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 "Food-web and ecosystem responses to global change: testing ecological theory in aquatic mesocosms" wird vom Umweltbundesamt gefördert und von Eawag - Das Wasserforschungsinstitut des ETH-Bereichs durchgeführt. How will the current rate and spatial extent of environmental change affect the functioning of future ecosystems? Food webs are structurally diverse and are remarkably persistent despite multifaceted and spatially variable environmental change. Ecological theory posits that the structural complexity of food webs will help ecosystems weather environmental change, but few experiments have tested this idea. To truly understand how ecosystems and their constituent food webs will respond, we must explore, experimentally, how environmental change affects the structure of food webs, for example the number of species and the interactions among them, and, consequently, the the functioning of ecosystems, for example, the rates of biomass production, decomposition, and sequestration. Our proposed research focuses on the environmental changes associated with rising levels of dissolved organic carbon (DOC) in freshwater ecosystems, but also considers climate warming, eutrophication, and changes in biodiversity. As microbial communities closely regulate the decomposition of DOC, we propose to examine the effect of changes in the environment and in the architecture of food webs on the composition of microbial communities, including viruses and prokaryotes. In doing so, we can link the ecological structure and evolutionary dynamics of food webs to the biogeochemistry of ecosystems. We propose a series of experiments to test how environmental change affects the complex interactions between food web assemblages and ecosystem functioning. The experiments test predictions from three bodies of ecological theory, namely the theory of biodiversity and ecosystem functioning, the theory of evolving metacommunities, and the landscape theory of food-web structure. These theories provide a strong foundation for understanding interactions between environmental change, food-web architecture, and ecosystem functioning, but they fail to fully address the feedbacks between structural changes of food-webs at upper trophic levels (e.g. plankton and fish) and the biogeochemistry of ecosystems that is regulated by microbial communities. Our experiments bridge this gap, and will improve our ability to predict how entire ecosystems respond to environmental change.