In the Earth, the dynamo action is strongly linked to core freezing. There is a solid inner core, the growth of which provides a buoyancy flux that drives the dynamo. The buoyancy in this case derives from a difference in composition between the solid inner core and the fluid outer core. In planetary bodies smaller than the Earth, however, this core differentiation process may differ - Fe may precipitate at the core-mantle boundary (CMB) rather than in the center and may fall as iron snow and initially remelt with greater depth. A chemical stable sedimentation zone develops that comprises with time the entire core - at that time a solid inner core starts to grow. The dynamics of this system is not well understood and also whether it can generate a magnetic field or not. The Jovian moon Ganymede, which shows a present-day magnetic dipole field, is a candidate for which such a scenario has been suggested. We plan to study this Fe-snow regime with both a numerical and experimental approach. In the numerical study, we use a 2D/3D thermo-chemical convection model that considers crystallization and sinking of iron crystals together with the dynamics of the liquid core phase (for the 3D case the influence of the rotation of the Fe snow process is further studied).The numerical calculations will be complemented by two series of experiments: (1) investigations in metal alloys by means of X-ray radioscopy, and (2) measurements in transparent analogues by optical techniques. The experiments will examine typical features of the iron snow regime. On the one hand they will serve as a tool to validate the numerical approach and on the other hand they will yield important insight into sub-processes of the iron snow regime, which cannot be accessed within the numerical approach due to their complexity.
Agriculture is the major contributor of nitrogen to ecosystems, both by organic and inorganic fertilizers. Percolation of nitrate to groundwater and further transport to surface waters is assumed to be one of the major pathways in the fate of this nitrogen. The quantification of groundwater and associated nitrate flux to streams is still challenging. In particular because we lack understanding of the spatial distribution and temporal variability of groundwater and associated NO3- fluxes. In this preliminary study we will focus on the identification and quantification of groundwater and associated nitrate fluxes by combining high resolution distributed fiber-optic temperature sensing (DTS) with in situ UV photometry (ProPS). DTS is a new technique that is capable to measure temperature over distances of km with a spatial resolution of ca1 m and an accuracy of 0.01 K. It has been applied successfully to identify and quantify sources of groundwater discharge to streams. ProPS is a submersible UV process photometer, which uses high precision spectral analyses to provide single substance concentrations, in our case NO3-, at minute intervals and a detection limit of less than 0.05 mg l-1 (ca.0.01 mg NO3--Nl-1). We will conduct field experiments using artificial point sources of lateral inflow to test DTS and ProPS based quantification approaches and estimate their uncertainty. The selected study area is the Schwingbach catchment in Hessen, Germany, which has a good monitoring infrastructure. Preliminary research on hydrological fluxes and field observations indicate that the catchment favors the intended study.
Laminierte Seesedimente sind unschätzbare Informationsquellen zur Geschichte der Umwelt und des Klimas direkt aus der Lebenssphäre des Menschen. Ein exzellentes Beispiel dafür ist der Sihailongwan-Maarsee aus NE-China. In einem immer noch dicht bewaldeten Vulkangebiet gelegen, bieten seine Sedimente ein ungestörtes Abbild der Monsunvariationen über zehntausende von Jahren. Nur die letzten ca. 200 Jahre zeigen einen deutlichen lokalen anthropogenen Einfluss. Das Monsunklima der Region mit Hauptniederschlägen während des Sommers und extrem kalten Wintern unter dem Einfluss des Sibirischen Hochdrucksystems bildet die Voraussetzung für die Bildung von saisonal deutlich geschichteten Sedimenten (Warven), die in dem tiefen Maarsee dann auch überwiegend ungestört erhalten bleiben. Insbesondere die Auftauphase im Frühjahr bringt einen regelmässigen Sedimenteintrag in den See, der das Gerüst für eine derzeit bis 65.000 Jahre vor heute zurückreichende Warvenchronologie bildet. Für das letzte Glazial zeigen Pollenspektren aus dem Sihailongwan-Profil