Land-use intensification and agroforestry in the Kenyan highland: impacts on soil microbial community composition and functional capacity

This study investigates microbial communities in soil from sites under different land use in Kenya. We sampled natural forest, forest plantations, agricultural fields of agroforestry farms,agricultural fields with traditional farming and eroded soil on the slopes of Mount Elgon,Kenya. We hypothesised that microbial decomposition capacity, biomass and diversity 1)decreases with intensified cultivation; and 2)can be restored by soil and land management in agroforestry. Functional capacity of soil microbial communities was estimated by degradation of 31 substrates on Biolog EcoPlates™. Microbial community composition and biomass were characterised by phospholipid fatty acid (PLFA)and microbial C and N analyses. All 31 substrates were metabolised in all studied soil types, i.e. functional diversity did not differ. However,both the substrate utilisation rates and the microbial biomass decreased with intensification of land use, and the biomass was positively correlated with organic matter content. Multivariate analysis of PLFA and Biolog EcoPlate™ data showed clear differences 25 between land uses, also indicated by different relative abundance of PLFA markers for certain microorganism groups. In conclusion, our results show that vegetation and land use control the substrate utilisation capacity and microbial community composition and that functional capacity of depleted soils can be restored by active soil management, e.g. forest plantation. However, although 20 to 30 years of agroforestry farming practises did result in improved soil microbiological and chemical conditions of agricultural soil as compared to traditional agricultural fields, the change was not statistically significant

Entwicklungsperspektiven der ökologischen Landwirtschaft in Deutschland (Langversion)

Unsere heutige Landwirtschaft muss nachhaltiger werden um die negativen Umweltwirkungen der derzeitigen Anbaupraktiken, wie beispielsweise Biodiversitätsverlust oder Nitratbelastung, zu verringern. Gleichzeitig muss die Produktivität gesteigert werden. In diesem Video erklären Prof. Urs Niggli und Judith Riedel vom FiBL sowie Knut Ehlers vom deutschen Umweltbundesamt, wie Lösungen und Wege zu einem nachhaltigen Landwirtschaftssystem in Deutschland aussehen können. Ihre Analyse basiert auf der umfassenden Studie „Entwicklungsperspektiven der ökologischen Landwirtschaft in Deutschland“, die für die biologische als auch für die konventionelle Landwirtschaft Entwicklungsszenarien formuliert

Interface energy determination for the fully coherent β'' phase in Al-Mg-Si: making a case for a first principles based hybrid atomistic modelling scheme

Multiscale modelling of hardening precipitate interfaces in alloy design This project will develop a new multiscale modelling scheme used to investigate hardening precipitate interfaces in metal alloys. The major aim is to contribute to the fundamental understanding of precipitates and their interfaces in order to predict materials properties. The main idea is to combine models and important physics at different levels, from quantum mechanics and first principle density functional theory to continuum in a seamless integrated multiscale framework capable of predicting the evolution of the precipitate size distribution during heat treatment. A better understanding and control over this evolution would clear the way for major improvements in processing and alloy design. The project is a close collaboration between university and institute sector with validation performed by industry. Especially the fundamental parts of the project are computer intensive and hence urge the need for high performance computing facilities

FATIGUE STRENGTH OF FIXED OFFSHORE STRUCTURES UNDER VARIABLE AMPLITUDE LOADING DUE TO WIND, WAVE, AND ICE ACTION

Fixed offshore wind turbines are increasingly developed for high latitude areas where not only wind and wave loads need to be considered, but also moving sea ice. Current structural design rules do not adequately consider the effect of ice loading on fatigue life, due to missing studies on fatigue strength of welded joints under combined wind, wave, and ice action. Thus, a methodology to determine combined variable-amplitude loading (VAL) spectra was developed in a previous study. The stress state time-history at an exemplarily selected point in the support structure of an offshore wind energy monopile was translated into a VAL sequence. This sequence is used as an input for fatigue tests of butt-welded joints in the current study. The current study presents the VAL spectrum and the corresponding VAL time series, the results of the fatigue tests and compares them to typical fatigue damage sums for other stress spectr

Fatigue Strength Of Fixed Offshore Structures Under Variable Amplitude Loading Due To Wind, Wave, And Ice Action

Fixed offshore wind turbines are increasingly developed for high latitude areas where not only wind and wave loads need to be considered, but also moving sea ice. Current structural design rules do not adequately consider the effect of ice loading on fatigue life, due to missing studies on fatigue strength of welded joints under combined wind, wave, and ice action. Thus, a methodology to determine combined variable-amplitude loading (VAL) spectra was developed in a previous study. The stress state time-history at an exemplarily selected point in the support structure of an offshore wind energy monopile was translated into a VAL sequence. This sequence is used as an input for fatigue tests of butt-welded joints in the current study. The current study presents the VAL spectrum and the corresponding VAL time series, the results of the fatigue tests and compares them to typical fatigue damage sums for other stress spectra

Fatigue Strength Of Fixed Offshore Structures Under Variable Amplitude Loading Due To Wind, Wave, And Ice Action

Fixed offshore wind turbines are increasingly developed for high latitude areas where not only wind and wave loads need to be considered, but also moving sea ice. Current structural design rules do not adequately consider the effect of ice loading on fatigue life, due to missing studies on fatigue strength of welded joints under combined wind, wave, and ice action. Thus, a methodology to determine combined variable-amplitude loading (VAL) spectra was developed in a previous study. The stress state time-history at an exemplarily selected point in the support structure of an offshore wind energy monopile was translated into a VAL sequence. This sequence is used as an input for fatigue tests of butt-welded joints in the current study. The current study presents the VAL spectrum and the corresponding VAL time series, the results of the fatigue tests and compares them to typical fatigue damage sums for other stress spectra.Accepted Author ManuscriptOffshore Engineerin

Development of Combined Load Spectra for Offshore Structures Subjected to Wind, Wave, and Ice Loading

Fixed offshore wind turbines continue to be developed for high latitude areas where not only wind and wave loads need to be considered but also moving sea ice. Current rules and regulations for the design of fixed offshore structures in ice-covered waters do not adequately consider the effects of ice loading and its stochastic nature on the fatigue life of the structure. Ice crushing on such structures results in ice-induced vibrations, which can be represented by loading the structure using a variable-amplitude loading (VAL) sequence. Typical offshore load spectra are developed for wave and wind loading. Thus, a combined VAL spectrum is developed for wind, wave, and ice action. To this goal, numerical models are used to simulate the dynamic ice-, wind-, and wave-structure interaction. The stress time-history at an exemplarily selected critical point in an offshore wind energy monopile support structure is extracted from the model and translated into a VAL sequence, which can then be used as a loading sequence for the fatigue assessment or fatigue testing of welded joints of offshore wind turbine support structures. This study presents the approach to determine combined load spectra and standardized time series for wind, wave, and ice action.Offshore Engineerin