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Die kontinentale Kruste, die für die biologische und geologische Geschichte der Erde von zentraler Bedeutung ist, weist eine andesitische bis dazitische Zusammensetzung auf mit einem vertikalen Aufbau von der mafischen unteren Kruste zur stärker entwickelten, felsischen oberen Kruste. Demnach dokumentieren felsische magmatische Gesteine die Bildung, Differenzierung und Rekonstruktion der kontinentalen Kruste sowie die Wechselwirkung der Kruste mit dem Erdmantel. Diese felsischen Magmen können durch Differenzierung von Primärmagmen durch fraktionierte Kristallisation innerhalb der Kruste oder des obersten Mantels oder durch teilweises Aufschmelzen von früherem Krustengestein entstehen. Für die Entstehung von Rhyolith hat sich in den letzten Jahrzehnten das "Mush-Modell" etabliert, bei dem allgemein davon ausgegangen wird, dass es sich bei Rhyolith um eine Schmelze handelt, die durch Fraktionierung von intermediären Magmen in der flachen Kruste entstanden ist. Es ist jedoch unklar, ob es sich bei felsischen Plutonen um erstarrte Schmelzen handelt, oder um die Überreste, die bei der Extraktion der entwickelten Schmelze zurückgeblieben sind. Daher ist ein besseres Verständnis der Prozesse erforderlich, die die Entstehung von felsischen plutonischen Gesteine steuern. Darüber hinaus sind adakitische Gesteine als eine Unterart von felsischen Gesteinen von entscheidender Bedeutung für die Entschlüsselung der Entwicklungsprozesse in der Kruste und der Bildung wirtschaftlicher Mineralisierungen, insbesondere der porphyrischen Kupferlagerstätten. Bisherige Studien konzentrierten sich jedoch vor allem auf die Quellen der adakitischen Magmen und ihre tektonische Umgebung, während über die Prozesse der Magmenentwicklung nach der Bildung dieser adakitischen Schmelzen relativ wenig bekannt ist.
Der magmatische Gürtel von Gangdese, der in Südtibet am südlichsten Zipfel Eurasiens liegt, wurde von der Subduktion der Neotethys und der anschließenden Kollision von Indien und Eurasien beeinflusst, die zur Bildung des riesigen Gangdese-Batholith führte und somit umfangreiche Möglichkeiten zur Untersuchung der Entstehung felsischer plutonischer Gesteine bietet. In dieser Arbeit sollen verschiedene Phasen des felsischen Magmatismus innerhalb des Gangdese-Batholiths untersucht werden, die sich auf den Beginn der Indien-Eurasien-Kollision zurückdatieren lassen und sich im Wesentlichen in den kalkalkalischen Magmatismus des Paläozän bis Eozän und den adakitischen Magmatismus des späten Eozän bis Miozän gliedern. Damit soll unser allgemeines Verständnis erstens der transkrustalen magmatischen Prozesse, die zur Bildung felsischer plutonischer Gesteine führen, und zweitens des Ursprungs, der geodynamischen Mechanismen und der Mineralisierung von adakitischen Gesteinen verbessert werden.
Um den paläozänen bis eozänen kalkalkalischen Magmatismus zu erforschen, untersuchten wir den ca. 50 Millionen Jahre (Ma) alten granitischen Pluton von Nyemo, der eine einzigartige geschichtete Zusammensetzung von mittleren bis hohen SiO2-Gehalten aufweist. Außerdem zeigt er einen Übergang von gleichkörnigen und porphyrischen Texturen an der Basis zu miarolitischen Texturen in der Dachzone und bietet somit eine einzigartige Gelegenheit, die Koexistenz von extrahierten Schmelzen und komplementären felsischen Kumulaten in einem der vollständigsten transkrustalen felsischen magmatischen Systeme der Erde zu belegen. Die einheitlichen Hf-Isotopenzusammensetzungen von Zirkon dieser Intrusivgesteine lassen auf eine gemeinsame, nicht-radiogene Magmenquelle mit Krustenassimilation in der tiefen Kruste schließen. Miarolit- und Rapakivi-Granite mit hohem SiO2-Gehalt weisen stark verarmte Ba-, Sr- und Eu-Gehalte und extrem niedrige Zirkon-Eu/Eu*- und -Dy/Yb-Verhältnisse auf, während der Monzogranit durch relativ angereicherte Ba- und Sr-Gehalte, niedrige Eu-Anomalien und hohe Zirkon-Eu/Eu*- und Dy/Yb-Verhältnisse gekennzeichnet ist. Wir argumentieren, dass die SiO2-reichen Granite hoch fraktionierte Schmelzen darstellen, die aus einem Kristallbrei-Reservoir gewonnen wurde, und dass der Monzogranit die komplementären restlichen felsischen Kumulate darstellt.
