Das Projekt "Einfluss von Dürre auf das Waldsterben in Europa und Westkanada (Water03 - IDDEC)" wird vom Umweltbundesamt gefördert und von Technische Universität München, Wissenschaftszentrum Weihenstephan für Ernährung, Landnutzung und Umwelt, Fachgebiet für Ökoklimatologie durchgeführt. While many forests and woodlands may be at increasing risk of climate-induced dieback, significant knowledge gaps remain in our understanding of the causes of climate-induced tree mortality. Recent publications underscore the critical importance of understanding the mechanisms that trigger plant mortality (Adams et al., 2009), particularly regarding features and traits that could be used as physiological indicators of tree death (McDowell et al., 2008). Alterations in wood formation and structure often occur prior to visual symptoms of crown decline. Thus, physiological, morphological, and anatomical traits related to xylem ('water-conducting pipes') may provide early-warning signals of drought-induced dieback. A better mechanistic understanding of drought-induced forest dieback would improve our ability to predict tree mortality and future changes in forest composition and coverage. The project aims at studying how drought episodes promote dieback via changes in xylem structure. Different genotypes of aspen (parkland region and the southern boundary of the boreal forest in western Canada), oak (Southern Europe) and pine (experiment) will be studied along gradients of moisture availability. Xylem-related traits that will be measured include ring-width, number of missing rings, quantitative wood anatomical structures (diameter and frequency of vessels/ tracheids, inter-vessel pit structure) as well as cavitation resistance, hydraulic conductivity, and water potentials.
Das Projekt "Effects of biochar amendment on plant growth, microbial communities and biochar decomposition in agricultural soils" wird vom Umweltbundesamt gefördert und von Forschungsinstitut für biologischen Landbau Deutschland e.V. durchgeführt. Biochar has a great potential to ameliorate arable soils, especially those that are low in organic matter due to intensive use or erosion. Biochar is carbonised organic material with high porosity that brings about changes in physical, chemical and biological soil functions. Biochar amended soils show a higher water and cation exchange capacity with reduced leaching and enhanced availability of plant nutrients. The microbial biomass in biochar amended soils is enhanced and more diverse. Biochar is stabilised organic material, which is likely to remain for hundreds of years in the soil. Photosynthetically fixed atmospheric CO2 stabilised in biochar may thus act as a direct carbon sink and help to mitigate climate change. As feedstock and production conditions produce different biochar qualities predictions of effects in soil need to consider biochar and soil properties case by case. To date biochar has been approved to ameliorate highly weathered tropical soils with positive effects on crop growth and yield. Distinct microbial groups were reported to be enhanced in soils but if this depends on the particular soil or biochar or a combination of both is an open question, especially in temperate climates. Likewise, it is not known if microorganisms colonising biochar surfaces are responsible for its mineralization or if they just use the new niches provided. The aim of the proposed project is to investigate the influence of two biochar types on soil-plant systems by determining i) soil nutrient availability, plant growth and nutrient uptake, ii) structure and function of soil microbial communities, iv) the decomposition and fate of biochar in soils. We will use two loessial soils from the well-known DOK-trial with different soil organic matter content. Other soils from the region will be selected to provide a wider range of soil quality, in particular pH. The biochars will be produced by pyrolysis and hydrothermal carbonization (HTC) from the C4-plant Miscanthus gigantea. Pyrolysis derived material has bigger pore sizes due to the evaporating gasses and is commonly alkaline, whereas the HTC derived biochar has a finer pore size, a much higher oxygen content and more acidic functional groups.
Das Projekt "Changing ground water levels: the impact on an invasive species and native plant communities in a Mediterranean dune ecosystem" wird vom Umweltbundesamt gefördert und von Universität Bayreuth, Fachgruppe Geowissenschaften, Bayreuther Zentrum für Ökologie und Umweltforschung (BayCEER), Lehrstuhl für Agrarökosystemforschung durchgeführt. The introduction of non-native species and its spread are recognized to be one of the major threats to biodiversity and ecosystem functioning. Climate change is expected to enhance ecosystem invasibility through changes in resource availability (e.g. water) and the risks of desertification in Mediterranean areas, however scientific studies are rare. This project will evaluate specific traits of a characteristic invader towards competition for limited resources and the consequent alteration of community functioning under decreasing ground water availability. We selected a protected Mediterranean costal dune system of high ecological value, where large-scale extraction of ground water provides excellent experimental conditions to study changes in the competitive balances among invasive and native species. We will analyse the effects i) at the seedling level to evaluate changes in plant establishment; ii) at the plant level to gain major insights on the spatial and temporal partitioning of water sources and regulating mechanisms of selected species and iii) at the community level to evaluate changes in water flow, competition and facilitation (e.g. hydraulic lift), community functioning, and changes in invasibility of the system. The aim is the identification of key processes controlling the competitive balances between invasive neophytes and native species and invasibility of semi-arid systems to contribute to a risk assessment under global change scenarios.