Vegetationsvariationen im Gleichklang mit bekannten klimatischen Variationen des zirkum-nordatlantischen Raumes (Dansgaard-Oeschger-Zyklen) zu dieser Zeit. Der Einfluss dieser Warmphasen auf das Ökosystem See war jedoch sehr unterschiedlich. So sind die Warven aus den Dansgaard-Oeschger (D/O) Zyklen 14 bis 17 mit extrem dicken Diatomeenlagen (hauptsächlich Stephanodiscus parvus/minutulus) denen vom Beginn der spätglazialen Erwärmung zum Verwechseln ähnlich, während Warven aus dem D/O-Zyklus 8 kaum Unterschiede zu überwiegend klastischen Warven aus kalten Interstadialen aufweisen. Gradierte Ereignislagen mit umgelagertem Bodenmaterial sind deutliche Hinweise auf ein Permafrost-Regime während der Kaltphasen. Auch während des Spätglazials treten deutliche klimatische Schwankungen auf, die der in europäischen Sedimentarchiven definierten Gerzensee-Oszillation und der Jüngeren Dryas zeitlich exakt entsprechen. Das frühe Holozän ist von einer Vielzahl Chinesischer Paläoklima-Archive als Phase mit intensiverem Sommermonsun bekannt. Überraschenderweise sind die minerogenen Fluxraten im Sihailongwan-See während des frühen Holozäns trotz dichter Bewaldung des Einzugsgebietes sehr hoch. Sowohl Mikrofaziesanalysen der Sedimente als auch geochemische Untersuchungen deuten auf remoten Staub als Ursache dieses verstärkten klastischen Eintrags hin. Der insbesondere in den letzten Jahrzehnten zunehmende Einfluss des Menschen zeigt sich in den Sedimenten des Sihailongwan-Maarsees vor allem in einem wiederum zunehmenden Staubeintrag und einer Versauerung im Einzugsgebiet. Der anthropogene Einflusss auf die lokale Vegetation ist immer noch gering.
This project will provide quantitative estimates of the flow of low-salinity warm water through the Indonesian Gateway on suborbital timescales during MIS 2 and 3 (focusing on Dansgaard Oeschger (D-O) oscillations) and will assess the Indonesian Throughflow (ITF) s impact on the hydrography of the eastern Indian Ocean and global thermohaline circulation during this critical interval of high climate variability. ITF fluctuations, associated with sea level change, temperature and salinity variations in the West Pacific Warm Pool (WPWP) strongly influence precipitation over Australia, the strength of the southeast-Asian summer monsoon, and the intensity of warm meridional currents in the Indian Ocean. We will test the hypothesis that increased ITF is associated with warm interstadials of MIS 3, whereas a strong reduction in ITF occurred during stadials. We will use as main proxies planktonic and benthic foraminiferal isotopes in conjunction with Mg/Ca temperature estimates and radiogenic isotopes (mainly Nd) as tracers of Pacific water masses along depth transects in the Timor Passage and the eastern Indian Ocean. This project will provide the paleoceanographic framework that will be crucial to validate and refine circulation models of D-O events and high-frequency climate variability on a global scale.
The proposal addresses the potential of subsoil to contribute to K nutrition of crops. More specifically we will address the processes controlling release of K from interlayer of 2:1 clay minerals as this is expected to be the dominant K fraction in the subsoil. While it has been shown in the past that this so called 'non-exchangeable' K can be released due to root activity, there are controversial results concerning the role of soil solution K concentration in the rhizosphere required to trigger the process. Likewise little information is available about the concentration dynamics of other cations (NH4, Ca) in the rhizosphere and their impact on K release and vermiculitization supposed to be associated with this process. Model studies with substrate from the central field trial will be conducted in compartment systems equipped with micro suction cups. The measurement of dynamic changes of soil solution composition with increasing distance from the root surface will be combined with investigations of changes in mineralogy by XRD, TEM and SEM-EDX. Changes of mineralogy as a result of plant induced K release from interlayer will also be studied on bulk soil and rhizosphere samples collected within the central field and the central microcosm experiment and with mineral bags exposed in the field during a cropping cycle. Finally, X-ray CT will be used to access changes in soil texture, i.e. clay distribution around roots and the temporal spread of roots in biopores which is a prerequisite for K uptake from such structures.