Die zusammengetragenen geochronologischen und geochemischen Daten des adakitischen Magmatismus des späten Eozäns bis Miozäns im südlichen Lhasa-Subterrane liefern Beweise für die Identifizierung von zwei Phasen des adakitischen Magmatismus nach Einsetzen der Kollision (ca. 38-25 Ma und ca. 20-10 Ma), die Unterschiede in der Fraktionierung zwischen leichten und mittleren seltenen Erdelementen (REE) aufweisen. Die untersuchten adakitischen Monzogranite (ca. 30 Ma) und Granodiorite (ca. 15 Ma) von den Standorten Gyaca und Nyemo weisen alle einheitliche chemische Signaturen auf, wie z.B. geringfügige Eu-Anomalien, niedrige MgO- und schwere REE-Konzentrationen sowie niedrige Gehalte an kompatiblen Elementen. Das deutet darauf hin, dass diese Gesteine aus dem partiellen Aufschmelzen von verdickter unterer Kruste mit Resten von Eklogit und Granatamphibolit stammen. Darüber hinaus sind diese Gesteine durch variable positive εHf(t)-Werte von Zirkon gekennzeichnet, was auf eine juvenile Magmaquelle mit variierenden Anteilen alter Kruste hindeutet. Wir vermuten außerdem, dass die adakitischen Gesteine der frühen Phase durch die Anatexis der unteren Kruste des Lhasa-Terranes infolge der Krustenverkürzung und -verdickung nach dem Beginn der Indien-Eurasien-Kollision und des Auftriebs der heißen Asthenosphäre unter dem Lhasa-Terran durch den Abbruch der ozeanischen Platte der Neotethys entstanden sind, während die adakitischen Gesteine der späten Phase auf das Aufsteigen der Asthenosphäre nach der Delamination und/oder dem Abbruch der subduzierenden indischen Kontinentalplatte zurückzuführen sind.
Um einen Einblick in die Entwicklung des adakitischen Magmas und die damit verbundenen wirtschaftlichen Mineralisierungsprozesse zu gewinnen, präsentieren wir die in situ-Spurenelementzusammensetzung von Zirkon der adakitischen Gesteine aus Nyemo aus dem Oligozän-Miozän in Kombination mit früheren geochemischen Gesamtgesteinsdaten. Systematische Variationen in der Spurenelementzusammensetzung von Zirkon belegen die fraktionierte Kristallisation bestimmter Minerale (z.B. Titanit, Magnetit) im Monzogranit und die Gleichgewichtskristallisation im Granodiorit. Dies wird auch durch thermodynamische Modellierungen bestätigt, die ergaben, dass die monzogranitischen und granodioritischen Magmen geringfügige fraktionierte Kristallisation (Schmelzanteil bis zu ~70 %) bzw. Gleichgewichtskristallisation durchliefen. Die progressiv verringerte Sauerstofffugazität während der Magnetitfraktionierung in den monzogranitischen Magmen führte zur Absonderung von Sulfiden, die der Schmelze Schwefel und chalcophile Elemente wie Ni und Cu entzogen. Daraus schließen wir, dass die Magnetitfraktionierung in der flachen bis mittelkontinentalen Kruste zur geringen Cu-Fertilität der Magmen beitragen kann, die einige der Cu-armen adakitischen Gesteine nach der Kollision im magmatischen Gürtel von Gangdese bilden.
