Restoration peatland and eLTER, case of France

International audienc

Restoration and meteorological variability highlight nestedwater supplies in middle altitude/latitude peatlands: Towards ahydrological conceptual model of the Frasne peatland, JuraMountains, France

Peatlands and associated ecosystem services are sensitive to climate changes and anthropogenic pressures such as drainage. This study illustrates these effects on the Forbonnet bog (7 ha), belonging to the Frasne peatland complex (~300 ha, French Jura Mountain) and shows how they can inform about the ecohydrological functioning of peatlands. The southern part of the Forbonnet bog was restored in 2015‐2016 by backfilling of artificial drains dating from the end of the 19th century. Piezometric data from 2014 to 2018 allow to evaluate the restoration effect on the Water Table Depth (WTD) and highlight the reactivation of lateral inflows from the surrounding raised peatland complex. Vertical EC profiles permit to identify 3 main peat compartments depending on different water supplies arguing for a nested hydrological functioning. This involves: (i) One‐off karst groundwater inputs at the substratum/peat interface supplying the deepest peat layer, (ii) lateral seepage inputs from the neighboring raised wooded peatlands sustaining the intermediate peat level, and (iii) direct rainfall infiltrating the most superficial peat layer. This nested multi‐reservoir model operates at various spatio‐temporal scales and is consistent with the complex seasonal hydrological and physico‐chemical response at the bog outlet, which will be increasingly affected by climate change in the coming decades

Ecological role of karstic groundwater in peatlands in the context of climate change. The case study of the Frasne peatland (Jura Mountains, France)

International audienceGroundwater (GW) inputs potentially modify the hydrological cycle of peatlands and associated downstream ecosystems in karstic regions. However, the interplay between ground and surface water is complex and depends on climatic conditions and land-use.Suspected in the Jura Mountains since decades, we present here a study on the ecological role of karst-peatland interactions realized in the Forbonnet bog (Frasne peatland complex, 46.826 N, 6.1754E, 852 m a.s.l). The bog has been restored in 2015-16 by backfilling of artificial drains.The site is located in a wide karstifed syncline covered by moraine deposits. We hypothesize the presence of complex interactions between peat, moraine and karst reservoirs dependent on hydraulic conditions and modified by climate change and mitigation programs. Five years of the peatland outlet monitoring highlights a multiscale range of water supply mechanisms. Mean summer Electrical Conductivities (EC, June-October) are positively correlated with total rainfall of the preceding winters (P, November-May), suggesting that karst GW inputs in winter mainly drive the summer baseflow. In spring and autumn, the non-linear relationships between P, T and discharge imply interactions between saturated and non-saturated peat layers. Finally, winter outflow is characterized by fast responses to P events, suggesting overflow of the saturated media. To better explain these interactions, both EC profiles variability and contrasted hydraulic head response to restoration allowed to identify various exchange processes. A range of advective-diffusive GW upflows from the karst could sustain the ecosystem functions.This multi-proxy approach argues in favor of a nested hydrological system involving various water origins: (i) regional karstic GW, (ii) lateral seepage from the neighboring elevated wooded peatlands and (iii) local rainfall. Ongoing work aims to quantify these water fluxes in more detail in order to improve peatland management

Réhabilitation de la rivière Drugeon et des zones humides limitrophes: impact sur les oiseaux nicheurs

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Restoration of the Drugeon River and adjacent wetlands (northeastern France): impact on breeding birds

International audienceThe channelizing of the minor bed of the Drugeon river and the drainage of adjacent marshes were carried out from 1961 to 1973 in the hope of gaining 2000 ha of farmland. Those works led to important damage to the wetlands of the Drugeon basin, a Ramsar site since 2003, under the protection of several national and European laws since 1992. Actually, two hundred hectares only were gained and the stream length was shortened by 30% (8km). This changed the river into a rectilinear channel with subsequent erosion increasing the river bottom depth from some tens of centimetres to two meters, decreasing the fish populations and leading to the extinction of the White-footed Crayfish (Austropotamobius pallipes). From 1993 to 1997 the combination of EU directives and national and regional protection laws led to achieve a LIFE programme aiming at restoring 30km of the Drugeon river. This included re-meandering the stream over 20km and filling the drains that have been dug in marshes in order to re-elevate the water table in adjacent areas. The first works begun in 1997 upstream and ended in 2001. Based on the IPA method (IBCC, 1977), the present study aims at comparing the nesting bird community between 1998-1999 (at the very beginning of the works) and 2006-2007 (5 years after the end of the works). A total of 104 nesting bird species were contacted at least once; 74 in 1998 on 15 IPAs, 80 in 1998, 94 in 2006 an 83 in 2007 on 20 IPAs. Total species richness per IPA was multiplied by 1.3 ten years after the beginning of the works and by 1.9 considering wetland species only (FIG. 2). Remarkably, bird abundance represented by the sum of the IPA scores also increased significantly (FIG. 3). Species number increase was observed all along the river but was neatly larger downstream (FIG. 4). Twelve species show a significant population increase (p < 0.05) or possibly an increase (0.05 < p < 0.1). The Willow Warbler, the MarshWarbler, the Coot, the Reed Bunting, the Mallard, the Northern Lapwing and the Little Grebe increased; the Meadow Pipit increased only in the Coot area (p < 0,05). The Common Pochard, the Tufted Duck and the Grey Wagtail possibly increased (0.05 < p < 0,1). Only theWhinchat showed a trend to decrease (0.05 < p < 0.1). Those results are discussed and compared with other bird censuses achieved along the first 80 kilometres of 5 French rivers (Seine, Saône, Loire, Allier, Loue). A remarkably high diversity of bird species was observed along the Drugeon river. The rehabilitation of the river led to improve the ecological conditions and the population of wetland species. Some of those species showed an increase in the area rehabilitated although they are known to markedly decline at European, French, Swiss and regional scales

Characterization of nested water supplies in a mid latitude/altitude peatland using long-term monitoring data before and after restoration. The case study of the Frasne peatland (Jura Mountains, France)

International audiencePeatland 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 suggest 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

Statistical hydrology for evaluating peatland water table sensitivity to simple environmental variables and climate changes application to the mid-latitude/altitude Frasne peatland (Jura Mountains, France)

International audiencePeatlands 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

Grève et droit public

Cessation collective et concertée du travail, la grève tient son nom d'une place, située devant l'Hôtel de Ville de Paris, où les hommes sans emploi attendaient l'accostage des bateaux pour les décharger. Mais il a fallu attendre que l'alinéa 7 du préambule de la Constitution du 27 octobre 1946 reconnaisse le droit de grève pour que celui-ci devienne un droit fondamental constitutionnellement garanti. 70 ans plus tard, ce droit est-il dépassé, voire menacé ? L'action collective, les droits syndicaux et le droit de grève peuvent-ils réfutés au nom de l'intérêt général et de la continuité des services publics ? Quelle place faut-il accorder au dialogue social ? Et quid des mouvements sociaux qui marquent régulièrement notre vie sociale ? Les dernières dispositions législatives relatives au droit de grève constituent-elles une atteinte à un droit fondamental ou un simple aménagement de la grève et de ses conséquences ? Des juristes principalement, mais aussi des historiens, des politistes et des sociologues proposent ainsi d'analyser les fondements de ce droit, de débattre de la grève et de ses modalités, d'en apprécier la portée mais aussi les limites. Cet ouvrage permet aussi de restituer les échanges qui se sont tenus lors du colloque coorganisé à Toulouse les 9 et 10 juin 2016 par l'IMH de l'Université Toulouse Capitole et le CRJ de l'Université Grenoble Alpes