@article{PoradaTammRaggioetal.2019,
  author    = {Porada, Philipp and Tamm, Alexandra and Raggio, Jose and Yafang, Cheng and Kleidon, Axel and P{\"o}schl, Ulrich and Weber, Bettina},
  title     = {Global NO and HONO emissions of biological soil crusts estimated by a process-based non-vascular vegetation model},
  series = {Biogeosciences},
  volume    = {16},
  journal   = {Biogeosciences},
  publisher = {Copernicus Publ.},
  address   = {G{\"o}ttingen},
  issn      = {1726-4170},
  doi       = {10.5194/bg-16-2003-2019},
  pages     = {2003 -- 2031},
  year      = {2019},
  abstract  = {The reactive trace gases nitric oxide (NO) and nitrous acid (HONO) are crucial for chemical processes in the atmosphere, including the formation of ozone and OH radicals, oxidation of pollutants, and atmospheric self-cleaning. Recently, empirical studies have shown that biological soil crusts are able to emit large amounts of NO and HONO, and they may therefore play an important role in the global budget of these trace gases. However, the upscaling of local estimates to the global scale is subject to large uncertainties, due to unknown spatial distribution of crust types and their dynamic metabolic activity. Here, we perform an alternative estimate of global NO and HONO emissions by biological soil crusts, using a process-based modelling approach to these organisms, combined with global data sets of climate and land cover. We thereby consider that NO and HONO are emitted in strongly different proportions, depending on the type of crust and their dynamic activity, and we provide a first estimate of the global distribution of four different crust types. Based on this, we estimate global total values of 1.04 Tg yr⁻¹ NO-N and 0.69 Tg yr⁻¹ HONO-N released by biological soil crusts. This corresponds to around 20\% of global emissions of these trace gases from natural ecosystems. Due to the low number of observations on NO and HONO emissions suitable to validate the model, our estimates are still relatively uncertain. However, they are consistent with the amount estimated by the empirical approach, which confirms that biological soil crusts are likely to have a strong impact on global atmospheric chemistry via emissions of NO and HONO.},
  language  = {en}
}
@article{MuellerHeinzeJoshietal.2014,
  author    = {M{\"u}ller, J{\"o}rg and Heinze, Johannes and Joshi, Jasmin Radha and Boch, Steffen and Klaus, Valentin H. and Fischer, Markus and Prati, Daniel},
  title     = {Influence of experimental soil disturbances on the diversity of plants in agricultural grasslands},
  series = {Journal of plant ecology},
  volume    = {7},
  journal   = {Journal of plant ecology},
  number    = {6},
  publisher = {Oxford Univ. Press},
  address   = {Oxford},
  issn      = {1752-9921},
  doi       = {10.1093/jpe/rtt062},
  pages     = {509 -- 517},
  year      = {2014},
  abstract  = {Disturbance is supposed to play an important role for biodiversity and ecosystem stability as described by the intermediate disturbance hypothesis (IDH), which predicts highest species richness at intermediate levels of disturbances. In this study, we tested the effects of artificial soil disturbances on diversity of annual and perennial vascular plants and bryophytes in a field experiment in 86 agricultural grasslands differing in land use in two regions of Germany. On each grassland, we implemented four treatments: three treatments differing in application time of soil disturbances and one control. One year after experimental disturbance, we recorded vegetation and measured biomass productivity and bare ground. We analysed the disturbance response taking effects of region and land-use-accompanied disturbance regimes into account. Region and land-use type strongly determined plant species richness. Experimental disturbances had small positive effects on the species richness of annuals, but none on perennials or bryophytes. Bare ground was positively related to species richness of bryophytes. However, exceeding the creation of 12\% bare ground further disturbance had a detrimental effect on bryophyte species richness, which corresponds to the IDH. As biomass productivity was unaffected by disturbance our results indicate that the disturbance effect on species richness of annuals was not due to decreased overall productivity, but rather due to short-term lowered inter- and intraspecific competition at the newly created microsites. Generally, our results highlight the importance of soil disturbances for species richness of annual plants and bryophytes in agricultural grasslands. However, most grasslands were disturbed naturally or by land-use practices and our additional experimental soil disturbances only had a small short-term effect. Overall, total plant diversity in grasslands seemed to be more limited by the availability of propagules rather than by suitable microsites for germination. Thus, nature conservation efforts to increase grassland diversity should focus on overcoming propagule limitation, for instance by additional sowing of seeds, while the creation of additional open patches by disturbance might only be appropriate where natural disturbances are scarce.},
  language  = {en}
}