Dissolved oxygen (DO) is crucial for aerobic life in streams and rivers and mostly depends on photosynthesis (P), ecosystem respiration (R) and atmospheric gas exchange (G). However, climate and land use changes progressively disrupt metabolic balances in natural streams as sensitive reflectors of their catchments. Comprehensive methods for mapping fundamental ecosystem services become increasingly important in a rapidly changing environment. In this work we tested DO and its stable isotope (18O/16O) ratios as novel tools for the status of stream ecosystems. For this purpose, six diel sampling campaigns were performed at three low-order and mid-latitude European streams with different land use patterns. Modelling of diel DO and its stable isotopes combined with land use analyses showed lowest P rates at forested sites, with a minimum of 17.9 mg m−2 h−1. Due to high R rates between 230 and 341 mg m−2 h−1 five out of six study sites showed a general heterotrophic state with P:R:G ratios between 0.1:1.1:1 and 1:1.9:1. Only one site with agricultural and urban influences showed a high P rate of 417 mg m−2 h−1 with a P:R:G ratio of 1.9:1.5:1. Between all sites gross G rates varied between 148 and 298 mg m−2 h−1. In general, metabolic rates depend on the distance of sampling locations to river sources, light availability, nutrient concentrations and possible exchanges with groundwater. The presented modelling approach introduces a new and powerful tool to study effects of land use on stream health. Such approaches should be integrated into future ecological monitoring.
Trait-based approaches are increasingly relevant to understand ecological and evolutionary patterns. A comprehensive trait database for extant reef corals is already available and widely used to reveal vulnerabilities to environmental disturbances including climate change. However, the lack of similar trait compilations for extinct reef builders prevents the derivation of generalities from the fossil record and to address similar questions. Here we present the Ancient Reef Traits Database (ARTD), which aims to compile trait information of various reef-building organisms in one single repository. ARTD contains specimen-level data from both published and unpublished resources. In this first version, we release 15 traits for 505 genera and 1129 species, comprising a dataset of 17,841 trait values of Triassic to mid-Holocene scleractinian corals, the dominant reef-builders in the modern ocean. Other trait data, including for other reef-building organisms, are currently being collated.
The Nepalese Mustang District is subject to profound environmental change. In recent decades, rising temperatures have been apparent, accompanied by increasing precipitation variability and a reduction in glacier extent. In a semi-arid climate, this reduces water availability and threatens irrigation-based subsidence agriculture. In addition, the region is experiencing rapid socio-economic change due to a new road connecting the former periphery to new markets downstream. This enables a higher market orientation for agricultural products and improved accessibility for tourists. In recent decades, these changes have triggered severe transformations in the local land-use systems and settlements, which are investigated in this study. Detailed on-site re-mappings of the settlements of Marpha and Kagbeni were performed based on historical maps from the early 1990s. Additionally, land-use patterns and functionality of buildings in the district capital of Jomsom and in the settlement Ranipauwa/Muktinath were mapped. For all settlements, a profound increase in cash crop (apple) cultivation can be observed since the 1990s. Recently, new cultivation practices such as intercropping have been extensively introduced as an adaptation strategy to climate extremes. Demand for different crops from the new markets downstream is causing a significant decline in local, well-established cultivation of traditional crops such as buckwheat. This corroborates with an increasing demand for freshwater for the enhanced vegetable cultivation used for inter-cropping. Simultaneously, the freshwater demands from the tourism sector are steadily increasing. In a region where water quality is deteriorating and springs are already drying up due to climate change, this will probably lead to further challenges regarding the allocation of water in the future.
