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@ARTICLE{Amelung:911173,
      author       = {Amelung, Wulf and Meyer, Nele and Rodionov, Andrey and
                      Knief, Claudia and Aehnelt, Michaela and Bauke, Sara L. and
                      Biesgen, Danh and Dultz, Stefan and Guggenberger, Georg and
                      Jaber, Maguy and Klumpp, Erwin and Kögel-Knabner, Ingrid
                      and Nischwitz, Volker and Schweizer, Steffen A. and Wu, Bei
                      and Totsche, Kai U. and Lehndorff, Eva},
      title        = {{P}rocess sequence of soil aggregate formation disentangled
                      through multi-isotope labelling},
      journal      = {Geoderma},
      volume       = {429},
      issn         = {0016-7061},
      address      = {Amsterdam [u.a.]},
      publisher    = {Elsevier Science},
      reportid     = {FZJ-2022-04485},
      pages        = {116226 -},
      year         = {2023},
      abstract     = {Microaggregates (<250 µm) are key structural subunits of
                      soils. However, their formation processes, rates, and
                      transformation with time are poorly understood. We took
                      advantage of multiple isotope labelling of potential organic
                      gluing agents and inorganic building units to unravel their
                      role in soil aggregation processes being initiated with and
                      without plant growth. We added 13C-labelled extracellular
                      polymeric substances (EPS), 15N-labelled bacteria,
                      57Fe-labelled goethite, and 29Si-labelled montmorillonite to
                      fine soil <250 µm of an Ap horizon from a Stagnic Luvisol,
                      which was planted with Festuca heteromalla or kept bare in a
                      climate chamber. Samples were taken after 4, 12, and 30
                      weeks, and separated into free (f) and occluded (o)
                      microaggregates of different sizes (<20 µm, 53–20 µm,
                      250–53 µm), and in stable macroaggregates (>250 µm) that
                      resisted 60 J mL−1 ultrasonic dispersion. Afterwards, we
                      assessed the C, N, Fe, and Si stable isotope composition in
                      each size fraction. After four weeks we found a rapid
                      build-up of stable macroaggregates comprising almost 50 $\%$
                      of soil mass in the treatment with plants and respective
                      soil rooting, but only 5 $\%$ when plants were absent. The
                      formation of these stable macroaggregates proceeded with
                      time. Soil organic carbon (SOC) contents were elevated by 15
                      $\%$ in the large macroaggregates induced by plant growth.
                      However, the recovery of EPS-derived 13C was below 20 $\%$
                      after 4 weeks, indicating rapid turnover in treatments both
                      with and without plants. The remaining EPS-derived C was
                      mainly found in macroaggregates when plants were present and
                      in the occluded small microaggregates (<20 µm) when plants
                      were absent. The excess of bacterial 15N closely followed
                      the pattern of EPS-derived 13C (R2 = 0.72). In contrast to
                      the organic gluing agents, the goethite-57Fe and
                      montmorillonite-29Si were relatively equally distributed
                      across all size fractions. Overall, microaggregates were
                      formed within weeks. Roots enforced this process by
                      stabilizing microaggregates within stable macroaggregates.
                      As time proceeded the labelled organic components
                      decomposed, while the labelled secondary oxides and clay
                      minerals increasingly contributed to aggregate stabilization
                      and turnover at the scale of months and beyond.
                      Consequently, the well-known hierarchical organization of
                      aggregation follows a clear chronological sequence of
                      stabilization and turnover processes.},
      cin          = {ZEA-3 / IBG-3},
      ddc          = {910},
      cid          = {I:(DE-Juel1)ZEA-3-20090406 / I:(DE-Juel1)IBG-3-20101118},
      pnm          = {2173 - Agro-biogeosystems: controls, feedbacks and impact
                      (POF4-217) / DFG project 251268514 - FOR 2179: MAD Soil -
                      Microaggregates: Formation and turnover of the structural
                      building blocks of soils (251268514)},
      pid          = {G:(DE-HGF)POF4-2173 / G:(GEPRIS)251268514},
      typ          = {PUB:(DE-HGF)16},
      UT           = {WOS:001029035800001},
      doi          = {10.1016/j.geoderma.2022.116226},
      url          = {https://juser.fz-juelich.de/record/911173},
}