EPOS : evolving personal to organizational knowledge spaces

EPOS will leverage the user´s personal workspace with its manyfold native information structures to his personal knowledge space and in cooperation with other personal workspaces contribute to the organizational knowledge space which is represented in the organizational memory. This first milestone presents results from the project´s first year in the areas of the personal informational model, user observation for context elicitation, collaborative information retrieval and information visualization

Intensive slurry management and climate change promote nitrogen mining from organic matter-rich montane grassland soils

Aims Consequences of climate change and land use intensification on the nitrogen (N) cycle of organic-matter rich grassland soils in the alpine region remain poorly understood. We aimed to identify fates of fertilizer N and to determine the overall N balance of an organic-matter rich grassland in the European alpine region as influenced by intensified management and warming. Methods We combined 15N cattle slurry labelling with a space for time climate change experiment, which was based on translocation of intact plant-soil mesocosms down an elevational gradient to induce warming of +1 °C and + 3 °C. Mesocosms were subject to either extensive or intensive management. The fate of slurry-N was traced in the plant-soil system. Results Grassland productivity was very high (8.2 t - 19.4 t dm ha$^{-1}$ yr$^{-1}$), recovery of slurry $^{15}$N in mowed plant biomass was, however, low (9.6–14.7%), illustrating low fertilizer N use efficiency and high supply of plant available N via mineralization of soil organic matter (SOM). Higher 15N recovery rates (20.2–31.8%) were found in the soil N pool, dominated by recovery in unextractable N. Total $^{15}$N recovery was approximately half of the applied tracer, indicating substantial loss to the environment. Overall, high N export by harvest (107–360 kg N ha$^{-1}$ yr$^{-1}$) markedly exceeded N inputs, leading to a negative grassland N balance. Conclusions Here provided results suggests a risk of soil N mining in montane grasslands, which increases both under climate change and land use intensification

EPOS : evolving personal to organizational knowledge spaces

EPOS will leverage the user´s personal workspace with its manyfold native information structures to his personal knowledge space and in cooperation with other personal workspaces contribute to the organizational knowledge space which is represented in the organizational memory. This first milestone presents results from the project´s first year in the areas of the personal informational model, user observation for context elicitation, collaborative information retrieval and information visualization

Nitrate leaching and soil nitrous oxide emissions diminish with time in a hybrid poplar short-rotation coppice in southern Germany

Hybrid poplar short-rotation coppices (SRC) provide feedstocks for bioenergy production and can be established on lands that are suboptimal for food production. The environmental consequences of deploying this production system on marginal agricultural land need to be evaluated, including the investigation of common management practices i.e., fertilization and irrigation. In this work, we evaluated (1) the soil-atmosphere exchange of carbon dioxide, methane, and nitrous oxide (N$_{2}$O); (2) the changes in soil organic carbon (SOC) stocks; (3) the gross ammonification and nitrification rates; and (4) the nitrate leaching as affected by the establishment of a hybrid poplar SRC on a marginal agricultural land in southern Germany. Our study covered one 3-year rotation period and 2 years after the first coppicing. We combined field and laboratory experiments with modeling. The soil N$_{2}$O emissions decreased from 2.2 kg N$_{2}$O-N ha$^{-1}$ a$^{-1}$ in the year of SRC establishment to 1.1–1.4 kg N$_{2}$ON ha$^{-1}$ a$^{-1}$ after 4 years. Likewise, nitrate leaching reduced from 13 to 1.5–8 kg N ha$^{-1}$ a$^{-1}$. Tree coppicing induced a brief pulse of soil N$_{2}$O flux and marginal effects on gross N turnover rates. Overall, the N losses diminished within 4 years by 80% without fertilization (irrespective of irrigation) and by 40% when 40–50 kg N ha$^{-1}$ a$^{-1}$ were applied. Enhanced N losses due to fertilization and the minor effect of fertilization and irrigation on tree growth discourage ist use during the first rotation period after SRC establishment. A SOC accrual rate of 0.4 Mg C ha$^{-1}$ a$^{-1}$(uppermost 25 cm, P = 0.2) was observed 5 years after the SRC establishment. Overall, our data suggest that SRC cultivation on marginal agricultural land in the region is a promising option for increasing the share of renewable energy sources due to its net positive environmental effects

An improved 15^{15} N tracer approach to study denitrification and nitrogen turnover in soil incubations

RationaleDenitrification (the reduction of oxidized forms of inorganic nitrogen (N) to N2O and N2) from upland soils is considered to be the least well-understood process in the global N cycle. The main reason for this lack of understanding is that the terminal product (N2) of denitrification is extremely difficult to measure against the large atmospheric background.MethodsWe describe a system that combines the 15N-tracer technique with a 40-fold reduced N2 (2% v/v) atmosphere in a fully automated incubation setup for direct quantification of N2 and N2O emissions. The δ15N values of the emitted N2 and N2O were determined using a custom-built gas preparation unit that was connected to a DELTA V Plus isotope ratio mass spectrometer. The system was tested on a pasture soil from sub-tropical Australia under different soil moisture conditions and combined with 15N tracing in extractable soil N pools to establish a full N balance.ResultsThe method proved to be highly sensitive for detecting N2 (1.12 μg N h−1 kg−1 dry soil (ds)) and N2O (0.36 μg N h−1 kg−1 ds) emissions. The main end product of denitrification in the investigated soil was N2O for both water contents, with N2 accounting for only 3% to 13% of the total denitrification losses. Between 90 and 95% of the added 15N fertiliser could be recovered in N gases and extractable soil N pools