Prehistoric pits are filled with ancient topsoil material, which has been preserved there over millennia. A characteristic of these pit fillings is that their colour is different depending on the time the soil material was relocated. Soil colour is the result of soil forming processes and soil properties, and it could therefore indicate the soil characteristics present during that specific period. To the best of our knowledge, no investigation analysed and explained the reasons for these soil colour changes over time. The proposed project will investigate soil parameters from pit fillings of different archaeological periods in the loess area of the Lower Rhine Basin (NW-Germany). It aims to implement the measurement of colour spectra as a novel analytical tool for the rapid analyses of a high number of soil samples: the main goal is to relate highresolution colour data measured by a spectrophotometer to soil parameters that were analysed by conventional pedogenic methods and by mid infrared spectroscopy (MIRS), with a main focus on charred organic matter (BPCAs). This tool would enable us to quantify the variation of soil properties over a timescale of several millennia, during different prehistoric periods at regional scale and for loess soils in general. Detailed information concerning changing soil properties on a regional scale is necessary to determine past soil quality and it helps to increase our understanding of prehistoric soil cultivation practices. Furthermore, these information could also help to increase our understanding about agricultural systems in different archaeological periods.
Various species of pest insects cause substantial damage to agriculture every year, or transmit deadly diseases to animals and humans. A successful strategy to control pest insect populations is based on the Sterile Insect Technique (SIT), which uses the release of mass-reared, radiation sterilized male insects to cause infertile matings and thus reduce the pest population level. However, irradiation is not applicable to every insect species. Thus, new strategies based on genetic modifications of pest insects have been developed or are currently under investigation.The goal of the proposed research is to improve the development and ecological safety of genetically engineered (GE) insects created for enhanced biological control programs, including the SIT and new strategies based on conditional lethality. A major concern for GE insect release programs is transgene stability, and maintenance of their consistent expression. Transgene loss or intra-genomic movement could result in loss of strain attributes, and may ultimately lead to interspecies movement resulting in ecological risks. To address potential transgene instability, a new transposon vector that allows post-integration immobilization will be tested in the Mediterranean, Mexican and Oriental fruit fly tephritid pest species. In addition, the system will be established in the mosquito species Aedes and Anopheles - carriers of dengue and malaria.Random genomic insertion is also problematic for GE strain development due to genomic position effects that suppress transgene expression, and insertional mutations that negatively affect host fitness and viability. Diminished transgene expression could result in the unintended survival of conditional lethal individuals, or the inability to identify them. To target transgene vectors to defined genomic insertion sites having minimal negative effects on gene expression and host fitness, a recombinase-mediated cassette exchange (RMCE) strategy will be developed that. RMCE will also allow for stabilization of the target site, will be tested in tephritid and mosquito species, and will aid to the development of stabilized target-site strains for conditional lethal biocontrol. This will include a molecular and organismal evaluation of an RNAi-based lethality approach. Lethality based on an RNAi mechanism in the proposed insects would increase the species specificity and having multiple targets for lethality versus one target in existing systems. By seeking to improve transgene expressivity and stabilization of transposon-based vector systems, this proposal specifically addresses issues related to new GE insects by reducing their unintended spread after field release, and by limiting the possibilities for transgene introgression.
