The role of plants on methane flux out of upland soils

Soils play an important role in cycling of methane (CH4), a greenhouse gas contributing roughly 20% to the observed climate warming. While knowledge about the influence of plants on methane cycling is growing for wetland ecosystems, we are still limited in our understanding for upland soils. Thus, the objectives of this study were to investigate the influence of plants on net CH4 fluxes from forest and grassland soils depending on bedrock, temperature, and plant species, and to determine if changes in CH4 fluxes are reflected on microbial level. The present study used soils from forest and grassland sites located in Tyrol, Austria. Soil sites were chosen to represent soils from limestone and siliceous bedrock. To study grassland soils, two site-specific plants, Plantago lanceolata and Poa pratensis, were grown from seeds in pots. In case of forest soils, two site-specific trees, Picea abies and Larix decidua, were chosen and grown from seedlings. Besides profound soil microbiological analyses, lab-scale gas measurements were conducted at different temperatures. To characterize the microbial community structure of bulk and rhizosphere soil, NGS (next-generation sequencing) was performed. Further microbiological and molecular analyses aimed to determine if changes in CH4 fluxes are reflected in the activity and abundance of microorganisms in rhizosphere soil compared with bulk soil. Results showed that forest and grassland soils had a high potential to consume methane under ambient conditions, thus serving as methane sinks. Distinct differences depending on bedrock, plant species, and temperature were established. The studied site-specific grassland plants P. lanceolata and P. pratensis significantly increased methane balances to a varying extent depending on temperature. In contrast, the studied forest plants P. abies and especially L. decidua significantly boosted methane consumption. Further studies have focused on the influence of photosynthetic rates of plants on CH4 fluxes out of soils and the indirect influence of plants on soil microorganisms engaged in the methane cycle

When workplace unionism in global value chains does not function well : exploring the impediments

Improving working conditions at the bottom of global value chains has become a central issue in our global economy. In this battle, trade unionism has been presented as a way for workers to make their voices heard. Therefore, it is strongly promoted by most social standards. However, establishing a well-functioning trade union is not as obvious as it may seem. Using a comparative case study approach, we examine impediments to farm-level unionism in the cut flower industry in Ethiopia. For this purpose, we propose an integrated framework combining two lenses, namely a vertical one (governance and structure of global value chains) and a horizontal one (socio-economic context). We identify 10 impediments that point to three major dimensions contributing to unionisation. These three dimensions include awareness of and interest from workers, legitimacy of trade unions, and capacity of trade unions to act. Furthermore, our results suggest that private social standards may, in certain cases, be counterproductive for the efficient functioning of trade unions. Although we argue that there is no ‘quick fix’ solution to weak workplace unionism at the bottom of global value chains, we stress the importance of considering the dynamics of, and interactions between, the impediments when designing potential support measures that mitigate negative impacts

Emerging IT risks: insights from German banking

How do German banks manage the emerging risks stemming from IT innovations such as cyber risk? With a focus on process, roles and responsibilities, field data from ten banks participating in the 2014 ECB stress test were collected by interviewing IT managers, risk managers and external experts. Current procedures for handling emerging risks in German banks were identified from the interviews and analysed, guided by the extant literature. A clear gap was found between enterprise risk management (ERM) as a general approach to risks threatening firms’ objectives and ERM’s neglect of emerging risks, such as those associated with IT innovations. The findings suggest that ERM should be extended towards the collection and sharing of knowledge to allow for an initial understanding and description of emerging risks, as opposed to the traditional ERM approach involving estimates of impact and probability. For example, as cyber risks emerge from an IT innovation, the focus may need to switch towards reducing uncertainty through knowledge acquisition. Since individual managers seldom possess all relevant knowledge of an IT innovation, various stakeholders may need to be involved to exploit their expertise

Louise Müller e o Jogo da Filosofia Africana: Lopes, Marcos Carvalho. Louise Müller e.o. Jogo Da Filosofia Africana." In Tcholonadur: Entrevistas Sobre Filosofia Africana, edited by Marcos Carvalho Lopes, 183-95. São Carlos: Pedro & João Editores, 2023.

