ACKNOWLEDGEMENTS
We thankfully acknowledge technical support by Terry Menard (light and electron microscopy), Dalinda Bouraoui (pedological assessments), James Whitby and Lex Pillatsch from EMPA in Thun, Switzerland (FIB-Tof-SIMS trials), Andres Kaech from ZMB, University of Zurich (cryo-fixation of samples and freeze substitution trials), Roger Wepf and Maja Günthert from ScopeM, ETH Zurich (cryo-sectioning). We are also grateful for financial support by the Sciex-NMSch program (grant 14.038), Wütrich and Mathey-Dupraz Fund, and the Basic Research Funding of University of Latvia for the project ZD2015/AZ81.