The use of accumulator species with high biomass production in phytoextraction scenarios is frequently studied, particularly in combination with treatments that increase the bioavailability of trace elements (TE) such as Cd(II) and Zn(II). In this context, this study aimed to test the potential of Alliaria petiolata and Salix aquatica grandis for phytoextraction through their tolerance and accumulation capacities in hydroponic conditions under increasing concentrations of Cd(II) or Zn(II).Both species showed high tolerance to these elements, in particular, A. petiolata showed few symptoms of phytotoxicity when grown under Cd(II) exposure. In addition, high maximum concentrations were observed in the leaves of A. petiolata (Cd(II): 332.1 mg kg-1 DW; Zn(II): 1614.8 mg kg-1 DW) and for S. aquatica grandis (Cd(II): 129.3 mg kg-1 DW; Zn(II): 2227.2 mg kg-1 DW). Our finding demonstrate that the extraction of Cd(II) and Zn(II) also increased with their concentrations in nutrient solution but is ultimately constrained by species-specific toxicity thresholds, highlighting an optimal range for assisted phytoextraction. The present study highlighted the potential and limitation of both A. petiolata and S. aquatica grandis for Cd(II) and Zn(II) extraction purpose when exposed to high concentrations. Field trials with these species are the next step in confirming their potential in a complex environment with environmental issues to consider.

The joint presence of various contaminant categories in soil reduces the remediation potential of numerous plant species. However, the mechanisms remain poorly understood, and particularly for tree species. To achieve this goal, we performed a co-contamination experiment with Salix aquatica grandis cuttings cultivated for two months under controlled conditions in two soils with two levels (low and high) of trace element (TE) contamination, spiked or not spiked with 600 mg·kg⁻¹ polycyclic aromatic hydrocarbons (PAHs). Our results revealed a significant negative impact of PAH spiking on the mobility of Zn, Cd, and Ni, with average reductions of approximately 35 %. These changes in mobility were associated with lower concentrations in Pb and Cd in plant shoots and a decrease in the total amount of Zn extracted by the plants. These findings emphasize the influence of co-contamination on the phytoremediation potential of high-biomass species. The physiological responses of plants were also affected. Malondialdehyde (MDA) concentrations in leaves increased in response to PAH contamination, indicating oxidative stress, whereas the total antioxidant content varied in relation to TE concentrations in the soil. Furthermore, analysis of the root exudates revealed that peroxidase activity-specifically when the diamonifluorene substrate was used-responded positively to the presence of PAHs, suggesting the activation of enzymatic pathways. Overall, the combination of PAHs and TEs induced diverse and complex effects on both contaminant dynamics and plant physiological health. These results highlight the need to consider co-contamination scenarios in the evaluation and design of phytoremediation strategies particularly for long time protocols.

Peatlands, though covering only 3 % of the global land surface, play an active role in the Critical Zone (CZ) by mediating substantial water and carbon exchanges with adjacent aquifers, surface waters, and the atmosphere. These ecosystems provide key services, such as carbon and water storage and local climate regulation, addressing contemporary challenges related to climate change, biodiversity loss, and water resource management. However, peatlands are increasingly threatened by global pressures, including climate change, and local disturbances, such as drainage for agriculture, forestry, and peat extraction. To mitigate these threats, it is essential to understand the hydrological, biogeochemical, and ecological processes governing peatland dynamics across spatiotemporal scales. To explore the factors controlling greenhouse gases sources, production, and transport in peatlands, an interdisciplinary field campaign was conducted at the Frasne peatland (7 ha, 46.826°N, 6.1754°E, 840 m a.s.l.), a long-term observatory since 2008. The site is part of the French CZ research infrastructure (OZCAR) and the long term ecological research site Jurassian Arc, which focuses on the interaction between human and nature. The campaign was supported by the TERRA FORMA project, which develops smart, connected, low-cost, and low-impact environmental sensors to monitor CZ trajectories in the Anthropocene. The fieldwork integrated microbiological analyses of peat material, including membrane lipid profiling to trace microbial metabolisms, combined with detailed hydrogeochemical investigations of peat pore water along lateral flow and depth gradients. Measurements included physicochemical parameters (temperature, electrical conductivity, pH) and major elements, dissolved organic and inorganic carbon (DOC and DIC), CO₂, and CH₄ concentration, as well as their isotopic characterization (δ¹⁸O, δ²H, δ¹³C) . Additionally, greenhouse gases fluxes were quantified at multiple scales, employing methods such as dissolved gas profiling, chamber measurements, eddy covariance, and UAV-based surveys. This multiscale approach aims to tackle critical challenges in peatland research and management, including three-dimensional quantification of carbon fluxes (lateral and vertical) at the ecosystem scale; characterization of hydrological, biogeochemical, and ecological processes that modulate greenhouse gases and dissolved carbon production and transport; and development of accessible and efficient tools for addressing these pressing environmental issues. three-dimensional quantification of carbon fluxes (lateral and vertical) at the ecosystem scale; characterization of hydrological, biogeochemical, and ecological processes that modulate greenhouse gases and dissolved carbon production and transport; and development of accessible and efficient tools for addressing these pressing environmental issues.