Submarine caldera volcanoes may host several hydrothermal systems along the caldera wall and related to volcanic cones. Fluid boiling and magmatic volatile influx are common processes in shallow (<2,000 mbsl) subduction zone-related environments causing variations in the mineralogical and chemical composition of seafloor hydrothermal mineralizations that remain poorly constrained. The submarine caldera of Niuatahi volcano, Tonga rear-arc, hosts four active vent sites discharging high temperature fluids (<334°C) with variable salinities (369–583 mM Cl) that are indicative of fluid boiling, recorded by distinct Te/As and Te/Au in pyrite, sphalerite, and chalcopyrite. High sulfidation mineral assemblages (e.g., enargite), stable S isotope data and similar trace element signatures in sulfides and native S condensates suggest a minor and/or infrequent contribution of magmatic SO2 to the hydrothermal systems located proximal to the caldera center causing a volatile element (e.g., Se, Bi, Te) enrichment. The hydrothermal system at the northern caldera wall is decoupled from the magmatic SO2 source, as revealed by radiogenic Pb isotopes. Instead, S isotope and trace element constraints propose a host rock-dominated hydrothermal system, lacking a magmatic volatile influx. The observed hydrothermal fractionation processes (fluid boiling) and the distinct metal (loid) sources (magmatic volatiles vs. host rock) represent a continuum from magmatic volatile- to host rock-dominated hydrothermal systems within the Niuatahi caldera. This leads to seafloor mineralizations with spatially selective trace element enrichments, like Te, Se, and Bi (±Au, Ag) in the caldera center compared to Au, Ag, Zn, Cd, and Pb at the northern caldera wall.
The Rio Grande Rise in the western South Atlantic Ocean has been interpreted as either an oceanic plateau related to the Tristan-Gough mantle plume, or a fragment of detached continental crust. Here we present new major and trace element data for volcanic rocks from the western and eastern Rio Grande Rise and the adjacent Jean Charcot Seamount Chain. The eastern Rio Grande Rise and older parts of the western Rio Grande Rise are comprised of tholeiitic basalt with moderately enriched trace element compositions and likely formed above the Tristan-Gough mantle plume close to the southern Mid-Atlantic Ridge. Younger alkalic lavas from the western Rio Grande Rise and the Jean Charcot Seamount Chain were formed by lower degrees of melting beneath thicker lithosphere in an intraplate setting possibly during rifting of the plateau. There is no clear geochemical evidence that remnants of continental crust are present beneath the Rio Grande Rise.
Two loess sections from the Upper Palaeolithic site of Kammern-Grubgraben (Lower Austria) were analysed to test geochemical proxies, as well as radiocarbon data of different components, for their reliability and consistency in an archaeological context. Only a reliable basal age (28.9–27.8 ka cal BP) was obtained from charcoal fragments derived from a tundra gley underlying the archaeological horizons and assigned to Greenland Interstadials 3 or 4. Grain size, organic and inorganic geochemistry, and stable isotopes of the fine organic fraction (δ13Corg) and of rhizoconcretions (δ13C, δ18O) were analysed to provide information on palaeoenvironmental conditions. Low-resolution geochemical and sedimentological analyses document a humidity-related variability, while δ13Corg values indicate predominant C3 vegetation. High-resolution elemental variations derived from X-ray fluorescence scanning exhibit increasing Ca and decreasing Fe and Ti values, indicating drier conditions towards the top. Secondary pedogenic carbonate concretions provide post-sedimentary (Holocene) ages and are not suitable for assessing climate and environmental changes for the Palaeolithic.