Louise Müller e o jogo da filosofia africana*“O conhecimento é como um baobá, nenhuma pessoa sozinha pode abraçá-lo”. Esse é um provérbio Akan que pode ser combinado com outro que diz “Que nenhuma cidade (polis) possui sozinha a verdade”. Nenhuma cidade poderia almejar a posse integral da verdade. É nesse sentido que a filósofa holandesaLouise Müller, especialista na cultura akan, tem se dedicado à filosofia africana, desenvolvendo diálogos interculturais, assim como, buscando se aprofundar nos conhecimentos de línguas e culturas africanas.Modern and Contemporary Studie

Growth and retreat of the last British–Irish Ice Sheet, 31 000 to 15 000 years ago: the BRITICE-CHRONO reconstruction

The BRITICE-CHRONO consortium of researchers undertook a dating programme to constrain the timing of advance, maximum extent and retreat of the British?Irish Ice Sheet between 31?000 and 15?000?years before present. The dating campaign across Ireland and Britain and their continental shelves, and across the North Sea included 1500?days of field investigation yielding 18?000?km of marine geophysical data, 377 cores of sea floor sediments, and geomorphological and stratigraphical information at 121 sites on land; generating 690 new geochronometric ages. These findings are reported in 28 publications including synthesis into eight transect reconstructions. Here we build ice sheet-wide reconstructions consistent with these findings and using retreat patterns and dates for the inter-transect areas. Two reconstructions are presented, a wholly empirical version and a version that combines modelling with the new empirical evidence. Palaeoglaciological maps of ice extent, thickness, velocity, and flow geometry at thousand-year timesteps are presented. The maximum ice volume of 1.8?m sea level equivalent occurred at 23?ka. A larger extent than previously defined is found and widespread advance of ice to the continental shelf break is confirmed during the last glacial. Asynchrony occurred in the timing of maximum extent and onset of retreat, ranging from 30 to 22?ka. The tipping point of deglaciation at 22?ka was triggered by ice stream retreat and saddle collapses. Analysis of retreat rates leads us to accept our hypothesis that the marine-influenced sectors collapsed rapidly. First order controls on ice-sheet demise were glacio-isostatic loading triggering retreat of marine sectors, aided by glaciological instabilities and then climate warming finished off the smaller, terrestrial ice sheet. Overprinted on this signal were second order controls arising from variations in trough topographies and with sector-scale ice geometric readjustments arising from dispositions in the geography of the landscape. These second order controls produced a stepped deglaciation. The retreat of the British?Irish Ice Sheet is now the world?s most well-constrained and a valuable data-rich environment for improving ice-sheet modelling

Investigation of the effects of the conversion of forests and rangeland to cropland on fertility and soil functions in mountainous semi-arid landscape

Soil fertility and (micro)biological activities are prominent indicators of soil ecological functions interrelated with nutrient cycles and stocks. The responses of soil functions and belowground biota to degradation of natural ecosystems and land use changes have received little attention, especially in semi-arid ecosystems of mountainous areas that are sensitive and fragile habitats. Soils were sampled from two natural vegetation types: forest (Carpinus orientalis - Zelkova carpinifolia) and rangeland (Berberis integerrima - Crataegus melanocarpa), and two cultivated croplands (under Triticum aestivum), located in a mountainous semi-arid region of northern Iran, that were converted from the forests and rangelands thirty years ago. Soil properties, C and N stocks and fractions, and related microbial activities were analysed in 0–10 and 10–20 cm. C stocks in the upper 10 cm soil were affected by land use, while no differences were found in the lower depth. C stocks in the topsoil reached 49, 37, 33 and 29 Mg ha−1 for forest, rangeland, croplands (converted from forest and converted from rangeland), respectively. Soil N stocks under forest (5.2 Mg ha−1 for top 10 cm and 4.8 Mg ha−1 for 10–20 cm depths) were higher compared to the other land use types. Particulate and dissolved organic matters under croplands were almost half of that under forest and rangeland. High soil respiration, microbial biomass, ammonium and nitrate content, as well as N mineralization in 0–10 cm under forest were 2 times larger than in 10–20 cm. Concluding, conversion of forest and rangeland to croplands (converted from forest > converted from rangeland) has decreased the functions of soil due to removal of tree cover, decreasing litter layer, organic matter input and soil moisture and also increase of soil temperature. Consequently, more care should be taken by preserving natural vegetation in mountainous semi-arid ecosystems, and higher organic inputs are necessary to maintain microbial properties and functions. © 2021 Elsevier B.V