Das Projekt "Large-Area CIS Based Thin-Film Solar Modules for Highly Productive Manufacturing (LARCIS)" wird vom Umweltbundesamt gefördert und von Zentrum für Sonnenenergie- und Wasserstoff-Forschung Baden-Württemberg durchgeführt. Objective: In order for the commercial production of large CIGS modules on the multi-MW scale to be successful, the processes must still be streamlined and optimised taking considering both economical and ecological aspects. This project aims to support the developme nt of this material- and energy-saving thin-film technology so it can gain a foothold in the free PV market. Promising laboratory results will be transferred to large-scale production, where the availability of appropriate production equipment and very hig h material and process yields are of decisive importance. 4 universities, 2 research institutes, and 4 companies will work closely together in order to merge the physical understanding of the processes and the engineering know-how, which are necessary for up-scaling the CIGS technology to a marketable multi-megawatt production volume. We will focus on: (1) very high-quality modules manufactured by coevaporation of CIGS and applying cost-effective methods, ETA up to 14 Prozent on 0.7 m2; (2) the development of Cd-free buffer layers for Cd-free CIGS modules on an area of up to 0.7 m2, ETA up to 12 Prozent; (3) and the development of a mid-term alternative: electrodeposition of low-cost CIS modules with ETA above 10 Prozent (estimated cost about 0.8 E/Wp). We will transfer the Mo back contact sputtering know-how to a specialised European large-area glass coater to provide substrates for both the coevaporation and the electrodeposition approaches. All process developments such as modifications of the back contact, wet- or vacuum-deposited buffer layers, the multi-stage coevaporation of CIGS, or improved Ga incorporation in electrodeposited absorbers will first be tested and evaluated on the laboratory scale. Successful approaches will be up-scaled and transferred to three independ ent commercial CIGS pilot lines located in three different European countries. Novel process and quality control techniques must also be developed and applied to reach these ambitious goals.
Das Projekt "Biological Regulation of Subsoil C-cycling under Field Conditions" wird vom Umweltbundesamt gefördert und von Universität Hohenheim, Institut für Bodenkunde und Standortslehre, Fachgebiet Bodenbiologie durchgeführt. The nature of the microbial communities inhabiting the deeper soil horizons is largely unknown. It is also not clear why subsurface microorganisms do not make faster use of organic compounds under field conditions. The answer could be provided by a reciprocal soil transfer experiment studying the response of transferred soils to fluctuations in microclimate, organic inputs, and soil biota. The subproject P9 will be responsible for the establishment of reciprocal transfer experiments offering a strong link between subgroups interested in organic matter quality, transport of organic substances, as well as functions of the soil microbial community. A single, high molecular weight substrate (13C labelled cellulose) will be applied at two different levels in the pre-experiment to understand the dose-dependent reaction of soil microorganisms in transferred surface and sub-soils. Uniformly 13C labelled beech roots - representing complex substrates - will be used for the main reciprocal soil transfer experiment. We hypothesize that transferring soil cores between subsoil and surface soil as well as addition of labelled cellulose or roots will allow us to evaluate the relative impact of surface/subsurface habitat conditions and resource availability on abundance, function, and diversity of the soil microbial community. The second objective of the subproject is to understand whether minerals buried within different soil compartments (topsoil vs. subsoil) in the field contribute to creation of hot spots of microbial abundance and activity within a period of two to five years. We hypothesize that soil microorganisms colonize organo-mineral complexes depending on their nutritional composition and substrate availability. The existence of micro-habitat specific microbial communities could be important for short term carbon storage (1 to 6 years). The third objective is to understand the biogeography and function of soil microorganisms in different subsoils. Parent material as well as mineral composition might control niche differentiation during soil development. Depending on size and interconnectedness of niches, colonization and survival of soil microbial communities might be different in soils derived from loess, sand, terra fusca, or sandstone. From the methodological point of view, our specific interest is to place community composition into context with soil microbial functions in subsoils. Our subgroup will be responsible for determining the abundance, diversity, und function of soil microorganisms (13C microbial biomass, 13C PLFA, enzyme activities, DNA extraction followed by quantitative PCR). Quantitative PCR will be used to estimate total abundances of bacteria, archaea and fungi as well as abundances of specific groups of bacteria at high taxonomic levels. We will apply taxa specific bacterial primers because classes or phyla might be differentiated into ecological categories on the basis of their life strategies.