Die Bevölkerungsstruktur und das Leben in ländlichen Räu-men wurden inden vergangenenJahren durch die AnkunftunddasBleibenvonGeflüchtetendiverser.DieTeilhabederNeuzu-gewanderten am Arbeitsmarkt ist einerseits aus integrations-politischerSichtwie auchfür die regionaleWirtschaftrelevantund erfüllt andererseits für sie selbst verschiedene Funktio-nen. Der (potenziellen) Selbstständigkeit von geflüchtetenNeuzugewanderten wurde in Deutschland bislang jedoch we-nig Aufmerksamkeit zuteil. Am Beispiel der Gründung vonLebensmittelgeschäften in ländlichen Räumen Deutschlandswurden multiperspektivisch die Aspirationen von Geflüchte-ten am Arbeitsmarkt,die Gründungs- und GeschäftspraxisvonBetreibern sowie die Sichtweisen der Kundinnen und Kundenuntersucht. Die durchgeführten qualitativen Interviews mit (potenziell) selbstständigen geflüchteten Neuzugewander-ten und (halb)standardisierten Befragungen von Kundinnenund Kunden bilden die Datengrundlage für diesen Beitrag.Konzeptionell gerahmt wird er von Forschungsarbeiten zurTeilhabe von Migrantinnen und Migranten am Arbeitsmarktund migrantischem Unternehmertum (immigrant entrepre-neurship)bzw.derUnterformFlüchtlingsunternehmertum(refugee entrepreneurship). Die Ergebnisse zeigen vielfälti-ge Bedeutungen von Beschäftigung und einen ausgeprägtenWunsch nach Selbstständigkeit, strukturelle wie auch indi-viduelle Hürden bei der Gründung von Geschäften und diePraxis co-ethnischer Beschäftigung.
Glaciers in the Russian High Arctic have been subject to extensive atmospheric warming due to global climate change, yet their contribution to sea level rise has been relatively small over the past decades. Here we show surface elevation change measurements and geodetic mass balances of 93 % of all glacierized areas of Novaya Zemlya, Severnaya Zemlya, and Franz Josef Land using interferometric synthetic aperture radar measurements taken between 2010 and 2017. We calculate an overall mass loss rate of Gt a−1, corresponding to a sea level rise contribution of 0.06±0.02 mm a−1. Compared to measurements prior to 2010, mass loss of glaciers on the Russian archipelagos has doubled in recent years.
Tight carbonate rocks are important hydrocarbon and potential geothermal reservoirs, for example, in CO2-Enhanced Geothermal Systems. We report a study of outcrop samples of tectonically undeformed tight carbonates from the upper Jurassic “Malm ß” formation in Southern Germany near the town of Simmelsdorf (38 km NE of Nuremberg) to understand bulk petrophysical properties in relation to microstructure and to compare models for permeability prediction in these samples. We applied Archimedes isopropanol immersion, Helium pycnometry, mercury injection, gamma density core logging, and gas permeability measurements, combined with microstructural investigations and liquid metal injection (LMI-BIB-SEM). In addition, ultrasonic velocity was measured to allow geomechanical comparison of stratigraphically equivalent rocks in the South German Molasse Basin (SGMB). Results show only small variations, showing that the formation is rather homogeneous with bulk porosities below 5% and argon permeabilities around 1.4E−17 m2. The presence of stylolites in some of the samples has neither a significant effect on porosity nor permeability. Pores are of submicron size with pore throats around 10 nm and connected as shown by Mercury injection and Liquid Metal injection. Samples have high dynamic Young’s Modulus of 73 ± 5 GPa as expected for lithified and diagenetically overmature limestones. Moreover, no trends in properties were observable toward the faults at meter scale, suggesting that faulting was post-diagenetic and that the matrix permeabilities were too low for intensive post-diagenetic fluid–rock interaction. Petrophysical properties are very close to those measured in the SGMB, illustrating the widespread homogeneity of these rocks and justifying the quarry as a reasonable reservoir analog. Permeability prediction models, such as the percolation theory-based Katz-Thompson Model, Poiseuille-based models, like the Winland, the Dastidar, the capillary tube, and the Kozeny-Carman Models, as well as several empirical models, namely, the Bohnsack, the Saki, and the GPPT Models, were applied. It is shown that the capillary tube Model and the Saki Model are best suited for permeability predictions from BIB-SEM and mercury injection capillary pressure results, respectively, providing a method to estimate permeability in the subsurface from drill cuttings. Matrix permeability is primarily controlled by the pore (throat) diameters rather than by the effective porosity.