The aim of the present study is to understand the variability and the environmental factors controlling the fluxes of carbonaceous greenhouse gases (GHGs), methane (CH~4~) and carbon dioxide (CO~2~) between a temperate _Sphagnum_-dominated mid-altitude mountain peatland and the atmosphere. We conducted monthly measurements of GHG fluxes over 20 months using the chamber method. Specifically, we assessed the effects of (1) air temperature and (2) water level (WL) on GHG emissions. Open Top Chambers (OTC) were used to simulate a warming effect by passive heating of the air above the soil. To assess the effect of WL, we studied a hydrological gradient along a 35 m long transect from a near-surface “WET” area, through an “INTER” area with an intermediate WL, to a “DRY” area with a lower WL. The WET area featured a higher cover of _Sphagnum_ species while the vegetation cover in the DRY area contained more vascular plants. Although all plots showed the same seasonality of GHG fluxes, considerable variability was observed among them. Raising the temperature using OTCs, which increased annual average air temperature by 0.2 °C to 0.6 °C, did not significantly affect CH~4~ and CO~2~ respiration (Reco) fluxes. In contrast, hydrological conditions played an important role in explaining flux variability. CH~4~ fluxes were significantly higher in the WET and INTER areas (median [95 % CI] values: 17.5 [14.2, 29.0] and 20.0 [14.8, 30.4] nmol m^-2^ s^-1^) compared to the DRY area (3.4 [1.9, 9.4] nmol m^-2^ s^-1^) during all hydrological periods, i.e., humid spring, humid summer and dry summer. Reco did not vary significantly along the hydrological gradient overall, but the fluxes were lower in the WET area under humid spring (0.4 [0.3, 0.6] µmol m^-2^ s^-1^) and summer (1.7 [1.25, 2.75] µmol m^-2^ s^-1^) conditions compared to the DRY area (1.6 [1.3, 2.0] µmol m^-2^ s^-1^ in spring and 3.8 [2.7, 4.6] µmol m^-2^ s^-1^ in summer). Conversely, greater fluxes (by ~ 0.5 µmol m^-2^ s^-1^) were observed in the WET area during summer drought. Given that Reco emissions are expected to be higher during droughts in the DRY area, we hypothesise a possible threshold effect, such as inhibition of phenoloxidase activity and/or other enzymatic activities, which would limit organic matter decomposition. Moreover, increasing WL in the WET and INTER areas led to a drastic drop in gross primary production (GPP) corresponding to _Sphagnum_ immersion.

The management of polluted soils requires a comprehensive risk assessment, based on a combined human health and ecological risk, in accordance with the One Health concept. To this end, a risk assessment was carried out on a former industrial site, based on its potential future use as a recreational park. The site was divided into 20 zones, and trace element (TE) total and bioaccessible concentrations were measured. From those data, hazardous index (HI) and carcinogenic index (CI) were calculated. The accumulation of TEs into snail guts was also measured using a standard test. The HIs and CI values (based on bioaccessibility) for adults showed two zones with an unacceptable risk, due to high Pb concentrations, with HI of 1.77 and 19.24 and CI of 12.3e-6 and 87.1e-6. For children, almost half of the site presented unacceptable risks, due to high Pb, Zn, Ni and Cr contents. The HI ranged from 1.42 to 164, while the CI was above threshold only in one zone (63.4e-6). In terms of ecological risk, the snail test revealed nine areas with no risk and 11 with uncertain risk. From this analysis, we could conclude on the future site management: (i) access to the area presenting an unacceptable risk to adults and children should be prohibited; (ii) for areas presenting risk to children but not to adults, access should be restricted to adults, by converting the areas into research areas; and (iii) areas presenting no risk to adults and children can be transformed into recreational areas.

