@article{KlausKleinebeckerHoelzeletal.2011,
  author    = {Klaus, Valentin H. and Kleinebecker, Till and Hoelzel, Norbert and Bluethgen, Nico and Boch, Steffen and M{\"u}ller, J{\"o}rg and Socher, Stephanie A. and Prati, Daniel and Fischer, Markus},
  title     = {Nutrient concentrations and fibre contents of plant community biomass reflect species richness patterns along a broad range of land-use intensities among agricultural grasslands},
  series = {Perspectives in plant ecology, evolution and systematics},
  volume    = {13},
  journal   = {Perspectives in plant ecology, evolution and systematics},
  number    = {4},
  publisher = {Elsevier},
  address   = {Jena},
  issn      = {1433-8319},
  doi       = {10.1016/j.ppees.2011.07.001},
  pages     = {287 -- 295},
  year      = {2011},
  abstract  = {Understanding changes in biodiversity in agricultural landscapes in relation to land-use type and intensity is a major issue in current ecological research. In this context nutrient enrichment has been identified as a key mechanism inducing species loss in Central European grassland ecosystems. At the same time, insights into the linkage between agricultural land use and plant nutrient status are largely missing. So far, studies on the relationship between chemical composition of plant community biomass and biodiversity have mainly been restricted to wetlands and all these studies neglected the effects of land use. Therefore, we analyzed aboveground biomass of 145 grassland plots covering a gradient of land-use intensities in three regions across Germany. In particular, we explored relationships between vascular plant species richness and nutrient concentrations as well as fibre contents (neutral and acid detergent fibre and lignin) in the aboveground community biomass. We found the concentrations of several nutrients in the biomass to be closely linked to plant species richness and land use. Whereas phosphorus concentrations increased with land-use intensity and decreased with plant species richness, nitrogen and potassium concentrations showed less clear patterns. Fibre fractions were negatively related to nutrient concentrations in biomass, but hardly to land-use measures and species richness. Only high lignin contents were positively associated with species richness of grasslands. The N:P ratio was strongly positively related to species richness and even more so to the number of endangered plant species, indicating a higher persistence of endangered species under P (co-)limited conditions. Therefore, we stress the importance of low P supply for species-rich grasslands and suggest the N:P ratio in community biomass to be a useful proxy of the conservation value of agriculturally used grasslands.},
  language  = {en}
}
@article{BalckeHahnOswald2011,
  author    = {Balcke, Gerd U. and Hahn, M. and Oswald, Sascha},
  title     = {Nitrogen as an indicator of mass transfer during in-situ gas sparging},
  series = {Journal of contaminant hydrology},
  volume    = {126},
  journal   = {Journal of contaminant hydrology},
  number    = {1-2},
  publisher = {Elsevier},
  address   = {Amsterdam},
  issn      = {0169-7722},
  doi       = {10.1016/j.jconhyd.2011.05.005},
  pages     = {8 -- 18},
  year      = {2011},
  abstract  = {Aiming at the stimulation of intrinsic microbial activity, pulses of pure oxygen or pressurized air were recurrently injected into groundwater polluted with chlorobenzene. To achieve well-controlled conditions and intensive sampling, a large, vertical underground tank was filled with the local unconfined sandy aquifer material. In the course of two individual gas injections, one using pure oxygen and one using pressurized air, the mass transfer of individual gas species between trapped gas phase and groundwater was studied. Field data on the dissolved gas composition in the groundwater were combined with a kinetic model on gas dissolution and transport in porous media. Phase mass transfer of individual gas components caused a temporary enrichment of nitrogen, and to a lower degree of methane, in trapped gas leading to the formation of excess dissolved nitrogen levels downgradient from the dissolving gas phase. By applying a novel gas sampling method for dissolved gases in groundwater it was shown that dissolved nitrogen can be used as a partitioning tracer to indicate complete gas dissolution in porous media.},
  language  = {en}
}