Das Projekt "The detritusphere as the biogeochemical interface for bacterial and fungal degradation of MCPA" wird vom Umweltbundesamt gefördert und von Universität Hohenheim, Institut für Bodenkunde und Standortslehre durchgeführt. The detritusphere is an excellent model to study microbial-physicochemical interactions during degradation of the herbicide MCPA. Whereas during the first phase of SPP 1315 we focused on bacterial and fungal abundance at the soil litter interface and carbon flow between different compartments, the second phase will be devoted to elucidating complex regulation mechanisms of MCPA degradation in the detritusphere: (1) At the cellular level, co-substrate availability and laccase abundance might be important regulators, (2) at the community level, bacteria harbouring different classes of tfdA genes might control degradation of MCPA and (3) at the microhabitat level, interaction between MCPA degraders and organo-mineral surfaces as well as transport processes might be important regulators. The concept of hierarchical regulation of MCPA degradation will be included into the modelling of small-scale microbial growth, MCPA transport and MCPA degradation near the soil-litter interface.
Das Projekt "Spatial heterogeneity and substrate availability as limiting factors for subsoil C-turnover" wird vom Umweltbundesamt gefördert und von Universität Bochum, Geographisches Institut durchgeführt. In subsoils, organic matter (SOM) concentrations and microbial densities are much lower than in topsoils and most likely highly heterogeneously distributed. We therefore hypothesize, that the spatial separation between consumers (microorganisms) and their substrates (SOM) is an important limiting factor for carbon turnover in subsoils. Further, we expect microbial activity to occur mainly in few hot spots, such as the rhizosphere or flow paths where fresh substrate inputs are rapidly mineralized. In a first step, the spatial distribution of enzyme and microbial activities in top- and subsoils will be determined in order to identify hot spots and relate this to apparent 14C age, SOM composition, microbial community composition and soil properties, as determined by the other projects within the research unit. In a further step it will be determined, if microbial activity and SOM turnover is limited by substrate availability in spatially distinct soil microsites. By relating this data to root distribution and preferential flow paths we will contribute to the understanding of stabilizing and destabilizing processes of subsoil organic matter. As it is unclear, at which spatial scale these differentiating processes are effective, the analysis of spatial variability will cover the dm to the mm scale. As spatial segregation between consumers and substrates will depend on the pore and aggregate architecture of the soil, the role of the physical integrity of these structures on SOM turnover will also be investigated in laboratory experiments.
Das Projekt "Steady-State Dilution and Mixing-Controlled Reactions in Three-Dimensional Heterogeneous Porous" wird vom Umweltbundesamt gefördert und von Eberhard Karls Universität Tübingen, Zentrum für Angewandte Geowissenschaften (ZAG), Arbeitsgruppe Hydrogeology durchgeführt. Understanding transport of contaminants is fundamental for the management of groundwater re-sources and the implementation of remedial strategies. In particular, mixing processes in saturated porous media play a pivotal role in determining the fate and transport of chemicals released in the subsurface. In fact, many abiotic and biological reactions in contaminated aquifers are limited by the availability of reaction partners. Under steady-state flow and transport conditions, dissolved reactants come into contact only through transverse mixing. In homogeneous porous media, transverse mixing is determined by diffusion and pore-scale dispersion, while in heterogeneous formations these local mixing processes are enhanced. Recent studies investigated the enhancement of transverse mixing due to the presence of heterogeneities in two-dimensional systems. Here, mixing enhancement can solely be attributed to flow focusing within high-permeability inclusions. In the proposed work, we will investigate mixing processes in three dimensions using high-resolution laboratory bench-scale experiments and advanced modeling techniques. The objective of the proposed research is to quantitatively assess how 3-D heterogeneity and anisotropy of hydraulic conductivity affect mixing processes via (i) flow focusing and de-focusing, (ii) increase of the plume surface, (iii) twisting and intertwining of streamlines and (iv) compound-specific diffusive/dispersive properties of the solute species undergoing transport. The results of the experimental and modeling investigation will allow us to identify effective large-scale parameters useful for a correct description of conservative and reactive mixing at field scales allowing to explain discrepancies between field observations, bench-scale experiments and current stochastic theory.