To improve trace element (TE) phytoextraction techniques, the use of soil amendments and the co-cropping of accumulator species have been often studied. This study aimed to evaluate the possibility of combining the application of elemental sulfur (S8) with the co-cropping of two TE accumulating species, Alliaria petiolata and Salix aquatica grandis. A pot experiment was conducted with two soils, lightly (LC) and heavily contaminated (HC) by TE, originated from an industrial wasteland. The application of S8 significantly reduced pH by 1.17 and 1.23 unit after 64 days in LC and HC soils, respectively, and increased Cd, Cr, Mn, Ni, Pb and Zn contents in soil extractable fraction and plants. An increase in the TE-extraction potential was observed and was greater in LC soil, as the S8 application led to a reduction of biomass produced by both plants in HC soil. However, co-cropping treatment on HC soil maximized the extraction of TE, especially for Cr and Ni when S8 treatment was applied, since the plants showed no competition but rather differences in the elements accumulated. Consequently, the combination of S8 and the co-cropping of A. petiolata and S. aquatica grandis was shown to be relevant for the phytoextraction of TE in HC soils.

This study aimed to determine the trace element accumulation in the soil and plants in an industrial wasteland and to estimate the extent of transfer to humans to measure the effects on and risks to vegetation and human health and find bioindicator plants representative of the levels of the main contaminants. In areas with the highest extractable trace element levels, we observed decreases in plant biodiversity explained by the disappearance of several families, favouring the coverage of tolerant species, such as Urtica dioica and Hedera helix. Trace elements were also found in the leaves of several plants, especially in a dominant species that is poorly studied, Alliaria petiolata. Indeed, this species had the highest contents of Zn (1750 mg.kg-1 DW), Ni (13.1 mg.kg-1 DW), and Cd (18 mg.kg-1 DW) found at the site and is a potential Zn bioindicator since its leaf contents were also representative of the Zn extractable contents in soil (R2 = 0.94). The hazard quotient and carcinogen risk revealed that most of the site had an identified or possible risk, mainly due to Pb and As. Native species, especially A. petiolata, could be used in phytoextraction to manage and limit these human and environmental risks.

Soil microbial communities are vital for multiple ecosystem processes and services. In particular, soil microbial food webs are key determinants of soil biodiversity, functioning and stability. Unclear, however, is how struc-tural features of food webs, such as species richness and turnover, biomass and energy transfer across trophic levels, influence the provisioning and stability of ecosystem functioning. Here, we explore the relationships between different facets of microbial food web structure (e.g. species richness, connectance, biomass and energy fluxes across trophic levels) and ecosystem functions (i.e. decomposition and microbial enzyme activity) across different habitats and depths in a peatland. We show that no aspect of taxonomic richness directly explained variation in ecosystem functions. Instead, we find that trophic interactions between basal species and primary consumers, and especially increasing connectance, biomass and energy flux transiting from decomposers and phototrophs to algivores, bacterivores and fungivores, enhance ecosystem functions in the peatland. These findings demonstrate that focusing on taxonomic diversity without explicit inclusion of food web structure and energy flows therein gives an incomplete and uninformative comprehension of relationships between biodi-versity and ecosystem functioning, at least in peatlands. Our findings further suggest that the inclusion of soil microbial food webs in large-scale biogeochemical models is of fundamental importance to provide the necessary guidance for managing and mitigating the effects of environmental change.

