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@ARTICLE{Kbert:873310,
      author       = {Kübert, Angelika and Götz, Miriam and Kuester, Emma and
                      Piayda, Arndt and Werner, Christiane and Rothfuss, Youri and
                      Dubbert, Maren},
      title        = {{N}itrogen {L}oading {E}nhances {S}tress {I}mpact of
                      {D}rought on a {S}emi-natural {T}emperate {G}rassland},
      journal      = {Frontiers in Functional Plant Ecology},
      volume       = {10},
      issn         = {1664-462X},
      address      = {Lausanne},
      publisher    = {Frontiers Media88991},
      reportid     = {FZJ-2020-00628},
      pages        = {1051},
      year         = {2019},
      abstract     = {Two important threats to the sustainable functioning of
                      seminatural grasslands in temperate zones are (1) nutrient
                      loading due to agricultural fertilization and pollution, and
                      (2) the increase of extreme drought events due to climate
                      change. These threats may cause substantial shifts in
                      species diversity and abundance and considerably affect the
                      carbon and water balance of ecosystems. The synergistic
                      effects between those two threats, however, can be complex
                      and are poorly understood. Here, we experimentally
                      investigated the effects of nitrogen addition and extreme
                      drought (separately and in combination) on a seminatural
                      temperate grassland, located in Freiburg (South Germany). To
                      study the grassland response, we combined eddy-covariance
                      techniques with open gas exchange systems. Open gas exchange
                      chambers were connected to an infrared gas analyzer and
                      water isotope spectrometer, which allowed the partitioning
                      of net ecosystem exchange and evapotranspiration. Vegetation
                      parameters were described by species richness, species
                      abundance, and leaf area index. Our results suggest that
                      grassland communities, strongly weakened in their stress
                      response by nitrogen loading, can substantially lose their
                      carbon sink function during drought. While nitrogen addition
                      caused a significant loss in forb species $(−25\%),$
                      precipitation reduction promoted a strong dominance of grass
                      species at season start. Consequently, the grass-dominated
                      and species-poor community suffered from a strong
                      above-ground dieback during the dry summer months, likely
                      caused by lower water use efficiency and weaker drought
                      adaptations of the species community. Over the growing
                      season (April-September), the carbon sequestration of the
                      studied grassland was reduced by more than $60\%$ as a
                      consequence of nitrogen addition. Nitrogen addition in
                      combination with precipitation reduction decreased carbon
                      sequestration by $73\%.$ Eutrophication can severely
                      threaten the resilient functioning of grasslands, in
                      particular when drought periods will increase as predicted
                      by future climate scenarios. Our findings emphasize the
                      importance of preserving high diversity of grasslands to
                      strengthen their resistance against extreme events such as
                      droughts.},
      cin          = {IBG-3},
      ddc          = {570},
      cid          = {I:(DE-Juel1)IBG-3-20101118},
      pnm          = {255 - Terrestrial Systems: From Observation to Prediction
                      (POF3-255)},
      pid          = {G:(DE-HGF)POF3-255},
      typ          = {PUB:(DE-HGF)16},
      pubmed       = {pmid:31543886},
      UT           = {WOS:000483313900001},
      doi          = {10.3389/fpls.2019.01051},
      url          = {https://juser.fz-juelich.de/record/873310},
}