Gas hydrates in the Nile deep-sea fan : a restricted BSR vs widespread fluid venting

International audienceThe Nile deep-sea fan is the largest Plio-Quaternary depocentre in the Mediterranean Sea, extending over an area of >150,000 km2 within which rapid deposition drives syn-sedimentary collapse tectonics, as well as widespread seafloor venting of mixed thermogenic and biogenic gases. It is thus an ideal setting for the near-seabed accumulation of gas hydrates, which are stable below water depths of about 1100 m in the warm waters of the eastern Mediterranean. Gas hydrates have yet to be sampled on the Nile fan, although their presence has been suggested from semi-published industry seismic and well log data. Here we integrate available industry data with a regional grid of academic geophysical data (seismic and multibeam) acquired by Géoazur, in order to identify a BSR on the central Nile fan, invert it to geothermal gradients, and examine its relationship to fluid venting. The BSR is observed on several intersecting seismic profiles of varying frequency content and offset, as a discontinuous reflection of negative polarity that lies 220-330 ms below seafloor, deepening downslope in water depths of 2000-2500 m. The BSR occurs within a relatively small area (2500 km2), among a larger system of slope-parallel extensional faults. Inversion of BSR depth to temperature gradients was performed using a velocity-depth function for deep-sea sediments, a phase boundary for methane hydrate in equilibrium with seawater of 3.86% salinity (Mediterranean average), and water temperatures from MEDATLAS. The results indicate spatially varying gradients of 27-42˚C/km, up to twice background values reported in the geothermally cool eastern Mediterranean offshore. ‘Shallow’ BSRs yielding elevated thermal gradients within the Nile fan can be explained in terms of advective heat transfer by upward fluid flux. Upward fluid migration is supported by evidence of widespread seafloor fluid venting, but seafloor data indicate few or no vents in the area of the BSR. In contrast, in an area with many gas vents over 50 km from the BSR, subsurface gas hydrate accumulations are indicated by resistivity log data at two well-sites. If gas and gas hydrates are present across wider areas, why is the BSR so restricted? We hypothesise that these observations can be explained in terms of spatially varying fluid flux, such that away from the BSR a greater flux of fluids rich in dissolved gas leads to rapid gas hydrate formation and the growth of gas chimneys. We intend to test this hypothesis during a forthcoming Franco-Brazilian campaign, focused on understanding the dynamics of the fluid vents. Acknowledgement : this work has received funding from the European Union’s Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement No. 656821 (SEAGAS project)

Geophysical Evidence of Gas Hydrates Associated with Widespread Gas Venting on the Central Nile Deep-Sea Fan, Offshore Egypt