Continental hydrosystems and in particular peatlands play an important role in the carbon cycle of the Critical Zone (CZ). Peatlands are important sinks for organic carbon and have therefore been extensively studied. However, peatlands are not only important for the fate of organic carbon, but they also affect the cycle of Dissolved Inorganic Carbon (DIC) of the peatland and the surrounding watershed. The fate of DIC is particularly complex in peatlands in limestone-dominated regions, because bicarbonate concentrations in surface and groundwater are high and the interaction between peatlands and surrounding hydrosystems are facilitated by the presence of highly permeable karst aquifers. In the present paper we study the origin and the fractionation of DIC in a peatland located on top of a karst aquifer. The study is based on hydrochemical and isotopic (delta C-13(DIC)) data from samples recovered during 2 campaigns (low flow, high flow) at various depths within the Forbonnet peatland (Jura Mountains, eastern France), at the peatland outlet and at adjacent karst springs representing the underlying aquifer. In order to evaluate secondary fractionation processes, the measured delta C-13(DIC) compositions were compared to modeled values considering the origin of DIC and potentially associated fractionation and speciation processes. The main results are: (1) DIC is lost at the bog surface by CO2 outgassing. (2) The delta(13)C(DIC )compositions of deep catotelm pore waters from the bog were much heavier than the modeled values. We relate this discrepancy to methanogenesis and show that this process is favored by reduced conditions at pH similar to 6 and a HCO3- content of similar to 1 mmol/L, most probably due to punctual groundwater inflows at the base of the bog. Finally, contrasted delta C-13(DIC) compositions between the bog and the fen of the peatland reveal an additional ecohydrological control on DIC speciation.

Peatlands cover only 3 % of emerged lands, but their carbon stock represents about 30 % of the global soil organic carbon. Climate change and local anthropogenic disturbances deeply affect the hydrological functioning of peatlands. This may trigger carbon fluxes to surface waters and the atmosphere, thus leading to a positive feedback for global warming. It is therefore crucial to better estimate carbon fluxes between peatlands and the atmosphere and to delineate their major controlling constraints. To achieve this goal, we studied the functioning of a temperate mid-mountain peatland located in the French Jura Mountains, named the Frasne peatland.The methane (CH4) dynamics of the Frasne peatland appear to be constrained by a range of hydrological, physical, biogeochemical, and biotic factors. From a hydrological point of view, the system is fed by local rainwater and injection of carbonated groundwater at the bottom of the peatland, which provides a major input of dissolved inorganic carbon (DIC) to the system. Values of the δ13CDIC were high (even reaching positive values up to 8.1 ‰) compared to the expected values in a limestone and C3 plant-dominated area such as the Jura Mountains, supporting biotic CH4 production within the peatland. Consistently, high-frequency eddy-covariance monitoring during 2.5 years allowed us to show that the site acted as a source of CH4 to the atmosphere (23.9 ± 0.6 g C m-2 year-1) with interannual, seasonal, and diurnal time scale dynamics. In particular, we found an outstanding diurnal cycle for CH4 with the highest fluxes at night and lower ones at mid-day. In addition, the mid-day fluxes were negative in spring, highlighting larger oxidative processes than CH4 production attributed to photosynthesis activity (i.e., soil oxygen penetration and endosymbiotic methanotrophs of Sphagnum). The range of CH4 emissions was also controlled by the interannual variation in precipitation amounts and by the seasonal temperature variation.This conceptual production-emission model highlights that water-carbon interactions in the peatland depend on local biotic and abiotic factors but also on hydrological processes at the watershed scale. This also highlights the need to further constrain carbon transfers between the production and the emission zones (i.e., peatland-atmosphere interface and surface water exports). For this purpose, we will soon carry out a field campaign to measure the concentrations and isotopic values of dissolved gases in peat pore water along with an upstream downstream and a vertical gradient.

