Increased methane uptake but unchanged nitrous oxide flux in montane grasslands under simulated climate change conditions

Montane grasslands of Central Europe are expected to be exposed to strong warming and to altered precipitation patterns, suggesting that biosphere-atmosphere-hydrosphere exchange of carbon (C) and nitrogen (N) compounds may be vulnerable to future climatic conditions. By transferring small lysimeters along an altitudinal gradient, we assessed the impact of climate change conditions on soil-atmosphere exchange of methane (CH4) and nitrous oxide (N2O) as well as on ammonium (NH4+) and nitrate (NO3-) in soil water in extensively managed montane grassland in southern Germany. Lysimeter transfer to lower altitude increased air and soil temperatures by more than 2 degrees C and reduced summer precipitation as well as soil moisture throughout the year compared with a control transfer within the high altitude site. This simulation of climate change conditions almost doubled the CH4 sink strength from -0.11 to -0.19gCm(-2)year(-1), which appeared to be mainly related to improved gas diffusion after reduced soil moisture. Mean NH4+ and NO3- concentrations in soil water (0.05mg NH4+-Nl(-1) and 0.08mg NO3--Nl(-1)) and N2O emissions (approximately 0.03gNm(-2)year(-1)) remained small and unaffected by climate change simulation. Our study suggests that expected climate change conditions will have positive effects on the non-CO2 greenhouse gas balance in extensively managed montane grassland because of increased net CH4 uptake in soil. For N2O emission, we conclude that potential effects of management changes may override the small effects of simulated climate change on N2O emissions observed in this study

On particulate characterization in a heavy-duty diesel engine by time-resolved laser-induced incandescence

Contains fulltext : 35588.pdf (publisher's version ) (Closed access)Time-resolved laser-induced incandescence (TR-LII) measurements have been performed inside the combustion chamber of a heavy-duty diesel engine running at low load and with regular diesel fuel. The LII traces were interpreted in terms of primary particle sizes, comparing two different assumed particle-size distributions: a mono-disperse and a log-normal distribution. The initial temperature of the particles (immediately after the laser pulse) is estimated by two-color pyrometry. We conclude that the initial temperature of the particles is not very critical for the outcome of the fitting procedure for the (mean) radius. Under the high-pressure conditions in the engine, the time dependence of the LII intensity contains sufficient structure to allow retrieval of details of the particle-size distribution