International audienceDeep-sea fans are favoured settings for the formation of gas hydrates, due to high sedimentation rates and organic matter content that promote the upwelling of methane-rich fluids. Gas hydrates have not been sampled on the Nile fan, but geophysical evidence of their presence is known to the Egyptian hydrocarbon industry. Here we use academic data to document a bottom-simulating reflection (BSR) on the central Nile fan, and examine its relationship to evidence of seabed fluid seepage. We use reprocessed multi-channel seismic profiles acquired from 1973-2002, of varying offset (0.3-4 km) and peak frequency content (10 1-10 2 Hz), together with sonar imagery and subottom profiles (10 3-10 5 Hz). The regional methane hydrate stability zone (RMHSZ) is modeled using a phase boundary for methane hydrate in equilibrium with bottom water of 3.86% salinity (Mediterranean average) and gridded inputs for bathymetry, bottom water temperatures and geothermal gradients. A BSR is observed across the central Nile fan in water depths of 2000-2500 m, as a discontinuous reflection of negative polarity at depths of 220-330 ms below seabed. BSR 'patches' vary in extent and character, but are mainly of low amplitude and, on higher frequency data, may be associated with reduced amplitudes or blanking in the overlying succession. The BSR is observed both in stratified intervals and within interbedded unstratified mass-transport deposits (MTDs, up to 200 ms thick). The depth below seabed of the BSR is comparable to the base of the modeled RMHSZ (converted to travel-time at sediment velocities of 1.6-1.8 km/s). The presence of gas hydrates in the lower part of the RMHSZ is indicated by published resistivity logs from two exploration wells, here located in areas lacking a BSR. We infer that on the central Nile fan gas hydrates are present within a sub-seabed interval up to 250 m thick, that is in places associated with a weak BSR recording basal accumulations of free gas. Previous work shows the central Nile fan is also characterised by widspread phenonema of fluid seepage, expressed at seabed as sonar backscatter anomalies that correspond to authigenic carbonate pavements, developed over timescales of at least 10 3 years, some associated with hydroacoustic flares at their edges recording ongoing gas venting to the water column. The carbonate pavements lie within stratified sediments up to 110 m thick that, in most areas, have been affected by post-depositional deformation of underlying MTDs. Seismic profiles across seepage areas show the stratified sediments to contain pipes linked to faults rooted within the MTDs; the latter are offset in places by more deeply-rooted faults, but the seeps do not correspond to vertical structures rising beneath the RMHSZ. These observations suggest that seabed seeps across the central Nile fan record the long-term rise of gas-rich fluids rich from sources within the hydrate stability zone, in places facilitated by faults rooted in MTDs. Different mechanisms have been suggested to explain gas migration through the stability zone : one is the rise from depth of hot and/or saline fluids in focused flows capable of locally displacing the phase boundary upwards to seabed; an alternative involves the diffuse upwelling of methane-rich fluids over wider areas to drive salt-exclusion at the base of the stability zone, a process proposed to lead to the rise of the 3-phase boundary to seabed within hydrate-choked chimneys. We note that the diffuse upwelling of fluids rich in dissolved methane could also account for the weak and discontinuous BSR, in terms of an upward flux of dissolved methane at rates high enough to limit gas accumulation beneath the stability zone, assuming there to be a minimum in the gas solubility curve. Our calculations of gas solubility show that a minimum is present below the RMHSZ, despite low geothermal gradients on the Nile fan, due to downward-increasing pore water salinities (as recorded at DSDP/ODP sites). We hypothesise the central Nile fan to contain a gas hydrate system driven by the upwelling of pore fluids rich in dissolved methane, at rates that result in: a) a discontinuous BSR beneath gas hydrate deposits; b) salt exclusion at the basal 3-phase boundary which rises to seabed along hydrate-choked vents (chimneys and/or faults). This model of a stability zone containing widely distributed phase-boundary vents is of interest as it implies a system in which temporal fluid fluxes, and perhaps pore pressures, may be regulated by seepage. A gas hydrate system containing vents that connect the basal phase boundary to seabed has been argued to be more sensitive to climate forcing from above. The abundance of seeps on the central Nile fan raises the question whether, by facilitating fluid venting to seabed, it might also be less likely to to result in slope failures? This is of particular interest on the Nile fan as it contains a stratigraphic record of recurrent large-scale failures and has experienced large changes in bottom water temperatures during glacial-interglacial climate cycles that imply basin-wide changes gas hydrate stability. Modeling of the RMGHZ for the last glacial maximum (LGM : -140 m sea level, -4˚C bottom waters) suggests that since deglaciation the stability zone on the Nile fan has reduced in thickness by 160 m (30%) at all water depths below about 800 m. Thus if gas hydrate dissociation during glacial to interglacial transitions can trigger slope failures, the Nile fan is an ideal location for it to take place. The question is whether it has occured, or if transient fluid fluxes were instead relieved by fluid venting? We aim to address the above questions during a forthcoming Franco-Brazilian campaign, focused on understanding the nature and dynamics of the gas vents. The Nile fan contains a gas hydrate system that is associated with widespread gas venting and has experienced large temporal changes, making it an ideal location to explore the linkages between gas hydrate stability, fluid flux and sediment failure over glacial-interglacial timescales