AimsAfforestation of trace-element contaminated soils, notably with fast growing trees, has been demonstrated to be an attractive option for bioremediation due to the lower costs and dispersion of contaminants than conventional cleanup methods. Mycorrhizal fungi form symbiotic associations with plants, contributing to their tolerance towards toxic elements and actively participating to the biorestoration processes. The aim of this study was to deepen our understanding on the effects of mycorrhizal inoculation on plant development and fungal community at two trace-element contaminated sites (Pierrelaye and Fresnes-sur-Escaut, France) planted with poplar (Populus trichocarpa x Populus maximowiczii).MethodsThe 2 sites were divided into 4 replicated field blocks with a final plant density of 2200 tree h-1. Half of the trees were inoculated with a commercial inoculum made of a mix of mycorrhizal species. The sites presented different physico-chemical characteristics (e.g., texture: sandy soil versus silty-loam soil and organic matter: 5.7% versus 3.4% for Pierrelaye and Fresnes-sur-Escaut, respectively) and various trace element contamination levels.ResultsAfter 7 years of plantation, inoculation showed a significant positive effect on poplar biomass production at the two sites. Fungal composition study demonstrated a predominance of the phylum Ascomycota at both sites, with a dominance of Geopora Arenicola and Mortierella elongata, and a higher proportion of ectomycorrhizal and endophytic fungi (with the highest values observed in Fresnes-sur-Escaut: 45% and 28% for ECM and endophytic fungi, respectively), well known for their capacity to have positive effects on plant development in stressful conditions. Furthermore, Pierrelaye site showed higher frequency (%) of mycorrhizal tips for ectomycorrhizal fungi (ECM) and higher intensity (%) of mycorrhizal root cortex colonization for arbuscular mycorrhizal fungi (AMF) than Fresnes-sur-Escaut site, which translates in a higher level of diversity.ConclusionsFinally, this study demonstrated that this biofertilization approach could be recommended as an appropriate phytomanagement strategy, due to its capacity to significantly improve poplar productivity without any perturbations in soil mycobiomes.

To understand the variability of methane (CH 4 ) fluxes between a temperate mid-altitude Sphagnum- dominated peatland and the atmosphere, we monitored simultaneously eddy covariance, hydrometeorological and physical parameters between April 2019 and December 2021. The site was a CH 4 source for the atmosphere, with a cumulative emission of 23.9 ± 0.6 g C m −2 year −1 . At the interannual scale, deeper water table during vegetation growth periods resulted in lower CH 4 fluxes (FCH4), and reciprocally. Furthermore, the seasonal temperature variation in the anaerobic peat layer was a good predictor for FCH4. However, while the lowest temperatures occurred between December and February, the lowest FCH4 were observed between March and May, with around 30% of negative FCH4. Indeed, the fastest increase in temperature of the aerobic layer likely stimulated methanotrophy at the expense of methanogenesis. Negative FCH4, systematically observed at midday, were concurrent with high photon flux densities, latent heat fluxes and net negative ecosystem CO 2 exchanges, suggesting the control of photosynthesis over CH 4 oxidation. Moreover, our results highlighted marked diurnal cycles with FCH4 maximal at night and minimal at midday for all seasons. This diurnal cyclicity is in opposition to what is typically known for peatlands dominated by vascular plants. Physical parameters, such as soil surface temperature and sensible heat fluxes, likely contribute to this diurnal FCH4 cyclicity and require further investigation. Our study thus demonstrates that diurnal variations in FCH4 must be considered before upscaling to seasonal or annual cycles, along with the effect of vegetation on CH 4 transfer and oxidation processes.

Sphagnum mosses are considered peatland engineers because of their ability to create conditions inducing carbon accumulation. Here, we report on a review of the effects of four environmental variables (elevated temperature, N and CO2 and reduced moisture) on the capitulum biomass, length increment, respiration, photosynthetic capability, N and P exchange and content of the 3 most studied Sphagnum subgenera (Acutifolia, Cuspidata, Sphagnum). Overall, we observe that, when compared to in situ experiments, laboratory experiments tend to exacerbate length increments and underestimate maximum photosynthesis in most of the studies inventoried. This review underscores some differences among results that can be associated with the used of different protocols (e.g. exposure time, instrumental analysis). Studies that investigated the impact of elevated temperature (2–5 °C) on Sphagnum reveal an increase in length, respiration and photosynthesis regardless of the experimental conditions and subgenus. Elevated N (3–23 g Nm−2y−1) on the other hand appears to reduce the length increment but had contrasting effects on photosynthesis. Some divergent responses are found with Cuspidata species because of their tolerance to high doses of N. Low moisture reduces the length increment and photosynthesis of species of the Cuspidata and Sphagnum subgenera but has different effects on species of the Acutifolia subgenus, which are relatively tolerant to water fluctuations. Responses to elevated CO2 have no clear trends reported. Allelochemical interactions between Sphagnum, their microbiome or surrounding mosses or other plants were found to be determinant to Sphagnum responses under those variables and reinforce the interest of such investigations.