This study addresses transpiration in a tropical evergreen mountain forest in the Ecuadorian Andes from the leaf to the stand level, with emphasis on nocturnal plant-water relations. The stand level: Evapotranspiration (ET) measured over 12 months with the Eddy-Covariance (ECov) technique proved as the major share (79%) of water received from precipitation. Irrespective of the humid climate, the vegetation transpired day and night. On average, 15.3% of the total daily ET were due to nocturnal transpiration. Short spells of drought increased daily ET, mainly by enhanced nighttime transpiration. Following leaf transpiration rather than air temperature and atmospheric water vapor deficit, ET showed its maximum already in the morning hours. The tree level: Due to the humid climate, the total water consumption of trees was generally low. Nevertheless, xylem sap flux measurements separated the investigated tree species into a group showing relatively high and another one with low sap flux rates. The leaf level: Transpiration rates of Tapirira guianensis, a member of the high-flux-rate group, were more than twice those of Ocotea aciphylla, a representative of the group showing low sap flux rates. Representatives of the Tapirira group operated at a relatively high leaf water potential but with a considerable diurnal amplitude, while the leaves of the Ocotea group showed low water potential and small diurnal fluctuations. Overall, the Tapirira group performed anisohydrically and the Ocotea group isohydrically. Grouping of the tree species by their water relations complied with the extents of the diurnal stem circumference fluctuations. Nighttime transpiration and hydrological type: In contrast to the isohydrically performing trees of the Ocotea group, the anisohydric trees showed considerable water vapour pressure deficit (VPD)-dependent nocturnal transpiration. Therefore, we conclude that nighttime ET at the forest level is mainly sourced by the tree species with anisohydric performance.
Abstract
The siliciclastic Jhuran Formation of the Kachchh Basin, a rift basin bordering the Malagasy Seaway, documents the filling of the basin during the late syn-rift stage. The marine, more than 700-m-thick Tithonian part of the succession in the western part of the basin is composed of highly asymmetric transgressive–regressive cycles and is nearly unfossiliferous except for two intervals, the Lower Tithonian Hildoglochiceras Bed (HB) and the upper Lower Tithonian to lowermost Cretaceous Green Ammonite Beds (GAB). Both horizons represent maximum flooding zones (MFZ) and contain a rich fauna composed of ammonites and benthic macroinvertebrates. Within the HB the benthic assemblages change, concomitant with an increase in the carbonate content, from the predominantly infaunal “Lucina” rotundata to the epifaunal Actinostreon marshii and finally to the partly epifaunal, partly infaunal Eoseebachia sowerbyana assemblage. The Green Ammonite Beds are composed of three highly ferruginous beds, which are the MFZ of transgressive–regressive cycles forming the MFZ of a 3rd-order depositional sequence. The GAB are highly ferruginous, containing berthieroid ooids and grains. GAB I is characterized by the reworked Gryphaea moondanensis assemblage, GAB II by an autochthonous high-diversity assemblage dominated by the brachiopods Acanthorhynchia multistriata and Somalithyris lakhaparensis, whereas GAB III is devoid of fossils except for scarce ammonites. The GAB are interpreted to occupy different positions along an onshore–offshore transect with increasing condensation offshore. Integrated analyses of sedimentological, taphonomic, and palaeoecological data allow to reconstruct, in detail, the sequence stratigraphic architecture of sedimentary successions and to evaluate their degree of faunal condensation.
Abstract
Understanding farmers’ perceptions of and preferences towards agroforestry is essential to identify systems with the greatest likelihood of adoption to inform successful rural development projects. In this study we offer a novel approach for evaluating agroforestry systems from the farmer perspective. The approach couples rapid rural appraisal and normative optimisation techniques to determine favourable land-use compositions for meeting various socio-economic and ecological goals, based on farmers’ empirical knowledge and preferences. We test our approach among smallholder farmers in Eastern Panama, obtaining data from household interviews and using hierarchical cluster analysis to identify farm groups with similar land-use and income characteristics. We found that moderate differences in farmers’ perceptions between these groups altered the type and share of agroforestry included in the optimised land-use portfolios that balance the achievement of 10 pre-selected socio-economic and ecological objectives. Such differences provide valuable information about potential acceptability of agroforestry within each group. For example, we found that farmers who derive most of their farm income from crops may be more willing to adopt silvopasture, whereas farmers who are more economically dependent on cattle may benefit from diversifying their land-use with alley cropping. We discuss the potential of this modelling approach for participatory land-use planning, especially when dealing with small sample sizes and uncertainty in datasets.
