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@ARTICLE{Zhang:909452,
      author       = {Zhang, Yonggen and Weihermüller, Lutz and Toth, Brigitta
                      and Noman, Muhammad and Vereecken, Harry},
      title        = {{A}nalyzing dual porosity in soil hydraulic properties
                      using soil databases for pedotransfer function development},
      journal      = {Vadose zone journal},
      volume       = {21},
      number       = {5},
      issn         = {1539-1663},
      address      = {Hoboken, NJ},
      publisher    = {Wiley},
      reportid     = {FZJ-2022-03198},
      pages        = {e20227},
      year         = {2022},
      abstract     = {Current databases of soil hydraulic properties (SHPs) have
                      typically been used to develop pedotransfer functions (PTFs)
                      to estimate water retention [θ(h)] assuming a unimodal
                      pore-size distribution. However, natural soils often show
                      the presence of bimodal to multimodal pore-size
                      distributions. Here, we used three widely spread databases
                      for PTF development: UNsaturated SOil hydraulic DAtabase
                      (UNSODA) 2.0, Vereecken, and European hydropedological data
                      inventory (EU-HYDI), to analyze the presence of structural
                      effects in both θ(h) and hydraulic conductivity [K(h)].
                      Only undisturbed samples were included in the analysis that
                      contained enough datapoints for both θ(h) and K(h)
                      properties, especially in the wet range. One-hundred
                      ninety-two samples were suitable for our analysis, which is
                      only $1\%$ of the total samples in the three databases.
                      Results showed that $65\%$ of the samples exhibited a
                      bimodal pore-size distribution, and bimodality was not
                      limited to fine-textured but also coarser-textured soils.
                      The Mualem–van Genuchten (MvG) expression for both
                      unimodal and bimodal soils was not able to predict the
                      observed unsaturated K. Only a joint fitting of measured
                      θ(h) and K(h) functions provided parameter estimates that
                      were able to describe unsaturated K for uni- and bimodal
                      soils. In addition, we observed a negative relationship
                      between α and n in the case of low sand content $(<52\%)$
                      for both unimodal and bimodal matrix domain properties,
                      contradicting the classical notion. The ratio of α for the
                      macropore and matrix domain was positively correlated with
                      the fraction of macropores and sand content. We anticipate
                      that the results will contribute to deriving PTF for
                      structured soils and avoid unrealistic combinations of MvG
                      parameters.},
      cin          = {IBG-3},
      ddc          = {550},
      cid          = {I:(DE-Juel1)IBG-3-20101118},
      pnm          = {2173 - Agro-biogeosystems: controls, feedbacks and impact
                      (POF4-217)},
      pid          = {G:(DE-HGF)POF4-2173},
      typ          = {PUB:(DE-HGF)16},
      UT           = {WOS:000847638400001},
      doi          = {10.1002/vzj2.20227},
      url          = {https://juser.fz-juelich.de/record/909452},
}