Characteristics of temporal variability of urban ecosystem-atmosphere CO2, CH4, and N2O fluxes

Understanding the origin and mechanisms controlling GHGs (CO2, CH4 and N2O) emission spatially and temporally is critical for evaluating future climate changes. Whether the controls on GHG dynamics in urban ecosystem are similar to those in natural ecosystems are not fully understood. In the current study, the aboveground (cover vegetation + soil) and soil (including autotrophic and heterotrophic) CO2, N2O and CH4 fluxes and respective carbon stable isotopic composition (delta C-13) of respired CO2 at natural abundance level were simultaneously measured from a reestablished grassland in the urban area of central Germany. The static chamber system (combination of transparent and opaque modes) was applied to assess the effects of intensive vegetation growth during two weeks of April 2017. The values of CO2 fluxes obtained with both transparent and opaque chambers differed significantly due to the combined effects of the incoming photosynthetically active radiation (PAR) and temperature on vegetation and belowground processes. The average value of measured CO2 flux with opaque chambers was 9.14 +/- 1.9 (mg m(-2) min(-1)) vs. 2.37 +/- 0.9 (mg m(-2) min(-1)) with transparent chambers for the re-established grassland. In contrast, soil CH4, as well as N2O fluxes were not different significantly for both opaque-transparent chamber measurements. Current magnitude provides the pattern of the urban ecosystem source/sinks potential during ambient light conditions.