Mitigating and adapting to global changes requires a better understanding of the response of the Biosphere to these environmental variations. Human disturbances and their effects act in the long term (decades to centuries) and consequently, a similar time frame is needed to fully understand the hydrological and biogeochemical functioning of a natural system. To this end, the ‘Centre National de la Recherche Scientifique’ (CNRS) promotes and certifies long‐term monitoring tools called national observation services or ‘Service National d'Observation’ (SNO) in a large range of hydrological and biogeochemical systems (e.g., cryosphere, catchments, aquifers). The SNO investigating peatlands, the SNO ‘Tourbières’, was certified in 2011 (https://www.sno-tourbieres.cnrs.fr/). Peatlands are mostly found in the high latitudes of the northern hemisphere and French peatlands are located in the southern part of this area. Thus, they are located in environmental conditions that will occur in northern peatlands in coming decades or centuries and can be considered as sentinels. The SNO Tourbières is composed of four peatlands: La Guette (lowland central France), Landemarais (lowland oceanic western France), Frasne (upland continental eastern France) and Bernadouze (upland southern France). Thirty target variables are monitored to study the hydrological and biogeochemical functioning of the sites. They are grouped into four datasets: hydrology, fluvial export of organic matter, greenhouse gas fluxes and meteorology/soil physics. The data from all sites follow a common processing chain from the sensors to the public repository. The raw data are stored on an FTP server. After operator or automatic processing, data are stored in a database, from which a web application extracts the data to make them available (https://data-snot.cnrs.fr/data-access/). Each year at least, an archive of each dataset is stored in Zenodo, with a digital object identifier (DOI) attribution (https://zenodo.org/communities/sno_tourbieres_data/).

Peatland hydrology forms, together with vegetation cover and carbon dynamics, a sensitive interconnected three-pillar system, which furnishes essential ecosystem services from the local (specific biodiversity, interaction with the watershed) to the global scale (carbon and fresh water storage). The present study focuses on the hydrological function of the Frasne peatland, and especially investigates how restoration of water supplies can be used to mitigate climate change effects on peatland hydrology and sustainability. In this perspective, the Forbonnet bog, belonging to the Frasne peatland complex (300 ha; French Jura Mountains; 46.826 N, 6.1754 E; 850 m a.s.l) is monitored in the framework of the French observatory of peatland (SNO Tourbières) since 2008. The site, restored in 2015 (European program "Life Tourbières"), is located in a wide karstifed syncline overlain by moraine deposits. Between 2009 and 2019, mean annual precipitation and air temperature were respectively 1618 mm and 7 °C. In order to identify and model water supply and transfers at the ecosystem scale, this study combines a range of hydrological, geochemical and reservoir modeling approaches. This enabled us to propose a conceptual scheme of the hydrological functioning that implies a nested organization of 3 water origins: (1) The superficial reservoir (acrotelm) featuring a low mineralization, has a fast (daily) reactivity to precipitation, suggesting a strong dependence to direct atmospheric inputs. In addition, the outlet discharge shows a complex relation with the water level of this layer, highlighting a threshold effect where the saturation degree of the acrotelm seems to be involved. (2) Five years of outlet discharge and electrical conductivity (EC) monitoring highlight a seasonal pattern. During low flow periods (June-Oct.) EC is positively correlated with rainfall recharge of the previous winter (Nov.-May). Furthermore, the bog water budget is loss-making when only considering the topographical watershed. Considering the geological context, these elements argue for groundwater inflows from the surrounding karst aquifer likely occurring at the base of the bog, throughout the permeable or discontinuous moraine layers. Vertical EC profiles show that these inflows supply the mineralized water deep reservoir of the bog. (3) The monitoring of the restoration effects (by backfilling of drainage channels) through panpipe piezometers suggests that lateral seepage from the neighboring wooded, more elevated and mature peatlands supplies a transitional peat reservoir. Moreover, spatial (horizontal and vertical) and temporal EC variability argue for advective water transfers through the bog. This work supports the interest in monitoring over the long-term (several and contrasted hydrological years) for constraining hydrological processes. The three water supplies delineated could have contrasted responses to climate change and then impact both biological and carbon cycles. This work also highlights the importance to integrate hydrological processes beyond the ecosystem scale, to consider climate change and anthropogenic pressure effects on the regional hydrology that probably interact with peatlands in mountainous environments. In this perspective, the current hydrological monitoring is nowadays combined with isotopic (δ18O and δ2H) evaluation to refine this conceptual scheme and quantify the contribution of the 3 identified water flow paths.