Das Projekt "Flooding, sediment and salt transport in the Okavango Delta, Botswana. Improved quantitative understanding based on remote sensing and airborne geophysics" wird vom Umweltbundesamt gefördert und von Eidgenössische Technische Hochschule Zürich, Professur für Siedlungswasserwirtschaft, Institut für Umweltingenieurwissenschaften durchgeführt. The Okavango is a large African wetland of prime ecological importance. Its existence is in jeopardy due to upstream development and increasing water demand in combination with predicted climatic change. Less water means a reduction of the permanent and seasonal swamp areas. The project creates a computer model serving as a tool to predict the impact of upstream hydraulic measures, channel management and changes in climate on the availability of water in the delta and its spatial distribution. It also looks at the sediment transport. The availability of water e.g. expressed by the frequency of flooding at a location is essential for the type of habitat prevailing at that point. Changes of water availability will therefore also cause changes in the habitat composition of the delta. Management of channels by cutting of papyrus or dredging will change the distribution of flooded areas. The interaction of the channels of the Okavango Delta with the floodplains and the underlying groundwater is of crucial importance. Vegetation on the islands gets its water through infiltration from the river channels and the yearly flood propagates both in the channels and in the groundwater. Therefore the model couples the surface water flow - in channels and overland during flooding - with the groundwater flow. In a region with little infrastructure it is hard to find data for this modelling effort. However, nowadays many data can be found through remote sensing techniques both from satellite and airborne platforms. These include the topography (from the Shuttle Mission), the rainfall (from METOESAT 5), the evapotranspiration (from NOAA-AVHRR) and the extension of water surfaces in their temporal development (from radar satellites and others). The thickness of the groundwater body is evaluated from aeromagnetic records provided by the geological Survey of Botswana. The infiltration zones can be seen through another airborne geophysical technique, the TEM-method. This survey is financed by the Botswanan government and will take place in April 2007. All satellite and airborne information needs calibration and interpretation through ground truth which is obtained in yearly field campaigns. The water areas serve as data for the adjustment and verification of the model. The insight gained through the model will flow into the work of the Okavango River Commission (OKACOM) which has to negotiate the permissible water use in the upstream.
Das Projekt "Calcium cycling in the soil-fig-bat compartment of a neotropical rain forest on spatially heterogeneous substrate" wird vom Umweltbundesamt gefördert und von Universität Bern, Geographisches Institut, Gruppe Bodenkunde durchgeführt. Calcium supply in tropical soils is variable and frequently low. In spite of the heterogeneous Ca supply, some plant species, such as figs, maintain high Ca concentrations in their tissues. Figs are keystone species with more than proportional importance for the functioning of a tropical rain forest. High Ca concentrations in fig fruits may render them particularly attractive for frugivorous vertebrates. We propose to study the whole Ca cycling from soil through a selected fig species, Ficus insipida Willd. and frugivorous bats, their main dispersers, back to soil. The study will be conducted in Panama on sites differing in soil Ca status to assess the importance of soil Ca availability for fig fruit content and bat reproduction. We will quantify aboveground Ca fluxes for 16 trees along a gradient of Ca availability in soil. We will determine (1) Ca concentrations in soils, figs and leaves, (2) nutritional quality of fig and other bat-dispersed fruits and their importance for Ca balance in relation to reproduction of fruit-eating bats, (3) Ca fluxes with litterfall, throughfall, stemflow, bat pellets and faeces, (4) the importance of the contribution of bats to the Ca cycle of individual fig trees, and (5) the effect of fig trees on soil Ca concentrations.
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