Abstract
In the Global South, including the Sub-Saharan African city-regions, the possible future urban expansion patterns may pose a challenge towards improving environmental sustainability. Land use planning strategies and instruments for regulating urban expansion are faced with challenges, including insufficient data availability to offer insights into the possible future urban expansion. This study integrated empirical data derived from Geographic Information Systems, Remote Sensing, and surveys of experts to offer insights into the possible future urban expansion under spatial planning scenarios to support land use planning and environmental sustainability of city-regions. We analyzed the spatial determinants of urban expansion, calibrated the land cover model using the Multi-Layer Perceptron Neural Network and Markov, and developed three scenarios to simulate land cover from 2017 to 2030 and to 2050. The scenarios include Business As Usual that extrapolates past trends; Regional Land Use Plan that restricts urban expansion to the land designated for urban development, and; Adjusted Urban Land that incorporates the leapfrogged settlements into the land designated for urban development. Additionally, we quantified the potential degradation of environmentally sensitive areas by future urban expansion under the three scenarios. Results indicated a high, little, and no potential degradation of environmentally sensitive areas by the future urban expansion under the Business As Usual, Adjusted Urban Land, and Regional Land Use Plan scenarios respectively. The methods and the baseline information provided, especially from the Adjusted Urban Land scenario showed the possibility of balancing the need for urban expansion and the protection of environmentally sensitive areas. This would be useful to improve the environmental sustainability of the Sub-Saharan African city-regions and across the Global South, where insufficient data availability challenges land use planning.
Abstract
Thermal conductivity is a key parameter for many soil applications, especially for dimensioning shallow and very shallow geothermal systems based on the possible heat extraction rate and for modelling heat transfer processes around high voltage underground cables. Due to the limited purview of direct thermal conductivity measurements, for an investigation of extensive areas, usually other geophysical methods like electrical resistivity tomography measurements are applied. To derive thermal conductivity of soil from geoelectrical measurements a relation between electrical and thermal conductivity is needed. Until now only few approaches worked on a direct correlation between both conductivities. Due to the difficulties of a direct relation, within this study a modular approach of a mediate correlation between electrical and thermal conductivity was investigated. Therefore, a direct relationship between a corrected electrical conductivity and water content as well as the standard and simple thermal conductivity model of Kersten (Bull of the Univ Minnesota 28:1–227, 1949) was used. To develop this concept soil types of sand, silt loam and clay were investigated where different saturation steps and pressure loads were applied. For each configuration electrical and thermal conductivity as well as water content and bulk density was determined. To refine the results of the calculated water content a corrective factor was applied. Furthermore, bulk density as an inlet parameter of the Kersten equation was also derived based on electrical conductivity. The suggested proceeding enables the determination of thermal conductivity solely based on electrical conductivity without prior soil property information.
Abstract
GIS-based multicriteria evaluation (MCE) provides a framework for analysing complex decision problems by quantifying variables of interest to score potential locations according to their suitability. In the context of earthquake preparedness and post-disaster response, MCE has relied mainly on uninformed or non-expert stakeholders to identify high-risk zones, prioritise areas for response, or highlight vulnerable populations. In this study, we compare uninformed, informed non-expert, and expert stakeholders’ responses in MCE modelling for earthquake response planning in Vancouver, Canada. Using medium- to low-complexity MCE models, we highlight similarities and differences in the importance of infrastructural and socioeconomic variables, emergency services, and liquefaction potential between a non-weighted MCE, a medium-complexity informed non-expert MCE, and a low-complexity MCE informed by 35 local earthquake planning and response experts from governmental and non-governmental organisations. Differences in the observed results underscore the importance of accessible, expert-informed approaches for prioritising locations for earthquake response planning and for the efficient and geographically precise allocation of resources.