The hypothesis that the dark septate root endophyte Phialocephala fortinii provides biological control of Phytophthora diseases to trees is tested under two temperature regimes. Phytophthora spp. are very aggressive plant pathogens affecting also woody plants in the natural environment. Studies on biological control of Phytophthora diseases are scarce, but antagonistic effects of endophytic fungi have been demonstrated in a few cases. In temperate and boreal forests, conifers are much less susceptible to Phytophthora diseases than deciduous broadleaf trees, whereas their roots are very frequently colonized by dark septate endophytes (DSE) with Phialocephala fortinii s.l., a supposedly asexual ascomycete, being the dominant component. This fungus also colonizes hardwoods, but to a lesser degree. Recent population genetic studies showed that P. fortinii s.l. consists of at least 15 reproductively isolated cryptic species (CSP). We hypothesise that P. fortinii s.l. may protect its host from Phytophthora disease depending on CSP and environmental conditions. A model system will be developed and applied to test this hypothesis using Norway spruce (Picea abies), beech (Fagus sylvatica) and Phytophthora citricola. The experimental program will be multidisciplinary in approach and include molecular, mycological, phytopathological (infection experiments, epifluorescence microscopy) and statistical methods.
Bamboos (Poaceae) are widespread in tropical and subtropical forests. Particularly in Asia, bamboos are cultivated by smallholders and increasingly in large plantations. In contrast to trees, reliable assessments of water use characteristics for bamboo are very scarce. Recently we tested a set of methods for assessing bamboo water use and obtained first results. Objectives of the proposed project are (1) to further test and develop the methods, (2) to compare the water use of different bamboo species, (3) to analyze the water use to bamboo size relationship across species, and (4) to assess effects of bamboo culm density on the stand-level transpiration. The study shall be conducted in South China where bamboos are very abundant. It is planned to work in a common garden (method testing), a botanical garden (species comparison, water use to size relationship), and on-farm (effects of culm density). Method testing will include a variety of approaches (thermal dissipation probes, stem heat balance, deuterium tracing and gravimetry), whereas subsequent steps will be based on thermal methods. The results may contribute to an improved understanding of bamboo water use characteristics and a more appropriate management of bamboo with respect to water resources.
Background: Ghanas transition forests, neighbouring savannahs and timber plantations in the Ashanti region face a constant degradation due to the increased occurrence of fires. In most cases the fires are deliberately set by rural people for hunting purposes. Main target is a cane rat, here called grasscutter (Thryonomys swinderianus), whose bushmeat is highly esteemed throughout the country. The animal is a wild herbivorous rodent of subhumid areas in Africa south of the Sahara. The grasscutter meat is an important source of animal protein. Existing high-value timber plantations (mainly Teak, Tectona grandis) are affected by fires for hunting purposes. Thus resulting in growth reduction, loss of biomass or even complete destruction of the forest stands. It became obvious that solutions had to be sought for the reduction of the fire risk. Objectives: Since 2004 the Institute for World Forestry of the Federal Research Centre for Forestry and Forest Products, Hamburg, Germany is cooperating with a Ghanaian timber plantation company (DuPaul Wood Treatment Ltd.) the German Foundation for Forest Conservation in Africa (Stiftung Walderhaltung in Afrika) and the Center for International Migration with the purpose to improve the livelihood of the rural population in the surroundings of the forest plantation sites and simultaneously to safeguard and improve the timber plantations. The introduction of grasscutter rearing systems to local farmers accompanied by permanent agricultural and agroforestry practices appeared to be a promising approach for the prevention of fires in the susceptible areas. Additionally a functioning grasscutter breeding system could contribute to the improvement of food security, development of income sources and the alleviation of poverty. The following measures are implemented: - Identification of farmers interested in grasscutter captive breeding, - Implementation of training courses for farmers on grasscutter rearing, - Delivery of breeding animals, - Supervision of rearing conditions by project staff, - Development of a local extension service for monitoring activities, - Evaluation of structures for grasscutter meat marketing. Results: After identification of key persons for animal rearing training courses were successfully passed and animals were delivered subsequently. Further investigations will evaluate the effects of the grasscutter rearing in the project region. This will be assessed through the - Acceptance of grasscutter rearing by farmers, - Success of the animal caging, - Reproduction rate, - Meat quality, - Marketing success of meat, - Reduction of fire in the vicinity of the timber plantations, - Improvement of peoples livelihood.
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