Although peatlands occupy only 3 % of the global continental surface, they constitute a Critical Zone’s outstanding compartment. They provide socio-ecosystemic services such as water and hydrochemical regulation, carbon storage and biodiversity conservation. These latter depend directly on the complex interaction between chemical-water fluxes, vegetation cover, and carbon exchange dynamics. Fluvial carbon exports are critical for establishing peatland carbon budgets. In order to evaluate the origin (organic matter mineralization and/or weathering) of inorganic carbon exported from peatlands, we studied the Frasne peatland (French Jura Mountains; 46.826 N, 6.1754 E; 850 m a.s.l), located in a karstified syncline overlain by fluvio-glacial deposits. Rainwater, porewater and outflow waters are sampled monthly since October 2019 and analyzed for physico-chemical parameters (T, Eh, pH, electrical conductivity), major elements, DOC, DIC and isotopic signatures ( δ 18 O H2O , δ 2 H H2O , δ 13 C DIC ). Preliminary results show that outflow water presents signature close to recent local rainfall ( δ 18 O = -7.6 ‰ VSMOW; δ 2 H = -50 ‰ VSMOW) suggesting a direct link between local inputs and outflow during high Water Level Period (WLP). In contrast, pore

Peatlands are habitats for a range of fragile flora and fauna species. Their eco-physicochemical characteristics make them as outstanding global carbon and water storage systems. These ecosystems occupy 3% of the worldwide emerged land surface but represent 30% of the global organic soil carbon and 10% of the global fresh water volumes. In such systems, carbon speciation depends to a large extent on specific redox conditions which are mainly governed by the depth of the water table. Hence, understanding their hydrological variability, that conditions both their ecological and biogeochemical functions, is crucial for their management, especially when anticipating their future evolution under climate change. This study illustrates how long-term monitoring of basic hydro-meteorological parameters combined with statistical modeling can be used as a tool to evaluate i) the horizontal (type of peat), ii) vertical (acrotelm/catotelm continuum) and iii) future hydrological variability. Using cross-correlations between meteorological data (precipitation, potential evapotranspiration) and water table depth (WTD), we primarily highlight the spatial heterogeneity of hydrological reactivity across the Sphagnum-dominated Frasne peatland (French Jura Mountain). Then, a multiple linear regression model allows performing hydrological projections until 2100, according to regionalized IPCC RCP4.5 and 8.5 scenarios. Although WTD remains stable during the first half of 21th century, seasonal trends beyond 2050 show lower WTD in winter and markedly greater WTD in summer. In particular, after 2050, more frequent droughts in summer and autumn should occur, increasing WTD. These projections are completed with risk evaluations for peatland droughts until 2100 that appear to be increasing especially for transition seasons, i.e. May-June and September-October. Comparing these trends with previous evaluations of phenol concentrations in water throughout the vegetative period, considered as a proxy of plant functioning intensity, highlights that these hydrological modifications during transitional seasons could be a great ecological perturbation, especially by affecting Sphagnum metabolism.

Metal trace elements accumulate in soils mainly because of anthropic activities, leading living organisms to develop strategies to handle metal toxicity. Plants often associate with root endophytic fungi, including nonmycorrhizal fungi, and some of these organisms are associated with metal tolerance. The lack of synthetic analyses of plant-endophyte-metal tripartite systems and the scant consideration for taxonomy led to this review aiming (1) to inventory non-mycorrhizal root fungal endophytes described with respect to their taxonomic diversity and (2) to determine the mutualistic roles of these plant-fungus associations under metal stress. More than 1500 species in 100 orders (mainly Hypocreales and Pleosporales) were reported from a wide variety of environments and hosts. Most reported endophytes had a positive effect on their host under metal stress, but with various effects on metal uptake or translocation and no clear taxonomic consistency. Future research considering the functional patterns and dynamics of these associations is thus encouraged. ? 2020 British Mycological Society. Published by Elsevier Ltd. All rights reserved.