Abstract
Global environmental research requires long-term climate data. Yet, meteorological infrastructure is missing in the vast majority of the world’s protected areas. Therefore, gridded products are frequently used as the only available climate data source in peripheral regions. However, associated evaluations are commonly biased towards well observed areas and consequently, station-based datasets. As evaluations on vegetation monitoring abilities are lacking for regions with poor data availability, we analyzed the potential of several state-of-the-art climate datasets (CHIRPS, CRU, ERA5-Land, GPCC-Monitoring-Product, IMERG-GPM, MERRA-2, MODIS-MOD10A1) for assessing NDVI anomalies (MODIS-MOD13Q1) in two particularly suitable remote conservation areas. We calculated anomalies of 156 climate variables and seasonal periods during 2001–2018, correlated these with vegetation anomalies while taking the multiple comparison problem into consideration, and computed their spatial performance to derive suitable parameters. Our results showed that four datasets (MERRA-2, ERA5-Land, MOD10A1, CRU) were suitable for vegetation analysis in both regions, by showing significant correlations controlled at a false discovery rate < 5% and in more than half of the analyzed areas. Cross-validated variable selection and importance assessment based on the Boruta algorithm indicated high importance of the reanalysis datasets ERA5-Land and MERRA-2 in both areas but higher differences and variability between the regions with all other products. CHIRPS, GPCC and the bias-corrected version of MERRA-2 were unsuitable and not important in both regions. We provide evidence that reanalysis datasets are most suitable for spatiotemporally consistent environmental analysis whereas gauge- or satellite-based products and their combinations are highly variable and may not be applicable in peripheral areas.
The rhodolith-forming coralline red algal species Lithothamnion glaciale is the key ecosystem engineer of rhodolith beds on the coast of Svalbard. Because it significantly increases local biodiversity in this high-Arctic environment, we investigate the potential impact of changing environmental parameters on its calcite skeleton. Using energy-dispersive X-ray spectroscopy and environmental data from the Norwegian government’s environmental monitoring, we show that the magnesium concentration within an analysed algal calcite skeleton decreases linearly and significantly over a 40-year time span (R2 = 0.267, pperm < 0.001). Mg/Ca ratios show the most significant correlation with atmospheric CO2 concentrations (R2 = 0.614, p < 0.001), and lower correlations to sea ice cover and seawater temperature. This raises the question of whether the Mg/Ca in the rhodolith skeleton is reflecting an increase in aqueous pCO2 that drives ongoing ocean acidification. Since such a change in geochemistry may alter the stability of the calcite skeleton, our results could imply an impact on the future role of the rhodoliths as ecosystem engineers and consequently on Arctic biodiversity.
Abstract
The current research of carbon cycling in inland waters lacks a sound knowledge of carbon outgassing from small streams. As a consequence, these compartments of the terrestrial water cycle might still be seriously underrepresented in estimates of global carbon transfer budgets from land surfaces. This study investigated carbon sources and sinks of a mountain river in a silicate catchment. For this purpose, the high‐relief Gravona river, in the western part of the island of Corsica (France) in the Western Mediterranean, was investigated for field parameters, dissolved inorganic carbon (DIC) and its stable carbon isotopes (δ13CDIC). The source region was characterized by low DIC contents and high δ13CDIC values that decreased further downstream due to increasing soil respiration. Associated increasing DIC concentrations and elevated seasonality in the lower river section also indicated more respiration and subsequent DIC‐input by weathering. The aqueous partial pressure (pCO2(aq)) was lowest at the source of the Gravona river and samples from the cold season even showed undersaturation that led to uptake of atmospheric CO2. Further downstream, the seasonality of pCO2(aq) increased and was particularly pronounced near the river mouth where CO2 degassing took place. Average DIC flux along the river was 0.129 Gg C year−1 and was almost equal to CO2 degassing from the river surface with 0.128 Gg C year−1. Our study showed that on an annual basis the river is an overall weak to medium source of CO2 to the atmosphere even though headwater parts of the river seasonally act as CO2 sinks.