Authorship statement:
TMB designed the field experiment. RH, FZ, MH, TMB, executed the first phase of the field experiment. All authors contributed to maintenance of the second phase of the experiment. RH, EH, JDL, FZ, KS, MH, RJ, TMB collected field data. EH, RH and JDL analyzed soil microbial and vegetation data. RH led the writing of the manuscript, in close collaboration with EH, JDL and TMB. All co-authors contributed critically to the manuscript and approved the final version for publication.