Gray, 1842, recently had four new species discovered in China over the last four years, suggesting its diversity may have been previously underestimated. Herein, we describe four new species—Murina beibengensis sp. nov., Murina medogensis sp. nov., Murina milinensis sp. nov., and Murina yadongensis sp. nov.—based on morphological and genetic evidence from specimens collected during bat diversity surveys conducted in the Xizang Autonomous Region of China over the past three years. Each of these four new species forms an independent lineage on a phylogenetic tree reconstructed using the mitochondrial COI and Cyt b genes, and each is genetically distinct from its congeners. Morphologically, the new species can be distinguished from the 43 recognized congeners by features including forearm length, hair color, and skull morphology. We elevated M. huttoni rubella from a subspecies of M. huttoni to a species based on morphological and genetic evidence. The new species discussed herein increase the number of species in the genus Murina to four worldwide and from 23 to 28 in China. This study not only enriches our understanding of bat species diversity but also underscores the importance of conducting bat surveys in the specialized highland habitats of the Himalayas
A new microendemic gecko from the small forest fragments of south-eastern Madagascar (Squamata, Gekkonidae, Paragehyra)
No full textHistorically, herpetological research in Madagascar has largely overlooked small forest fragments outside the country protected area network. Despite substantial declines in species diversity compared to large continuous forests, these fragments continue to sustain diverse herpetological communities and frequently harbour microendemic species. We describe a new gecko belonging to the genus Paragehyra, apparently microendemic to small and isolated forest fragments surrounding the Andringitra Massif in south-eastern Madagascar. Paragehyra tsaranoro sp. nov. is different from its congeneric species based on genetic distances in mitochondrial markers (16S and COI), phylogenetic position, and the lack of haplotype sharing at one nuclear locus (POMC). The new species is also distinguishable from its congeners based on a combination of 14 morphological characters. New genetic and morphological data are also provided for the sympatric P. felicitae and we propose a new assessment of its conservation status within the IUCN Red List. Paragehyra tsaranoro sp. nov. and P. felicitae are mostly found in forest fragments managed by local communities (community-managed reserves) outside legally protected areas. This study highlights the importance of community-based management for the conservation of local herpetofauna, particularly in regions heavily impacted by anthropogenic pressure and largely unsuitable for forest-dwelling species. The findings emphasise the importance of conducting research on small forest fragments, as they are essential for completing the inventory of Malagasy herpetofauna
